[{"content":"ALARP Principles ALARP (As Low As Reasonably Practicable) is a risk management principle requiring that risks be reduced to the lowest level that is reasonably practicable. This page covers what ALARP means in practice and how to implement it for ocean operations.\nWhy This Exists ALARP is a legal requirement in many jurisdictions and a best practice in others. It provides a framework for making risk decisions that balances risk reduction with practical constraints. Understanding ALARP is essential for regulatory compliance and defensible risk management.\nWho This Is For Safety officers implementing risk management Operations managers making risk decisions Regulators reviewing risk assessments Auditors verifying ALARP compliance Legal counsel defending risk decisions ALARP Definition ALARP means reducing risk to the lowest level that is:\nTechnically feasible — Can it be done with available technology? Economically reasonable — Is the cost justified by the risk reduction? Operationally practical — Can it be implemented in practice? Key point: ALARP is not zero risk. It is the lowest risk that is reasonably practicable given constraints.\nALARP Assessment Process Step 1: Identify All Reasonably Practicable Controls For each identified risk, identify all controls that could reasonably be implemented:\nElimination — Can the hazard be eliminated? Substitution — Can a less hazardous approach be used? Engineering controls — Can equipment or systems reduce risk? Administrative controls — Can procedures, training, or supervision reduce risk? Personal protective equipment — What PPE is available? What can go wrong: Controls not identified, controls dismissed without assessment, impractical controls included. Assessment must be thorough and realistic.\nStep 2: Assess Cost vs. Risk Reduction For each control, assess:\nRisk reduction — How much does this control reduce risk? (quantified where possible) Implementation cost — What does it cost to implement? (capital, operational, maintenance) Cost-effectiveness — Is the cost justified by the risk reduction? Operational reality: Cost includes not just money, but also operational complexity, maintenance burden, and other practical constraints.\nStep 3: Implement Controls Where Justified Implement controls where:\nRisk reduction is significant — Control meaningfully reduces risk Cost is reasonable — Cost is justified by risk reduction Implementation is practical — Control can be implemented in practice What can go wrong: Controls not implemented despite justification, controls implemented without justification, implementation incomplete. Decisions must be documented.\nStep 4: Document Decisions For each control decision, document:\nControl description — What control was considered? Risk reduction — How much risk reduction would it provide? Implementation cost — What would it cost to implement? Decision — Implement or not implement, and why Decision authority — Who made the decision? Legal requirement: ALARP decisions must be documented and defensible. Undocumented decisions create legal and regulatory risk.\nALARP Zones Intolerable Risk Risk that is unacceptable regardless of cost:\nMust be reduced — Risk must be reduced below intolerable level No cost-benefit analysis — Cost is not a factor; risk must be reduced Regulatory intervention — Regulators may prohibit operations if risk is intolerable Operational reality: Intolerable risk is rare but serious. Operations with intolerable risk should not proceed.\nALARP Zone Risk that is tolerable but should be reduced:\nMust demonstrate ALARP — Must show that risk is ALARP Cost-benefit analysis — Cost vs. risk reduction must be assessed Documentation required — Decisions must be documented Most operations fall here: Most operational risks are in the ALARP zone, requiring assessment and documentation.\nBroadly Acceptable Risk Risk that is so low that further reduction is not required:\nNo further action — No need to reduce risk further No documentation required — May not require detailed documentation Rare in practice — Most operational risks are not broadly acceptable Operational reality: Broadly acceptable risk is rare in commercial diving and subsea operations.\nPractical Implementation Risk Assessment Start with thorough risk assessment:\nIdentify hazards — All significant hazards must be identified Assess risk — Quantify risk where possible, qualitatively where not Compare to criteria — Compare risk to intolerable and broadly acceptable criteria What can go wrong: Hazards not identified, risk underestimated, criteria not applied correctly. Risk assessment must be thorough.\nControl Identification Identify all reasonably practicable controls:\nBrainstorm controls — Consider all possible controls Assess feasibility — Determine which controls are technically feasible Assess practicality — Determine which controls are operationally practical Operational reality: Control identification requires experience and creativity. External expertise may be needed.\nCost-Benefit Analysis Assess cost vs. risk reduction:\nQuantify risk reduction — How much does control reduce risk? (where possible) Quantify cost — What does control cost? (capital, operational, maintenance) Compare — Is cost justified by risk reduction? What can go wrong: Risk reduction overestimated, cost underestimated, comparison not done. Analysis must be realistic and documented.\nDecision Making Make and document decisions:\nDecision authority — Who has authority to make ALARP decisions? Decision process — What process is used to make decisions? Documentation — How are decisions documented? Responsibility: Management typically has decision authority. Decisions must be documented and defensible.\nCommon Pitfalls \u0026ldquo;We Can\u0026rsquo;t Afford It\u0026rdquo; Cost alone is not sufficient reason to not implement a control:\nMust assess — Cost must be assessed against risk reduction Must justify — Decision not to implement must be justified Must document — Justification must be documented What can go wrong: Controls dismissed based on cost without assessment, decisions not documented. Cost is a factor, but not the only factor.\n\u0026ldquo;It\u0026rsquo;s Too Complex\u0026rdquo; Complexity alone is not sufficient reason:\nMust assess — Complexity must be assessed against risk reduction Must consider alternatives — Simpler alternatives may exist Must document — Decision must be documented Operational reality: Complexity is a valid constraint, but must be assessed, not assumed.\n\u0026ldquo;We\u0026rsquo;ve Always Done It This Way\u0026rdquo; Tradition is not justification:\nMust assess — Existing practices must be assessed against ALARP Must improve — If better practices exist, they should be considered Must document — Decision to continue existing practice must be documented What can go wrong: Existing practices not assessed, better practices not considered, status quo assumed acceptable. ALARP requires continuous improvement.\nRegulatory Considerations Legal Requirements ALARP may be a legal requirement:\nUK regulations — ALARP is a legal requirement under UK health and safety law Other jurisdictions — Similar requirements may exist in other jurisdictions Industry standards — IMCA, DNV, and other standards may require ALARP Responsibility: Operators must comply with legal requirements. Non-compliance creates legal risk.\nRegulatory Review Regulators may review ALARP assessments:\nDocumentation review — Regulators may review ALARP documentation Decision challenge — Regulators may challenge ALARP decisions Enforcement — Non-compliance may result in enforcement action Audit-worthiness: ALARP documentation must be suitable for regulatory review. Inadequate documentation creates regulatory risk.\nRelated Topics Operational Risk Models Hazard Identification (HAZID/HAZOP) Dive Planning \u0026amp; Risk Assessment ","permalink":"/melon-wiki/safety-compliance/alarp/","summary":"\u003ch1 id=\"alarp-principles\"\u003eALARP Principles\u003c/h1\u003e\n\u003cp\u003eALARP (As Low As Reasonably Practicable) is a risk management principle requiring that risks be reduced to the lowest level that is reasonably practicable. This page covers what ALARP means in practice and how to implement it for ocean operations.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eALARP is a legal requirement in many jurisdictions and a best practice in others. It provides a framework for making risk decisions that balances risk reduction with practical constraints. Understanding ALARP is essential for regulatory compliance and defensible risk management.\u003c/p\u003e","title":"ALARP Principles"},{"content":"Audit Logs \u0026amp; Immutability Audit logs record what happened, when, and by whom — and must be structured so that no one can alter them without that alteration being detectable. In subsea operations, audit logs support incident investigation, regulatory compliance, and data integrity verification.\nWhy This Exists Raw data and derived products are only trustworthy if the chain of custody can be proven. Audit logs provide the evidence trail. Without tamper-evident logs, data can be altered after the fact — intentionally or accidentally — and the alteration cannot be detected. Regulatory bodies and legal proceedings require that evidence of data integrity be demonstrable.\nWho This Is For Data managers designing data storage and access systems Safety officers investigating incidents Regulators reviewing operational records Legal and compliance teams responding to disputes or incidents What Audit Logs Must Record A complete audit log entry records:\nTimestamp — When the event occurred (UTC, with sub-second precision where relevant) Actor — Who or what performed the action (user ID, system ID, software version) Action — What was done (create, read, update, delete, export) Object — What was acted upon (file path, record ID, dataset name) Source address — Where the action originated (IP address, terminal ID) Result — Whether the action succeeded or failed Context — Any relevant operational context (dive ID, deployment ID) Immutability Requirements Append-Only Design Audit logs must be append-only: entries can be added but not modified or deleted. Systems that allow modification or deletion of audit log entries are not audit logs — they are records that can be falsified.\nImplementation options:\nWrite-once storage media Cryptographic chaining (each entry includes a hash of the previous entry) Append-only log services with access controls preventing modification Offsite replication to an independent system Cryptographic Chaining Each log entry can include a cryptographic hash of the previous entry, creating a chain. Altering any entry breaks all subsequent hashes, making tampering detectable:\nE E n n t t r r y y N N : + 1 { : d { a t d a a , t a h , a s h h a ( s E h n ( t E r n y t r N y - 1 N ) ) } } This structure is the basis of blockchain-style data integrity, applied here without the distributed consensus overhead.\nTimestamping Timestamps must come from a trusted, authoritative source:\nNTP-synchronised clocks — Synchronised to a trusted time server GPS time — For systems deployed at sea where NTP may be unavailable Third-party timestamping — Cryptographic timestamps from a trusted authority prove data existed at a particular time Log Retention and Access Retention Periods Retention requirements vary by jurisdiction and data type:\nOperational logs — Typically 2–5 years Incident-related records — Often retained indefinitely pending investigation closure Environmental data — May have regulatory-defined retention periods Organisations must define and enforce retention policies. Automatic deletion before retention periods expire must be prevented.\nAccess Controls Access to audit logs must itself be logged:\nReading logs is an auditable action Administrators who can manage log systems must not be able to delete entries Separation of duties: those who generate data should not be the sole custodians of that data\u0026rsquo;s logs Operational Context Dive Operations For diving operations, audit logs should capture:\nGas mix preparation and verification sign-offs Dive supervisor authorisation entries In-water communication transcripts (or references to recordings) Equipment inspection completion records Any deviations from the approved dive plan ROV/AUV Operations For autonomous and remotely operated vehicles:\nMission file versions and upload timestamps Parameter changes made during operations Sensor data file creation and transfer records Operator intervention events Integration with Data Provenance Audit logs and data provenance are related but distinct:\nAudit logs — Record system events and user actions Data provenance — Track the lineage of data products (where data came from and how it was processed) Both are required for full accountability. See Data Provenance \u0026amp; Chain-of-Custody for provenance-specific guidance.\nRelated Topics Data Provenance \u0026amp; Chain-of-Custody Timestamp Integrity Raw vs Derived Data Regulatory Landscape Overview ","permalink":"/melon-wiki/ocean-data/audit-logs/","summary":"\u003ch1 id=\"audit-logs--immutability\"\u003eAudit Logs \u0026amp; Immutability\u003c/h1\u003e\n\u003cp\u003eAudit logs record what happened, when, and by whom — and must be structured so that no one can alter them without that alteration being detectable. In subsea operations, audit logs support incident investigation, regulatory compliance, and data integrity verification.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eRaw data and derived products are only trustworthy if the chain of custody can be proven. Audit logs provide the evidence trail. Without tamper-evident logs, data can be altered after the fact — intentionally or accidentally — and the alteration cannot be detected. Regulatory bodies and legal proceedings require that evidence of data integrity be demonstrable.\u003c/p\u003e","title":"Audit Logs \u0026 Immutability"},{"content":"Autonomy Challenges \u0026amp; Legacy Assumptions Autonomous subsea systems operate in ways that existing regulatory frameworks were not designed to accommodate. Rules written for human divers, remotely operated vehicles with continuous operator control, or surface vessels with crews do not map cleanly onto systems that make independent decisions in real time. This page examines where legacy assumptions break down and what that means for operations, liability, and standards development.\nWhy This Exists Deploying autonomous systems without understanding the gaps in applicable frameworks creates legal, regulatory, and operational risk. Organisations must identify which assumptions underlie their regulatory compliance posture and whether those assumptions still hold when the system acts autonomously.\nWho This Is For Engineers designing autonomous subsea systems Legal and compliance teams reviewing regulatory applicability Standards bodies developing new frameworks Project managers identifying regulatory risks before deployment What Makes Autonomy Different Continuous Human Control Assumption Most existing regulations for subsea vehicles assume a human operator is continuously monitoring and controlling the vehicle. Regulations specify:\n\u0026ldquo;The operator shall ensure…\u0026rdquo; — Who is the operator of an AUV completing a long-duration mission? \u0026ldquo;The pilot shall maintain…\u0026rdquo; — An autonomous vehicle has no pilot Response time requirements — An AUV operating beyond acoustic communication range cannot respond to real-time commands Gap: Regulations that specify continuous operator control are unenforceable for, and inapplicable to, truly autonomous systems.\nDefined Operating Area Assumption ROV regulations assume the vehicle operates in a defined, known, and cleared area within the umbilical\u0026rsquo;s reach. AUVs may traverse large areas including:\nRegions not cleared for operations Areas with unknown hazards Zones where other operations are underway Gap: Safe area definitions and exclusion zones designed for tethered operations do not account for autonomous navigation through variable terrain.\nImmediate Abort Capability Assumption Emergency procedures in existing frameworks assume operations can be halted immediately on command. An AUV:\nMay be beyond acoustic communication range May be executing a manoeuvre that cannot be safely interrupted May experience communication loss at a critical moment Gap: Emergency stop requirements presuppose communication that autonomous systems cannot guarantee.\nLiability and Accountability Gaps Distributed Decision-Making When an autonomous system makes a decision that results in an incident, attributing responsibility is complex:\nDesigner — Did the system behave as specified? Operator — Was the mission planned appropriately? Programmer — Was the decision logic correct? Certifier — Was the system properly assessed before deployment? Existing liability frameworks typically assign responsibility to an operator/employer. They do not describe how to assign liability when the decision was made by an algorithm.\nSoftware as Evidence If an autonomous vehicle is involved in an incident, the software state at the time of the incident is critical evidence. This requires:\nLogging of all autonomous decisions with sufficient context to reconstruct the decision process Version control and immutable deployment records Black-box equivalent capabilities for autonomous vehicles See Why Auditability Matters for the logging requirements that follow from this.\nLegacy Assumptions in Standards Manned Submersible Rules Applied to AUVs Some regulators apply manned submersible rules to AUVs because no AUV-specific rules exist. This creates:\nOver-specified requirements (life support systems for a vehicle with no crew) Under-specified requirements (no guidance on autonomous decision-making) Arbitrary interpretations that vary by jurisdiction and inspector ROV Rules Applied to AUVs ROV rules typically require:\nContinuous surface monitoring Umbilical as a physical lifeline Defined safe areas matching the umbilical radius None of these translate to AUV operations. Applying ROV rules to AUVs either prevents AUV operations entirely or forces fictitious compliance.\nPaths Forward New Regulatory Categories Effective frameworks will likely need separate regulatory categories for:\nFully supervised ROVs (existing frameworks apply) Supervised AUVs (periodic communication required) Extended autonomous AUVs (pre-mission approval model) Persistent autonomous systems (continuous environmental monitoring) Performance-Based vs Prescriptive Standards Prescriptive standards (do X, use Y) cannot anticipate autonomous system designs. Performance-based standards (achieve outcome Z, demonstrate how) allow innovation while maintaining safety objectives. The challenge is defining measurable performance criteria for autonomous behaviour.\nRelated Topics Why Auditability Matters Gaps in Current Standards Open Problems in Subsea Operations Failure Modes \u0026amp; Recovery Loss-of-Comms Behavior ","permalink":"/melon-wiki/open-standards/autonomy-challenges/","summary":"\u003ch1 id=\"autonomy-challenges--legacy-assumptions\"\u003eAutonomy Challenges \u0026amp; Legacy Assumptions\u003c/h1\u003e\n\u003cp\u003eAutonomous subsea systems operate in ways that existing regulatory frameworks were not designed to accommodate. Rules written for human divers, remotely operated vehicles with continuous operator control, or surface vessels with crews do not map cleanly onto systems that make independent decisions in real time. This page examines where legacy assumptions break down and what that means for operations, liability, and standards development.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eDeploying autonomous systems without understanding the gaps in applicable frameworks creates legal, regulatory, and operational risk. Organisations must identify which assumptions underlie their regulatory compliance posture and whether those assumptions still hold when the system acts autonomously.\u003c/p\u003e","title":"Autonomy Challenges \u0026 Legacy Assumptions"},{"content":"AUV Platforms Overview Autonomous underwater vehicles (AUVs) operate without tethers and without continuous operator control. They execute pre-programmed missions, collecting data and performing tasks while navigating independently. This page covers the major AUV platform categories, their capabilities, and the operational considerations specific to each.\nWhy This Exists AUVs are becoming central to subsea inspection, survey, and monitoring operations. Understanding the platform options, their capabilities, and their limitations is essential for selecting the right vehicle for a given mission and for planning operations that use AUVs effectively and safely.\nWho This Is For Engineers and project managers selecting AUV platforms ROV pilots and operators transitioning to AUV operations Operations managers planning AUV deployments Safety officers assessing AUV operational risks AUV Categories by Form Factor Torpedo/Streamlined AUVs The most common form factor: an elongated, hydrodynamically optimised body with a propeller aft and control surfaces.\nCharacteristics:\nSpeed: 1.5–4 knots transit; optimised for efficient forward flight Range: 10–100+ km depending on battery capacity and speed Depth: From shallow (\u0026lt;100m) to full ocean depth (6000m+) depending on model Manoeuvrability: Low — cannot hover or work in confined spaces Typical applications:\nWide-area bathymetric survey Pipeline and cable route survey Environmental monitoring transects Mine countermeasures (military) Examples: Kongsberg Hugin, Teledyne REMUS, L3 OceanServer Iver\nHovering/Work-Class AUVs Multi-thruster vehicles designed for station-keeping and precision manoeuvre, similar to ROVs but without a tether.\nCharacteristics:\nSpeed: Slow — typically \u0026lt;1 knot transit, hovering capability Range: Limited by battery capacity; typically \u0026lt;10 km Depth: Mission-specific, typically 3000–6000m for work-class variants Manoeuvrability: High — can work in confined spaces, maintain precise positioning Typical applications:\nSubsea infrastructure inspection Intervention tasks (with manipulator arms) Precision survey of specific targets Examples: Saab Sabertooth, ECA H800\nGliders Buoyancy-driven vehicles that move by changing buoyancy and use wings to convert vertical motion into horizontal motion.\nCharacteristics:\nSpeed: Very slow — typically \u0026lt;0.5 knots Range: Very long — weeks to months of operation Depth: From surface to 1000m+ depending on model Manoeuvrability: Very low — long turning radius, cannot hold station Power: Extremely low power consumption; very long endurance Typical applications:\nSustained oceanographic monitoring Climate and environmental research Persistent surveillance Examples: Teledyne Webb Slocum, Kongsberg Seaglider, iRobot Ocean Aura\nHybrid AUV/ROVs (Hybrid Vehicles) Vehicles designed to operate both as AUVs and as ROVs (tethered from a depressor or buoy rather than a surface vessel).\nApplications: Combining AUV survey capability with ROV intervention capability in a single deployment.\nAUV vs. ROV Selection Criteria Criterion AUV Advantage ROV Advantage Large area coverage Yes — no tether drag, efficient transit No — tether limits range Continuous monitoring Yes — long endurance possible No — vessel must remain on station Real-time observation No — delayed data recovery Yes — live video and control Intervention tasks No — limited without manipulators Yes — purpose-built for intervention Communication during mission No — typically none underwater Yes — through tether Emergency recovery Slower — must wait for vehicle return Faster — pull on tether Launch and Recovery Surface Launch and Recovery Most AUVs are launched and recovered from a surface vessel:\nA-frame or crane — For large vehicles or rough sea states Stern ramp — For smaller vehicles in benign conditions ROV-assisted — In deepwater operations, an ROV may be used to release/recover the AUV at depth Sea state limits: AUV launch and recovery is more weather-sensitive than ROV operations because the vehicle has no tether for control during deployment.\nSubsea Docking Some AUV systems use subsea docking stations for deployment, recharging, and data upload:\nEnables persistent monitoring without repeated surface vessel visits Requires accurate AUV homing capability Introduces single points of failure (dock power, dock communication) Related Topics ROV Systems Overview Vehicle Classes \u0026amp; Capabilities Sensor Payloads Control Frameworks Failure Modes \u0026amp; Recovery Loss-of-Comms Behavior ","permalink":"/melon-wiki/subsea-robotics/auv-platforms/","summary":"\u003ch1 id=\"auv-platforms-overview\"\u003eAUV Platforms Overview\u003c/h1\u003e\n\u003cp\u003eAutonomous underwater vehicles (AUVs) operate without tethers and without continuous operator control. They execute pre-programmed missions, collecting data and performing tasks while navigating independently. This page covers the major AUV platform categories, their capabilities, and the operational considerations specific to each.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eAUVs are becoming central to subsea inspection, survey, and monitoring operations. Understanding the platform options, their capabilities, and their limitations is essential for selecting the right vehicle for a given mission and for planning operations that use AUVs effectively and safely.\u003c/p\u003e","title":"AUV Platforms Overview"},{"content":"Commercial Dive Logs \u0026amp; Operational Records Dive logs and operational records provide traceability and auditability for commercial diving operations. This page covers what must be recorded, how records must be maintained, and why this matters for regulatory compliance, incident investigation, and legal defense.\nWhy This Exists Operational records serve multiple critical purposes:\nRegulatory compliance — Required by IMCA, ADCI, HSE, OSHA, and national regulations Incident investigation — Essential for reconstructing what happened and why Insurance claims — Required documentation for commercial diving insurance coverage Legal defense — Proper records protect operators, supervisors, and divers in disputes Operational improvement — Historical data informs future planning and risk assessment What can go wrong: Incomplete records, lost records, altered records, untraceable records. Each failure mode creates regulatory, legal, and operational risk — including criminal liability for supervisors in some jurisdictions.\nWho This Is For Dive supervisors maintaining operational records Safety officers auditing record-keeping compliance Regulators reviewing diving operations Incident investigators reconstructing dive events Insurance underwriters assessing operational risk Legal counsel defending diving operations Printable Dive Log Template Use this template for a single dive entry. All fields meet IMCA / ADCI / USN Diving Manual requirements. Fill in your browser and print, or use as a reference for your own system.\nDive Log Entry Clear Download PDF Log # Rev COMMERCIAL DIVE LOG U.S. Navy / IMCA / ADCI Compliant Record 1. OPERATION DETAILS Vessel / Platform Contract / Project Work Site / Block Date Latitude Longitude Water Depth (FSW) 2. DIVE TEAM Dive Supervisor Supervisor Cert # Supervisor Exp (yrs) Working Diver Diver Cert # Medical Expiry Standby Diver Tender Diving Physician 3. DIVE PROFILE Dive # Left Surface Reached Depth Max Depth (FSW) Left Bottom Surfaced Bottom Time (min) Descent Rate (FPM) Ascent Rate (FPM) Pre-Dive Rep Group Post-Dive Rep Group Prior Surface Int. 4. DECOMPRESSION Table Used Schedule In-Water O2 Stop (ft/min) Chamber O2 Periods Decompression Deviations / Extensions Deco Completed Post-Dive O2 Monitoring (hrs) 5. BREATHING GAS Gas Mix O2 % (Analyzed) He % (Analyzed) Cylinder Start PSI Cylinder End PSI Compressor Hours (start) CO Filter Last Changed Air Quality Test (date) 6. ENVIRONMENTAL CONDITIONS Visibility (ft) Current (kts / direction) Sea State (Beaufort) Water Temp (°F / °C) Tide State Wave Height (ft) Air Temp (°F) Hazardous Materials? 7. WORK PERFORMED Task Description Equipment Used 8. INCIDENTS, ANOMALIES \u0026 NEAR-MISSES Incidents / Near-Misses DCS Signs / Symptoms? Chamber Treatment? Equipment Failure? Safety Stop Taken? 9. CERTIFICATION \u0026 SIGNATURES Working Diver Signature Dive Supervisor Signature Supervisor Certification I certify that this dive was conducted in accordance with applicable regulations, the diving safety manual, and the procedures contained herein. All information is accurate and complete to the best of my knowledge.\nRetain for minimum 5 years (IMCA) / per applicable regulations. Incident records: retain indefinitely.\nReference: IMCA M 103, ADCI Consensus Standards, USN Diving Manual Rev 7 (SS521-AG-PRO-010)\nRequired Records Dive Log Entries Each dive must be logged with:\nDate and time — Start time, bottom time, surface time, completion time Location — Geographic coordinates (GPS), water depth at dive site, structure or work site ID Diver information — Diver name, certification level, certification number, medical clearance expiry Depth profile — Maximum depth (FSW), time at depth, descent and ascent rates Gas information — Gas mix specified and analyzed, O2%, He%, CO analysis date, cylinder pressures Decompression — Table and schedule used, stops completed with depths and times, deviations if any Work performed — Tasks completed, equipment used, findings, issues encountered Environmental conditions — Current speed and direction, visibility, sea state, water temperature Team composition — Supervisor name, standby diver name, tender name, DMO contact Equipment — Primary and backup equipment used, pre-dive inspection results, equipment issues Traceability: Each entry must be timestamped and attributable to a specific person. Records must be immutable once created — corrections require amendment notes, not erasures.\nEquipment Records Equipment must be tracked:\nInspection records — Pre-dive and post-dive inspections, periodic maintenance, out-of-service events Calibration records — Gas analyzers, depth gauges, communication equipment, O2 analyzers Maintenance records — Repairs, replacements, modifications with part numbers and dates Failure records — Equipment failures, near-misses, corrective actions taken Audit-worthiness: Equipment records must demonstrate that equipment was maintained in accordance with manufacturer recommendations and regulatory requirements.\nTraining Records Personnel qualifications must be documented:\nCertifications — Diver certifications (ADCI, IMCA, HSE, or equivalent), supervisor qualifications, medical fitness certificates Training history — Training completed, competency assessments, refresher training, emergency drills Dive history — Cumulative dive hours, types of operations, specific qualifications (bell diving, saturation, etc.) Incident Reports Incidents, near-misses, and anomalies must be documented:\nIncident description — What happened, when, where, who was involved Causal analysis — Why it happened, contributing factors, root cause Response actions — What was done in response, immediate and follow-up Preventive measures — What will prevent recurrence Legal sensitivity: Incident reports may be discoverable in legal proceedings. They must be factual and accurate. Do not speculate or assign blame — describe what happened and what was done.\nRecord-Keeping Requirements Timeliness Records must be created:\nDuring operations — Real-time logging of depth, time, and gas data Immediately after — Post-dive debrief, decompression completion, supervisor countersignature Within 24 hours — Final log review, incident notification if required What can go wrong: Delayed logging leads to incomplete or inaccurate records. Memory degrades quickly — records must be contemporaneous to be credible in investigation or litigation.\nAccuracy Records must use measured values, not estimates:\nDepth — From calibrated depth gauge, not estimated Time — From synchronized timepieces, not reconstructed Gas — Analyzed O2%, not assumed from cylinder label Pressure — From calibrated gauges, with before/after readings Completeness All required fields completed — no blank mandatory fields All dives logged — no skipped entries regardless of dive duration All decompression stops recorded with actual times, not planned times Immutability Records must be immutable once signed:\nNo overwriting — Errors corrected with a single line strike-through, initialed and dated Amendment process — Significant corrections require a separate amendment note with reason, date, and signature No backdating — All entries dated and timed at creation Data Provenance Records must demonstrate data provenance:\nSource — Where did the data originate? Instrument? Observation? Calculation? Method — Direct measurement, estimation, or derived value? Chain of custody — Who recorded the data, who verified it, how was it transferred? Audit-worthiness: Data provenance enables auditors to verify record accuracy and identify potential errors. Records that cannot be traced to a source are not credible.\nStorage \u0026amp; Retention Storage Requirements Secure storage — Protected from loss, damage, fire, water, and unauthorized access Backup — Redundant copies in separate physical locations or cloud storage with access controls Access control — Only authorized personnel can view or modify records Format — Readable format that will remain accessible for the full retention period Retention Periods Record Type Minimum Retention Basis Dive logs (routine) 5 years IMCA M 103, ADCI Equipment inspection records 5 years or equipment life Manufacturer / regulator Training \u0026amp; certification records Duration of employment + 5 years Standard practice Incident reports Indefinite Statute of limitations Personal injury records Indefinite Legal requirement Gas analysis records 5 years Standard practice Operational reality: Many jurisdictions and contracts require retention beyond these minimums. When in doubt, retain longer.\nDigital vs. Paper Records Digital records — Advantages: searchable, easily backed up, can support audit trails, integrates with decompression software. Challenges: format obsolescence, system dependencies, cybersecurity requirements, integrity verification.\nPaper records — Advantages: universally readable, legally established, no technology dependency. Challenges: physical storage, difficult to search at scale, backup requires physical copying.\nBest practice: Dual records (digital primary, paper backup for critical dives) provide the advantages of both. The paper record must be a faithful copy of the digital record, not a summary.\nAudit Requirements Records must support the following audit types:\nRegulatory audits — IMCA, ADCI, HSE, OSHA, flag state, coastal state Client audits — Third-party verification of contract compliance Insurance audits — Risk assessment and claims verification Internal audits — Quality assurance and continuous improvement What auditors look for: Complete entries, supervisor signatures, calibration records, training records cross-referenced to personnel, gas analysis certificates, incident report trails. Gaps in any of these create audit findings.\nFrequently Asked Questions What must be in a commercial diving log? Every commercial dive log entry must include: date and times (start, max depth, surfaced), GPS location, diver identity and certification, maximum depth reached, bottom time, breathing gas mix and analyzed O2%, decompression schedule followed and any deviations, work performed, environmental conditions, and supervisor signature. See the printable template above for a complete field reference.\nHow long must records be kept? Minimum 5 years for routine logs (IMCA/ADCI). Indefinite for incident reports and records involving personal injury. Many operators keep all records for 7-10 years. Check your contract, your jurisdiction, and your insurer\u0026rsquo;s requirements — they may be more stringent.\nWhat makes a record legally defensible? Contemporaneous creation (not reconstructed from memory), measured values from calibrated instruments, complete required fields, supervisor countersignature, immutable storage with audit trail. Records that can be shown to have been altered, backdated, or estimated rather than measured are not credible in legal proceedings.\nRelated Topics USN Dive Tables — Decompression table reference Dive Planning \u0026amp; Risk Assessment Ocean Data \u0026amp; Trust — Data provenance and integrity principles Safety, Risk \u0026amp; Compliance — Regulatory requirements ","permalink":"/melon-wiki/commercial-diving/dive-logs/","summary":"\u003ch1 id=\"commercial-dive-logs--operational-records\"\u003eCommercial Dive Logs \u0026amp; Operational Records\u003c/h1\u003e\n\u003cp\u003eDive logs and operational records provide traceability and auditability for commercial diving operations. This page covers what must be recorded, how records must be maintained, and why this matters for regulatory compliance, incident investigation, and legal defense.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eOperational records serve multiple critical purposes:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eRegulatory compliance\u003c/strong\u003e — Required by IMCA, ADCI, HSE, OSHA, and national regulations\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eIncident investigation\u003c/strong\u003e — Essential for reconstructing what happened and why\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eInsurance claims\u003c/strong\u003e — Required documentation for commercial diving insurance coverage\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eLegal defense\u003c/strong\u003e — Proper records protect operators, supervisors, and divers in disputes\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eOperational improvement\u003c/strong\u003e — Historical data informs future planning and risk assessment\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eWhat can go wrong:\u003c/strong\u003e Incomplete records, lost records, altered records, untraceable records. Each failure mode creates regulatory, legal, and operational risk — including criminal liability for supervisors in some jurisdictions.\u003c/p\u003e","title":"Commercial Dive Logs \u0026 Operational Records"},{"content":"Communication Systems Subsea communication is fundamentally different from terrestrial communication. This page covers acoustic, RF, and hybrid communication systems, their capabilities, limitations, and failure modes.\nWhy This Exists Communication enables coordination, control, and data transfer in subsea operations. Understanding communication options, tradeoffs, and failure modes is essential for designing and operating multi-vehicle systems.\nWho This Is For Robotics engineers designing communication systems Operations managers planning multi-vehicle operations ROV pilots operating in communication-limited environments System architects designing networked systems Communication Options Acoustic Communication Acoustic modems use sound waves to transmit data through water:\nRange — Typically 1-10km depending on frequency and power Bandwidth — Low bandwidth (typically \u0026lt;10 kbps) Latency — High latency (speed of sound in water ~1500 m/s) Reliability — Affected by noise, multipath, and environmental conditions Operational reality: Acoustic communication is the standard for long-range subsea communication, but it is slow and unreliable.\nWhat can go wrong: Communication loss due to range, noise, multipath, equipment failure. Acoustic communication is inherently unreliable.\nRF Communication Radio frequency communication through water:\nRange — Very limited (typically \u0026lt;100m in seawater) Bandwidth — Higher bandwidth than acoustic (typically 100+ kbps) Latency — Low latency (speed of light) Reliability — Good reliability at short range Operational reality: RF is only practical at very short range. Seawater is highly conductive, severely limiting RF range.\nWhat can go wrong: Range exceeded, interference, equipment failure. RF is not practical for most subsea operations.\nHybrid Systems Combining acoustic and RF:\nAcoustic for long-range — Use acoustic for vehicle-to-surface or vehicle-to-vehicle at range RF for short-range — Use RF for high-bandwidth at short range Automatic switching — Switch between systems based on range and requirements Operational reality: Hybrid systems provide best of both worlds, but add complexity.\nWhat can go wrong: Switching failures, system complexity, increased failure modes. Hybrid systems must be carefully designed.\nTether (ROV) Hard-wired connection for ROVs:\nRange — Limited by tether length (typically \u0026lt;1000m) Bandwidth — Very high bandwidth (fiber optic) Latency — Very low latency Reliability — High reliability if tether intact Operational reality: Tether provides best communication but limits vehicle mobility and range.\nWhat can go wrong: Tether damage, tether length limitations, entanglement. Tether is not practical for all operations.\nCommunication Characteristics Latency Communication latency affects:\nReal-time control — High latency makes real-time control difficult Coordination — High latency affects coordination capability Data freshness — High latency means data is stale when received Operational reality: Acoustic latency (speed of sound) is ~0.67 seconds per kilometer. At 5km range, round-trip latency is ~6.7 seconds. This is too slow for real-time control.\nBandwidth Communication bandwidth affects:\nData transfer — How much data can be transferred Video feeds — High-bandwidth required for video Sensor data — Bandwidth limits sensor data transfer Operational reality: Acoustic bandwidth is typically \u0026lt;10 kbps, insufficient for video. RF provides higher bandwidth but limited range.\nReliability Communication reliability affects:\nMission success — Unreliable communication may cause mission failure Safety — Unreliable communication creates safety risk Coordination — Unreliable communication makes coordination difficult What can go wrong: Communication loss, intermittent communication, degraded communication. Systems must be designed for unreliable communication.\nFailure Modes Range Exceeded Communication lost because range exceeded:\nAcoustic — Range typically 1-10km depending on conditions RF — Range typically \u0026lt;100m in seawater Tether — Range limited by tether length Response: Vehicle must operate autonomously when communication lost. See Loss-of-Comms Behavior .\nEnvironmental Interference Communication degraded by environmental conditions:\nAcoustic noise — Ship noise, biological noise, other acoustic sources Multipath — Acoustic signals reflected off surfaces Attenuation — Signal strength reduced by distance and conditions What can go wrong: Communication degraded or lost due to environmental conditions. Systems must be robust to environmental interference.\nEquipment Failure Communication equipment fails:\nModem failure — Acoustic or RF modem fails Antenna failure — Antenna damaged or disconnected Power failure — Communication equipment loses power Response: Backup communication systems, or vehicle operates autonomously. See Graceful Degradation .\nCommunication Protocols Message-Based Protocols Send discrete messages:\nAdvantages — Simple, robust to loss, works with low bandwidth Disadvantages — No continuous data streams, higher overhead Operational reality: Message-based protocols are common for acoustic communication due to low bandwidth and high latency.\nStream-Based Protocols Continuous data streams:\nAdvantages — Efficient for continuous data, lower overhead Disadvantages — Requires reliable connection, not suitable for low bandwidth Operational reality: Stream-based protocols are used for tethered systems with high bandwidth and low latency.\nHybrid Protocols Combine message-based and stream-based:\nMessages for control — Use messages for commands and status Streams for data — Use streams for high-bandwidth data when available Operational reality: Hybrid protocols provide flexibility but add complexity.\nOperational Considerations Communication Planning Plan communication for operations:\nRange requirements — What range is needed? Bandwidth requirements — What bandwidth is needed? Latency requirements — What latency is acceptable? Reliability requirements — What reliability is needed? What can go wrong: Communication not planned, requirements not met, backup not available. Communication planning is essential.\nBackup Communication Provide backup communication:\nMultiple systems — Acoustic and RF, or multiple acoustic systems Redundant equipment — Backup modems and antennas Alternative methods — Surface-to-surface coordination, visual signals Operational reality: Backup communication is essential. Single point of failure is unacceptable.\nAutonomous Operation Vehicles must operate autonomously:\nWhen communication lost — Vehicle continues mission autonomously When communication degraded — Vehicle adapts to available communication Pre-programmed behavior — Vehicle follows pre-programmed procedures Responsibility: Vehicle designers must ensure autonomous capability. Operators must understand autonomous behavior.\nRelated Topics Multi-Vehicle Coordination Latency \u0026amp; Bandwidth Tradeoffs Graceful Degradation Loss-of-Comms Behavior ","permalink":"/melon-wiki/swarm-systems/communications/","summary":"\u003ch1 id=\"communication-systems\"\u003eCommunication Systems\u003c/h1\u003e\n\u003cp\u003eSubsea communication is fundamentally different from terrestrial communication. This page covers acoustic, RF, and hybrid communication systems, their capabilities, limitations, and failure modes.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eCommunication enables coordination, control, and data transfer in subsea operations. Understanding communication options, tradeoffs, and failure modes is essential for designing and operating multi-vehicle systems.\u003c/p\u003e\n\u003ch2 id=\"who-this-is-for\"\u003eWho This Is For\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eRobotics engineers designing communication systems\u003c/li\u003e\n\u003cli\u003eOperations managers planning multi-vehicle operations\u003c/li\u003e\n\u003cli\u003eROV pilots operating in communication-limited environments\u003c/li\u003e\n\u003cli\u003eSystem architects designing networked systems\u003c/li\u003e\n\u003c/ul\u003e\n\u003ch2 id=\"communication-options\"\u003eCommunication Options\u003c/h2\u003e\n\u003ch3 id=\"acoustic-communication\"\u003eAcoustic Communication\u003c/h3\u003e\n\u003cp\u003eAcoustic modems use sound waves to transmit data through water:\u003c/p\u003e","title":"Communication Systems"},{"content":"Confidence Calibration Confidence calibration is the process of measuring whether operator confidence in their abilities matches their actual performance. In simulation-based training, poorly calibrated confidence is a serious hazard: operators who are overconfident will take risks they are not equipped to handle; operators who are underconfident will hesitate when decisive action is needed.\nWhy This Exists Simulation training creates a risk that is not present in apprenticeship-based training: the trainee may perform well in simulation without that performance transferring to the real environment. If trainees exit training believing they are more capable than they are, the training has created a hazard rather than eliminating one.\nWho This Is For Training designers building simulation curricula Instructors assessing trainee readiness Operations managers making deployment decisions Safety officers reviewing training programme effectiveness What Is Confidence Calibration? A well-calibrated operator:\nCorrectly identifies situations they can handle competently Correctly identifies situations that exceed their current capability Knows when to ask for assistance or defer to more experienced colleagues Adjusts confidence appropriately as experience accumulates Overconfidence: Performance is worse than the operator believes. This is more dangerous — the operator takes on situations they cannot handle safely.\nUnderconfidence: Performance is better than the operator believes. This is less dangerous but reduces operational efficiency and may prevent deployment of a competent operator.\nMeasuring Confidence Calibration Self-Assessment vs. Objective Performance Calibration is measured by comparing:\nSubjective confidence — How certain is the operator that they can perform a task correctly? Objective performance — How well do they actually perform the task? If an operator says \u0026ldquo;I\u0026rsquo;m 90% confident I can complete this task\u0026rdquo; and completes it correctly 90% of the time across many trials, they are well-calibrated for that task.\nCalibration Methods Scenario-based assessment: Present the operator with scenarios of varying difficulty. Before each, ask for confidence rating. After each, assess performance. Plot confidence vs. performance.\nKnowledge questions: Present questions about procedures, limits, and emergency actions. Ask for confidence in each answer. Score the answers. Compare.\nJudgment tasks: Ask operators to assess whether a simulated situation is within limits. Compare judgments to correct answers.\nFactors That Distort Confidence Simulator Fidelity Gaps If the simulator is easier than reality (smoother controls, cleaner sensor data, more forgiving physics), operators may perform well in simulation without real capability. They exit training overconfident.\nMitigation: Introduce realistic noise, failure modes, and environmental variability in simulation. See Physics vs Control Realism .\nLack of Failure Consequences In simulation, failure is safe. This can reduce the psychological pressure that affects real performance. Operators may perform better in simulation than they would in a real emergency.\nMitigation: Structured debriefs that emphasise what would have happened in reality; progressive assessment of performance under simulated pressure.\nInstructor Feedback Effects Positive instructor feedback can inflate confidence. Critical feedback without performance data can deflate it unnecessarily.\nMitigation: Feedback should be based on objective performance metrics, not instructor impression. Distinguish between praise for effort (appropriate) and claims about competence (must be evidence-based).\nCalibration in Training Programmes Entry Assessment Assess baseline confidence and performance at programme entry:\nIdentifies trainees with prior experience that may or may not match their confidence Sets a baseline for measuring programme effectiveness Progressive Calibration Checkpoints Throughout training:\nRegular calibration assessments as capability is built Trainees should see their confidence and performance data together Instructors should intervene when significant miscalibration is detected Certification Readiness Assessment Before certification:\nFull calibration assessment across the scope of the certification Trainees must demonstrate not just performance but appropriate confidence in that performance Significant overconfidence should delay certification even if raw performance meets criteria Calibration for New Technology When operators are transitioning to new systems (e.g., from manual ROV operation to autonomy-assisted operation), confidence calibration is especially important:\nPrior experience may create false confidence about new system behaviour New failure modes may not be intuited from old experience Performance in the new system must be specifically assessed before deployment Related Topics Why Simulation Matters Physics vs Control Realism Pre-Mission Rehearsal Digital Twins Human Factors in Diving Operations ","permalink":"/melon-wiki/simulation-training/confidence/","summary":"\u003ch1 id=\"confidence-calibration\"\u003eConfidence Calibration\u003c/h1\u003e\n\u003cp\u003eConfidence calibration is the process of measuring whether operator confidence in their abilities matches their actual performance. In simulation-based training, poorly calibrated confidence is a serious hazard: operators who are overconfident will take risks they are not equipped to handle; operators who are underconfident will hesitate when decisive action is needed.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eSimulation training creates a risk that is not present in apprenticeship-based training: the trainee may perform well in simulation without that performance transferring to the real environment. If trainees exit training believing they are more capable than they are, the training has created a hazard rather than eliminating one.\u003c/p\u003e","title":"Confidence Calibration"},{"content":"Control Frameworks The control framework of an autonomous or remotely operated vehicle defines how it translates goals, sensor inputs, and operator commands into actuator outputs. Different architectures make different tradeoffs between responsiveness, planning capability, safety, and complexity.\nWhy This Exists Choosing an inappropriate control architecture can make a vehicle unsafe (too slow to react to hazards), ineffective (unable to plan complex missions), or unpredictable (brittle in unexpected situations). Understanding the options and their tradeoffs is essential for designing and operating subsea vehicles safely.\nWho This Is For Engineers designing vehicle control systems Operations managers evaluating AUV and ROV systems Pilots and operators understanding why vehicles behave as they do Safety engineers assessing autonomous system safety ROV Control Frameworks Manual Control The baseline ROV mode: the pilot commands thrusters directly (or through a thin layer of rate control), and the vehicle responds. The pilot provides all sensing and decision-making.\nAdvantages: Maximum operator flexibility; operator can respond to anything they observe Disadvantages: Highly skill-dependent; fatiguing in complex environments; no automatic safety functions Heading and Depth Hold Auto-pilot functions that maintain a commanded heading and/or depth using feedback control:\nAdvantages: Reduces pilot workload; maintains station in currents; improves sensor data quality Disadvantages: Still requires pilot for all other tasks; may conflict with environmental conditions Dynamic Positioning (DP) DP systems maintain position and heading automatically in all three horizontal dimensions, using sensor fusion (USBL, DVL, heading) and thruster coordination:\nAdvantages: Accurate station-keeping; frees pilot to focus on the task; essential for precision survey Disadvantages: Requires high-quality positioning sensors; can fail if sensors fail; may consume significant thrust Fully Supervised Autonomous Functions Some ROV systems include autonomous functions (auto-tracking of a pipeline, auto-hover during inspection) with the pilot monitoring and overriding:\nAdvantages: Consistent, precise execution of repetitive tasks Disadvantages: Autonomous functions have limited environmental adaptability; supervisor must remain vigilant AUV Control Architectures Deliberative (Sense-Plan-Act) The deliberative architecture builds a world model, plans a sequence of actions to achieve the goal, and executes the plan:\nSense — Gather sensor data Plan — Plan actions to achieve goals given current world state Act — Execute the planned actions Advantages: Optimal or near-optimal planning; handles complex multi-step goals Disadvantages: Slow to react to unexpected events; world model may be stale or wrong; computationally expensive Reactive (Subsumption/Behaviour-Based) Reactive architectures connect sensors directly to behaviours without maintaining a world model. Behaviours are prioritised and the highest-priority applicable behaviour controls the vehicle:\nLow-level behaviours — Obstacle avoidance, collision prevention (highest priority) Mid-level behaviours — Station-keeping, target tracking High-level behaviours — Mission execution (lowest priority, can be pre-empted) Advantages: Fast reaction to hazards; robust to unexpected events; simple to implement and test Disadvantages: Cannot plan complex multi-step actions; may exhibit emergent behaviour that is difficult to predict Hybrid Architectures Most practical AUV systems combine deliberative and reactive elements:\nReactive layer — Handles immediate safety and environmental response (obstacle avoidance, emergency behaviours) Deliberative layer — Plans mission execution and handles complex sequencing The reactive layer can pre-empt the deliberative layer when safety-critical situations arise.\nModel Predictive Control (MPC) MPC uses a vehicle dynamics model to predict future behaviour and optimises control inputs over a receding horizon:\nAdvantages: Handles constraints explicitly (thruster limits, current limits); optimal within prediction horizon Disadvantages: Computationally intensive; requires accurate vehicle model; prediction errors accumulate Safety Architecture Considerations Fail-Safe Behaviours Safety-critical behaviours must be implemented in the highest-priority layer and must activate on component failure:\nLoss of communication → abort and return to surface (or defined safe point) Low battery → abort and return to surface Sensor failure → fall back to conservative navigation; surface if critical sensor lost Obstacle detection → stop and request guidance or execute avoidance Watchdog Systems Independent hardware or software monitors that trigger fail-safe behaviour if the main control system stops responding:\nMust be independent of the main control system (cannot share the processor that might be frozen) Must be tested regularly Must act on a short timeout (seconds, not minutes) State Machines Explicit state machines make vehicle behaviour predictable and auditable:\nEach state defines what the vehicle does and what transitions are possible Transitions require specific conditions to be met State is logged continuously to support incident investigation Related Topics ROV Systems Overview AUV Platforms Overview Failure Modes \u0026amp; Recovery Loss-of-Comms Behavior Multi-Vehicle Coordination Why Auditability Matters ","permalink":"/melon-wiki/subsea-robotics/control-frameworks/","summary":"\u003ch1 id=\"control-frameworks\"\u003eControl Frameworks\u003c/h1\u003e\n\u003cp\u003eThe control framework of an autonomous or remotely operated vehicle defines how it translates goals, sensor inputs, and operator commands into actuator outputs. Different architectures make different tradeoffs between responsiveness, planning capability, safety, and complexity.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eChoosing an inappropriate control architecture can make a vehicle unsafe (too slow to react to hazards), ineffective (unable to plan complex missions), or unpredictable (brittle in unexpected situations). Understanding the options and their tradeoffs is essential for designing and operating subsea vehicles safely.\u003c/p\u003e","title":"Control Frameworks"},{"content":"Data Provenance \u0026amp; Chain-of-Custody Data provenance is the record of where data came from, how it was created, and who handled it. Chain-of-custody tracks data as it moves through systems and organizations. This page covers why this matters for ocean operations and how to implement it in practice.\nWhy This Exists Data provenance enables:\nAudit verification — Auditors can verify data accuracy by tracing to source Incident investigation — Investigators can reconstruct what happened from data records Regulatory compliance — Regulators require traceable data for compliance verification Legal defense — Provenance protects operators in disputes by demonstrating data integrity Operational trust — Operators can trust data when they know its source and handling What can go wrong: Data without provenance cannot be verified, data with broken chain-of-custody is not credible, missing provenance creates legal and operational risk.\nWho This Is For Data engineers designing data systems Operations personnel recording operational data Auditors verifying data accuracy Incident investigators reconstructing events Legal counsel defending operations Regulators reviewing compliance Provenance Requirements Source Identification Every data record must identify:\nSource system — What system created the data? (sensor, instrument, calculation, human entry) Source location — Where was the data created? (vehicle, surface system, geographic location) Creation method — How was the data created? (direct measurement, calculation, estimation, observation) Creation time — When was the data created? (timestamp with timezone and synchronization method) Operational reality: Source identification must be automatic where possible. Manual entry is error-prone and should be minimized.\nTransformation Tracking When data is transformed, track:\nTransformation type — What transformation was applied? (filtering, calibration, unit conversion, calculation) Transformation parameters — What parameters were used? (calibration coefficients, filter settings, algorithm version) Transformation time — When was the transformation applied? Transformation system — What system performed the transformation? What can go wrong: Transformations not documented, transformation parameters lost, transformations applied incorrectly. Each transformation must be traceable.\nChain-of-Custody As data moves through systems, track:\nTransfer events — When data was transferred, from where to where Transfer method — How data was transferred (network, storage media, manual) Transfer integrity — How integrity was verified (checksums, signatures) Custodian — Who or what system had custody at each point Legal requirement: Chain-of-custody must be unbroken. Gaps in chain-of-custody reduce data credibility in legal proceedings.\nImplementation Approaches Metadata Embedding Embed provenance in data records:\nStructured metadata — JSON, XML, or structured fields in data records Header information — Provenance in file headers or message headers Database fields — Provenance columns in database tables Advantages: Provenance travels with data, no separate tracking system required.\nChallenges: Metadata can be lost or altered, requires discipline to maintain.\nSeparate Provenance Logs Maintain separate logs tracking data:\nEvent logs — Log each data creation, transformation, and transfer event Data registry — Registry mapping data identifiers to provenance records Audit trails — Immutable audit trails of all data operations Advantages: Centralized tracking, easier to audit, can be made tamper-resistant.\nChallenges: Requires infrastructure, must be kept synchronized with data.\nHybrid Approaches Combine embedding and logging:\nEmbedded metadata — Lightweight provenance in data records Centralized logs — Detailed provenance in centralized systems Cross-references — Data records reference centralized logs Operational reality: Hybrid approaches balance convenience and auditability. Most practical systems use hybrid approaches.\nProvenance for Different Data Types Sensor Data Sensor data provenance must include:\nSensor identification — Sensor type, serial number, calibration status Measurement conditions — Environmental conditions, sensor configuration Calibration information — Calibration date, coefficients, traceability Data acquisition — Sampling rate, filtering, timestamp synchronization What can go wrong: Sensor misidentified, calibration not recorded, conditions not documented. Sensor data without provenance is not credible.\nCalculated Data Calculated data provenance must include:\nInput data — What data was used as input? (with provenance) Calculation method — What algorithm or formula was used? Calculation parameters — What parameters were used? Calculation system — What system performed the calculation? (software version, configuration) What can go wrong: Input data not identified, calculation method not documented, parameters lost. Calculated data must be reproducible.\nHuman-Entered Data Human-entered data provenance must include:\nEntered by — Who entered the data? Entry time — When was it entered? Entry method — How was it entered? (form, log, voice transcription) Source information — What was the source of the information? (observation, measurement, communication) What can go wrong: Entered by not recorded, entry time inaccurate, source not documented. Human-entered data requires careful provenance tracking.\nChain-of-Custody Procedures Data Transfer When transferring data:\nVerify source — Confirm data source and provenance Transfer securely — Use secure transfer methods with integrity verification Record transfer — Log transfer event with timestamp and parties Verify receipt — Confirm data received and integrity verified Update custody — Update chain-of-custody records Responsibility: Both sender and receiver must verify and record transfer.\nData Storage When storing data:\nSecure storage — Protect from unauthorized access and modification Access logging — Log all access to stored data Integrity verification — Regularly verify data integrity (checksums, signatures) Backup procedures — Backup data with provenance intact What can go wrong: Unauthorized access, data modification, integrity loss, backup without provenance. Storage systems must protect data and provenance.\nData Access When accessing data:\nAccess logging — Log who accessed what data when Purpose documentation — Document why data was accessed Integrity verification — Verify data integrity before use Provenance review — Review provenance before relying on data Audit requirement: Access logs must be maintained for audit. Unauthorized or undocumented access creates risk.\nVerification \u0026amp; Validation Provenance Verification Verify provenance:\nSource verification — Can source be verified? Is source credible? Chain verification — Is chain-of-custody unbroken? Transformation verification — Can transformations be verified? Are they correct? Timeline verification — Do timestamps make sense? Are they consistent? What can go wrong: Provenance cannot be verified, chain-of-custody broken, transformations incorrect, timestamps inconsistent. Unverifiable provenance reduces data credibility.\nData Validation Validate data against provenance:\nSource validation — Does data match expected source characteristics? Range validation — Is data within expected ranges for source? Consistency validation — Is data consistent with other data from same source? Temporal validation — Does data make sense temporally? Operational reality: Validation catches errors early. Invalid data should trigger investigation.\nRegulatory \u0026amp; Legal Considerations Regulatory Requirements Regulators may require:\nProvenance documentation — Detailed provenance records Chain-of-custody maintenance — Unbroken chain-of-custody Audit access — Ability for regulators to audit provenance Retention — Provenance records retained for specified periods Responsibility: Operators must comply with regulatory requirements. Non-compliance creates legal and operational risk.\nLegal Considerations In legal proceedings:\nEvidence admissibility — Data with proper provenance is more likely to be admissible Credibility — Data with broken provenance is less credible Burden of proof — Operators may need to prove data integrity Discovery — Provenance records may be discoverable Legal risk: Data without provenance or with broken chain-of-custody may not be credible in legal proceedings.\nRelated Topics Sensor Calibration Traceability Timestamp Integrity Audit Logs \u0026amp; Immutability Dive Logs \u0026amp; Operational Records ","permalink":"/melon-wiki/ocean-data/provenance/","summary":"\u003ch1 id=\"data-provenance--chain-of-custody\"\u003eData Provenance \u0026amp; Chain-of-Custody\u003c/h1\u003e\n\u003cp\u003eData provenance is the record of where data came from, how it was created, and who handled it. Chain-of-custody tracks data as it moves through systems and organizations. This page covers why this matters for ocean operations and how to implement it in practice.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eData provenance enables:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eAudit verification\u003c/strong\u003e — Auditors can verify data accuracy by tracing to source\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eIncident investigation\u003c/strong\u003e — Investigators can reconstruct what happened from data records\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eRegulatory compliance\u003c/strong\u003e — Regulators require traceable data for compliance verification\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eLegal defense\u003c/strong\u003e — Provenance protects operators in disputes by demonstrating data integrity\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eOperational trust\u003c/strong\u003e — Operators can trust data when they know its source and handling\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eWhat can go wrong:\u003c/strong\u003e Data without provenance cannot be verified, data with broken chain-of-custody is not credible, missing provenance creates legal and operational risk.\u003c/p\u003e","title":"Data Provenance \u0026 Chain-of-Custody"},{"content":"Decompression Theory (Operational) Decompression theory explains why divers must ascend slowly and make stops after breathing compressed gas at depth. This page covers the operational aspects: what causes decompression sickness, how dive tables encode safe ascent profiles, and how to apply the theory in practice.\nWhy This Exists Every diver working with compressed gas at depth is subject to decompression obligations. Understanding the theory behind those obligations allows supervisors and divers to plan dives safely, recognize when tables apply, and respond appropriately when exposures exceed planned limits.\nWho This Is For Diving supervisors planning and approving dive plans Commercial divers understanding their decompression obligations Safety officers reviewing dive plans and incident reports Medical staff treating potential decompression sickness Inert Gas Uptake and Elimination How Gas Enters Tissues When breathing compressed gas at depth, inert gas (nitrogen or helium) dissolves into tissues under pressure. The amount dissolved depends on:\nPartial pressure of the gas — Higher pressure = more gas dissolved Time at depth — Tissues absorb gas at different rates (compartments) Tissue type — Different tissues (blood, fat, muscle) absorb and release gas at different rates Tissue Compartments Decompression models use multiple theoretical tissue compartments with different half-times:\nFast compartments (e.g., 5-minute half-time) — Absorb and release gas quickly; limiting at shorter exposures Slow compartments (e.g., 120-minute half-time) — Absorb gas slowly but retain it for longer; limiting for repetitive or long dives Operational implication: The slowest compartment that has absorbed significant gas determines the required decompression.\nSupersaturation and Bubble Formation During ascent, pressure decreases and inert gas comes out of solution. If ascent is too fast, gas forms bubbles in tissues and blood — the cause of decompression sickness (DCS).\nTolerated supersaturation: Tissues can tolerate some level of supersaturation without forming symptomatic bubbles. Decompression tables are designed to keep supersaturation within tolerable limits.\nUSN Decompression Model The U.S. Navy Diving Manual uses the Workman M-value model:\nM-values define the maximum tolerable inert gas pressure in each tissue compartment at each ambient pressure Decompression stops are required whenever inert gas pressure in any compartment approaches its M-value during ascent Tables encode pre-calculated ascent profiles that keep all compartments within safe limits Table Structure USN dive tables are organized by:\nBottom depth — Maximum depth reached during the dive Bottom time — Time from leaving the surface until beginning ascent Repetitive group — Letter designation indicating residual nitrogen carried into the next dive No-Decompression Limits (NDL) The NDL is the maximum time a diver can remain at a given depth and ascend directly to the surface without required decompression stops. Exceeding the NDL creates an obligatory decompression stop requirement.\nSee No-Decompression Limits (Tables 9-7 \u0026amp; 2A-1) for specific USN NDL values.\nDecompression Stop Procedures When a dive exceeds the NDL:\nBegin ascent at the prescribed rate (typically 9 m/min or 30 ft/min) Stop at the first required decompression stop depth Wait the prescribed time at each stop Ascend to the next stop (or surface) after completing each stop time Do not skip or shorten stops Stop breathing gas: For air dives, stops are performed breathing air. Oxygen-enriched gas at stops accelerates inert gas elimination.\nRepetitive Diving Residual nitrogen from a previous dive adds to inert gas loading on subsequent dives. USN tables account for this through:\nRepetitive group letters — Track residual nitrogen after a dive Surface interval credit — Nitrogen eliminated during surface intervals is credited Residual nitrogen time — Added to actual bottom time for table entry on the second dive Operational rule: Always calculate cumulative nitrogen loading for multiple-dive days.\nDecompression Sickness Recognition Type I (Musculoskeletal/Skin) Joint pain (\u0026ldquo;the bends\u0026rdquo;) Skin mottling (cutis marmorata) Lymphatic swelling Type II (Neurological/Cardiopulmonary) Weakness, paralysis, numbness Visual disturbances Respiratory distress (\u0026ldquo;chokes\u0026rdquo;) Loss of consciousness Any DCS symptoms require immediate recompression treatment. Do not wait to see if symptoms resolve.\nRelated Topics USN Dive Tables No-Decompression Limits (Tables 9-7 \u0026amp; 2A-1) USN Air Decompression Table (Table 9-9) Saturation Diving Overview Dive Planning \u0026amp; Risk Assessment Emergency Response Frameworks ","permalink":"/melon-wiki/commercial-diving/decompression-theory/","summary":"\u003ch1 id=\"decompression-theory-operational\"\u003eDecompression Theory (Operational)\u003c/h1\u003e\n\u003cp\u003eDecompression theory explains why divers must ascend slowly and make stops after breathing compressed gas at depth. This page covers the operational aspects: what causes decompression sickness, how dive tables encode safe ascent profiles, and how to apply the theory in practice.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eEvery diver working with compressed gas at depth is subject to decompression obligations. Understanding the theory behind those obligations allows supervisors and divers to plan dives safely, recognize when tables apply, and respond appropriately when exposures exceed planned limits.\u003c/p\u003e","title":"Decompression Theory (Operational)"},{"content":"Digital Twins A digital twin is a computational model that mirrors a physical system in real or near-real time. For subsea operations, digital twins can represent vehicles, structures, environmental conditions, and operations. They support simulation, condition monitoring, maintenance planning, and training in ways that static models cannot.\nWhy This Exists Physical assets operating in the subsea environment are expensive to inspect and difficult to access. A digital twin provides a continuously updated representation of the asset\u0026rsquo;s state, making it possible to monitor performance, detect degradation, plan maintenance, and train operators without repeated physical access.\nWho This Is For Engineers designing digital twin systems for subsea assets Operations managers using digital twins for planning and monitoring Training designers building high-fidelity training environments Data managers integrating sensor data with asset models What Makes a Digital Twin A digital twin has three components:\nPhysical asset — The real-world system being modelled Digital model — A computational representation of the asset Data connection — Sensor data flowing from the physical asset to update the model Without the data connection, it is a simulation model, not a digital twin. The defining characteristic is real-time or near-real-time synchronisation between physical and digital.\nTypes of Digital Twins in Subsea Operations Vehicle Twins A digital twin of an ROV or AUV models:\nVehicle dynamics (hydrodynamics, thruster response) Sensor suite (coverage, accuracy, noise characteristics) Power system state (battery charge, consumption rates) Fault state (which systems are healthy, degraded, or failed) Applications:\nPre-mission rehearsal with accurate vehicle behaviour Mission planning (endurance, sensor coverage) Fault diagnosis (comparing actual vs. expected behaviour) Maintenance prediction (power consumption trends indicating degradation) Structure Twins A digital twin of a subsea structure (pipeline, riser, manifold) models:\nStructural integrity and stress state Corrosion rates and protection system performance Inspection history and known defects Environmental loading Applications:\nCondition monitoring without every inspection requiring physical access Anomaly detection (comparing sensor readings with model predictions) Maintenance planning based on modelled degradation rates Environmental Twins A digital twin of the marine environment models:\nCurrent profiles and variability Seabed topography Water column properties (temperature, salinity, acoustic velocity) Applications:\nMission planning for vehicles operating in complex environments Training scenarios with realistic environmental conditions Communication planning (acoustic propagation modelling) Keeping Twins Current Data Ingestion Digital twins must ingest data from sensors on the physical asset:\nReal-time streaming — For continuous monitoring applications Batch updates — After inspection events, incorporating new inspection findings Hybrid — Continuous monitoring supplemented by periodic high-resolution updates Model Updating As new data arrives, the model must be updated:\nState estimation — Use sensor data to update the modelled state of the asset Parameter estimation — Update model parameters as behaviour deviates from predictions Uncertainty tracking — Model uncertainty grows between data updates and shrinks when new data arrives Model Validation A digital twin is only useful if it accurately represents the physical asset. Validation requires:\nComparing model predictions with independent measurements Tracking prediction error over time Updating or revalidating the model when significant deviations occur Digital Twins for Training High-fidelity digital twins of operational assets provide training environments that are:\nAccurate to the specific asset — Not a generic model but the actual asset being operated Current — Reflects the current state of the asset including known defects and modifications Safe — Operators can train on realistic failure scenarios without risk Requirement: Training twins must be explicitly marked and controlled to ensure trainees do not confuse training scenarios with operational reality.\nData Integration Challenges Data Quality Digital twins are only as good as the data feeding them. Poor sensor calibration, missing data, and data integrity issues degrade twin accuracy. See Sensor Calibration Traceability and Raw vs Derived Data .\nData Latency The value of a digital twin depends in part on how current it is. High-latency data connections (acoustic modems, satellite uplinks) limit how often the twin can be updated.\nModel-Reality Divergence Models become less accurate over time as the physical asset changes (corrosion, modifications, damage) in ways the model doesn\u0026rsquo;t capture. Regular inspection and model update cycles are required.\nRelated Topics Why Simulation Matters Physics vs Control Realism Pre-Mission Rehearsal Sensor Calibration Traceability Data Provenance \u0026amp; Chain-of-Custody ","permalink":"/melon-wiki/simulation-training/digital-twins/","summary":"\u003ch1 id=\"digital-twins\"\u003eDigital Twins\u003c/h1\u003e\n\u003cp\u003eA digital twin is a computational model that mirrors a physical system in real or near-real time. For subsea operations, digital twins can represent vehicles, structures, environmental conditions, and operations. They support simulation, condition monitoring, maintenance planning, and training in ways that static models cannot.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003ePhysical assets operating in the subsea environment are expensive to inspect and difficult to access. A digital twin provides a continuously updated representation of the asset\u0026rsquo;s state, making it possible to monitor performance, detect degradation, plan maintenance, and train operators without repeated physical access.\u003c/p\u003e","title":"Digital Twins"},{"content":"Dive Planning \u0026amp; Risk Assessment Dive planning is the process of identifying hazards, assessing risks, and developing operational procedures before a dive commences. This page covers the frameworks and considerations that matter in practice.\nWhy This Exists Proper dive planning prevents incidents. By identifying hazards, assessing risks, and developing response procedures before the dive, operations can proceed with clear understanding of what can go wrong and how to respond.\nWho This Is For Dive supervisors planning operations Commercial divers reviewing dive plans Safety officers assessing operational risk Auditors reviewing planning procedures Contractors developing operational procedures Planning Framework Hazard Identification Before planning, identify all hazards:\nEnvironmental hazards — Current, visibility, sea state, temperature, marine life Equipment hazards — Equipment failure modes, umbilical management, tool hazards Task hazards — Work complexity, confined spaces, entanglement risks Human factors — Fatigue, experience level, team composition Organizational hazards — Communication protocols, emergency response capability, support resources What can go wrong: Hazards not identified, hazards underestimated, new hazards emerge during operations. Planning must be thorough and account for uncertainty.\nRisk Assessment For each identified hazard, assess:\nLikelihood — How likely is this hazard to cause an incident? Severity — How severe would the consequences be? Mitigation — What controls reduce likelihood or severity? Residual risk — What risk remains after mitigation? Operational reality: Risk assessment is not academic. It must reflect actual operational conditions and account for how operations degrade under stress.\nControl Measures Develop control measures for each significant risk:\nElimination — Can the hazard be eliminated? Substitution — Can a less hazardous approach be used? Engineering controls — Can equipment or procedures reduce risk? Administrative controls — Can procedures, training, or supervision reduce risk? Personal protective equipment — What PPE is required? What can go wrong: Controls not implemented, controls ineffective, controls degrade during operations. Controls must be practical and verifiable.\nEmergency Procedures For each significant risk, develop emergency response procedures:\nTrigger conditions — What conditions trigger emergency response? Response actions — What actions are taken in response? Responsibility — Who is responsible for each action? Communication — How is emergency communicated? Recovery — How is normal operations restored? Responsibility boundaries: Emergency procedures must clearly define who does what. Ambiguity in emergency response leads to delayed or incorrect actions.\nDive Plan Components Operational Parameters Depth — Maximum operating depth Bottom time — Planned bottom time and decompression schedule Gas requirements — Gas mix, volume, and consumption estimates Work scope — Tasks to be performed and equipment required Environmental conditions — Expected current, visibility, sea state What can go wrong: Parameters set beyond equipment or diver capabilities, environmental conditions worse than expected, work scope exceeds available time. Plans must be conservative and account for uncertainty.\nTeam Composition Diver — Primary diver qualifications and experience Standby diver — Standby diver qualifications and readiness Supervisor — Supervisor qualifications and experience Support personnel — Tenders, equipment operators, medical support Human factors: Team composition affects operational capability. Inexperienced teams require more conservative planning.\nEquipment Requirements Diving equipment — Helmet/mask, bailout, tools, work equipment Surface equipment — Gas supply, communication, monitoring, recovery Emergency equipment — Standby diver equipment, emergency gas, medical equipment Backup systems — Redundant systems for critical functions What can go wrong: Equipment not available, equipment not functional, backup systems not tested. Equipment must be verified before dive commences.\nCommunication Protocols Check-in procedures — Frequency and format of check-ins Emergency communication — How emergencies are communicated Backup communication — Alternative communication methods Surface-to-surface communication — Coordination with other operations Operational reality: Communication protocols must work in practice, not just on paper. Test communication before operations.\nRisk Assessment Methods Qualitative Risk Assessment Simple risk matrix approach:\nLikelihood: Rare, Unlikely, Possible, Likely, Almost Certain Severity: Negligible, Minor, Moderate, Major, Catastrophic Risk level: Low, Medium, High, Extreme Use when: Quick assessment needed, resources limited, risk levels clearly distinguishable.\nWhat can go wrong: Subjective assessment, inconsistent application, risks underestimated. Requires experienced assessors.\nQuantitative Risk Assessment Numerical assessment of likelihood and consequences:\nProbability estimates — Based on historical data or expert judgment Consequence estimates — Quantified in terms of injury, equipment damage, or operational impact Risk calculation — Probability × Consequence = Risk Use when: Detailed analysis required, historical data available, regulatory requirements mandate quantitative assessment.\nWhat can go wrong: False precision, data not applicable to current conditions, calculations not understood by operational personnel. Results must be interpreted in operational context.\nALARP Assessment As Low As Reasonably Practicable (ALARP) assessment:\nIdentify all reasonably practicable controls Assess cost vs. risk reduction for each control Implement controls where risk reduction justifies cost Document why controls are or are not implemented Use when: Regulatory requirements mandate ALARP, high-risk operations, significant resources available for risk reduction.\nResponsibility: Management decides what is \u0026ldquo;reasonably practicable.\u0026rdquo; Decisions must be documented and defensible.\nPre-Dive Briefing Before dive commences, conduct briefing covering:\nDive plan review — Parameters, procedures, and emergency response Hazard review — Identified hazards and control measures Team roles — Responsibilities of each team member Communication protocols — Check-in procedures and emergency communication Equipment verification — Confirmation that all equipment is ready What can go wrong: Briefing not conducted, briefing incomplete, team members not paying attention. Briefing must be interactive and verified.\nPost-Dive Review After dive completion, review:\nPlan vs. execution — What differed from plan and why? Hazards encountered — Were all hazards identified? Any new hazards? Control effectiveness — Did controls work as intended? Lessons learned — What should be done differently next time? Operational improvement: Post-dive review drives continuous improvement. Document lessons learned and update procedures.\nRegulatory Considerations Dive planning must comply with applicable regulations:\nIMCA guidelines — International Marine Contractors Association guidelines ADCI standards — Association of Diving Contractors International standards National regulations — Country-specific requirements Client requirements — Contract-specific requirements Responsibility: Operator ensures compliance. Auditors verify compliance. Non-compliance creates legal and operational risk.\nRelated Topics Surface-Supplied Diving Systems Emergency Response Frameworks Safety, Risk \u0026amp; Compliance Human Factors in Diving Operations ","permalink":"/melon-wiki/commercial-diving/dive-planning/","summary":"\u003ch1 id=\"dive-planning--risk-assessment\"\u003eDive Planning \u0026amp; Risk Assessment\u003c/h1\u003e\n\u003cp\u003eDive planning is the process of identifying hazards, assessing risks, and developing operational procedures before a dive commences. This page covers the frameworks and considerations that matter in practice.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eProper dive planning prevents incidents. By identifying hazards, assessing risks, and developing response procedures before the dive, operations can proceed with clear understanding of what can go wrong and how to respond.\u003c/p\u003e\n\u003ch2 id=\"who-this-is-for\"\u003eWho This Is For\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eDive supervisors planning operations\u003c/li\u003e\n\u003cli\u003eCommercial divers reviewing dive plans\u003c/li\u003e\n\u003cli\u003eSafety officers assessing operational risk\u003c/li\u003e\n\u003cli\u003eAuditors reviewing planning procedures\u003c/li\u003e\n\u003cli\u003eContractors developing operational procedures\u003c/li\u003e\n\u003c/ul\u003e\n\u003ch2 id=\"planning-framework\"\u003ePlanning Framework\u003c/h2\u003e\n\u003ch3 id=\"hazard-identification\"\u003eHazard Identification\u003c/h3\u003e\n\u003cp\u003eBefore planning, identify all hazards:\u003c/p\u003e","title":"Dive Planning \u0026 Risk Assessment"},{"content":"Emergency Response Frameworks This page covers operational frameworks for emergency response in commercial diving operations. It documents response structures, responsibility boundaries, and decision-making frameworks—not step-by-step rescue procedures.\nWhy This Exists Emergency response requires clear frameworks: who responds, how decisions are made, and what resources are available. This page provides the operational structure for emergency response, not medical or rescue instruction.\nWho This Is For Dive supervisors planning emergency response Safety officers developing emergency procedures Operations managers ensuring emergency readiness Auditors reviewing emergency procedures Emergency Response Structure Response Roles Emergency response requires defined roles:\nIncident commander — Overall responsibility for emergency response Dive supervisor — Diving-specific response coordination Standby diver — Immediate response capability Medical support — Medical response (if available) Surface support — Surface equipment and personnel Responsibility boundaries: Each role must have clear responsibilities. Ambiguity in roles leads to delayed or incorrect response.\nDecision-Making Authority Emergency response requires clear decision-making:\nWho decides — Who has authority to make emergency decisions? Decision criteria — What criteria guide emergency decisions? Escalation — When are decisions escalated? Documentation — How are emergency decisions documented? Operational reality: Emergency decisions must be made quickly. Decision-making authority must be clear and documented.\nResource Availability Emergency response requires resources:\nPersonnel — Trained personnel available for response Equipment — Emergency equipment ready and functional Communication — Communication systems for coordination Medical — Medical support available (if applicable) What can go wrong: Resources not available, resources not ready, resources not sufficient. Emergency readiness must be verified.\nEmergency Categories Diver Emergency Emergency involving the diver:\nLoss of communication — Diver cannot communicate Equipment failure — Critical equipment failure Medical emergency — Medical issue requiring response Entanglement — Diver entangled and unable to free self Response framework: Standby diver deployment, surface support, medical response (if applicable). Specific procedures depend on circumstances.\nSurface Emergency Emergency involving surface systems:\nGas supply failure — Loss of primary gas supply Communication failure — Loss of communication systems Equipment failure — Critical surface equipment failure Personnel emergency — Medical emergency on surface Response framework: Backup systems activation, alternative procedures, medical response (if applicable).\nEnvironmental Emergency Emergency due to environmental conditions:\nRapid weather change — Weather conditions deteriorate Current increase — Current becomes too strong Visibility loss — Visibility becomes insufficient Marine life — Dangerous marine life encounter Response framework: Mission abort, diver recovery, surface operations secured.\nResponse Procedures Immediate Response Immediate actions upon emergency recognition:\nRecognize emergency — Identify that emergency exists Alert team — Alert response team Initiate response — Begin response procedures Monitor situation — Continuously monitor situation What can go wrong: Emergency not recognized, alert not sent, response delayed, situation not monitored. Immediate response must be practiced and automatic.\nResponse Execution Execution of response procedures:\nFollow procedures — Execute documented procedures Adapt as needed — Adapt procedures to circumstances Coordinate resources — Coordinate available resources Document actions — Document all response actions Operational reality: Procedures provide framework, but response must adapt to circumstances. Documentation is essential for post-incident review.\nPost-Emergency Actions after emergency resolved:\nSecure situation — Ensure situation is secure Assess condition — Assess condition of personnel and equipment Debrief — Conduct debrief of response Document incident — Document incident and response Responsibility: Supervisor ensures proper post-emergency procedures. Documentation is essential for learning and improvement.\nCommunication During Emergency Emergency Communication Communication during emergency:\nAlert communication — How emergency is communicated Status updates — Regular status updates during response Resource coordination — Communication for resource coordination External communication — Communication with external resources (if needed) What can go wrong: Communication breakdown, unclear communication, delayed communication. Emergency communication must be practiced and reliable.\nBackup Communication Backup communication methods:\nAlternative systems — Alternative communication systems Visual signals — Visual signals when communication lost Surface-to-surface — Surface-to-surface coordination External resources — Communication with external resources Operational reality: Backup communication is essential. Single point of failure is unacceptable.\nMedical Considerations Medical Support Medical support availability:\nOn-site medical — Medical personnel on-site (if available) Remote medical — Remote medical consultation (if available) Medical equipment — Medical equipment available Evacuation — Medical evacuation capability (if available) Operational reality: Medical support varies by operation. Operations must plan for available medical support.\nMedical Decision-Making Medical decision-making during emergency:\nWho decides — Who has medical decision-making authority? Decision criteria — What criteria guide medical decisions? Documentation — How are medical decisions documented? Legal sensitivity: Medical decisions have legal implications. Decision-making authority must be clear and documented.\nTraining \u0026amp; Readiness Emergency Training Emergency response training:\nRegular training — Regular emergency response training Scenario training — Training in realistic scenarios Role training — Training for specific roles Refresher training — Regular refresher training What can go wrong: Training not conducted, training not realistic, training not sufficient. Emergency training must be regular and realistic.\nReadiness Verification Verification of emergency readiness:\nEquipment checks — Regular equipment readiness checks Personnel verification — Verification of trained personnel availability Procedure review — Regular review of emergency procedures Drill execution — Regular emergency drills Operational reality: Readiness must be verified, not assumed. Regular verification is essential.\nDocumentation Requirements Emergency response documentation must include:\nEmergency description — What emergency occurred Response actions — What actions were taken Decision-making — How decisions were made Outcome — What was the outcome Lessons learned — What was learned Audit requirement: Emergency response documentation must be suitable for regulatory review and incident investigation.\nRelated Topics Dive Planning \u0026amp; Risk Assessment Safety, Risk \u0026amp; Compliance Human Factors in Diving Operations ","permalink":"/melon-wiki/commercial-diving/emergency-frameworks/","summary":"\u003ch1 id=\"emergency-response-frameworks\"\u003eEmergency Response Frameworks\u003c/h1\u003e\n\u003cp\u003eThis page covers operational frameworks for emergency response in commercial diving operations. It documents response structures, responsibility boundaries, and decision-making frameworks—not step-by-step rescue procedures.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eEmergency response requires clear frameworks: who responds, how decisions are made, and what resources are available. This page provides the operational structure for emergency response, not medical or rescue instruction.\u003c/p\u003e\n\u003ch2 id=\"who-this-is-for\"\u003eWho This Is For\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eDive supervisors planning emergency response\u003c/li\u003e\n\u003cli\u003eSafety officers developing emergency procedures\u003c/li\u003e\n\u003cli\u003eOperations managers ensuring emergency readiness\u003c/li\u003e\n\u003cli\u003eAuditors reviewing emergency procedures\u003c/li\u003e\n\u003c/ul\u003e\n\u003ch2 id=\"emergency-response-structure\"\u003eEmergency Response Structure\u003c/h2\u003e\n\u003ch3 id=\"response-roles\"\u003eResponse Roles\u003c/h3\u003e\n\u003cp\u003eEmergency response requires defined roles:\u003c/p\u003e","title":"Emergency Response Frameworks"},{"content":"Failure Modes \u0026amp; Recovery Subsea robotic systems fail. This page documents common failure modes, how operations degrade when failures occur, and recovery procedures. Understanding failure modes is essential for safe operations and realistic planning.\nWhy This Exists Failures happen offshore. By understanding failure modes, operators can plan for degraded operations, develop recovery procedures, and make informed decisions about when to continue vs. when to abort.\nWho This Is For ROV pilots and supervisors Operations managers planning missions Safety officers assessing operational risk Robotics engineers designing systems Auditors reviewing operational procedures Failure Mode Categories Single Point Failures Failures that immediately disable the system:\nPower loss — Complete loss of vehicle power Tether severance — Complete loss of connection Critical sensor failure — Loss of essential situational awareness Control system failure — Loss of vehicle control Operational impact: Mission abort, emergency recovery required.\nWhat can go wrong: No recovery possible, vehicle lost, mission failure.\nDegraded Mode Failures Failures that reduce capability but allow continued operations:\nThruster failure — Reduced maneuverability Sensor degradation — Reduced situational awareness Manipulator failure — Loss of work capability Communication degradation — Reduced data bandwidth Operational impact: Reduced capability, mission may continue with limitations.\nWhat can go wrong: Degraded operations exceed safe limits, secondary failures occur, mission objectives not achievable.\nCascading Failures Initial failure leads to additional failures:\nTether damage → Power loss → Vehicle loss Thruster failure → Loss of control → Collision → Vehicle damage Sensor failure → Loss of awareness → Navigation error → Entanglement Operational impact: Rapid degradation, mission abort likely.\nWhat can go wrong: Cascading failures are difficult to predict and may progress faster than recovery procedures can execute.\nSpecific Failure Modes Power System Failures Primary power loss:\nCauses: Generator failure, tether damage, power distribution failure Effect: Immediate loss of vehicle power, unresponsive vehicle Recovery: Switch to backup power, or recover via winch if tether intact Prevention: Redundant power systems, backup generators, power monitoring Battery failure (AUV):\nCauses: Battery degradation, over-discharge, thermal issues Effect: Loss of propulsion and systems, vehicle may surface or sink Recovery: Emergency surface procedures, recovery at surface Prevention: Battery monitoring, conservative depth-of-discharge limits What can go wrong: Backup power not available, backup power insufficient, recovery procedures not executed correctly.\nCommunication Failures Tether severance (ROV):\nCauses: Snagging, excessive tension, mechanical damage Effect: Complete loss of communication and power Recovery: Vehicle may have emergency systems (acoustic release, buoyancy), surface recovery Prevention: Tether management, tension monitoring, protective routing Acoustic link loss (AUV):\nCauses: Range exceeded, acoustic interference, equipment failure Effect: Loss of real-time communication, vehicle continues mission or enters failsafe Recovery: Vehicle may surface at pre-programmed waypoint, or continue mission autonomously Prevention: Range management, acoustic link monitoring, failsafe programming What can go wrong: Emergency systems not functional, failsafe procedures not executed, vehicle lost.\nSensor Failures Camera failure:\nCauses: Water ingress, electronics failure, mechanical damage Effect: Loss of primary situational awareness Recovery: Continue with remaining cameras, or abort if no backup Prevention: Redundant cameras, watertight housings, pre-dive testing Sonar failure:\nCauses: Transducer failure, electronics failure, acoustic interference Effect: Loss of long-range awareness, navigation capability reduced Recovery: Continue with cameras and other sensors, or abort if navigation critical Prevention: Redundant sonar systems, pre-dive testing INS failure:\nCauses: Sensor failure, calibration drift, initialization error Effect: Loss of precise navigation, position uncertainty increases Recovery: Continue with dead reckoning, or abort if precision required Prevention: Redundant INS systems, regular calibration, initialization checks What can go wrong: Multiple sensor failures, no backup sensors, operations continue beyond safe limits.\nPropulsion Failures Thruster failure:\nCauses: Mechanical failure, electrical failure, entanglement Effect: Reduced maneuverability, inability to maintain position Recovery: Continue with remaining thrusters, or abort if insufficient control Prevention: Redundant thrusters, pre-dive testing, thruster monitoring Thruster entanglement:\nCauses: Debris, fishing line, umbilical contact Effect: Thruster unable to rotate, reduced or asymmetric thrust Recovery: Attempt to clear entanglement, or abort if unable to clear Prevention: Thruster guards, operational awareness, careful maneuvering What can go wrong: Multiple thruster failures, asymmetric failures cause instability, recovery not possible.\nManipulator Failures Manipulator mechanical failure:\nCauses: Overload, mechanical wear, water ingress Effect: Loss of work capability, manipulator may be stuck or uncontrolled Recovery: Abort work tasks, continue inspection if possible Prevention: Load monitoring, regular maintenance, pre-dive testing Tool failure:\nCauses: Tool-specific failures (cutting tool, sampling tool, etc.) Effect: Specific work task cannot be performed Recovery: Switch to backup tool, or abort specific task Prevention: Redundant tools, tool testing, proper tool selection What can go wrong: No backup tools, tool failure causes vehicle damage, mission objectives not achievable.\nRecovery Procedures Emergency Recovery When immediate recovery is required:\nAbort mission — Cease all work tasks, prepare for recovery Assess situation — Determine recovery method based on failure mode Execute recovery — Winch recovery (ROV), surface procedures (AUV), or alternative method Secure vehicle — Once recovered, secure vehicle and assess damage Document incident — Record failure mode, recovery actions, lessons learned Responsibility: Supervisor directs recovery; pilot executes recovery procedures.\nDegraded Operations When operations can continue with limitations:\nAssess capability — Determine remaining operational capability Revise mission — Adjust mission objectives to match capability Increase monitoring — Enhanced monitoring for additional failures Prepare recovery — Ready recovery procedures in case of further degradation Document status — Record degraded status and operational limitations What can go wrong: Degraded operations exceed safe limits, secondary failures occur, mission objectives not achievable.\nFailure Prevention Design Principles Redundancy — Critical systems should have backups Monitoring — Systems should monitor their own health Failsafes — Systems should fail to safe states Isolation — Failures should not cascade to other systems Operational reality: Redundancy adds cost and complexity. Tradeoffs must be made based on operational requirements and risk tolerance.\nOperational Practices Pre-dive testing — Verify all systems before deployment Regular maintenance — Prevent failures through maintenance Operational limits — Operate within system capabilities Training — Operators must understand failure modes and recovery What can go wrong: Testing incomplete, maintenance deferred, limits exceeded, training insufficient.\nData \u0026amp; Records Failure documentation must include:\nFailure description — What failed, when, under what conditions Root cause — Why it failed (if determinable) Operational impact — How operations were affected Recovery actions — What was done to recover Preventive measures — What will prevent recurrence Audit-worthiness: Failure records must be complete, accurate, and suitable for regulatory review. See Dive Logs \u0026amp; Operational Records for record-keeping requirements.\nRelated Topics ROV Systems Overview AUV Platforms Overview Control Frameworks Safety, Risk \u0026amp; Compliance ","permalink":"/melon-wiki/subsea-robotics/failure-modes/","summary":"\u003ch1 id=\"failure-modes--recovery\"\u003eFailure Modes \u0026amp; Recovery\u003c/h1\u003e\n\u003cp\u003eSubsea robotic systems fail. This page documents common failure modes, how operations degrade when failures occur, and recovery procedures. Understanding failure modes is essential for safe operations and realistic planning.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eFailures happen offshore. By understanding failure modes, operators can plan for degraded operations, develop recovery procedures, and make informed decisions about when to continue vs. when to abort.\u003c/p\u003e\n\u003ch2 id=\"who-this-is-for\"\u003eWho This Is For\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eROV pilots and supervisors\u003c/li\u003e\n\u003cli\u003eOperations managers planning missions\u003c/li\u003e\n\u003cli\u003eSafety officers assessing operational risk\u003c/li\u003e\n\u003cli\u003eRobotics engineers designing systems\u003c/li\u003e\n\u003cli\u003eAuditors reviewing operational procedures\u003c/li\u003e\n\u003c/ul\u003e\n\u003ch2 id=\"failure-mode-categories\"\u003eFailure Mode Categories\u003c/h2\u003e\n\u003ch3 id=\"single-point-failures\"\u003eSingle Point Failures\u003c/h3\u003e\n\u003cp\u003eFailures that immediately disable the system:\u003c/p\u003e","title":"Failure Modes \u0026 Recovery"},{"content":"Gaps in Current Standards Existing standards for subsea operations were developed primarily for human divers and remotely operated vehicles with continuous operator oversight. They do not adequately address autonomous vehicles, multi-vehicle systems, AI-assisted decision-making, or modern data integrity requirements. This page identifies the most significant gaps.\nWhy This Exists Operating in regulatory grey areas carries risk — legal, safety, and reputational. Identifying gaps explicitly allows operators to develop interim mitigations, engage with standards bodies, and make informed decisions about where to apply conservative interpretations.\nWho This Is For Standards body participants and contributors Regulatory compliance teams identifying risks Engineers designing systems that must operate within (or despite) current frameworks Project managers scoping regulatory engagement for novel operations Gap 1: Autonomous Decision-Making What standards say: Most standards require human decision-making for safety-critical actions. \u0026ldquo;The operator shall ensure…\u0026rdquo; assumes a human is making real-time decisions.\nWhat autonomous systems do: AUVs make decisions — about route, speed, sensor operation, and emergency response — without real-time human input.\nImpact: No standards specify how to validate autonomous decision logic, how to allocate liability for autonomous decisions, or how to certify autonomous safety behaviours.\nInterim approach: Treat autonomous systems as tools that extend human capability; define the operating envelope within which the vehicle may act autonomously; require human authorisation for actions outside that envelope.\nGap 2: Multi-Vehicle Coordination What standards say: Regulations define safety zones and operating envelopes for individual vehicles. Interaction between vehicles is addressed only for collision avoidance at the maritime level.\nWhat swarm systems do: Multiple vehicles operate in close proximity, share information, and make coordinated decisions. The safety of any one vehicle depends on the behaviour of others.\nImpact: No standards address minimum separation requirements for cooperative subsea vehicles, coordination protocol requirements, or how to handle loss of one vehicle in a multi-vehicle mission.\nInterim approach: Define mission-specific rules of encounter; require that each vehicle is safe to operate independently (no safety dependency on peer vehicles); document all coordination assumptions in the mission plan.\nGap 3: Software Verification and Validation What standards say: General safety management frameworks require that equipment is fit for purpose. Software is rarely addressed specifically, beyond requiring testing.\nWhat modern systems require: AUVs and autonomous systems depend on complex software stacks. Failure modes in software are not analogous to hardware failures. Software can fail in emergent, unanticipated ways.\nImpact: No standards specify software development lifecycle requirements, testing coverage expectations, or how to handle software updates to deployed systems.\nInterim approach: Apply aerospace or automotive software standards (DO-178C, ISO 26262) by analogy; maintain software version traceability; require controlled update processes for deployed vehicles.\nGap 4: Data Integrity and Provenance What standards say: Operational records must be maintained. Formats and content are sometimes specified for specific industries (diving logs, survey records).\nWhat modern operations produce: Large volumes of sensor data from multiple systems, processed through complex pipelines, stored in distributed systems. The lineage from raw measurement to delivered data product is rarely documented systematically.\nImpact: Data used for safety decisions, regulatory submissions, and legal proceedings may not be demonstrably reliable. Data integrity cannot be audited retrospectively.\nInterim approach: Implement data provenance tracking as described in Data Provenance \u0026amp; Chain-of-Custody ; apply audit log requirements from Audit Logs \u0026amp; Immutability .\nGap 5: Communication Loss Handling What standards say: Emergency procedures require that operations can be halted. The implicit assumption is that communication with the operating system is always available.\nWhat autonomous systems experience: Communication loss is an expected operational condition for AUVs operating at range or depth. Autonomous systems must handle communication loss safely without human intervention.\nImpact: No standards specify what behaviour is required of an autonomous system during communication loss, how long a vehicle may operate without communication before mission abort is required, or how communication loss events must be logged.\nInterim approach: Define explicit loss-of-comms behaviours for each mission type; require that vehicles default to a safe state on communication loss; log all communication loss events with duration and vehicle state.\nGap 6: AI and Machine Learning What standards say: Decision systems must be reliable and verifiable. Traditional engineering standards assume deterministic systems.\nWhat ML-based systems do: Learn from data; may behave differently on data outside their training distribution; cannot always explain decisions.\nImpact: No standards address how to validate ML models for safety-critical applications, what training data requirements apply, how to handle model drift, or how to audit ML-based decisions.\nInterim approach: Treat ML as advisory only; require human authorisation for safety-critical actions recommended by ML; maintain training data and model version records; monitor for performance degradation.\nRelated Topics Why Auditability Matters Autonomy Challenges \u0026amp; Legacy Assumptions Open Problems in Subsea Operations Regulatory Landscape Overview ","permalink":"/melon-wiki/open-standards/gaps/","summary":"\u003ch1 id=\"gaps-in-current-standards\"\u003eGaps in Current Standards\u003c/h1\u003e\n\u003cp\u003eExisting standards for subsea operations were developed primarily for human divers and remotely operated vehicles with continuous operator oversight. They do not adequately address autonomous vehicles, multi-vehicle systems, AI-assisted decision-making, or modern data integrity requirements. This page identifies the most significant gaps.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eOperating in regulatory grey areas carries risk — legal, safety, and reputational. Identifying gaps explicitly allows operators to develop interim mitigations, engage with standards bodies, and make informed decisions about where to apply conservative interpretations.\u003c/p\u003e","title":"Gaps in Current Standards"},{"content":"Geospatial Confidence \u0026amp; Uncertainty Subsea geospatial data — position fixes, survey tracks, sonar maps, pipeline routes — is used for safety-critical decisions. Position errors of a few metres can place an ROV on the wrong side of a pipeline or mis-identify the location of a discovered anomaly. Understanding and communicating positional uncertainty is essential for anyone using or producing subsea geospatial data.\nWhy This Exists Subsea positioning systems do not have the luxury of GPS, which loses signal underwater. Acoustic positioning systems, inertial navigation units, and Doppler velocity loggers all accumulate error over time and distance. Knowing how much to trust a position — and under what conditions — is as important as knowing the position itself.\nWho This Is For Survey engineers designing positioning systems ROV pilots and AUV operators interpreting positional data Data managers publishing survey products Project engineers using subsea geospatial data for engineering decisions Coordinate Reference Systems Why CRS Matters The same physical point has different numerical coordinates depending on the coordinate reference system (CRS) used. Mixing CRS without transformation causes positional errors that can be tens to hundreds of metres.\nRequired practice: All geospatial data must have an explicitly declared CRS. Datum and projection must be stated, not assumed.\nCommon CRS for Subsea Operations WGS84 — Global datum used by GPS; commonly used for vessel positions ETRS89 — European reference frame; stable relative to the European plate Local projections — UTM zones or project-specific projections for survey products Vertical datums — Depth below mean sea level, chart datum, or ellipsoid height must be stated Datum Shifts Transforming between datums introduces errors. The magnitude of the shift between WGS84 and older national datums can exceed 100m. Any transformation must use appropriate transformation parameters and the resulting uncertainty must be added to the positional uncertainty budget.\nSubsea Positioning Technologies Ultra-Short Baseline (USBL) USBL measures the range and bearing from a surface transducer to an underwater transponder:\nAccuracy — Typically 0.5–1% of slant range; degrades with depth and range Errors — Vessel motion, transducer alignment, sound speed profile Mitigation — Gyro-stabilised transducers, accurate sound speed profiling, USBL calibration transponders Long Baseline (LBL) LBL uses an array of seabed transponders to provide positioning independent of vessel motion:\nAccuracy — Typically 0.1–1m RMS in well-surveyed arrays Errors — Transponder position uncertainty, sound speed errors, acoustic multipath Deployment requirement — Transponder array must be surveyed before LBL can be used Inertial Navigation Systems (INS) INS integrates accelerometer and gyroscope data to propagate a position forward from a known starting point:\nAccuracy — Excellent over short periods; error accumulates over time (dead reckoning drift) Aiding — DVL (Doppler velocity log) and periodic USBL/LBL fixes constrain INS drift Reset — Errors must be reset by tying to a known position Doppler Velocity Log (DVL) DVL measures velocity over the seabed using acoustic Doppler:\nAccuracy — Velocity accuracy ~0.1–0.5% of speed; position error accumulates Bottom tracking required — DVL loses bottom-track in steep terrain or beyond range Integration — DVL is essential for INS aiding in subsea operations Uncertainty Quantification Sources of Positional Uncertainty Every position estimate carries contributions from multiple sources:\nSensor measurement uncertainty — Acoustic range/bearing measurement errors Sound speed uncertainty — Incorrect sound speed introduces systematic ranging errors Vessel position uncertainty — GNSS error propagates to seabed positions Time latency — Position timestamps may not align with observation timestamps Processing uncertainty — Filtering, smoothing, and interpolation introduce additional uncertainty Total Propagated Uncertainty (TPU) TPU combines all uncertainty sources into a single position uncertainty estimate, typically expressed as a 2D ellipse at a specified confidence level (e.g., 95%). Modern survey processing software calculates TPU automatically when given correct input uncertainties.\nRequirement: Survey products must include TPU fields or uncertainty layers. Users must not assume position accuracy without checking TPU.\nReporting Position Quality Minimum Requirements for Published Geospatial Data All published geospatial data must include:\nCoordinate reference system (EPSG code or equivalent) Horizontal positional uncertainty (at stated confidence level) Vertical positional uncertainty Positioning system and method used Date and time of position observation (UTC) Quality Flags Position fixes should carry quality flags indicating:\nSource system (USBL, LBL, INS, DVL-only) Data quality at time of observation (signal quality, vessel motion) Whether the position is measured or interpolated Related Topics Data Provenance \u0026amp; Chain-of-Custody Sensor Calibration Traceability Timestamp Integrity Raw vs Derived Data ","permalink":"/melon-wiki/ocean-data/geospatial/","summary":"\u003ch1 id=\"geospatial-confidence--uncertainty\"\u003eGeospatial Confidence \u0026amp; Uncertainty\u003c/h1\u003e\n\u003cp\u003eSubsea geospatial data — position fixes, survey tracks, sonar maps, pipeline routes — is used for safety-critical decisions. Position errors of a few metres can place an ROV on the wrong side of a pipeline or mis-identify the location of a discovered anomaly. Understanding and communicating positional uncertainty is essential for anyone using or producing subsea geospatial data.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eSubsea positioning systems do not have the luxury of GPS, which loses signal underwater. Acoustic positioning systems, inertial navigation units, and Doppler velocity loggers all accumulate error over time and distance. Knowing how much to trust a position — and under what conditions — is as important as knowing the position itself.\u003c/p\u003e","title":"Geospatial Confidence \u0026 Uncertainty"},{"content":"Graceful Degradation Graceful degradation means that when components fail, the system continues to operate safely at reduced capability rather than failing completely or unsafely. For subsea systems — where recovery is expensive and immediate intervention is impossible — graceful degradation is not optional; it is a fundamental design requirement.\nWhy This Exists Subsea systems face harsh environments and operate far from support. Component failures are inevitable. The question is not whether failures will occur but whether the system degrades gracefully when they do. Ungraceful degradation — catastrophic failure, unsafe behaviour, or silent data corruption — is the alternative.\nWho This Is For Engineers designing subsea vehicle and system architectures Safety engineers assessing system failure modes Operations managers planning for contingency scenarios Mission planners setting abort criteria What Graceful Degradation Means A system degrades gracefully when:\nFailures are detected — The system knows a component has failed The failure mode is safe — The system does not do anything dangerous when the component fails Capability is reduced, not lost — The system continues operating at reduced performance Operators are informed — The failure and its impact are communicated Recovery is possible — The system can be recovered without total mission abort The opposite of graceful degradation is brittle failure: the system works perfectly until a single component fails, at which point it fails entirely or dangerously.\nDegradation Hierarchy Design a degradation hierarchy for each critical capability:\nNavigation Example Mode Available Systems Position Accuracy Full INS + DVL + USBL Decimetre DVL lost INS + USBL (periodic) 1–5m USBL lost INS + DVL Grows over time (drift) DVL + USBL lost INS only Degrades rapidly (minutes) INS degraded Dead reckoning from last fix Poor, time-limited All lost Abort: surface for GPS fix — Each step down reduces capability but maintains safe operation within defined limits.\nPropulsion Example Mode Available Thrusters Capability Full All thrusters Full maneuverability One thruster failed Remaining thrusters Reduced, may have asymmetry Two thrusters failed Remaining thrusters Significantly reduced; may abort Critical thrusters failed — Abort: surface Design Principles for Graceful Degradation Fault Detection and Isolation (FDI) The system cannot degrade gracefully if it cannot detect its own failures:\nBuilt-in test — Components self-test on startup and continuously during operation Redundant sensors — Cross-checking between sensors reveals failures Plausibility checks — System checks whether sensor readings are consistent with expectations Watchdog timers — Detect processor hangs and communication timeouts A failure that goes undetected is more dangerous than a detected failure.\nModular Architecture Systems with modular, loosely coupled components fail more gracefully:\nA failed sensor does not crash the entire navigation system A failed communication module does not prevent thruster control Software failures in one module are contained and do not propagate Functional Priority Not all functions are equally important. Assign priorities:\nSafety functions (obstacle avoidance, emergency ascent) — Must work under all foreseeable conditions Mission-critical functions (navigation, primary sensors) — Mission continues if these work; abort if they fail Mission-enhancing functions (secondary sensors, optimisation) — Degrade gracefully without mission abort When resources (power, processing) are constrained by a failure, lower-priority functions are shed first.\nConservative Defaults When a sensor or subsystem fails, default to the conservative interpretation:\nUnknown obstacle position → assume obstacle is present Unknown battery level → assume low battery Unknown communication state → assume communication lost This is the \u0026ldquo;fail-safe\u0026rdquo; principle applied to uncertain state.\nCommunication Degradation Acoustic Modem Partial Failure Acoustic modems have multiple failure modes:\nComplete loss — No communication possible; trigger loss-of-comms procedure Reduced range — Communication works at short range only; adapt mission High error rate — Retransmission overhead reduces effective bandwidth; reduce communication rate Prioritised Message Queuing When bandwidth is reduced, prioritise critical messages:\nSafety-critical (abort, position, emergency) Mission-critical (navigation aiding, task updates) Telemetry (status, sensor data) Housekeeping (logging, diagnostics) Drop housekeeping and telemetry before dropping mission-critical messages.\nMonitoring Degradation State System Health Dashboard Operators must know the current degradation state in real time:\nWhich components are operating nominally Which are degraded (with details of the degradation) Which have failed Current capability given the degradation state Degradation Logging All degradation events must be logged with:\nTimestamp Component affected Nature of the failure/degradation System response (fallback mode activated) This supports post-mission incident analysis and predictive maintenance.\nRelated Topics Communication Systems Loss-of-Comms Behavior Failure Modes \u0026amp; Recovery Control Frameworks Multi-Vehicle Coordination ","permalink":"/melon-wiki/swarm-systems/degradation/","summary":"\u003ch1 id=\"graceful-degradation\"\u003eGraceful Degradation\u003c/h1\u003e\n\u003cp\u003eGraceful degradation means that when components fail, the system continues to operate safely at reduced capability rather than failing completely or unsafely. For subsea systems — where recovery is expensive and immediate intervention is impossible — graceful degradation is not optional; it is a fundamental design requirement.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eSubsea systems face harsh environments and operate far from support. Component failures are inevitable. The question is not whether failures will occur but whether the system degrades gracefully when they do. Ungraceful degradation — catastrophic failure, unsafe behaviour, or silent data corruption — is the alternative.\u003c/p\u003e","title":"Graceful Degradation"},{"content":"Hazard Identification (HAZID/HAZOP) Hazard identification is the first and most critical step in risk management. You cannot control a hazard you have not identified. HAZID (Hazard Identification) and HAZOP (Hazard and Operability Study) are structured, team-based techniques for systematically identifying hazards and operability problems before they result in incidents.\nWhy This Exists Unidentified hazards cannot be mitigated. HAZID and HAZOP provide structured methodologies that use team expertise and guidewords to surface hazards that might be missed by individuals working alone. The structured record produced by a HAZID/HAZOP study provides documented evidence of the risk assessment process.\nWho This Is For Safety engineers facilitating or contributing to HAZID/HAZOP studies Operations managers commissioning and reviewing hazard studies Project engineers providing technical input to hazard identification Auditors reviewing the completeness of risk assessment processes HAZID: Hazard Identification Purpose HAZID is a high-level, broad-scope study performed early in a project to identify all significant hazards associated with an operation, facility, or system. HAZID produces a register of hazards that is then carried forward into more detailed risk assessment.\nProcess Assemble the team — Multi-disciplinary team with relevant expertise (operations, engineering, safety, environment) Define the scope — What operation, system, or facility is being studied? Apply guidewords — Systematically work through hazard categories (e.g., fire, explosion, toxic release, struck by, loss of buoyancy) Identify causes and consequences — For each hazard, what could cause it and what are the consequences? Assess initial risk — Estimate likelihood and severity without controls Identify existing controls — What safeguards are already in place? Assess residual risk — Risk with existing controls applied Identify actions — What additional controls or studies are required? Record findings — Capture all findings in the hazard register HAZID Guidewords for Subsea/Diving Operations Personnel hazards:\nDrowning / entrapment Struck by (dropped objects, vessel, equipment) Caught in (entanglement, rotating machinery) Decompression sickness Gas toxicity Thermal stress (hypothermia, heat stress) Equipment hazards:\nLoss of pressure integrity (vessel, chamber, umbilical) Loss of lifting equipment integrity Fire / explosion Electrical hazard Environmental hazards:\nAdverse weather / sea state Strong currents Poor visibility Marine life (stinging, biting, entanglement) HAZOP: Hazard and Operability Study Purpose HAZOP is a more detailed, systematic technique applied to specific processes, procedures, or systems. It uses structured guidewords applied to process parameters to identify deviations from design intent and their potential consequences.\nProcess HAZOP applies guidewords to process parameters at defined nodes (specific points in the process or system):\nGuideword Meaning No / None Complete negation of design intent More Quantitative increase Less Quantitative decrease As well as Qualitative increase (additional component) Part of Qualitative decrease Reverse Logical opposite Other than Complete substitution Application to Diving Operations For a surface-supplied diving operation, a HAZOP might examine:\nGas supply node: No flow (supply failure), more flow (regulator failure), wrong gas (incorrect mixture connected) Umbilical: Loss of integrity, entanglement, excess tension Communication: No communication, degraded communication, communication to wrong diver Depth/pressure: Greater than planned depth, less than planned depth, rapid pressure change Documentation Requirements Hazard Register The output of a HAZID/HAZOP study is a hazard register containing:\nHazard number and description Causes Potential consequences (severity, affected parties) Existing controls Risk rating (with and without controls) Additional actions required Action owner and target date Close-out status Traceability All hazard identification studies must be traceable:\nDocument who participated, when, and what scope was covered Studies must be reviewed and updated when operations change significantly Actions must be tracked to close-out with evidence Integration with Risk Management HAZID/HAZOP outputs feed into:\nOperational Risk Models — Hazards are inputs to formal risk models ALARP Principles — Controls identified must be assessed for ALARP Dive Planning \u0026amp; Risk Assessment — Operation-specific hazard assessment Related Topics Operational Risk Models ALARP Principles Responsibility Boundaries Dive Planning \u0026amp; Risk Assessment Emergency Response Frameworks ","permalink":"/melon-wiki/safety-compliance/hazard-identification/","summary":"\u003ch1 id=\"hazard-identification-hazidhazop\"\u003eHazard Identification (HAZID/HAZOP)\u003c/h1\u003e\n\u003cp\u003eHazard identification is the first and most critical step in risk management. You cannot control a hazard you have not identified. HAZID (Hazard Identification) and HAZOP (Hazard and Operability Study) are structured, team-based techniques for systematically identifying hazards and operability problems before they result in incidents.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eUnidentified hazards cannot be mitigated. HAZID and HAZOP provide structured methodologies that use team expertise and guidewords to surface hazards that might be missed by individuals working alone. The structured record produced by a HAZID/HAZOP study provides documented evidence of the risk assessment process.\u003c/p\u003e","title":"Hazard Identification (HAZID/HAZOP)"},{"content":"Human Factors in Diving Operations Commercial diving incidents are rarely caused by equipment alone. Human factors — fatigue, communication failures, task saturation, and organisational pressures — are primary or contributing causes in the majority of diving accidents. This page covers how human performance affects dive safety and what operations can do to mitigate human error.\nWhy This Exists Understanding human factors is essential for designing safe diving operations. Technical knowledge of equipment and procedures is necessary but not sufficient. Supervisors, divers, and managers must understand how human performance degrades under realistic operational conditions.\nWho This Is For Diving supervisors responsible for crew performance Safety officers conducting incident investigations Operations managers designing work schedules Trainers developing dive team competency Fatigue Sources of Fatigue in Diving Thermal stress — Cold water accelerates fatigue; hot water suits add thermal load Physical exertion — Fighting currents, heavy manual tasks, awkward working positions Long duty cycles — Extended standby and preparation time before in-water work Night operations — Disrupted sleep cycles in continuous operations Travel and time zones — Mobilisation to remote locations Fatigue and Performance Fatigued divers exhibit:\nReduced concentration and increased error rates Slower decision-making Increased risk-taking Reduced emergency response capability Operational rule: Fatigue cannot be reliably self-assessed. Supervisors must enforce rest requirements regardless of diver willingness to continue.\nWork-Rest Requirements USN and IMCA guidance requires minimum rest periods between dives and overnight. Dive supervisors must track cumulative work hours and enforce limits.\nCommunication In-Water Communication Failures Voice communications in diving are affected by:\nHelium speech distortion — Heliox mixtures make speech difficult to understand Mask seal and regulator noise — Background noise masks communications Umbilical routing — Long umbilicals introduce electrical noise Task saturation — Divers may not acknowledge comms while focused on tasks Requirement: All in-water communications must be logged. The supervisor must confirm diver acknowledgement before issuing safety-critical instructions.\nSurface Team Communication Between the diving supervisor, crane operator, vessel master, and client:\nEstablish clear authority and communication protocols before diving commences Use standard terminology — avoid ambiguous terms Confirm safety-critical instructions with read-back Task Saturation Divers working on complex tasks can become task-saturated, failing to monitor gas supplies, track bottom time, or respond to surface communications.\nMitigation:\nSupervisor tracks all time and gas metrics from the surface Set explicit reminders for gas checks and ascent times Plan tasks to match cognitive load to conditions Situational Awareness Situational awareness (SA) is the perception and understanding of the current operational state. Loss of SA is a precursor to most serious incidents.\nFactors that degrade SA:\nInformation overload during emergencies Complacency during routine operations Team communication breakdowns Unexpected changes to the dive environment Organisational Pressures Production pressures — vessel day rates, weather windows, client timelines — create incentives to continue diving when conditions warrant a pause or abort.\nSupervisory authority: The diving supervisor has the authority and responsibility to halt diving at any time for safety reasons. This authority must be explicitly protected by management and cannot be overridden by client or commercial pressure.\nCrew Resource Management (CRM) CRM principles from aviation apply directly to diving operations:\nBriefings — Pre-dive briefing ensures shared understanding of the plan Challenge and response — Any team member can raise a safety concern Closed-loop communication — All instructions are confirmed with read-back Post-dive debrief — Identify what went well and what could be improved Incident Causation Models Reason\u0026rsquo;s Swiss Cheese Model Accidents occur when holes in multiple defensive layers align:\nEquipment failures, procedure violations, supervisory lapses, and organisational failures combine to allow an accident Bow-Tie Analysis Links hazard → top event → consequences, with barriers on each side. Human factors affect both threat barriers (preventing the top event) and recovery barriers (limiting consequences).\nRelated Topics Dive Planning \u0026amp; Risk Assessment Emergency Response Frameworks ALARP Principles Hazard Identification (HAZID/HAZOP) Operational Risk Models ","permalink":"/melon-wiki/commercial-diving/human-factors/","summary":"\u003ch1 id=\"human-factors-in-diving-operations\"\u003eHuman Factors in Diving Operations\u003c/h1\u003e\n\u003cp\u003eCommercial diving incidents are rarely caused by equipment alone. Human factors — fatigue, communication failures, task saturation, and organisational pressures — are primary or contributing causes in the majority of diving accidents. This page covers how human performance affects dive safety and what operations can do to mitigate human error.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eUnderstanding human factors is essential for designing safe diving operations. Technical knowledge of equipment and procedures is necessary but not sufficient. Supervisors, divers, and managers must understand how human performance degrades under realistic operational conditions.\u003c/p\u003e","title":"Human Factors in Diving Operations"},{"content":"Latency \u0026amp; Bandwidth Tradeoffs Subsea communication is constrained by physics: acoustic waves travel at ~1500 m/s through water, and the available bandwidth for acoustic modems is severely limited compared to terrestrial or satellite links. These constraints fundamentally shape how subsea systems can be designed and operated. Understanding them is essential for designing coordination systems that work within physical limits.\nWhy This Exists Systems designed without understanding communication constraints fail in the field. A coordination algorithm that requires 10 round-trip communications per second will not function on an acoustic link that takes 2 seconds for each exchange. Understanding latency and bandwidth drives realistic system design.\nWho This Is For Engineers designing subsea communication systems Architects designing multi-vehicle coordination protocols Operations managers setting realistic expectations for remote monitoring Mission planners designing communication schedules Acoustic Communication Fundamentals Propagation Speed Sound travels at approximately 1500 m/s in seawater (varying with temperature, salinity, and pressure). At 1500m range:\nOne-way latency: ~1 second Round-trip latency: ~2 seconds (minimum, without processing delays) At longer ranges:\n3000m → 2s one-way, 4s round-trip 10km → 6.7s one-way, 13.3s round-trip Implication: Real-time control at range is impossible. Any control loop that relies on acoustic feedback will have response delays measured in seconds to tens of seconds.\nBandwidth Acoustic modems in typical subsea configurations provide:\nShort range (\u0026lt;1km): Up to 50 kbps Medium range (1–5km): 1–10 kbps Long range (\u0026gt;5km): \u0026lt;1 kbps Compare to terrestrial WiFi (\u0026gt;100 Mbps) or satellite (1–100 Mbps): acoustic bandwidth is 3–8 orders of magnitude lower.\nImplication: Video streaming, large file transfers, and any high-volume data exchange are not possible acoustically at operational ranges. Only compact, compressed messages are feasible.\nBandwidth-Latency Product The bandwidth-delay product (BDP) determines the amount of data that can be \u0026ldquo;in flight\u0026rdquo; at any time. With high latency and low bandwidth, windowing protocols become critical, and protocol overhead can dominate useful payload.\nExample: At 1 kbps bandwidth and 4s round-trip time, the BDP is 4000 bits (500 bytes). A 50-byte message header represents 10% protocol overhead.\nEffects on System Design Control Loop Design Control systems must be designed for the available round-trip time:\nClosed-loop control requiring fast feedback cannot run over acoustic links at range Supervisory control with slow feedback (seconds to minutes) is feasible Pre-programmed missions with no feedback loop are the most robust approach For a vehicle at 1km range (2s RTT), any control loop with a bandwidth above 0.25 Hz is limited by communication, not vehicle dynamics.\nState Synchronisation Multi-vehicle systems that share state (position, task assignments, sensor data) must manage state synchronisation with high-latency, low-bandwidth links:\nEvent-driven updates — Send updates only when state changes significantly Dead-reckoning — Interpolate state between updates using physical models Eventual consistency — Accept that different vehicles have temporarily inconsistent views of shared state Conflict resolution — Define clear rules for resolving conflicting state updates when they arrive Message Prioritisation Given limited bandwidth, messages must be prioritised:\nSafety-critical: Abort commands, emergency position reports Navigation-critical: Position fixes, collision avoidance Mission-critical: Task updates, sensor alerts Monitoring: Status, telemetry Housekeeping: Logs, diagnostics Lower-priority messages should be queued and delayed (or dropped) when the channel is congested.\nBandwidth Budgeting Calculating a Communication Budget For each vehicle in a multi-vehicle system:\nIdentify all required messages — What must be exchanged for the mission to succeed? Estimate message sizes — How many bytes per message? Estimate message rates — How often must each message be sent? Calculate total bandwidth — Sum of (size × rate) for all messages Compare to available bandwidth — Must be less than available bandwidth with margin for retransmission Retransmission overhead: Acoustic links have high packet loss rates (10–30% in challenging conditions). ARQ (automatic repeat request) protocols can multiply effective bandwidth requirement by 1.3–2×.\nPer-Vehicle Allocation in Multi-Vehicle Systems Total acoustic bandwidth must be shared among all vehicles. With N vehicles:\nAverage per-vehicle bandwidth ≈ total bandwidth / N Critical vehicles (lead, emergency) may be allocated higher priority Optical Communication Tradeoffs Optical modems provide high bandwidth (100 Mbps+) but only at very short ranges (\u0026lt;100m in clear water, much less in turbid water):\nSuitable for: Docking stations, short-range vehicle-to-vehicle, AUV-to-lander Not suitable for: Long-range coordination, operational-scale multi-vehicle systems The latency of optical links is negligible — light travels 2×10⁸ m/s in water, giving \u0026lt;1 μs RTT at 100m range.\nSatellite and Radio Links (Surface) For vehicles that can surface:\nIridium satellite: Global coverage; ~2.4 kbps data (SBD messages) to 1 Mbps (Iridium NEXT terminals); latency ~1s WiFi/4G/5G: When in range; latency \u0026lt;100ms; bandwidth 1–1000 Mbps VHF/UHF radio: Short range (line-of-sight); low bandwidth; negligible latency Surfacing to communicate (scheduled or triggered) is a valid design pattern for AUVs when acoustic bandwidth is insufficient.\nRelated Topics Communication Systems Multi-Vehicle Coordination Loss-of-Comms Behavior Graceful Degradation Control Frameworks ","permalink":"/melon-wiki/swarm-systems/latency-bandwidth/","summary":"\u003ch1 id=\"latency--bandwidth-tradeoffs\"\u003eLatency \u0026amp; Bandwidth Tradeoffs\u003c/h1\u003e\n\u003cp\u003eSubsea communication is constrained by physics: acoustic waves travel at ~1500 m/s through water, and the available bandwidth for acoustic modems is severely limited compared to terrestrial or satellite links. These constraints fundamentally shape how subsea systems can be designed and operated. Understanding them is essential for designing coordination systems that work within physical limits.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eSystems designed without understanding communication constraints fail in the field. A coordination algorithm that requires 10 round-trip communications per second will not function on an acoustic link that takes 2 seconds for each exchange. Understanding latency and bandwidth drives realistic system design.\u003c/p\u003e","title":"Latency \u0026 Bandwidth Tradeoffs"},{"content":"Loss-of-Comms Behavior Loss of communication between a subsea vehicle and its operators is not an edge case — it is an expected operational condition. Acoustic communication links fail due to multipath, range, biological noise, and interference. Every autonomous vehicle must have a defined, tested, and reliable loss-of-comms (LOC) behavior that keeps the vehicle and its environment safe without operator input.\nWhy This Exists A vehicle without a defined LOC behavior is unpredictable. Operators cannot rely on the vehicle to behave safely if they lose contact. Regulators increasingly require explicit LOC behavior definitions for autonomous vehicles. Without it, vehicles should not be deployed.\nWho This Is For Engineers designing AUV and autonomous system control software Mission planners defining operational parameters and abort criteria Safety engineers reviewing autonomous system safety cases Operations managers approving autonomous vehicle deployments When Loss of Comms Occurs Detection The vehicle must detect communication loss reliably and promptly:\nHeartbeat monitoring — Surface system sends periodic heartbeat messages; vehicle enters LOC state if no heartbeat received within the timeout window Acoustic ping monitoring — Vehicle listens for scheduled acoustic pings; absence triggers LOC state Timeout threshold — The timeout should be long enough to avoid false triggers from temporary acoustic shadowing, but short enough to respond promptly Typical timeouts: 60–300 seconds for long-range AUVs; shorter for operations near infrastructure.\nDistinguishing Scenarios Communication loss can occur because:\nVehicle is in acoustic shadow — Terrain blocks the acoustic path; may clear as vehicle moves Modem failure — Hardware or software failure in acoustic modem Surface system failure — Surface operator station or topside modem has failed Vehicle is in an unexpected location — Outside planned communication range Environmental interference — Shipping noise, biological noise, multipath The LOC behavior cannot know which scenario it is in. It must be safe in all of them.\nLOC Behavior Design Core Principles Safety first — LOC behavior must prioritise avoiding harm over mission completion Conservative — In uncertainty, choose the more conservative action Deterministic — LOC behavior must be predictable and testable Independent — LOC behavior must not depend on communication to execute Tested — LOC behavior must be explicitly tested before operational deployment Common LOC Behavior Patterns Immediate Surface Vehicle aborts current task and ascends to the surface immediately:\nAdvantages: Simple; brings vehicle to where it can be found and recovered; enables satellite/RF communication Disadvantages: May interrupt a time-critical task; may surface in an unsafe location (vessel traffic, installation) Suitable for: Operations where surfacing is always safe; short-mission AUVs with low endurance Hold Position (Hover) Vehicle stops and holds position for a defined timeout:\nAdvantages: Gives temporary communication loss time to clear; does not interrupt mission Disadvantages: Expends battery holding station; requires hovering capability; if communication does not clear, must transition to another LOC behavior Suitable for: Hover-capable vehicles; short expected LOC durations Continue Mission with Scheduled Surface Vehicle continues executing its pre-planned mission and surfaces at a scheduled time or position to re-establish communication:\nAdvantages: Mission continues; communication recovery point is planned and known Disadvantages: Vehicle continues without oversight for an extended period; mission must be safe to execute autonomously Suitable for: Survey AUVs with collision-free pre-planned lanes; well-characterised environments Abort and Return to Datum Vehicle aborts the current mission and navigates to a pre-defined datum point (surface or subsurface):\nAdvantages: Vehicle returns to a known, planned location; recovery is straightforward Disadvantages: Mission is lost; return navigation requires reliable positioning Suitable for: When mission continuation without communication is unacceptably risky LOC Behavior State Machine LOC behavior should be implemented as an explicit state machine:\n[ C O M M S O K ] → → [ [ C L O O M C M S B E L H O A S V T I O ( R t A \u0026lt; C T w I a V r E n ] _ t → → i m [ [ e C M o O I u M S t M S ) S I ] O R N → E S C [ T O C O M O R P M E L M D E S ] T E L → ] O S [ → T C O [ ( M S t M U S R \u0026lt; F O A a K C b ] E o / r R t E _ C t O i V m E e R o Y u ] t ) ] Each state has defined entry conditions, actions, and exit conditions.\nHazard-Specific LOC Behaviors LOC Near Infrastructure Near offshore installations, pipelines, or other vehicles:\nImmediate surface or hold position — do not continue moving near infrastructure without oversight Maximum safe hold time may be short (battery, current drift) LOC During Intervention Tasks If the vehicle is performing a contact task (holding against a structure, operating a tool):\nImmediately release contact and back away Then apply standard LOC behavior Never hold contact position without operator oversight LOC for Multi-Vehicle Systems In a multi-vehicle fleet where each vehicle can communicate with peers:\nPeer vehicles can relay abort commands from the surface Peer awareness of LOC state allows coordinated response Each vehicle must still have an independent LOC behavior if peer communication also fails Operator Interface for LOC Pre-Mission LOC Configuration Operators must explicitly configure and confirm LOC behavior before each mission:\nLOC behavior type Communication timeout Abort datum (if applicable) Maximum hold time before surfacing LOC Event Notification When LOC is detected by the surface system:\nImmediate alert to operators Clear indication of last known vehicle position and state LOC timer displayed so operators know how long until LOC behavior activates Recovery guidance based on vehicle LOC configuration Post-LOC Debriefing After any LOC event (whether the vehicle recovered communication or executed LOC behavior):\nLog review: what was the vehicle doing when communication was lost? Root cause investigation: why did communication fail? LOC behavior review: did the vehicle execute LOC behavior correctly? Procedure update if LOC was caused by a systematic issue Testing LOC Behavior LOC behavior that has never been tested is not LOC behavior — it is untested software that may or may not work when needed.\nRequired testing:\nBench test: simulate communication loss and verify state machine transitions Pool test: verify LOC behavior in a controlled environment Field test (shallow): verify LOC behavior in realistic acoustic conditions before deep deployment Test each scenario: Complete communication loss, gradual degradation, intermittent communication, communication loss during intervention tasks.\nRelated Topics Communication Systems Multi-Vehicle Coordination Latency \u0026amp; Bandwidth Tradeoffs Graceful Degradation Failure Modes \u0026amp; Recovery Autonomy Challenges \u0026amp; Legacy Assumptions ","permalink":"/melon-wiki/swarm-systems/loss-of-comms/","summary":"\u003ch1 id=\"loss-of-comms-behavior\"\u003eLoss-of-Comms Behavior\u003c/h1\u003e\n\u003cp\u003eLoss of communication between a subsea vehicle and its operators is not an edge case — it is an expected operational condition. Acoustic communication links fail due to multipath, range, biological noise, and interference. Every autonomous vehicle must have a defined, tested, and reliable loss-of-comms (LOC) behavior that keeps the vehicle and its environment safe without operator input.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eA vehicle without a defined LOC behavior is unpredictable. Operators cannot rely on the vehicle to behave safely if they lose contact. Regulators increasingly require explicit LOC behavior definitions for autonomous vehicles. Without it, vehicles should not be deployed.\u003c/p\u003e","title":"Loss-of-Comms Behavior"},{"content":"Multi-Vehicle Coordination Multi-vehicle systems achieve objectives that single vehicles cannot — larger area coverage, redundant sensing, cooperative tasks requiring multiple simultaneous positions. But coordination introduces new failure modes and operational complexity. This page covers coordination strategies and the safety considerations specific to multi-vehicle subsea operations.\nWhy This Exists Multi-vehicle operations are becoming practical as AUVs become more capable and affordable. But deploying multiple vehicles without a coherent coordination strategy creates collision risk, duplicated effort, and unpredictable system behaviour. Understanding coordination approaches helps operators design safe and effective multi-vehicle missions.\nWho This Is For Engineers designing multi-vehicle systems Mission planners coordinating multiple subsea vehicles Safety officers assessing multi-vehicle operational risk Operations managers evaluating multi-vehicle systems Why Multi-Vehicle Operations Expanded Area Coverage A fleet of N vehicles can survey N times the area in a given time window, enabling:\nCompletion of large surveys within narrow weather windows Real-time monitoring of large geographic areas Redundant coverage for quality assurance Cooperative Sensing Multiple vehicles can observe the same target simultaneously from different angles or with complementary sensors:\nAcoustic ranging between vehicles (cooperative navigation) Simultaneous multi-aspect sonar imaging Triangulated position fixing using multiple observers Redundancy If one vehicle in a fleet fails, others can continue:\nMission completion despite individual vehicle failures Critical sensor or sampling can continue at reduced pace Recovery vehicle capability without ending the mission Coordination Architectures Centralised Coordination A single coordinator (surface system or lead vehicle) maintains the mission plan for all vehicles and issues commands:\nAdvantages: Globally optimal planning; single point for state awareness Disadvantages: Single point of failure; requires communication with all vehicles; high communication load Suitable for: Small fleets with reliable communication links Decentralised Coordination Each vehicle makes its own decisions based on local information and limited peer communication:\nAdvantages: Robust to communication loss; scales to large fleets Disadvantages: Sub-optimal globally; potential for conflicting decisions; harder to verify Suitable for: Large fleets; operations with unreliable communication Market-Based / Task Allocation Vehicles bid on tasks based on their position, remaining energy, and capability:\nTasks are allocated to the vehicle best placed to execute them Reallocation occurs when a vehicle fails or conditions change Advantages: Adaptive; handles vehicle failures gracefully Disadvantages: Requires communication for bidding; may not find optimal allocation Pre-Planned Deconflicted Missions In simple cases, each vehicle is assigned a fixed, independent sub-mission that does not require inter-vehicle coordination during execution:\nSeparate survey lanes with sufficient spacing Separate time windows for shared areas Advantages: No communication required during mission; simple to plan and verify Disadvantages: Not adaptive to vehicle failures; no cooperative sensing capability Collision Avoidance Deconfliction by Design The safest approach is to plan missions that physically separate vehicles at all times:\nAssign separate survey lanes with sufficient lateral separation Assign separate depth layers for vehicles operating in the same horizontal area Assign time-separated access to overlapping areas Reactive Collision Avoidance For systems that must operate in shared space:\nEach vehicle monitors the positions of other vehicles When separation falls below a threshold, vehicles execute avoidance manoeuvres Avoidance protocols must be agreed and consistent across all vehicles — conflicting avoidance manoeuvres can cause collisions Communication requirement: Reactive collision avoidance requires vehicles to share position information. This requires a reliable communication link, which is not guaranteed for acoustic modems at range.\nCommunication in Multi-Vehicle Systems Bandwidth Limitations Acoustic modems typically provide \u0026lt;10 kbps total bandwidth for a network of vehicles. With multiple vehicles sharing a channel:\nEach vehicle gets a fraction of total bandwidth Message collision must be managed (time-division or CDMA) High-rate data cannot be shared in real time Communication Protocols Multi-vehicle systems use protocols to manage shared communication channels:\nTime-division multiple access (TDMA) — Each vehicle has a time slot to transmit; predictable but wastes capacity when vehicles have nothing to say CSMA — Vehicles listen before transmitting; efficient but collision-prone in high-traffic conditions OFDM — Orthogonal frequency division; higher bandwidth but complex Minimum Required Communication A well-designed multi-vehicle system should function safely even with only a fraction of planned communications succeeding. Safety-critical coordination (collision avoidance, abort commands) must use the most reliable communication mode available.\nSafety Separation Standards No universal standard exists for minimum separation between subsea vehicles. Project-specific analysis should consider:\nVehicle speeds and turning radii Position uncertainty of each vehicle Time delay between position measurement and response Communication reliability Practical minimum: Separation should be sufficient that, even if both vehicles\u0026rsquo; positions are at the extremes of their uncertainty ellipses, they remain separated. Add a factor for response time.\nRelated Topics Communication Systems Loss-of-Comms Behavior Latency \u0026amp; Bandwidth Tradeoffs Graceful Degradation AUV Platforms Overview Control Frameworks ","permalink":"/melon-wiki/swarm-systems/coordination/","summary":"\u003ch1 id=\"multi-vehicle-coordination\"\u003eMulti-Vehicle Coordination\u003c/h1\u003e\n\u003cp\u003eMulti-vehicle systems achieve objectives that single vehicles cannot — larger area coverage, redundant sensing, cooperative tasks requiring multiple simultaneous positions. But coordination introduces new failure modes and operational complexity. This page covers coordination strategies and the safety considerations specific to multi-vehicle subsea operations.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eMulti-vehicle operations are becoming practical as AUVs become more capable and affordable. But deploying multiple vehicles without a coherent coordination strategy creates collision risk, duplicated effort, and unpredictable system behaviour. Understanding coordination approaches helps operators design safe and effective multi-vehicle missions.\u003c/p\u003e","title":"Multi-Vehicle Coordination"},{"content":"Open Problems in Subsea Operations Some challenges in subsea operations remain genuinely unsolved — not merely neglected, but actively difficult despite significant research and engineering effort. This page surveys the most significant open problems and why they matter for operational safety, data quality, and regulatory compliance.\nWhy This Exists Understanding that a problem is genuinely open (rather than just unimplemented) helps operators set realistic expectations, avoid overconfidence in inadequate solutions, and direct research and development investment appropriately.\nWho This Is For Engineers and researchers working at the frontier of subsea systems Standards body participants scoping future standards work Operators evaluating emerging technology claims Project managers setting realistic capability expectations Navigation Without Infrastructure The Problem Precise subsea positioning without pre-deployed infrastructure (LBL transponders, seabed beacons) remains unsolved at scale. USBL accuracy degrades with depth. INS/DVL systems accumulate error over time. GPS is unavailable underwater.\nCurrent State Best available solutions combine INS + DVL + periodic USBL aiding, achieving decimetre accuracy over kilometre-scale missions in good conditions. In challenging terrain or poor acoustic conditions, errors can be metres to tens of metres.\nWhy It Matters AUVs operating in unmapped terrain cannot verify their own position Autonomous collision avoidance requires reliable position knowledge Survey data attributed to incorrect positions is misleading Active Research Directions Terrain-relative navigation using sonar maps Cooperative navigation between multiple vehicles Improved acoustic methods for longer range/depth Long-Duration Energy Storage The Problem Underwater vehicles are energy-limited. Batteries have fixed capacity, and recharging requires surfacing or docking. Long-duration autonomous operations (days to weeks) require either very large batteries, slow speeds, or underwater recharging.\nCurrent State Lithium-based batteries provide energy density of ~200 Wh/kg. Fuel cells offer higher density but add complexity and hydrogen storage challenges. Underwater recharging works for vehicles that can return to a dock, but remains unreliable for extended range operations.\nWhy It Matters Mission duration limits what can be monitored or inspected autonomously Return-to-dock requirements constrain operational area Energy availability affects emergency response capability (a vehicle that cannot abort safely is a hazard) Reliable Subsea Communication The Problem Acoustic communication provides the only long-range data link for subsea vehicles, but bandwidth is severely limited (typically \u0026lt;10 kbps) and latency is high (seconds per exchange). Optical communication provides high bandwidth but over very short ranges (\u0026lt;100m in clear water).\nCurrent State No technology provides both long-range and high-bandwidth subsea communication. Operations requiring rich real-time data exchange must use short umbilicals or accept very low data rates.\nWhy It Matters Autonomous vehicles that cannot communicate cannot receive updated mission plans or abort commands Real-time monitoring of complex situations requires data rates that acoustic links cannot provide Swarm coordination at range is limited by available communication bandwidth Fault Tolerance in Autonomous Decisions The Problem How should an autonomous vehicle behave when it encounters a situation outside its design envelope? Sensors may fail partially (giving wrong data rather than no data). Environmental conditions may be outside tested ranges. Multiple faults may interact unexpectedly.\nCurrent State Most autonomous systems handle individual, anticipated faults. Combinations of faults, especially those involving sensor data that is wrong rather than missing, are much harder. There is no general solution for safe behaviour under arbitrary fault combinations.\nWhy It Matters Vehicles that behave dangerously under unexpected faults cannot be safely deployed in complex environments Regulatory certification of autonomous safety behaviours requires confidence in fault response Incident investigation requires understanding what the system \u0026ldquo;thought\u0026rdquo; it was doing Standardised Autonomy Certification The Problem There is no accepted standard for certifying that an autonomous subsea system is safe to operate. Aviation (DO-178C for software, DO-254 for hardware) and automotive (ISO 26262) have developed rigorous frameworks over decades. Subsea autonomy has none.\nCurrent State Certifiers apply analogous standards by judgement. Different jurisdictions require different approaches. Novel systems face multi-year regulatory uncertainty.\nWhy It Matters Operators cannot demonstrate regulatory compliance for autonomous deployments Liability is unclear when an autonomous system causes harm Innovation is slowed by regulatory uncertainty Subsea Environmental Interaction Prediction The Problem Predicting how a vehicle will interact with the environment — particularly in near-seabed operations, strong currents, and turbid water — is difficult. Vehicle dynamics models built in controlled conditions do not always transfer to field conditions.\nWhy It Matters Collision avoidance near seabed structures requires accurate motion prediction Safe operation near sensitive environmental sites requires knowing the vehicle\u0026rsquo;s footprint Survey quality depends on maintaining accurate track spacing Related Topics Gaps in Current Standards Autonomy Challenges \u0026amp; Legacy Assumptions Why Auditability Matters Loss-of-Comms Behavior Communication Systems ","permalink":"/melon-wiki/open-standards/open-problems/","summary":"\u003ch1 id=\"open-problems-in-subsea-operations\"\u003eOpen Problems in Subsea Operations\u003c/h1\u003e\n\u003cp\u003eSome challenges in subsea operations remain genuinely unsolved — not merely neglected, but actively difficult despite significant research and engineering effort. This page surveys the most significant open problems and why they matter for operational safety, data quality, and regulatory compliance.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eUnderstanding that a problem is genuinely open (rather than just unimplemented) helps operators set realistic expectations, avoid overconfidence in inadequate solutions, and direct research and development investment appropriately.\u003c/p\u003e","title":"Open Problems in Subsea Operations"},{"content":"Operational Risk Models Risk models provide a structured way to estimate the likelihood and consequences of hazardous events. They translate qualitative hazard identification into quantifiable risk estimates that support decision-making, ALARP demonstration, and regulatory submissions.\nWhy This Exists Risk management requires more than identifying hazards — it requires understanding their significance. Risk models provide the common language for comparing risks, prioritising mitigations, and demonstrating compliance with ALARP and regulatory requirements.\nWho This Is For Safety engineers building and reviewing risk assessments Operations managers making risk-based decisions Regulators reviewing safety cases Project managers allocating resources for risk reduction Risk Fundamentals The Risk Equation Risk = Likelihood × Consequence\nBoth dimensions must be assessed. A very unlikely event with catastrophic consequences may warrant more attention than a frequent event with minor consequences, depending on organisational risk tolerances.\nRisk Matrices A risk matrix categorises risks by likelihood and consequence into risk bands:\nLikelihood scale (example):\n5 — Frequent: Expected to occur more than once per year 4 — Probable: Expected to occur once per year 3 — Occasional: May occur once per 10 years 2 — Remote: May occur once per 100 years 1 — Improbable: Unlikely to occur in system lifetime Consequence scale (example):\n5 — Catastrophic: Multiple fatalities 4 — Critical: Single fatality or permanent disability 3 — Marginal: Lost-time injury; significant environmental damage 2 — Negligible: Minor injury; minor environmental effect 1 — Minimal: No injury; no environmental effect Risk band = Likelihood rating × Consequence rating\nThe risk band determines acceptability and required response.\nQualitative vs Quantitative Risk Assessment Qualitative Risk Assessment (QRA-L) Uses the risk matrix with expert judgement for likelihood and consequence ratings:\nFaster and less resource-intensive — Suitable for most operational decisions Dependent on expert judgement — Results reflect team experience and bias Limited comparability — Different teams may rate the same risk differently Quantitative Risk Assessment (QRA) Uses historical data, fault trees, and event trees to calculate numerical risk estimates:\nProvides numerical risk estimates (e.g., 1×10⁻⁴ fatalities per year) Enables comparison against numerical risk criteria (e.g., individual risk criteria) Resource-intensive — Requires significant data and expertise Appropriate for complex, high-consequence operations — Major facilities, novel systems Common Risk Models for Subsea Operations Bow-Tie Analysis Bow-tie diagrams link a central hazardous event (the \u0026ldquo;top event\u0026rdquo;) to its causes (threats) on the left and consequences on the right. Barriers are identified on each side:\nPrevention barriers — Prevent threats from causing the top event Recovery barriers — Limit consequences after the top event occurs Bow-ties are particularly useful for diving and subsea operations because they visualise the entire risk pathway clearly and support ALARP demonstration.\nFault Tree Analysis (FTA) FTA identifies combinations of failures that lead to an undesired top event:\nTop-down analysis — Start with the top event and work down to causes Logic gates — AND gates (all inputs required) and OR gates (any input sufficient) Minimum cut sets — Smallest combinations of failures that cause the top event Useful for: Complex systems with multiple independent failure modes Event Tree Analysis (ETA) ETA traces sequences of events from an initiating event to final outcomes:\nForward analysis — Start with the initiating event and trace forward Branch points — At each branch, success or failure of a safeguard is considered Outcome probabilities — Combined with FTA results to estimate consequence likelihood Individual Risk and Societal Risk Individual Risk The probability that a specific individual in a defined role or location will die due to the operation per year:\nTypical criterion for workers: \u0026lt;1×10⁻³ per year (broadly acceptable); intolerable above 1×10⁻² per year HSE guidance (UK): Maximum tolerable individual risk for workers is 1×10⁻³ per year Societal Risk (F-N Curves) Societal risk considers the risk to the public or workforce as a whole, accounting for both frequency and number of fatalities. Plotted as F-N curves (frequency vs. number of fatalities), these are compared against regulatory criteria lines.\nResidual Risk and ALARP Risk models quantify risk both before and after controls are applied. The residual risk (after controls) must be demonstrated as ALARP — that all reasonably practicable controls have been applied.\nSee ALARP Principles for the ALARP assessment process.\nRelated Topics ALARP Principles Hazard Identification (HAZID/HAZOP) Responsibility Boundaries Regulatory Landscape Overview Dive Planning \u0026amp; Risk Assessment ","permalink":"/melon-wiki/safety-compliance/risk-models/","summary":"\u003ch1 id=\"operational-risk-models\"\u003eOperational Risk Models\u003c/h1\u003e\n\u003cp\u003eRisk models provide a structured way to estimate the likelihood and consequences of hazardous events. They translate qualitative hazard identification into quantifiable risk estimates that support decision-making, ALARP demonstration, and regulatory submissions.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eRisk management requires more than identifying hazards — it requires understanding their significance. Risk models provide the common language for comparing risks, prioritising mitigations, and demonstrating compliance with ALARP and regulatory requirements.\u003c/p\u003e","title":"Operational Risk Models"},{"content":"Physics vs Control Realism Building a simulator involves fundamental tradeoffs: a system that models physics perfectly may not run fast enough for real-time training; a simplified physics model may not prepare operators for real conditions. Understanding these tradeoffs helps designers make informed choices about where fidelity matters and where simplification is acceptable.\nWhy This Exists Every simulation involves simplifications. Some simplifications matter enormously for training effectiveness; others are irrelevant. Knowing which is which allows resources to be directed toward the fidelity that counts, and prevents false confidence that \u0026ldquo;more realistic\u0026rdquo; always means \u0026ldquo;better training.\u0026rdquo;\nWho This Is For Simulation designers building training systems Training managers evaluating simulation platforms Engineers integrating real hardware with simulation environments Researchers studying simulation effectiveness The Fidelity Spectrum Physics Fidelity Physics fidelity refers to how accurately the simulation models the behaviour of physical systems:\nHigh physics fidelity — Accurately models fluid dynamics, structural mechanics, acoustic propagation Low physics fidelity — Uses simplified models (linear dynamics, lookup tables) that approximate behaviour Computational cost: High-fidelity physics (e.g., computational fluid dynamics) is computationally expensive and may not run at real-time rates.\nControl System Fidelity Control system fidelity refers to how accurately the simulation models the control software and hardware:\nHigh control fidelity — Runs actual vehicle control software against simulated sensor inputs Low control fidelity — Uses simplified models of vehicle response that may not match the real control system Testing value: High control fidelity is essential for testing control system software before deployment. Low control fidelity is acceptable for training operator skills that do not depend on control system specifics.\nWhere Fidelity Matters for Training Task-Dependent Fidelity Requirements The required fidelity depends on what is being trained:\nTraining Objective Required Fidelity Procedure knowledge Low — simulator only needs to present the right situations Emergency decision-making Medium — situation development must be plausible Manual vehicle control skills High — vehicle response must match reality Fault diagnosis High — failure modes must manifest as they do in reality Environmental hazard recognition High — environmental cues must be representative The Negative Transfer Problem Negative transfer occurs when simulation training teaches the wrong habits — habits that degrade performance in the real environment. Negative transfer is caused by:\nSimulator controls that differ from real controls — Operators learn control habits on the simulator that are wrong for the real system Physics that differs significantly from reality — Operators learn to anticipate vehicle response that does not match real behaviour Consequence-free failure — Operators learn that they can recover from errors that are unrecoverable in reality Principle: It is better to train with a lower-fidelity simulation that does not cause negative transfer than a high-fidelity simulation that teaches wrong habits for the wrong reasons.\nHardware-in-the-Loop (HIL) HIL simulation runs actual vehicle hardware (control electronics, actuator drivers) against a simulated environment. This provides:\nReal control system behaviour — Exactly the same response characteristics as the real vehicle Real failure modes — Hardware failures manifest as they do in deployment Software validation — Control software can be tested without deploying the vehicle Cost: HIL requires procuring additional hardware and integrating it with the simulation environment. For high-value vehicles, this investment is typically justified.\nSoftware-in-the-Loop (SIL) SIL runs the vehicle control software in simulation without physical hardware. This provides:\nControl software testing — Software bugs can be found without hardware Faster iteration — Easier to reset and re-run than HIL Limited hardware validation — Does not validate hardware implementation Physics Simplifications and Their Implications Simplified Hydrodynamics Real vehicle hydrodynamics are nonlinear and coupled. Simplified models (linear drag, decoupled axes) are adequate for:\nHigh-level mission planning Operator training in stable conditions Simplified models fail for:\nTraining in strong currents or near seabed Control system design and tuning Fault behaviour in unusual attitudes Simplified Acoustic Models Acoustic propagation in the ocean depends on the sound velocity profile, bathymetry, and sea state. Simplified models may not accurately represent:\nMultipath effects that cause ranging errors Communication blackout zones Sonar image artefacts Training implication: Operators trained only on simplified acoustic models may not recognise or respond correctly to multipath-induced errors in real operations.\nChoosing the Right Level of Fidelity A practical framework:\nDefine training objectives — What skills and knowledge must the training develop? Identify critical fidelity requirements — Which aspects of the simulation must be realistic to achieve those objectives? Identify acceptable simplifications — Which aspects can be simplified without affecting training effectiveness? Validate the training — Measure training transfer to confirm the chosen fidelity is adequate Related Topics Why Simulation Matters Confidence Calibration Digital Twins Pre-Mission Rehearsal ","permalink":"/melon-wiki/simulation-training/realism-tradeoffs/","summary":"\u003ch1 id=\"physics-vs-control-realism\"\u003ePhysics vs Control Realism\u003c/h1\u003e\n\u003cp\u003eBuilding a simulator involves fundamental tradeoffs: a system that models physics perfectly may not run fast enough for real-time training; a simplified physics model may not prepare operators for real conditions. Understanding these tradeoffs helps designers make informed choices about where fidelity matters and where simplification is acceptable.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eEvery simulation involves simplifications. Some simplifications matter enormously for training effectiveness; others are irrelevant. Knowing which is which allows resources to be directed toward the fidelity that counts, and prevents false confidence that \u0026ldquo;more realistic\u0026rdquo; always means \u0026ldquo;better training.\u0026rdquo;\u003c/p\u003e","title":"Physics vs Control Realism"},{"content":"Power Systems \u0026amp; Endurance Subsea vehicles carry their energy with them. Unlike surface vehicles that can refuel easily, an AUV or ROV (on battery backup) must complete its mission on the energy available at deployment. Power system design and endurance planning directly affect operational safety: a vehicle that runs out of power at depth is either lost or requires emergency response.\nWhy This Exists Power limitations constrain mission planning. Understanding battery capacity, consumption rates, and endurance margins is essential for planning missions that vehicles can complete safely with adequate reserve.\nWho This Is For AUV pilots and mission planners calculating endurance budgets Engineers designing vehicle power systems Operations managers planning multi-day deployments Safety engineers assessing mission risk Battery Technologies Lithium-Ion (Li-Ion) The dominant technology for high-performance subsea vehicles:\nEnergy density: 150–250 Wh/kg (mass); 300–700 Wh/L (volume) Discharge characteristics: Relatively flat discharge curve; capacity drops significantly at low temperatures Safety: Risk of thermal runaway if overcharged, overdischarged, or physically damaged Cycle life: 300–1000 cycles to 80% capacity retention Operational considerations:\nTemperature affects capacity significantly — cold water (4°C) can reduce effective capacity by 20–40% Never discharge below manufacturer minimum voltage; deep discharge causes permanent damage Charge state monitoring must account for temperature compensation Lithium-Ion Polymer (LiPo) Similar chemistry to Li-Ion with flexible form factor:\nAdvantages: Can be shaped to fill irregular spaces in vehicle hull Disadvantages: More vulnerable to puncture damage; similar safety concerns to Li-Ion Primary Lithium Batteries Non-rechargeable lithium batteries (lithium thionyl chloride, lithium manganese):\nEnergy density: Significantly higher than rechargeable cells (up to 500 Wh/kg) Shelf life: Very long (10+ years) Applications: Long-endurance gliders, one-time-use autonomous vehicles Disadvantages: Cannot be recharged; disposal requirements Fuel Cells Hydrogen-oxygen fuel cells offer higher energy density than batteries:\nEnergy density: 1000+ Wh/kg of hydrogen (stored as metal hydride) Applications: Long-endurance AUVs where battery swaps are impractical Disadvantages: Complex hydrogen storage; safety considerations; limited commercial availability for subsea Tethered Power (ROVs) Work-class ROVs receive power through the umbilical from the surface vessel:\nAdvantage: No energy limitation; can operate indefinitely Disadvantage: Tether drag limits speed and range; umbilical failure cuts power immediately Power Consumption Modelling Propulsion Thruster power is the dominant consumer for most vehicles:\nThrust vs. power: Thrust increases roughly as power^(2/3) — doubling thrust requires ~2.5× power Current effects: Fighting a 1-knot current while making 2 knots SOG costs significantly more power than making 2 knots in still water Practical implication: Reduce speed to extend endurance; route missions to minimise counter-current transits Hotel Loads Persistent power draws from navigation, communication, and payload systems:\nNavigation sensors (INS, DVL, USBL): 10–50W typically Communication (acoustic modems, satellite when surfaced): 1–100W depending on mode Payload sensors (sonar, camera): 10–500W depending on type Payload Power Budget Sensor payloads can consume as much or more power than propulsion:\nMultibeam sonars: 50–200W Sub-bottom profilers: 100–1000W Cameras and lighting: 50–500W Mission endurance cannot be calculated without accounting for payload power.\nEndurance Planning Energy Budget For each mission:\nCalculate propulsion energy — Distance ÷ speed × propulsion power at that speed Calculate hotel load energy — Mission duration × hotel load power Calculate payload energy — Payload-on time × payload power Sum total energy — Propulsion + hotel + payload Apply reserve margin — Total energy × (1 + reserve factor) Compare to available capacity — Total with reserve must not exceed battery capacity at expected temperature Reserve margin: A minimum 20% reserve is common practice; higher for longer or riskier missions. The reserve must account for unexpected events: longer transit due to unexpected currents, extended mission due to task complexity, contingency power for emergency surfacing.\nAbort Thresholds Define explicit battery level thresholds that trigger mission abort:\nWarning threshold — Alert at 40% remaining; complete current task and return Abort threshold — Abort at 25% remaining; return to surface immediately Emergency threshold — Emergency surface at 15% remaining (sufficient for emergency ascent and surface positioning) These thresholds must be implemented in the vehicle\u0026rsquo;s control system, not just in the mission plan.\nRelated Topics AUV Platforms Overview ROV Systems Overview Failure Modes \u0026amp; Recovery Control Frameworks Loss-of-Comms Behavior ","permalink":"/melon-wiki/subsea-robotics/power-systems/","summary":"\u003ch1 id=\"power-systems--endurance\"\u003ePower Systems \u0026amp; Endurance\u003c/h1\u003e\n\u003cp\u003eSubsea vehicles carry their energy with them. Unlike surface vehicles that can refuel easily, an AUV or ROV (on battery backup) must complete its mission on the energy available at deployment. Power system design and endurance planning directly affect operational safety: a vehicle that runs out of power at depth is either lost or requires emergency response.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003ePower limitations constrain mission planning. Understanding battery capacity, consumption rates, and endurance margins is essential for planning missions that vehicles can complete safely with adequate reserve.\u003c/p\u003e","title":"Power Systems \u0026 Endurance"},{"content":"Pre-Mission Rehearsal Pre-mission rehearsal uses simulation to walk through a planned mission before it occurs. Unlike general training, rehearsal is mission-specific: it uses the actual mission plan, the actual vehicle configuration, and a model of the actual site. The goal is to identify problems before they occur in the real environment.\nWhy This Exists Surprises during a mission are expensive: vessel standby time is costly, schedule disruption affects the entire project, and some surprises are safety-critical. Rehearsal shifts the point of discovery earlier — problems found in the simulator cost time measured in minutes, not hours or days.\nWho This Is For ROV pilots and AUV mission planners preparing for complex missions Dive supervisors reviewing dive plans before execution Operations managers assessing mission feasibility Training departments developing mission-specific preparation curricula What Rehearsal Is (and Isn\u0026rsquo;t) Rehearsal Is A specific walkthrough of the planned mission in simulation An opportunity to identify problems with the plan before committing to it A chance to rehearse emergency procedures specific to the mission A shared mental model builder — all team members see the same mission unfold Rehearsal Is Not General skills training (that happens in the training programme) A check of vehicle readiness (that happens in pre-deployment testing) A guarantee that the mission will succeed — the real environment always differs from the model What to Rehearse Mission Profile Walk through the complete planned mission sequence:\nLaunch and recovery procedures Transit to site Mission objectives in sequence Any complex manoeuvres (entry to confined spaces, precision positioning) Return to surface/dock Identify: Are there steps in the plan that are unclear, ambiguous, or poorly defined? Ambiguities in a rehearsal plan become ambiguities in the field plan.\nCritical Decision Points Identify points in the mission where decisions must be made:\nGo/no-go decision points based on observable conditions Points where timing constraints exist Points where resource consumption (power, gas, time) triggers decision thresholds Rehearse the decisions, not just the manoeuvres. A mission operator who has practiced the decision at the 20% battery threshold will make a better decision in reality.\nEmergency Scenarios Rehearse the most likely and most serious emergency scenarios:\nLoss of communication at a specific point in the mission Equipment failure (thruster, sensor) at the worst possible moment Diver emergency requiring immediate ascent Loss of station-keeping with divers in water Principle: Emergency response is fastest when it has been rehearsed. Operators who have walked through the emergency response have a shared plan and don\u0026rsquo;t need to improvise.\nSite Models for Rehearsal Sources of Site Data The quality of rehearsal depends on the quality of the site model:\nPrior survey data — Previous sonar surveys, bathymetric charts Design drawings — For structures and installations Previous inspection records — Known features, obstructions, growth Environmental data — Current profiles, visibility, sediment type Managing Site Model Uncertainty Site models are never complete. Rehearsal must account for this:\nIdentify the assumptions in the site model Rehearse what happens when those assumptions are wrong \u0026ldquo;What if the structure is further north than the chart shows?\u0026rdquo; The goal is not to eliminate uncertainty but to prepare operators to handle it.\nRehearsal for Diving Operations Pre-dive briefings are a form of rehearsal:\nWalk through the dive plan step by step Identify each diver\u0026rsquo;s tasks and the sequence Confirm communication procedures Confirm gas management plan (turning points, ascent triggers) Walk through emergency procedures Documented requirement: Many regulations require a documented pre-dive briefing. The briefing record serves as evidence that the team was prepared.\nDive Simulation Tools For complex dives, dedicated dive simulation software can model:\nDecompression profiles for the planned dive and alternatives Gas consumption under different work rates Ascent profiles for different emergency scenarios Recording and Debrief During Rehearsal Record:\nThe rehearsal run (video capture of the simulation) Deviations from plan Problems identified Questions raised by the team After Rehearsal Debrief:\nWhat problems were identified? What changes are required to the plan? Were all emergency responses adequate? Does the team have a shared understanding of the mission? Output: Updated mission plan with issues resolved; list of open questions requiring follow-up before the mission.\nRelated Topics Why Simulation Matters Digital Twins Physics vs Control Realism Confidence Calibration Dive Planning \u0026amp; Risk Assessment ","permalink":"/melon-wiki/simulation-training/rehearsal/","summary":"\u003ch1 id=\"pre-mission-rehearsal\"\u003ePre-Mission Rehearsal\u003c/h1\u003e\n\u003cp\u003ePre-mission rehearsal uses simulation to walk through a planned mission before it occurs. Unlike general training, rehearsal is mission-specific: it uses the actual mission plan, the actual vehicle configuration, and a model of the actual site. The goal is to identify problems before they occur in the real environment.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eSurprises during a mission are expensive: vessel standby time is costly, schedule disruption affects the entire project, and some surprises are safety-critical. Rehearsal shifts the point of discovery earlier — problems found in the simulator cost time measured in minutes, not hours or days.\u003c/p\u003e","title":"Pre-Mission Rehearsal"},{"content":"Raw vs Derived Data Raw data is what sensors record directly. Derived data is what you get after processing, filtering, correcting, or combining raw data. The distinction matters for data integrity, auditability, and reproducibility: anyone must be able to re-derive your derived products from the raw data and get the same result.\nWhy This Exists Processing transforms data. A temperature measurement corrected for sensor bias, smoothed over a time window, and converted to potential temperature is very different from the original thermistor voltage reading. If only the derived product is archived, you cannot go back to check whether the processing was correct, apply a new correction, or reproduce the result with different parameters. Raw data preservation is the foundation of reproducible science and auditable operations.\nWho This Is For Data managers designing data storage and archiving pipelines Engineers and scientists processing sensor data Auditors reviewing data quality and processing lineage Project managers specifying data deliverable requirements Definitions Raw Data Raw data is the unmodified output of a sensor or measurement system:\nVoltage readings from a thermistor before temperature conversion Acoustic travel times from a ranging system before position calculation Raw ADC counts from a sonar system before processing Video frames from a camera before compression or enhancement Raw data should be archived exactly as received, with timestamps and calibration metadata.\nCalibrated Data Calibrated data is raw data with calibration corrections applied:\nSensor offsets and gains applied Temperature compensation applied Factory calibration coefficients applied Calibrated data is still close to the measurement; it should be reproducible from raw data plus the calibration coefficients.\nProcessed Data Processed data has undergone further transformation:\nFiltering — Smoothing, outlier removal Gridding — Interpolating point data to a regular grid Fusion — Combining data from multiple sensors Derived quantities — Computing salinity from conductivity, temperature, and pressure Data Products Data products are the final outputs delivered to end users:\nBathymetric maps Current profiles Anomaly detection reports Inspection reports The Preservation Imperative What Must Be Preserved At minimum, archive:\nRaw data — Original sensor outputs, exactly as received Calibration records — Coefficients used to convert raw data Processing code and version — The software used, with version numbers Processing parameters — Configuration files, filter settings, parameter choices Processing logs — Records of what was done, when, and by whom Why You Cannot Rely on Derived Products Alone If only the derived product is kept:\nErrors cannot be corrected — A discovered calibration error requires re-processing from raw data Replication is impossible — Third parties cannot verify your results Regulatory defence is weakened — Cannot demonstrate that data was not manipulated Scientific value is reduced — Future reprocessing with improved methods is impossible Processing Pipelines Version Control for Processing Code Processing software must be version-controlled:\nEvery version that was used to process data must be preserved Processing outputs must reference the software version that produced them Changes to processing software must be documented and reviewed Reproducibility Requirements A processing pipeline is reproducible if:\nStarting from the same raw data Using the same processing code (same version) Using the same processing parameters You get bit-for-bit identical output. Non-deterministic processing (random seeds, floating-point non-determinism) must be documented and managed.\nFlagging and Quality Control Quality Flags on Raw Data Individual raw data records should carry quality flags:\n0 — Good — Data passed all quality checks 1 — Probably good — Data passed automated checks but not manually reviewed 2 — Suspect — Automated checks raised a flag; manual review required 3 — Bad — Data failed quality checks; do not use 9 — Missing — No data available These flags must propagate through processing: derived products should carry the worst quality flag of any contributing raw data.\nGap Handling Data gaps must be documented:\nGap start and end times Reason for gap (sensor failure, communication loss, maintenance) Whether gaps are filled (interpolated) and if so, how Filled or interpolated values must be flagged as such and never presented as measured data.\nRelated Topics Data Provenance \u0026amp; Chain-of-Custody Sensor Calibration Traceability Audit Logs \u0026amp; Immutability Timestamp Integrity ","permalink":"/melon-wiki/ocean-data/raw-derived/","summary":"\u003ch1 id=\"raw-vs-derived-data\"\u003eRaw vs Derived Data\u003c/h1\u003e\n\u003cp\u003eRaw data is what sensors record directly. Derived data is what you get after processing, filtering, correcting, or combining raw data. The distinction matters for data integrity, auditability, and reproducibility: anyone must be able to re-derive your derived products from the raw data and get the same result.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eProcessing transforms data. A temperature measurement corrected for sensor bias, smoothed over a time window, and converted to potential temperature is very different from the original thermistor voltage reading. If only the derived product is archived, you cannot go back to check whether the processing was correct, apply a new correction, or reproduce the result with different parameters. Raw data preservation is the foundation of reproducible science and auditable operations.\u003c/p\u003e","title":"Raw vs Derived Data"},{"content":"Regulatory Landscape Overview Commercial diving and subsea operations are governed by a complex patchwork of national regulations, international conventions, and industry standards. No single framework covers all aspects of all operations. Operators must identify which regulations apply, in which jurisdictions, and how potentially conflicting requirements are resolved.\nWhy This Exists Regulatory compliance is not optional, but the landscape is genuinely complex. Jurisdiction, activity type, depth, location (offshore vs. inland), and vehicle type all affect which rules apply. This page provides an orientation to the major frameworks without substituting for qualified legal and regulatory advice.\nWho This Is For Operations managers planning activities in new jurisdictions Safety officers building compliance frameworks Legal and compliance teams assessing regulatory exposure Project managers identifying regulatory risks Regulatory Principles Jurisdiction Who regulates an activity depends on where it happens and who is doing it:\nFlag state — The country whose flag a vessel flies has jurisdiction over that vessel Coastal state — The country whose territorial waters or EEZ an operation is in has jurisdiction over the activity Employer state — The country in which a company is registered has jurisdiction over its employees Multiple overlapping jurisdictions — Common in international offshore operations When jurisdictions overlap, the most stringent requirement typically applies in practice.\nFlag State vs. Port State Control Flag states register and inspect vessels; port state control authorities inspect foreign-flagged vessels when they visit ports. Port state control can detain non-compliant vessels regardless of flag state inspection status.\nMajor Regulatory Bodies United Kingdom HSE (Health and Safety Executive) — Regulates diving operations under the Diving at Work Regulations 1997 OPRED (Offshore Petroleum Regulator for Environment and Decommissioning) — Offshore environmental regulations MCA (Maritime and Coastguard Agency) — Vessel safety Key regulation: Diving at Work Regulations 1997 require a written diving project plan, competent diving contractor, and compliance with approved codes of practice (ACOPs).\nUnited States OSHA — Occupational Safety and Health Administration; regulates commercial diving under 29 CFR 1910 Subpart T (general industry) and 29 CFR 1926 Subpart Y (construction) USCG (US Coast Guard) — Vessel safety, diving from vessels BSEE (Bureau of Safety and Environmental Enforcement) — Offshore oil and gas operations Key standard: OSHA 29 CFR 1910.410-440 sets detailed requirements for commercial diving including equipment, procedures, records, and emergency support.\nInternational Maritime Organisation (IMO) IMO develops international conventions adopted by member states:\nSOLAS (Safety of Life at Sea) — Vessel safety MARPOL — Marine pollution prevention ISM Code (International Safety Management) — Safety management systems for vessels IMO conventions apply to vessels of signatory states operating internationally.\nKey Industry Standards IMCA (International Marine Contractors Association) IMCA produces guidance documents widely adopted as industry best practice:\nIMCA D 014 — Guidance for diving supervisors IMCA D 022 — Guidance on competence assessment IMCA D 018 — Air diving operations IMCA ROV series — ROV operations guidance IMCA standards are not legally binding but are frequently referenced by regulators as indicators of industry best practice.\nDNV (Det Norske Veritas) DNV produces classification rules for offshore vessels, diving systems, and subsea equipment. Classification by DNV (or other class societies) provides assurance of system integrity and is often required for insurance and contracting.\nISO Standards Relevant ISO standards include:\nISO 24801 — Recreational scuba diver training (less relevant for commercial) ISO 9001 — Quality management systems ISO 45001 — Occupational health and safety management systems NFPA and ASTM US-focused standards bodies with relevance to hyperbaric facilities and equipment.\nOperational Frameworks Safety Case Regime Some jurisdictions (UK, Australia, Norway) require operators to produce a Safety Case — a structured document demonstrating that major accident risks have been identified and reduced to ALARP. The Safety Case must be accepted by the regulator before operations can commence.\nPrescriptive Regulation Other jurisdictions (some OSHA regimes) specify exactly what operators must do (equipment specifications, procedure requirements) rather than requiring the operator to demonstrate outcomes. Prescriptive rules are easier to audit but may be less flexible for novel operations.\nRegulatory Gaps for Novel Operations Existing regulations were not designed for autonomous vehicles, swarm systems, or AI-assisted operations. See Gaps in Current Standards and Autonomy Challenges \u0026amp; Legacy Assumptions for discussion of where current frameworks fail.\nRelated Topics ALARP Principles Operational Risk Models Hazard Identification (HAZID/HAZOP) Responsibility Boundaries Gaps in Current Standards ","permalink":"/melon-wiki/safety-compliance/regulatory-landscape/","summary":"\u003ch1 id=\"regulatory-landscape-overview\"\u003eRegulatory Landscape Overview\u003c/h1\u003e\n\u003cp\u003eCommercial diving and subsea operations are governed by a complex patchwork of national regulations, international conventions, and industry standards. No single framework covers all aspects of all operations. Operators must identify which regulations apply, in which jurisdictions, and how potentially conflicting requirements are resolved.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eRegulatory compliance is not optional, but the landscape is genuinely complex. Jurisdiction, activity type, depth, location (offshore vs. inland), and vehicle type all affect which rules apply. This page provides an orientation to the major frameworks without substituting for qualified legal and regulatory advice.\u003c/p\u003e","title":"Regulatory Landscape Overview"},{"content":"Responsibility Boundaries In commercial diving and subsea operations, multiple parties are involved — diving contractors, vessel operators, clients, equipment manufacturers, and regulatory bodies. Ambiguous responsibility is a leading contributor to incidents and to inadequate responses when things go wrong. Clear responsibility allocation is both a safety requirement and a legal necessity.\nWhy This Exists When responsibility is unclear, decisions go unmade, safety checks are assumed to be someone else\u0026rsquo;s job, and post-incident accountability is contested. Defining responsibility boundaries explicitly — in contracts, in pre-dive briefings, and in the operational management system — reduces these risks.\nWho This Is For Diving supervisors managing multi-party operations Operations managers building contracts and management systems Legal teams advising on liability allocation Clients and contractors entering into diving services agreements Key Roles and Their Responsibilities Diving Supervisor The diving supervisor has operational authority over all in-water operations. Under UK regulations (Diving at Work Regulations 1997) and equivalent international frameworks:\nSole authority over the decision to dive, continue, or abort Cannot be overridden by client, vessel master, or commercial pressure on safety grounds Accountable for ensuring diving is conducted in accordance with the approved dive plan Empowered to call for additional resources, refuse unsafe work, and document deviations Critical principle: The diving supervisor\u0026rsquo;s safety authority must be explicitly protected in the contract and cannot be contractually limited.\nDiving Contractor / Employer The diving contractor employs divers and supervisors and is responsible for:\nProviding competent personnel (appropriately trained and certificated) Providing fit-for-purpose equipment (inspected, maintained, calibrated) Developing the dive management system and procedures Ensuring compliance with applicable regulations Insuring the operation Vessel Master The vessel master is responsible for:\nVessel safety and seaworthiness Safe positioning and station-keeping during diving Crew safety and emergency response at the vessel level Decisions about vessel movement Interface issue: The vessel master may need to move the vessel for safety reasons (weather, collision risk) while divers are in the water. Protocols for emergency vessel movement with divers deployed must be agreed and briefed before diving.\nClient / Principal The client commissions the diving operation and is responsible for:\nProviding accurate information about the work site (existing infrastructure, hazards, access) Defining the work scope clearly Not pressuring the diving contractor to proceed unsafely Ensuring their own personnel do not create hazards for the diving operation Limitation: Clients cannot direct diving operations. The diving contractor retains operational control.\nEquipment Manufacturer / Supplier Manufacturers are responsible for:\nEquipment performing to specification under stated operating conditions Providing adequate documentation and training materials Communicating known defects or limitations promptly Supporting incident investigation when equipment failure may be involved Responsibility Allocation in Contracts What Must Be in the Contract Diving services contracts must specify:\nWhich party provides each category of equipment Which party is responsible for equipment inspection and maintenance The diving contractor\u0026rsquo;s exclusive operational authority Insurance requirements for each party Incident reporting and investigation obligations What constitutes a safe/unsafe worksite and who makes that determination Indemnities and Liability Caps Contracts typically allocate liability through mutual indemnities — each party takes responsibility for loss to its own personnel and property. Liability caps limit exposure for consequential losses.\nWarning: Indemnity structures that shift safety liability to the diving contractor for client-caused conditions (inadequate site information, client-created hazards) create perverse incentives. Contracts should allocate liability to the party in control of the risk.\nResponsibility in Multi-Contractor Operations Complex offshore operations may involve multiple contractors operating simultaneously. In these situations:\nInterface agreements — Formal agreements between contractors defining responsibility at operational interfaces Permit to work — Authority for concurrent operations must be clearly assigned to a single coordinating party Simultaneous operations (SIMOPS) — Formal SIMOPS procedures required when diving and other activities occur concurrently Autonomous Systems and Responsibility Autonomous vehicles and AI-assisted systems create novel responsibility questions: when an autonomous system makes a decision that causes harm, who is responsible? See Autonomy Challenges \u0026amp; Legacy Assumptions for discussion of how existing responsibility frameworks fail to address autonomous systems.\nRelated Topics Operational Risk Models ALARP Principles Hazard Identification (HAZID/HAZOP) Regulatory Landscape Overview Autonomy Challenges \u0026amp; Legacy Assumptions ","permalink":"/melon-wiki/safety-compliance/responsibility/","summary":"\u003ch1 id=\"responsibility-boundaries\"\u003eResponsibility Boundaries\u003c/h1\u003e\n\u003cp\u003eIn commercial diving and subsea operations, multiple parties are involved — diving contractors, vessel operators, clients, equipment manufacturers, and regulatory bodies. Ambiguous responsibility is a leading contributor to incidents and to inadequate responses when things go wrong. Clear responsibility allocation is both a safety requirement and a legal necessity.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eWhen responsibility is unclear, decisions go unmade, safety checks are assumed to be someone else\u0026rsquo;s job, and post-incident accountability is contested. Defining responsibility boundaries explicitly — in contracts, in pre-dive briefings, and in the operational management system — reduces these risks.\u003c/p\u003e","title":"Responsibility Boundaries"},{"content":"ROV Systems Overview Remotely Operated Vehicles (ROVs) are tethered underwater robots controlled from the surface. This page covers operational capabilities, limitations, and failure modes as they exist in practice.\nWhy This Exists ROVs provide a means to perform work and inspection tasks at depth without exposing human divers to risk. They are the standard tool for deepwater operations, hazardous environments, and tasks requiring precision or extended duration.\nWho This Is For ROV pilots and supervisors Operations managers planning ROV work Safety officers assessing ROV operations Auditors reviewing ROV procedures Robotics engineers developing ROV systems System Architecture Vehicle The underwater vehicle contains:\nPropulsion — Thrusters for maneuvering and station-keeping Buoyancy — Variable ballast or syntactic foam for depth control Sensors — Cameras, sonar, depth sensors, attitude sensors Manipulators — Arms and tools for work tasks Payload — Mission-specific equipment (cutting tools, sampling, etc.) Electronics — Control systems, power distribution, data acquisition What can go wrong: Thruster failure, buoyancy system failure, sensor failure, manipulator failure, electronics failure. Each failure mode affects operational capability differently.\nTether (Umbilical) The tether connects vehicle to surface:\nPower conductors — High-voltage power for vehicle systems Fiber optics — High-bandwidth data transmission Strength member — Load-bearing capability for vehicle recovery Buoyancy — Neutral or positive buoyancy to reduce drag What can go wrong: Tether damage, power loss, communication loss, entanglement, excessive drag. Tether management is critical for operations.\nSurface Control System Surface systems provide:\nControl console — Pilot interface for vehicle control Video displays — Real-time camera feeds and sensor data Power supply — Surface power generation and distribution Winch system — Tether deployment and recovery Data recording — Mission data logging and storage What can go wrong: Control system failure, power supply failure, winch failure, data loss. Surface systems must be redundant where possible.\nOperational Capabilities Depth Capability ROVs operate at various depths:\nObservation-class — Typically 300-1000m depth rating Work-class — Typically 3000-4000m depth rating, some to 6000m+ Specialty systems — Custom depth ratings for specific applications Operational reality: Depth ratings are maximum operating depths. Actual operational depth depends on tether length, power requirements, and mission duration.\nWork Capabilities ROVs can perform:\nInspection — Visual inspection, NDT, structural assessment Manipulation — Tool use, object recovery, installation Survey — Bathymetry, pipeline inspection, seabed mapping Sampling — Environmental sampling, biological sampling Construction — Pipeline installation, structure assembly What can go wrong: Work tasks exceed vehicle capability, tools not compatible, manipulator reach limitations, visibility constraints. Work scope must match vehicle capability.\nEndurance ROV endurance depends on:\nPower consumption — Vehicle systems, sensors, manipulators Surface power — Generator capacity and fuel supply Tether length — Power loss over tether length Mission profile — Station-keeping vs. transit, tool use intensity Operational reality: Endurance is not unlimited. Power management is critical for extended operations.\nFailure Modes Vehicle Failures Thruster failure:\nEffect: Reduced maneuverability, inability to maintain position Degradation: Vehicle may still be recoverable with remaining thrusters Response: Abort mission, recover vehicle, repair or replace thruster Buoyancy system failure:\nEffect: Inability to control depth, potential uncontrolled ascent/descent Degradation: Vehicle may become unstable or uncontrollable Response: Emergency recovery procedures, surface intervention Sensor failure:\nEffect: Loss of situational awareness, inability to perform tasks Degradation: Operations may continue with reduced capability Response: Continue with available sensors, or abort if critical sensor fails Manipulator failure:\nEffect: Inability to perform work tasks Degradation: Inspection-only operations may continue Response: Abort work tasks, continue inspection if possible Tether Failures Tether damage:\nEffect: Power loss, communication loss, or both Degradation: Partial failure may allow limited operations Response: Immediate recovery, assess damage, repair or replace Tether entanglement:\nEffect: Vehicle movement restricted, potential tether damage Degradation: Operations may continue with reduced mobility Response: Attempt to clear entanglement, or recover if unable to clear Power loss:\nEffect: Vehicle loses power, becomes unresponsive Degradation: Vehicle may be recoverable via winch if tether intact Response: Emergency recovery procedures, surface recovery Surface System Failures Control system failure:\nEffect: Loss of vehicle control Degradation: Vehicle may continue last command or enter failsafe mode Response: Switch to backup control system, or initiate recovery Power supply failure:\nEffect: Loss of surface power, vehicle loses power Degradation: Backup power may allow controlled recovery Response: Switch to backup power, recover vehicle Winch failure:\nEffect: Inability to deploy or recover vehicle Degradation: Vehicle may remain operational but unrecoverable Response: Repair winch, or use alternative recovery method Operational Procedures Pre-Dive Checks Before deployment, verify:\nVehicle systems — All systems functional, sensors calibrated Tether — No damage, proper routing, adequate length Surface systems — Control, power, winch all operational Tools and payload — Required equipment installed and functional Emergency procedures — Recovery procedures understood and ready Responsibility: ROV supervisor verifies systems; pilot verifies controls. Both must confirm before deployment.\nDuring Operations Standard operational practices:\nVehicle monitoring — Continuous monitoring of vehicle status Tether management — Monitoring tether position and condition Mission execution — Following planned work procedures Data recording — Continuous recording of mission data Communication — Regular status updates to surface team What can go wrong: Task fixation, missed anomalies, tether management errors, communication breakdown. Pilots must maintain situational awareness.\nPost-Dive Procedures After recovery:\nVehicle inspection — Post-dive inspection for damage Data download — Mission data retrieval and backup Equipment maintenance — Cleaning, inspection, repairs as needed Debrief — Mission review, lessons learned, documentation Responsibility: Supervisor ensures proper recovery and documentation; pilot reports any issues or anomalies.\nHuman Factors ROV operations depend on human operators:\nPilot skill — Experience and training affect operational capability Fatigue — Extended operations lead to degraded performance Situational awareness — Limited by sensor data and video feeds Decision-making — Operators must make decisions with incomplete information What can go wrong: Operator error, fatigue-induced mistakes, loss of situational awareness, poor decision-making. Human factors must be managed through procedures and training.\nData \u0026amp; Records ROV operations generate records:\nMission logs — Vehicle position, depth, time, tasks performed Video records — Camera feeds recorded for later analysis Sensor data — Sonar, depth, attitude, environmental data Equipment records — Maintenance, repairs, failures Incident reports — Anomalies, near-misses, incidents Audit-worthiness: Records must be traceable, timestamped, and suitable for regulatory review. See Ocean Data \u0026amp; Trust for data integrity requirements.\nRelated Topics AUV Platforms Overview Vehicle Classes \u0026amp; Capabilities Failure Modes \u0026amp; Recovery Control Frameworks Ocean Data \u0026amp; Trust ","permalink":"/melon-wiki/subsea-robotics/rov-systems/","summary":"\u003ch1 id=\"rov-systems-overview\"\u003eROV Systems Overview\u003c/h1\u003e\n\u003cp\u003eRemotely Operated Vehicles (ROVs) are tethered underwater robots controlled from the surface. This page covers operational capabilities, limitations, and failure modes as they exist in practice.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eROVs provide a means to perform work and inspection tasks at depth without exposing human divers to risk. They are the standard tool for deepwater operations, hazardous environments, and tasks requiring precision or extended duration.\u003c/p\u003e\n\u003ch2 id=\"who-this-is-for\"\u003eWho This Is For\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eROV pilots and supervisors\u003c/li\u003e\n\u003cli\u003eOperations managers planning ROV work\u003c/li\u003e\n\u003cli\u003eSafety officers assessing ROV operations\u003c/li\u003e\n\u003cli\u003eAuditors reviewing ROV procedures\u003c/li\u003e\n\u003cli\u003eRobotics engineers developing ROV systems\u003c/li\u003e\n\u003c/ul\u003e\n\u003ch2 id=\"system-architecture\"\u003eSystem Architecture\u003c/h2\u003e\n\u003ch3 id=\"vehicle\"\u003eVehicle\u003c/h3\u003e\n\u003cp\u003eThe underwater vehicle contains:\u003c/p\u003e","title":"ROV Systems Overview"},{"content":"Saturation Diving Overview Saturation diving allows divers to live and work at pressure for extended periods, eliminating repeated compression and decompression cycles. Divers saturate their tissues with breathing gas at the working depth and remain at that pressure for days or weeks, decompressing only once at the end of the dive system.\nWhy This Exists Saturation diving is the only practical method for prolonged work at depths beyond 50m (165 ft). Without it, surface-supplied divers would spend more time in decompression than on the work site. Understanding saturation systems is essential for planning deep inspection, installation, and repair work.\nWho This Is For Saturation diving supervisors and system operators Offshore installation managers overseeing deep work Engineers specifying diving systems for deep projects Safety officers reviewing saturation diving plans How Saturation Diving Works The Saturation Principle Once a diver\u0026rsquo;s tissues are fully saturated with inert gas at a given pressure, the decompression obligation does not increase with additional bottom time. This allows divers to remain at depth for days or weeks with only a single decompression at the end of the saturation period.\nKey advantage: A diver working at 150m for 30 days faces the same decompression obligation as one working there for 1 day.\nSystem Components A saturation diving system consists of:\nLiving chambers — Pressurized habitat where divers sleep, eat, and rest between bell runs Transfer lock — Connects living chambers to the diving bell at pressure Diving bell — Closed bell that transports divers from the living chamber to depth and back Life support control — Monitors and controls gas mixture, temperature, and CO₂ scrubbing Deck decompression chambers (DDC) — The main pressure vessel on deck Umbilicals — Hot water, communications, and breathing gas supply from the bell to the diver Gas Mixtures Saturation diving uses heliox (helium/oxygen) breathing mixtures:\nHelium replaces nitrogen to eliminate nitrogen narcosis and reduce decompression time Oxygen partial pressure is maintained at 0.4–0.5 bar to prevent oxygen toxicity while ensuring adequate oxygen delivery Depth-specific mixtures are calculated for each operation to maintain safe gas partial pressures Operational Procedures Bell Run Cycle A typical bell run involves:\nDivers transfer from living chamber through the transfer lock into the bell Bell is sealed and lowered to the working depth Bell hatch is opened; divers exit on umbilicals to perform work Divers return to the bell after the planned work period Bell hatch is closed and bell ascends to the deck Bell locks onto the living system and divers transfer back Work period limits: Diver excursion time is limited by CO₂ scrubber capacity, thermal protection, and fatigue.\nSaturation Decompression Decompression from saturation follows a slow, controlled ascent:\nRate — Typically 1.8m (6 ft) per hour, slowing at shallower depths Duration — A saturation at 100m requires approximately 60 hours of decompression Stops — Decompression may include stops at prescribed depths Monitoring — Divers are monitored continuously for signs of decompression sickness Depth Limits and Pressure Considerations Operational Depth Limits Air diving — Not suitable for saturation (narcosis, oxygen toxicity) Heliox saturation — Routinely to 300m, experimentally to 600m+ High-pressure nervous syndrome (HPNS) — A compression-related condition limiting very deep saturation HPNS At very high pressures, divers may experience tremors, cognitive impairment, and EEG changes. This limits the rate of compression and the practical depth ceiling for saturation diving.\nSafety Considerations System Integrity Saturation divers are entirely dependent on the system maintaining pressure. Any pressure loss is immediately life-threatening. Key safety requirements:\nRedundant gas supplies Backup life support systems Emergency breathing systems inside chambers Trained standby diver ready for emergency bell recovery Medical Support A diving medical officer must be available throughout saturation operations. Medical emergencies inside the system require treatment under pressure or controlled recompression followed by decompression — both complex procedures.\nRelated Topics Surface-Supplied Diving Systems Dive Planning \u0026amp; Risk Assessment USN Dive Tables Decompression Theory (Operational) Emergency Response Frameworks ","permalink":"/melon-wiki/commercial-diving/saturation-overview/","summary":"\u003ch1 id=\"saturation-diving-overview\"\u003eSaturation Diving Overview\u003c/h1\u003e\n\u003cp\u003eSaturation diving allows divers to live and work at pressure for extended periods, eliminating repeated compression and decompression cycles. Divers saturate their tissues with breathing gas at the working depth and remain at that pressure for days or weeks, decompressing only once at the end of the dive system.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eSaturation diving is the only practical method for prolonged work at depths beyond 50m (165 ft). Without it, surface-supplied divers would spend more time in decompression than on the work site. Understanding saturation systems is essential for planning deep inspection, installation, and repair work.\u003c/p\u003e","title":"Saturation Diving Overview"},{"content":"Sensor Calibration Traceability A measurement is only as good as the calibration of the sensor that produced it. Calibration traceability links every field measurement back to a national or international measurement standard through an unbroken chain of comparisons, each with documented uncertainty. Without traceability, measurements cannot be compared across systems, time periods, or organisations.\nWhy This Exists Subsea sensors measure pressure, temperature, salinity, acoustic distance, and many other quantities. Decisions — about dive safety, environmental impact, infrastructure integrity — depend on these measurements being accurate. Traceability ensures that \u0026ldquo;accurate\u0026rdquo; means something: that measurements can be compared, replicated, and defended.\nWho This Is For Instrument technicians managing sensor calibration Data managers documenting measurement uncertainty Project managers specifying calibration requirements in contracts Regulators and auditors reviewing measurement data quality The Calibration Chain National and International Standards At the top of the calibration hierarchy are primary standards maintained by national metrology institutes (NMIs):\nNIST (USA) — National Institute of Standards and Technology NPL (UK) — National Physical Laboratory PTB (Germany) — Physikalisch-Technische Bundesanstalt These institutes maintain primary standards for physical quantities (length, mass, temperature, pressure). All traceable calibrations ultimately link back to these standards.\nWorking Standards and Reference Instruments Below NMI standards:\nReference standards — Calibrated directly against NMI standards; used in calibration laboratories Working standards — Calibrated against reference standards; used for field instrument calibration Field instruments — Calibrated against working standards before deployment Each comparison in this chain must be documented with calibration certificates and uncertainty estimates.\nCalibration Documentation Requirements A valid calibration record must include:\nInstrument identifier — Serial number, asset tag Calibration date — Date calibration was performed Calibration laboratory — Name and accreditation status of the performing laboratory Standards used — Identification and certificate numbers of reference standards Measurement results — As-found and as-left readings at each calibration point Uncertainty — Measurement uncertainty at each calibration point (k=2, 95% confidence) Pass/fail determination — Whether the instrument meets its specification Next calibration due — Date or interval for next calibration Technician signature — Identity of the person performing the calibration Calibration Intervals Calibration intervals balance cost against the risk of operating with out-of-specification sensors:\nHigh-risk sensors — Shorter intervals (e.g., pressure sensors used for dive safety calculations) Stable, low-risk sensors — Longer intervals based on historical stability data Event-triggered recalibration — After physical shock, repair, unusual readings, or suspected damage Operational rule: Instruments used beyond their calibration due date should be flagged and their data marked as potentially invalid until recalibration is completed.\nCommon Subsea Sensor Types Pressure/Depth Sensors Criticality: High — used for dive depth monitoring, decompression calculations Calibration requirements: Traceable to primary pressure standards; calibrate at multiple points across the operating range Common issues: Zero drift, span drift after exposure to pressure cycling CTD (Conductivity, Temperature, Depth) Sensors Criticality: High for oceanographic data quality Calibration requirements: Temperature traceable to ITS-90; conductivity calibrated against standard seawater; pressure as above Common issues: Conductivity cell fouling, thermal lag Acoustic Sensors (USBL, DVL, ADCP) Criticality: Medium to high depending on application Calibration requirements: Sound speed corrections; alignment surveys for USBL Common issues: Sound speed profile errors, transducer fouling Dissolved Oxygen Sensors Criticality: Medium for environmental monitoring Calibration requirements: Two-point calibration (zero and saturated); temperature compensation Common issues: Membrane fouling, electrolyte depletion Measurement Uncertainty Every measurement has uncertainty — a range within which the true value lies with specified probability. Uncertainty must be:\nQuantified — Not just \u0026ldquo;we calibrated it\u0026rdquo; but \u0026ldquo;uncertainty is ±0.1°C at k=2\u0026rdquo; Propagated — When measurements are combined or processed, uncertainties combine Reported — Data products must include uncertainty estimates Ignoring uncertainty leads to false confidence in data quality. See Raw vs Derived Data for how uncertainty propagates through data processing.\nRelated Topics Data Provenance \u0026amp; Chain-of-Custody Raw vs Derived Data Timestamp Integrity Geospatial Confidence \u0026amp; Uncertainty ","permalink":"/melon-wiki/ocean-data/calibration/","summary":"\u003ch1 id=\"sensor-calibration-traceability\"\u003eSensor Calibration Traceability\u003c/h1\u003e\n\u003cp\u003eA measurement is only as good as the calibration of the sensor that produced it. Calibration traceability links every field measurement back to a national or international measurement standard through an unbroken chain of comparisons, each with documented uncertainty. Without traceability, measurements cannot be compared across systems, time periods, or organisations.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eSubsea sensors measure pressure, temperature, salinity, acoustic distance, and many other quantities. Decisions — about dive safety, environmental impact, infrastructure integrity — depend on these measurements being accurate. Traceability ensures that \u0026ldquo;accurate\u0026rdquo; means something: that measurements can be compared, replicated, and defended.\u003c/p\u003e","title":"Sensor Calibration Traceability"},{"content":"Sensor Payloads The sensor payload defines what a subsea vehicle can observe and measure. Payload selection drives mission capability, power consumption, data volume, and vehicle configuration. Understanding sensor types, their capabilities, and their limitations is essential for mission planning and data quality assessment.\nWhy This Exists Sensors are how subsea vehicles perceive and record their environment. The right sensor for a job depends on the target, the environment, the required resolution and accuracy, and the vehicle\u0026rsquo;s power and space budget. A mismatch between sensor capability and mission requirement produces poor data and wasted effort.\nWho This Is For Mission planners selecting sensor configurations for specific tasks Data managers understanding the characteristics of sensor data products Engineers integrating sensors into vehicle systems Scientists and engineers using sensor data for decision-making Acoustic Sensors Multibeam Echosounder (MBES) MBES emits acoustic pulses in a fan pattern across-track and measures depth across a swath:\nSwath width: Typically 2–5× water depth (altitude above seabed) Resolution: Function of beam width, frequency, and altitude Frequency range: 200 kHz (shallow, high resolution) to 12 kHz (deep, lower resolution) Applications: Bathymetric survey, seabed mapping, pipeline route survey Data products: Bathymetric grids, water column data (backscatter, biology)\nSide-Scan Sonar (SSS) SSS emits acoustic pulses to each side and measures the backscattered intensity:\nRange: Each side typically 10–200m depending on frequency Resolution: Finer than MBES at equivalent range; no depth data Frequency range: 100–1000 kHz Applications: Object detection, seabed characterisation, pipeline and cable inspection Data products: Sonar mosaic images; target detection reports\nSub-Bottom Profiler (SBP) SBP penetrates the seabed with low-frequency acoustic energy to image sub-seabed structure:\nPenetration: Typically 10–50m depending on sediment type and frequency Resolution: Decimetres vertically Applications: Buried pipeline detection, sediment characterisation, geohazard assessment Acoustic Doppler Current Profiler (ADCP) ADCP measures current velocity profiles through the water column using Doppler shift of backscattered sound:\nRange: Typically 10–300m depending on frequency Applications: Current measurement, water column monitoring, vehicle navigation (as DVL) Doppler Velocity Log (DVL) DVL uses Doppler shift to measure vehicle velocity relative to the seabed (or water column):\nCritical for navigation — DVL aiding of INS is the primary method for accurate AUV navigation Altitude limit — DVL loses bottom-track when vehicle is too far above the seabed Applications: Vehicle navigation, aided INS Optical Sensors Cameras (Video and Still) Optical imaging requires light:\nVisibility limit: Typically \u0026lt;30m in coastal waters; further in clear oceanic water Resolution: From standard definition to 4K and beyond Lighting: LED arrays required; colour rendering affects image quality Applications: Visual inspection, biological observation, documentation Laser Scanners Line-scanning lasers provide high-resolution 3D point clouds:\nRange: Typically \u0026lt;5m Resolution: Sub-millimetre Applications: Precision metrology, corrosion mapping, anode measurement Oceanographic Sensors CTD (Conductivity, Temperature, Depth) Measures the fundamental oceanographic state variables:\nRequired for: Correcting acoustic sensor performance (sound speed is a function of CTD) Applications: Oceanographic profiling, water mass characterisation Dissolved Oxygen Measures oxygen concentration, an indicator of biological productivity and water mass age.\nFluorometers Measure chlorophyll fluorescence as a proxy for phytoplankton biomass.\nTurbidity Sensors Measure suspended particle concentration — important for acoustic sensor performance and sediment transport monitoring.\nPayload Integration Considerations Power Budget Each sensor adds to the vehicle\u0026rsquo;s power demand. See Power Systems \u0026amp; Endurance for calculating the combined power budget and its effect on mission endurance.\nData Volume High-resolution sensors generate large data volumes:\nMBES at 400 kHz: ~1 GB/hour of raw data 4K video: 10–100 GB/hour depending on compression CTD: negligible AUV storage capacity and data transfer time at the end of the mission must be planned.\nAcoustic Interference Multiple acoustic sensors operating simultaneously can interfere. Multibeam sonar, DVL, USBL, and acoustic modems may use overlapping frequency bands. Careful frequency planning and time-division schemes are required.\nCalibration Requirements All sensors must be calibrated before deployment. See Sensor Calibration Traceability for requirements. For acoustic sensors, in-situ calibration checks (sound velocity profile measurement, patch test for MBES) are required before data collection.\nRelated Topics ROV Systems Overview AUV Platforms Overview Sensor Calibration Traceability Power Systems \u0026amp; Endurance Geospatial Confidence \u0026amp; Uncertainty ","permalink":"/melon-wiki/subsea-robotics/sensor-payloads/","summary":"\u003ch1 id=\"sensor-payloads\"\u003eSensor Payloads\u003c/h1\u003e\n\u003cp\u003eThe sensor payload defines what a subsea vehicle can observe and measure. Payload selection drives mission capability, power consumption, data volume, and vehicle configuration. Understanding sensor types, their capabilities, and their limitations is essential for mission planning and data quality assessment.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eSensors are how subsea vehicles perceive and record their environment. The right sensor for a job depends on the target, the environment, the required resolution and accuracy, and the vehicle\u0026rsquo;s power and space budget. A mismatch between sensor capability and mission requirement produces poor data and wasted effort.\u003c/p\u003e","title":"Sensor Payloads"},{"content":"Surface-Supplied Diving Systems Surface-supplied diving is the standard operational mode for most commercial diving work. This page covers the equipment, procedures, and operational considerations that matter in practice.\nWhy This Exists Surface-supplied diving provides continuous gas supply, real-time communication, and direct surface supervision. Unlike scuba, the diver remains connected to the surface, enabling longer bottom times, better safety oversight, and support for complex work tasks.\nWho This Is For Commercial divers working surface-supplied Dive supervisors planning and overseeing operations Tenders and support personnel Safety officers reviewing procedures Auditors assessing operational compliance System Components Gas Supply System The surface gas supply provides breathing gas to the diver through an umbilical. In practice, this means:\nPrimary gas supply — Typically air or nitrox for shallow work, helium-oxygen (heliox) or trimix for deeper operations Backup gas supply — Independent secondary system with sufficient capacity for emergency ascent Gas quality monitoring — Continuous analysis of oxygen content, contaminants, and pressure Emergency gas — Bailout cylinder carried by diver for emergency ascent What can go wrong: Gas supply failure, contamination, incorrect gas mix, umbilical damage. Each failure mode requires specific response procedures documented in dive plans.\nDiving Umbilical The umbilical carries gas, communication, and sometimes power to the diver. Operational considerations:\nGas hose — Primary breathing gas supply, typically 3/8\u0026quot; to 1/2\u0026quot; ID Communication cable — Hard-wired or fiber-optic voice communication Hot water hose — For thermal protection in cold water (if applicable) Strength member — Steel wire or Kevlar strength member for load handling Umbilical management — Tending, deployment, and recovery procedures What can go wrong: Umbilical entanglement, damage from sharp edges, communication loss, gas supply interruption. Umbilical management is a critical operational skill.\nDiving Helmet or Full-Face Mask The diver\u0026rsquo;s interface with the surface-supplied system:\nHelmet systems — Hard hat with integrated communication, gas supply, and exhaust Full-face mask systems — Lighter weight alternative with similar functionality Communication — Hard-wired voice communication with surface Gas flow — Demand valve or free-flow system depending on design What can go wrong: Communication failure, mask flooding, gas flow interruption, vision obstruction. Divers must be trained in emergency procedures for each failure mode.\nDiver Monitoring Surface personnel monitor diver status through:\nVoice communication — Continuous or periodic check-ins Depth monitoring — Depth gauge or transducer on surface Gas consumption — Flow meters and pressure monitoring Visual observation — When visibility permits, direct observation from surface What can go wrong: Communication loss, depth monitoring failure, missed check-ins. Supervisors must have clear procedures for handling loss of communication.\nOperational Procedures Pre-Dive Checks Before each dive, verify:\nGas supply — Primary and backup systems operational, correct gas mix, sufficient volume Umbilical — No damage, proper routing, adequate length for planned work Communication — Two-way communication functional, backup communication available Diver equipment — Helmet/mask, bailout, tools, work equipment checked Surface support — Tender, supervisor, standby diver, emergency equipment ready Responsibility: Dive supervisor verifies surface systems; diver verifies personal equipment. Both must confirm before dive commences.\nDuring Dive Operations Standard operational practices:\nCheck-in procedures — Regular voice check-ins at specified intervals Depth/time tracking — Continuous monitoring of depth and bottom time Gas management — Monitoring consumption and remaining supply Work task execution — Following planned work procedures Umbilical management — Maintaining proper umbilical routing and avoiding entanglement What can go wrong: Task fixation leading to missed check-ins, umbilical entanglement, gas consumption exceeding plan, communication degradation. Supervisors must maintain situational awareness and intervene when necessary.\nPost-Dive Procedures After dive completion:\nEquipment recovery — Safe recovery of diver and umbilical Equipment inspection — Post-dive inspection for damage or wear Debrief — Discussion of dive execution, issues encountered, lessons learned Documentation — Recording dive details in dive log Responsibility: Supervisor ensures proper recovery and documentation; diver reports any issues or anomalies.\nFailure Modes \u0026amp; Response Communication Loss What happens: Diver cannot communicate with surface, or surface cannot hear diver.\nResponse framework:\nSurface attempts to re-establish communication If no response, initiate emergency procedures Standby diver may be deployed to locate and assist Emergency ascent procedures activated if necessary Responsibility: Supervisor initiates response; standby diver executes if deployed.\nGas Supply Failure What happens: Primary gas supply interrupted or contaminated.\nResponse framework:\nDiver switches to bailout cylinder Surface attempts to restore primary supply If restoration fails, initiate emergency ascent Standby diver may be deployed to assist Responsibility: Diver executes immediate bailout; surface supports recovery.\nUmbilical Entanglement What happens: Umbilical becomes entangled in structure or equipment.\nResponse framework:\nDiver attempts to clear entanglement Surface provides guidance and support If unable to clear, standby diver may be deployed Emergency procedures activated if diver cannot be freed Responsibility: Diver attempts self-rescue first; surface coordinates response.\nOperational Limits Surface-supplied diving has practical limits:\nDepth limits — Typically 50-60m on air, deeper with mixed gas (subject to gas mix and decompression requirements) Bottom time — Limited by decompression requirements and gas supply Work complexity — Constrained by umbilical management and communication requirements Environmental conditions — Current, visibility, and sea state affect operational feasibility What can go wrong: Operations planned beyond practical limits, environmental conditions worse than anticipated, equipment limitations not recognized. Dive planning must account for these limits.\nData \u0026amp; Records Surface-supplied diving operations generate records:\nDive logs — Depth, time, gas consumption, work performed Communication records — Voice logs (if recorded) Equipment records — Maintenance, inspection, and failure records Incident reports — Documentation of anomalies, near-misses, or incidents Audit-worthiness: Records must be traceable, timestamped, and suitable for regulatory review. See Dive Logs \u0026amp; Operational Records for detailed requirements.\nRelated Topics Dive Planning \u0026amp; Risk Assessment Emergency Response Frameworks Human Factors in Diving Operations Dive Logs \u0026amp; Operational Records ","permalink":"/melon-wiki/commercial-diving/surface-supplied/","summary":"\u003ch1 id=\"surface-supplied-diving-systems\"\u003eSurface-Supplied Diving Systems\u003c/h1\u003e\n\u003cp\u003eSurface-supplied diving is the standard operational mode for most commercial diving work. This page covers the equipment, procedures, and operational considerations that matter in practice.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eSurface-supplied diving provides continuous gas supply, real-time communication, and direct surface supervision. Unlike scuba, the diver remains connected to the surface, enabling longer bottom times, better safety oversight, and support for complex work tasks.\u003c/p\u003e\n\u003ch2 id=\"who-this-is-for\"\u003eWho This Is For\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eCommercial divers working surface-supplied\u003c/li\u003e\n\u003cli\u003eDive supervisors planning and overseeing operations\u003c/li\u003e\n\u003cli\u003eTenders and support personnel\u003c/li\u003e\n\u003cli\u003eSafety officers reviewing procedures\u003c/li\u003e\n\u003cli\u003eAuditors assessing operational compliance\u003c/li\u003e\n\u003c/ul\u003e\n\u003ch2 id=\"system-components\"\u003eSystem Components\u003c/h2\u003e\n\u003ch3 id=\"gas-supply-system\"\u003eGas Supply System\u003c/h3\u003e\n\u003cp\u003eThe surface gas supply provides breathing gas to the diver through an umbilical. In practice, this means:\u003c/p\u003e","title":"Surface-Supplied Diving Systems"},{"content":"Timestamp Integrity Timestamps are fundamental to operational records, incident investigation, and audit. This page covers why timestamp integrity matters and how to ensure timestamps are accurate, synchronized, and tamper-resistant.\nWhy This Exists Timestamps enable:\nTemporal ordering — Understanding the sequence of events Incident reconstruction — Reconstructing what happened when Regulatory compliance — Demonstrating compliance with time-based requirements Legal defense — Defending operations with accurate timelines What can go wrong: Inaccurate timestamps, unsynchronized timestamps, tampered timestamps. Each failure mode creates legal and operational risk.\nWho This Is For System engineers designing timestamp systems Operations personnel recording timestamps Incident investigators reconstructing timelines Auditors verifying timestamp accuracy Legal counsel defending operations Timestamp Requirements Accuracy Timestamps must be accurate:\nClock accuracy — System clocks must be accurate Clock synchronization — Clocks must be synchronized across systems Timezone handling — Timezones must be handled correctly Leap second handling — Leap seconds must be handled correctly Operational reality: Clock accuracy degrades over time. Clocks must be regularly synchronized.\nSynchronization Timestamps must be synchronized:\nAcross systems — Timestamps from different systems must be synchronized With reference time — Timestamps must be synchronized with reference time (UTC) Synchronization method — Method of synchronization must be documented Synchronization accuracy — Synchronization accuracy must be known What can go wrong: Systems not synchronized, synchronization lost, synchronization method not documented. Unsynchronized timestamps create confusion and legal risk.\nTamper Resistance Timestamps must be tamper-resistant:\nImmutable records — Timestamp records must be immutable Cryptographic verification — Timestamps must be cryptographically verifiable Access control — Timestamp systems must be access-controlled Audit logging — Access to timestamp systems must be logged Legal requirement: Tampered timestamps are not credible in legal proceedings. Timestamps must be tamper-resistant.\nImplementation Approaches Network Time Protocol (NTP) NTP for clock synchronization:\nNTP servers — Synchronize with NTP servers Stratum levels — Understand NTP stratum levels Accuracy — NTP provides millisecond accuracy typically Reliability — NTP requires network connectivity Operational reality: NTP is standard for network-connected systems. Accuracy depends on network conditions and NTP server quality.\nGPS Time GPS for precise time:\nGPS receivers — GPS receivers provide precise time Accuracy — GPS provides microsecond accuracy Reliability — GPS requires satellite visibility Independence — GPS is independent of network Operational reality: GPS is standard for systems requiring precise time. GPS requires satellite visibility, which may not be available underwater.\nHardware Timestamps Hardware-based timestamps:\nHardware clocks — Hardware clocks with battery backup Accuracy — Hardware clocks maintain accuracy when powered Independence — Hardware clocks are independent of software Limitations — Hardware clocks drift over time Operational reality: Hardware clocks provide backup when network time is unavailable, but require regular synchronization.\nTimestamp Formats ISO 8601 ISO 8601 standard format:\nFormat — YYYY-MM-DDTHH:MM:SS.sssZ Timezone — UTC indicated by \u0026lsquo;Z\u0026rsquo;, or timezone offset Precision — Can include fractional seconds Standard — International standard, widely supported Operational reality: ISO 8601 is recommended for interoperability. Most systems support ISO 8601.\nUnix Timestamp Unix timestamp (seconds since epoch):\nFormat — Integer seconds since 1970-01-01 00:00:00 UTC Precision — Second precision (or fractional with extensions) Simplicity — Simple integer format Limitations — Year 2038 problem (32-bit), no timezone information Operational reality: Unix timestamps are common but have limitations. Use 64-bit timestamps to avoid year 2038 problem.\nTimestamp Uncertainty Clock Drift Clocks drift over time:\nDrift rate — Clocks drift at different rates Temperature effects — Temperature affects clock drift Aging effects — Clock accuracy degrades with age Compensation — Drift can be compensated with synchronization Operational reality: Clock drift is inevitable. Regular synchronization compensates for drift.\nSynchronization Uncertainty Synchronization has uncertainty:\nNetwork latency — Network latency affects synchronization accuracy Reference uncertainty — Reference time has uncertainty Synchronization method — Method affects accuracy Measurement — Uncertainty can be measured What can go wrong: Synchronization uncertainty not known, uncertainty not documented. Uncertainty must be quantified and documented.\nTimestamp Verification Post-Facto Verification Verify timestamps after the fact:\nClock logs — Review clock synchronization logs Cross-reference — Cross-reference timestamps from different systems Anomaly detection — Detect timestamp anomalies Validation — Validate timestamps are reasonable Audit requirement: Timestamps must be verifiable. Verification enables audit and legal defense.\nCryptographic Verification Cryptographically verify timestamps:\nDigital signatures — Sign timestamps with digital signatures Hash chains — Use hash chains for timestamp sequences Blockchain — Use blockchain for immutable timestamps (if applicable) Trust anchors — Establish trust anchors for verification Legal requirement: Cryptographic verification provides strong evidence of timestamp integrity. Tampered timestamps cannot be verified.\nOperational Considerations Timestamp Recording Record timestamps correctly:\nAt creation — Record timestamp when data is created Not on access — Do not update timestamp on access Immutable — Timestamps must be immutable once recorded Documented — Timestamp recording must be documented What can go wrong: Timestamps recorded incorrectly, timestamps updated, timestamps not documented. Timestamp recording must be correct and documented.\nTimestamp Display Display timestamps correctly:\nFormat — Display in consistent, readable format Timezone — Display timezone clearly Precision — Display appropriate precision Uncertainty — Display uncertainty if significant Operational reality: Timestamp display affects usability. Display must be clear and consistent.\nRelated Topics Data Provenance \u0026amp; Chain-of-Custody Audit Logs \u0026amp; Immutability Dive Logs \u0026amp; Operational Records ","permalink":"/melon-wiki/ocean-data/timestamps/","summary":"\u003ch1 id=\"timestamp-integrity\"\u003eTimestamp Integrity\u003c/h1\u003e\n\u003cp\u003eTimestamps are fundamental to operational records, incident investigation, and audit. This page covers why timestamp integrity matters and how to ensure timestamps are accurate, synchronized, and tamper-resistant.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eTimestamps enable:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eTemporal ordering\u003c/strong\u003e — Understanding the sequence of events\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eIncident reconstruction\u003c/strong\u003e — Reconstructing what happened when\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eRegulatory compliance\u003c/strong\u003e — Demonstrating compliance with time-based requirements\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eLegal defense\u003c/strong\u003e — Defending operations with accurate timelines\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eWhat can go wrong:\u003c/strong\u003e Inaccurate timestamps, unsynchronized timestamps, tampered timestamps. Each failure mode creates legal and operational risk.\u003c/p\u003e","title":"Timestamp Integrity"},{"content":"U.S. Navy Diving Manual — Revision 7 Air Dive Tables Source: SS521-AG-PRO-010, U.S. Navy Diving Manual, Revision 7, 01 December 2016 NAVSEA Reference: Published by Direction of Commander, Naval Sea Systems Command\nCRITICAL WARNING: These tables are transcribed from the official USN Diving Manual Revision 7. They must be verified against the original publication before operational use. Transcription errors, however unlikely, could be fatal. Always cross-reference with the official NAVSEA publication.\nDownload Tables as PDF Opens print dialog — choose \"Save as PDF\" to download Interactive NDL Lookup — Tables 9-7 \u0026amp; 9-8 Use this tool to instantly determine your no-decompression status, repetitive group, and residual nitrogen time for repetitive dives. All values from USN Diving Manual Rev 7.\nSingle Dive Repetitive Dive Enter depth and bottom time to find your no-decompression status and repetitive group (Table 9-7).\nDepth (FSW) Select… 101520 253035 404550 556070 8090100 110120130 140150160 170180190 Bottom Time (min) Look Up Plan a second dive using Table 9-8. Enter your post-dive group, surface interval, and next dive depth.\nStep 1 — Surface interval credit (Table 9-8, Part 1) Post-Dive Group Select… ZONM LKJI HGFE DCBA Surface Interval : Next Depth (FSW) Select… 101520 253035 404550 556070 8090100 110120130 140150160 170180190 Look Up Verify before operational use. These values are transcribed from USN Diving Manual Rev 7 (SS521-AG-PRO-010). Cross-reference with the official NAVSEA publication before any dive. Transcription errors, however unlikely, can be fatal. Table 9-5. Repetitive Groups Associated with Initial Ascent to Altitude Altitude (feet) Repetitive Group 1,000 A 2,000 A 3,000 B 4,000 C 5,000 D 6,000 E 7,000 F 8,000 G 9,000 H 10,000 I WARNING: Altitudes above 10,000 feet can impose serious stress on the body resulting in significant medical problems while the acclimatization process takes place. Ascents to these altitudes must be slow to allow acclimatization to occur and prophylactic drugs may be required to prevent the occurrence of altitude sickness. These exposures should always be planned in consultation with a Diving Medical Officer. Commands conducting diving operations above 10,000 feet may obtain the appropriate decompression procedures from NAVSEA 00C.\nTable 9-6. Required Surface Interval Before Ascent to Altitude After Diving Times shown in h:mm format.\nRep Group 1,000 ft 2,000 ft 3,000 ft 4,000 ft 5,000 ft 6,000 ft 7,000 ft 8,000 ft 9,000 ft 10,000 ft A 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 B 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 1:42 C 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 1:48 6:23 D 0:00 0:00 0:00 0:00 0:00 0:00 0:00 1:45 5:24 9:59 E 0:00 0:00 0:00 0:00 0:00 0:00 1:37 4:39 8:18 12:54 F 0:00 0:00 0:00 0:00 0:00 1:32 4:04 7:06 10:45 15:20 G 0:00 0:00 0:00 0:00 1:19 3:38 6:10 9:13 12:52 17:27 H 0:00 0:00 0:00 1:06 3:10 5:29 8:02 11:04 14:43 19:18 I 0:00 0:00 0:56 2:45 4:50 7:09 9:41 12:44 16:22 20:58 J 0:00 0:41 2:25 4:15 6:19 8:39 11:11 14:13 17:52 22:27 K 0:30 2:03 3:47 5:37 7:41 10:00 12:33 15:35 19:14 23:49 L 1:45 3:18 5:02 6:52 8:56 11:15 13:48 16:50 20:29 25:04 M 2:54 4:28 6:12 8:01 10:06 12:25 14:57 18:00 21:38 26:14 N 3:59 5:32 7:16 9:06 11:10 13:29 16:02 19:04 22:43 27:18 O 4:59 6:33 8:17 10:06 12:11 14:30 17:02 20:05 23:43 28:19 Z 5:56 7:29 9:13 11:03 13:07 15:26 17:59 21:01 24:40 29:15 Exceptional Exposure Wait 48 hours before ascent Notes:\nWhen using Table 9-6, use the highest repetitive group designator obtained in the previous 24-hour period. Table 9-6 may only be used when the maximum altitude achieved is 10,000 feet or less. For ascents above 10,000 feet, consult NAVSEA 00C for guidance. The cabin pressure in commercial aircraft is maintained at a constant value regardless of the actual altitude of the flight. Though cabin pressure varies somewhat with aircraft type, the nominal value is 8,000 feet. For commercial flights, use a final altitude of 8,000 feet to compute the required surface interval before flying. No surface interval is required before taking a commercial flight if the dive site is at 8,000 feet or higher. In this case, flying results in an increase in atmospheric pressure rather than a decrease. For ascent to altitude following a non-saturation helium-oxygen dive, wait 12 hours if the dive was a no-decompression dive. Wait 24 hours if the dive was a decompression dive. Table 9-7. No-Decompression Limits and Repetitive Group Designators for No-Decompression Air Dives * = Highest repetitive group that can be achieved at this depth regardless of bottom time. Blank cells = Group not achievable at this depth.\nDepth (fsw) No-Stop Limit (min) A B C D E F G H I J K L M N O Z 10 Unlimited 57 101 158 245 426 * 15 Unlimited 36 60 88 121 163 217 297 449 * 20 Unlimited 26 43 61 82 106 133 165 205 256 330 461 * 25 1102 20 33 47 62 78 97 117 140 166 198 236 285 354 469 992 1102 30 371 17 27 38 50 62 76 91 107 125 145 167 193 223 260 307 371 35 232 14 23 32 42 52 63 74 87 100 115 131 148 168 190 215 232 40 163 12 20 27 36 44 53 63 73 84 95 108 121 135 151 163 45 125 11 17 24 31 39 46 55 63 72 82 92 102 114 125 50 92 9 15 21 28 34 41 48 56 63 71 80 89 92 55 74 8 14 19 25 31 37 43 50 56 63 71 74 60 63 7 12 17 22 28 33 39 45 51 57 63 70 48 6 10 14 19 23 28 32 37 42 47 48 80 39 5 9 12 16 20 24 28 32 36 39 90 33 4 7 11 14 17 21 24 28 31 33 100 25 4 6 9 12 15 18 21 25 110 20 3 6 8 11 14 16 19 20 120 15 3 5 7 10 12 15 130 12 2 4 6 9 11 12 140 10 2 4 6 8 10 150 8 3 5 7 8 160 7 3 5 6 7 170 6 4 6 180 6 4 5 6 190 5 3 5 Table 9-8. Residual Nitrogen Time Table for Repetitive Air Dives This table has two parts:\nSurface Interval Credit Table — Determines new repetitive group after a surface interval Residual Nitrogen Times — Minutes of residual nitrogen time for the repetitive dive Part 1: Surface Interval Credit Table Locate your previous repetitive group designation. Read horizontally to find the column where your surface interval falls. Read down to find your new repetitive group.\n* = Dives following surface intervals longer than this are not repetitive dives. Use actual bottom times in the Air Decompression Tables.\nAll times in h:mm format.\nPrevious Group New Group: Z O N M L K J I H G F E D C B A Not Rep (\u0026gt;) Z 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:50 7:51–8:42 8:43–9:34 9:35–10:27 10:28–11:19 11:20–12:13 12:14–13:30 13:31–15:50 15:50 O 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:50 7:51–8:42 8:43–9:34 9:35–10:27 10:28–11:21 11:22–12:37 12:38–14:58 14:58 N 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:50 7:51–8:42 8:43–9:34 9:35–10:29 10:30–11:45 11:46–14:05 14:05 M 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:50 7:51–8:42 8:43–9:37 9:38–10:53 10:54–13:13 13:13 L 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:50 7:51–8:44 8:45–10:01 10:02–12:21 12:21 K 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:52 7:53–9:09 9:10–11:29 11:29 J 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–7:00 7:01–8:16 8:17–10:36 10:36 I 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:08 6:09–7:24 7:25–9:44 9:44 H 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:16 5:17–6:32 6:33–8:52 8:52 G 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:23 4:24–5:40 5:41–8:00 8:00 F 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:31 3:32–4:48 4:49–7:08 7:08 E 0:10–0:52 0:53–1:44 1:45–2:39 2:40–3:55 3:56–6:15 6:15 D 0:10–0:52 0:53–1:47 1:48–3:03 3:04–5:23 5:23 C 0:10–0:55 0:56–2:11 2:12–4:31 4:31 B 0:10–1:16 1:17–3:36 3:36 A 0:10–2:20 2:20 Part 2: Residual Nitrogen Times (Minutes) Enter with Dive Depth (rows) and Repetitive Group at End of Surface Interval (columns).\n** = Residual Nitrogen Time cannot be determined using this table (see paragraph 9-9.1 subparagraph 8 for instructions). † = Read vertically downward to the 30 fsw repetitive dive depth. Use the corresponding residual nitrogen times to compute the equivalent single dive time. Decompress using the 30 fsw air decompression table.\nDepth (fsw) Z O N M L K J I H G F E D C B A 10 ** ** ** ** ** ** ** ** ** ** ** 427 246 159 101 58 15 ** ** ** ** ** ** ** ** 450 298 218 164 122 89 61 37 20 ** ** ** ** ** 462 331 257 206 166 134 106 83 62 44 27 25 † † 470 354 286 237 198 167 141 118 98 79 63 48 34 21 30 372 308 261 224 194 168 146 126 108 92 77 63 51 39 28 18 35 245 216 191 169 149 132 116 101 88 75 64 53 43 33 24 15 40 188 169 152 136 122 109 97 85 74 64 55 45 37 29 21 13 45 154 140 127 115 104 93 83 73 64 56 48 40 32 25 18 12 50 131 120 109 99 90 81 73 65 57 49 42 35 29 23 17 11 55 114 105 96 88 80 72 65 58 51 44 38 32 26 20 15 10 60 101 93 86 79 72 65 58 52 46 40 35 29 24 19 14 9 70 83 77 71 65 59 54 49 44 39 34 29 25 20 16 12 8 80 70 65 60 55 51 46 42 38 33 29 25 22 18 14 10 7 90 61 57 52 48 44 41 37 33 29 26 22 19 16 12 9 6 100 54 50 47 43 40 36 33 30 26 23 20 17 14 11 8 5 110 48 45 42 39 36 33 30 27 24 21 18 16 13 10 8 5 120 44 41 38 35 32 30 27 24 22 19 17 14 12 9 7 5 130 40 37 35 32 30 27 25 22 20 18 15 13 11 9 6 4 140 37 34 32 30 27 25 23 21 19 16 14 12 10 8 6 4 150 34 32 30 28 26 23 21 19 17 15 13 11 9 8 6 4 160 32 30 28 26 24 22 20 18 16 14 13 11 9 7 5 4 170 30 28 26 24 22 21 19 17 15 14 12 10 8 7 5 3 180 28 26 25 23 21 19 18 16 14 13 11 10 8 6 5 3 190 26 25 23 22 20 18 17 15 14 12 11 9 8 6 5 3 Table 9-9. Air Decompression Table (DESCENT RATE 75 FPM — ASCENT RATE 30 FPM)\nStop times (min) include travel time, except first air and first O2 stop. Each depth section shows AIR decompression and AIR/O2 decompression schedules.\nExposure Categories:\nEntries before any marker line = Normal Exposure (No Decompression) SurDO2 Rec = In-Water Air/O2 Decompression or Surface Decompression Using Oxygen Recommended EE: Air / O2 Req = Exceptional Exposure: In-Water Air Decompression — In-Water Air/O2 Decompression or SurDO2 Required EE: O2 Req = Exceptional Exposure: In-Water Air/O2 Decompression — SurDO2 Required EE: SurDO2 = Exceptional Exposure: SurDO2 Required 30 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 371 1:00 AIR 0 1:00 0 Z Normal AIR/O2 0 1:00 380 0:20 AIR 5 6:00 0.5 Z Normal AIR/O2 1 2:00 420 0:20 AIR 22 23:00 0.5 Z SurDO2 Rec AIR/O2 5 6:00 480 0:20 AIR 42 43:00 0.5 SurDO2 Rec AIR/O2 9 10:00 540 0:20 AIR 71 72:00 1 SurDO2 Rec AIR/O2 14 15:00 600 0:20 AIR 92 93:00 1 EE: Air / O2 Req AIR/O2 19 20:00 660 0:20 AIR 120 121:00 1 EE: Air / O2 Req AIR/O2 22 23:00 720 0:20 AIR 158 159:00 1 EE: Air / O2 Req AIR/O2 27 28:00 35 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 232 1:10 AIR 0 1:10 0 Z Normal AIR/O2 0 1:10 240 0:30 AIR 4 5:10 0.5 Z Normal AIR/O2 2 3:10 270 0:30 AIR 28 29:10 0.5 Z SurDO2 Rec AIR/O2 7 8:10 300 0:30 AIR 53 54:10 0.5 Z SurDO2 Rec AIR/O2 13 14:10 330 0:30 AIR 71 72:10 1 Z SurDO2 Rec AIR/O2 17 18:10 40 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 163 1:20 AIR 0 1:20 0 O Normal AIR/O2 0 1:20 170 0:40 AIR 6 7:20 0.5 O Normal AIR/O2 2 3:20 180 0:40 AIR 14 15:20 0.5 Z Normal AIR/O2 5 6:20 190 0:40 AIR 21 22:20 0.5 Z SurDO2 Rec AIR/O2 7 8:20 200 0:40 AIR 27 28:20 0.5 Z SurDO2 Rec AIR/O2 9 10:20 210 0:40 AIR 39 40:20 0.5 Z SurDO2 Rec AIR/O2 11 12:20 220 0:40 AIR 52 53:20 0.5 Z SurDO2 Rec AIR/O2 12 13:20 230 0:40 AIR 64 65:20 1 Z SurDO2 Rec AIR/O2 16 17:20 240 0:40 AIR 75 76:20 1 Z SurDO2 Rec AIR/O2 19 20:20 270 0:40 AIR 101 102:20 1 Z EE: Air / O2 Req AIR/O2 26 27:20 300 0:40 AIR 128 129:20 1.5 EE: Air / O2 Req AIR/O2 33 34:20 330 0:40 AIR 160 161:20 1.5 EE: Air / O2 Req AIR/O2 38 44:20 360 0:40 AIR 184 185:20 2 EE: Air / O2 Req AIR/O2 44 50:20 420 0:40 AIR 248 249:20 2.5 EE: Air / O2 Req AIR/O2 56 62:20 480 0:40 AIR 321 322:20 2.5 EE: Air / O2 Req AIR/O2 68 79:20 540 0:40 AIR 372 373:20 3 EE: O2 Req AIR/O2 80 91:20 600 0:40 AIR 410 411:20 3.5 EE: O2 Req AIR/O2 93 104:20 660 0:40 AIR 439 440:20 4 EE: O2 Req AIR/O2 103 119:20 720 0:40 AIR 461 462:20 4.5 EE: SurDO2 AIR/O2 112 128:20 45 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 125 1:30 AIR 0 1:30 0 N Normal AIR/O2 0 1:30 130 0:50 AIR 2 3:30 0.5 O Normal AIR/O2 1 2:30 140 0:50 AIR 14 15:30 0.5 O Normal AIR/O2 5 6:30 150 0:50 AIR 25 26:30 0.5 Z SurDO2 Rec AIR/O2 8 9:30 160 0:50 AIR 34 35:30 0.5 Z SurDO2 Rec AIR/O2 11 12:30 170 0:50 AIR 41 42:30 1 Z SurDO2 Rec AIR/O2 14 15:30 180 0:50 AIR 59 60:30 1 Z SurDO2 Rec AIR/O2 17 18:30 190 0:50 AIR 75 76:30 1 Z SurDO2 Rec AIR/O2 19 20:30 200 0:50 AIR 89 90:30 1 Z EE: Air / O2 Req AIR/O2 23 24:30 210 0:50 AIR 101 102:30 1 Z EE: Air / O2 Req AIR/O2 27 28:30 220 0:50 AIR 112 113:30 1.5 Z EE: Air / O2 Req AIR/O2 30 31:30 230 0:50 AIR 121 122:30 1.5 Z EE: Air / O2 Req AIR/O2 33 34:30 240 0:50 AIR 130 131:30 1.5 Z EE: Air / O2 Req AIR/O2 37 43:30 270 0:50 AIR 173 174:30 2 EE: Air / O2 Req AIR/O2 45 51:30 300 0:50 AIR 206 207:30 2 EE: Air / O2 Req AIR/O2 51 57:30 330 0:50 AIR 243 244:30 2.5 EE: Air / O2 Req AIR/O2 61 67:30 360 0:50 AIR 288 289:30 3 EE: Air / O2 Req AIR/O2 69 80:30 420 0:50 AIR 373 374:30 3.5 EE: O2 Req AIR/O2 84 95:30 480 0:50 AIR 431 432:30 4 EE: O2 Req AIR/O2 101 117:30 540 0:50 AIR 473 474:30 4.5 EE: SurDO2 AIR/O2 117 133:30 50 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 92 1:40 AIR 0 1:40 0 M Normal AIR/O2 0 1:40 95 1:00 AIR 2 3:40 0.5 M Normal AIR/O2 1 2:40 100 1:00 AIR 4 5:40 0.5 N Normal AIR/O2 2 3:40 110 1:00 AIR 8 9:40 0.5 O Normal AIR/O2 4 5:40 120 1:00 AIR 21 22:40 0.5 O SurDO2 Rec AIR/O2 7 8:40 130 1:00 AIR 34 35:40 0.5 Z SurDO2 Rec AIR/O2 12 13:40 140 1:00 AIR 45 46:40 1 Z SurDO2 Rec AIR/O2 16 17:40 150 1:00 AIR 56 57:40 1 Z SurDO2 Rec AIR/O2 19 20:40 160 1:00 AIR 78 79:40 1 Z SurDO2 Rec AIR/O2 23 24:40 170 1:00 AIR 96 97:40 1 Z EE: Air / O2 Req AIR/O2 26 27:40 180 1:00 AIR 111 112:40 1.5 Z EE: Air / O2 Req AIR/O2 30 31:40 190 1:00 AIR 125 126:40 1.5 Z EE: Air / O2 Req AIR/O2 35 36:40 200 1:00 AIR 136 137:40 1.5 Z EE: Air / O2 Req AIR/O2 39 45:40 210 1:00 AIR 147 148:40 2 EE: Air / O2 Req AIR/O2 43 49:40 220 1:00 AIR 166 167:40 2 EE: Air / O2 Req AIR/O2 47 53:40 230 1:00 AIR 183 184:40 2 EE: Air / O2 Req AIR/O2 50 56:40 240 1:00 AIR 198 199:40 2 EE: Air / O2 Req AIR/O2 53 59:40 270 1:00 AIR 236 237:40 2.5 EE: Air / O2 Req AIR/O2 62 68:40 300 1:00 AIR 285 286:40 3 EE: Air / O2 Req AIR/O2 74 85:40 330 1:00 AIR 345 346:40 3.5 EE: O2 Req AIR/O2 83 94:40 360 1:00 AIR 393 394:40 3.5 EE: O2 Req AIR/O2 92 103:40 420 1:00 AIR 464 465:40 4.5 EE: SurDO2 AIR/O2 113 129:40 55 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 74 1:50 AIR 0 1:50 0 L Normal AIR/O2 0 1:50 75 1:10 AIR 1 2:50 0.5 L Normal AIR/O2 1 2:50 80 1:10 AIR 4 5:50 0.5 M Normal AIR/O2 2 3:50 90 1:10 AIR 10 11:50 0.5 N Normal AIR/O2 5 6:50 100 1:10 AIR 17 18:50 0.5 O SurDO2 Rec AIR/O2 8 9:50 110 1:10 AIR 34 35:50 0.5 O SurDO2 Rec AIR/O2 12 13:50 120 1:10 AIR 48 49:50 1 Z SurDO2 Rec AIR/O2 17 18:50 130 1:10 AIR 59 60:50 1 Z SurDO2 Rec AIR/O2 22 23:50 140 1:10 AIR 84 85:50 1 Z SurDO2 Rec AIR/O2 26 27:50 150 1:10 AIR 105 106:50 1.5 Z EE: Air / O2 Req AIR/O2 30 31:50 160 1:10 AIR 123 124:50 1.5 Z EE: Air / O2 Req AIR/O2 34 35:50 170 1:10 AIR 138 139:50 1.5 Z EE: Air / O2 Req AIR/O2 40 46:50 180 1:10 AIR 151 152:50 2 Z EE: Air / O2 Req AIR/O2 45 51:50 190 1:10 AIR 169 170:50 2 EE: Air / O2 Req AIR/O2 50 56:50 200 1:10 AIR 190 191:50 2 EE: Air / O2 Req AIR/O2 54 60:50 210 1:10 AIR 208 209:50 2.5 EE: Air / O2 Req AIR/O2 58 64:50 220 1:10 AIR 224 225:50 2.5 EE: Air / O2 Req AIR/O2 62 68:50 230 1:10 AIR 239 240:50 2.5 EE: Air / O2 Req AIR/O2 66 77:50 240 1:10 AIR 254 255:50 3 EE: Air / O2 Req AIR/O2 69 80:50 270 1:10 AIR 313 314:50 3.5 EE: O2 Req AIR/O2 83 94:50 300 1:10 AIR 380 381:50 3.5 EE: O2 Req AIR/O2 94 105:50 330 1:10 AIR 432 433:50 4 EE: O2 Req AIR/O2 106 122:50 360 1:10 AIR 474 475:50 4.5 EE: SurDO2 AIR/O2 118 134:50 60 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 63 2:00 AIR 0 2:00 0 K Normal AIR/O2 0 2:00 65 1:20 AIR 2 4:00 0.5 L Normal AIR/O2 1 3:00 70 1:20 AIR 7 9:00 0.5 L Normal AIR/O2 4 6:00 80 1:20 AIR 14 16:00 0.5 N Normal AIR/O2 7 9:00 90 1:20 AIR 23 25:00 0.5 O SurDO2 Rec AIR/O2 10 12:00 100 1:20 AIR 42 44:00 1 Z SurDO2 Rec AIR/O2 15 17:00 110 1:20 AIR 57 59:00 1 Z SurDO2 Rec AIR/O2 21 23:00 120 1:20 AIR 75 77:00 1 Z SurDO2 Rec AIR/O2 26 28:00 130 1:20 AIR 102 104:00 1.5 Z EE: Air / O2 Req AIR/O2 31 33:00 140 1:20 AIR 124 126:00 1.5 Z EE: Air / O2 Req AIR/O2 35 37:00 150 1:20 AIR 143 145:00 2 Z EE: Air / O2 Req AIR/O2 41 48:00 160 1:20 AIR 158 160:00 2 Z EE: Air / O2 Req AIR/O2 48 55:00 170 1:20 AIR 178 180:00 2 EE: Air / O2 Req AIR/O2 53 60:00 180 1:20 AIR 201 203:00 2.5 EE: Air / O2 Req AIR/O2 59 66:00 190 1:20 AIR 222 224:00 2.5 EE: Air / O2 Req AIR/O2 64 71:00 200 1:20 AIR 240 242:00 2.5 EE: Air / O2 Req AIR/O2 68 80:00 210 1:20 AIR 256 258:00 3 EE: Air / O2 Req AIR/O2 73 85:00 220 1:20 AIR 278 280:00 3 EE: Air / O2 Req AIR/O2 77 89:00 230 1:20 AIR 300 302:00 3.5 EE: O2 Req AIR/O2 82 94:00 240 1:20 AIR 321 323:00 3.5 EE: O2 Req AIR/O2 88 100:00 270 1:20 AIR 398 400:00 4 EE: O2 Req AIR/O2 102 119:00 300 1:20 AIR 456 458:00 4.5 EE: SurDO2 AIR/O2 115 132:00 70 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 48 2:20 AIR 0 2:20 0 K Normal AIR/O2 0 2:20 50 1:40 AIR 2 4:20 0.5 K Normal AIR/O2 1 3:20 55 1:40 AIR 9 11:20 0.5 L Normal AIR/O2 5 7:20 60 1:40 AIR 14 16:20 0.5 M Normal AIR/O2 8 10:20 70 1:40 AIR 24 26:20 0.5 N SurDO2 Rec AIR/O2 13 15:20 80 1:40 AIR 44 46:20 1 O SurDO2 Rec AIR/O2 17 19:20 90 1:40 AIR 64 66:20 1 Z SurDO2 Rec AIR/O2 24 26:20 100 1:40 AIR 88 90:20 1.5 Z EE: Air / O2 Req AIR/O2 31 33:20 110 1:40 AIR 120 122:20 1.5 Z EE: Air / O2 Req AIR/O2 38 45:20 120 1:40 AIR 145 147:20 2 Z EE: Air / O2 Req AIR/O2 44 51:20 130 1:40 AIR 167 169:20 2 Z EE: Air / O2 Req AIR/O2 51 58:20 140 1:40 AIR 189 191:20 2.5 EE: Air / O2 Req AIR/O2 59 66:20 150 1:40 AIR 219 221:20 2.5 EE: Air / O2 Req AIR/O2 66 78:20 160 1:20 AIR 1 244 247:00 3 EE: O2 Req AIR/O2 1 72 85:00 170 1:20 AIR 2 265 269:00 3 EE: O2 Req AIR/O2 1 78 91:00 180 1:20 AIR 4 289 295:00 3.5 EE: O2 Req AIR/O2 2 83 97:00 190 1:20 AIR 5 316 323:00 3.5 EE: O2 Req AIR/O2 3 88 103:00 200 1:20 AIR 9 345 356:00 4 EE: O2 Req AIR/O2 5 93 115:00 210 1:20 AIR 13 378 393:00 4 EE: O2 Req AIR/O2 7 98 122:00 240 1:20 AIR 25 454 481:00 5 EE: SurDO2 AIR/O2 13 110 140:00 80 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 39 2:40 AIR 0 2:40 0 J Normal AIR/O2 0 2:40 40 2:00 AIR 1 3:40 0.5 J Normal AIR/O2 1 3:40 45 2:00 AIR 10 12:40 0.5 K Normal AIR/O2 5 7:40 50 2:00 AIR 17 19:40 0.5 M SurDO2 Rec AIR/O2 9 11:40 55 2:00 AIR 24 26:40 0.5 M SurDO2 Rec AIR/O2 13 15:40 60 2:00 AIR 30 32:40 1 N SurDO2 Rec AIR/O2 16 18:40 70 2:00 AIR 54 56:40 1 O SurDO2 Rec AIR/O2 22 24:40 80 2:00 AIR 77 79:40 1.5 Z SurDO2 Rec AIR/O2 30 32:40 90 2:00 AIR 114 116:40 1.5 Z EE: Air / O2 Req AIR/O2 39 46:40 100 1:40 AIR 1 147 150:20 2 Z EE: Air / O2 Req AIR/O2 1 46 54:20 110 1:40 AIR 6 171 179:20 2 Z EE: Air / O2 Req AIR/O2 3 51 61:20 120 1:40 AIR 10 200 212:20 2.5 EE: Air / O2 Req AIR/O2 5 59 71:20 130 1:40 AIR 14 232 248:20 3 EE: Air / O2 Req AIR/O2 7 67 86:20 140 1:40 AIR 17 258 277:20 3.5 EE: O2 Req AIR/O2 9 73 94:20 150 1:40 AIR 19 285 306:20 3.5 EE: O2 Req AIR/O2 10 80 102:20 160 1:40 AIR 21 318 341:20 4 EE: O2 Req AIR/O2 11 86 114:20 170 1:40 AIR 27 354 383:20 4 EE: O2 Req AIR/O2 14 90 121:20 180 1:40 AIR 33 391 426:20 4.5 EE: SurDO2 AIR/O2 17 96 130:20 210 1:40 AIR 51 473 526:20 5 EE: SurDO2 AIR/O2 26 110 158:20 90 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 33 3:00 AIR 0 3:00 0 J Normal AIR/O2 0 3:00 35 2:20 AIR 4 7:00 0.5 J Normal AIR/O2 2 5:00 40 2:20 AIR 14 17:00 0.5 L Normal AIR/O2 7 10:00 45 2:20 AIR 23 26:00 0.5 M SurDO2 Rec AIR/O2 12 15:00 50 2:20 AIR 31 34:00 1 N SurDO2 Rec AIR/O2 17 20:00 55 2:20 AIR 39 42:00 1 O SurDO2 Rec AIR/O2 21 24:00 60 2:20 AIR 56 59:00 1 O SurDO2 Rec AIR/O2 24 27:00 70 2:20 AIR 83 86:00 1.5 Z SurDO2 Rec AIR/O2 32 35:00 80 2:00 AIR 5 125 132:40 2 Z EE: Air / O2 Req AIR/O2 3 40 50:40 90 2:00 AIR 13 158 173:40 2 Z EE: Air / O2 Req AIR/O2 7 46 60:40 100 2:00 AIR 19 185 206:40 2.5 EE: Air / O2 Req AIR/O2 10 53 70:40 110 2:00 AIR 25 224 251:40 3 EE: Air / O2 Req AIR/O2 13 61 86:40 120 1:40 AIR 2 28 256 288:20 3.5 EE: O2 Req AIR/O2 2 14 70 98:40 130 1:40 AIR 5 28 291 326:20 3.5 EE: O2 Req AIR/O2 5 14 79 110:40 140 1:40 AIR 8 28 330 368:20 4 EE: O2 Req AIR/O2 8 14 87 126:40 150 1:40 AIR 11 34 378 425:20 4.5 EE: SurDO2 AIR/O2 11 17 94 139:40 160 1:40 AIR 13 40 418 473:20 4.5 EE: SurDO2 AIR/O2 13 20 101 151:40 170 1:40 AIR 15 45 451 513:20 5 EE: SurDO2 AIR/O2 15 23 106 166:40 180 1:40 AIR 16 51 479 548:20 5.5 EE: SurDO2 AIR/O2 16 26 112 176:40 240 1:40 AIR 42 68 592 704:20 7.5 EE: SurDO2 AIR/O2 42 34 159 267:40 100 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 25 3:20 AIR 0 3:20 0 H Normal AIR/O2 0 3:20 30 2:40 AIR 3 6:20 0.5 J Normal AIR/O2 2 5:20 35 2:40 AIR 15 18:20 0.5 L Normal AIR/O2 8 11:20 40 2:40 AIR 26 29:20 1 M SurDO2 Rec AIR/O2 14 17:20 45 2:40 AIR 36 39:20 1 N SurDO2 Rec AIR/O2 19 22:20 50 2:40 AIR 47 50:20 1 O SurDO2 Rec AIR/O2 24 27:20 55 2:40 AIR 65 68:20 1.5 Z SurDO2 Rec AIR/O2 28 31:20 60 2:40 AIR 81 84:20 1.5 Z SurDO2 Rec AIR/O2 33 36:20 70 2:20 AIR 11 124 138:00 2 Z EE: Air / O2 Req AIR/O2 6 39 53:00 80 2:20 AIR 21 160 184:00 2.5 Z EE: Air / O2 Req AIR/O2 11 45 64:00 90 2:00 AIR 2 28 196 228:40 2.5 EE: Air / O2 Req AIR/O2 2 14 53 82:00 100 2:00 AIR 9 28 241 280:40 3 EE: O2 Req AIR/O2 9 14 66 102:00 110 2:00 AIR 14 28 278 322:40 3.5 EE: O2 Req AIR/O2 14 14 76 117:00 120 2:00 AIR 19 28 324 373:40 4 EE: O2 Req AIR/O2 19 14 85 136:00 150 1:40 AIR 3 26 46 461 538:20 5 EE: SurDO2 AIR/O2 3 26 23 109 183:40 110 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 20 3:40 AIR 0 3:40 0 H Normal AIR/O2 0 3:40 25 3:00 AIR 5 8:40 0.5 I Normal AIR/O2 3 6:40 30 3:00 AIR 14 17:40 0.5 K Normal AIR/O2 7 10:40 35 3:00 AIR 27 30:40 1 M SurDO2 Rec AIR/O2 14 17:40 40 3:00 AIR 39 42:40 1 N SurDO2 Rec AIR/O2 20 23:40 45 3:00 AIR 50 53:40 1 O SurDO2 Rec AIR/O2 26 29:40 50 3:00 AIR 71 74:40 1.5 Z SurDO2 Rec AIR/O2 32 35:40 55 2:40 AIR 5 85 93:20 1.5 Z EE: Air / O2 Req AIR/O2 3 33 44:20 60 2:40 AIR 13 111 127:20 2 Z EE: Air / O2 Req AIR/O2 7 36 51:20 70 2:40 AIR 26 155 184:20 2.5 Z EE: Air / O2 Req AIR/O2 14 42 64:20 80 2:20 AIR 9 28 200 240:00 2.5 EE: O2 Req AIR/O2 9 14 54 90:20 90 2:20 AIR 18 28 249 298:00 3.5 EE: O2 Req AIR/O2 18 14 68 113:20 100 2:20 AIR 25 28 295 351:00 3.5 EE: O2 Req AIR/O2 25 14 79 131:20 110 2:00 AIR 5 26 28 353 414:40 4 EE: O2 Req AIR/O2 5 26 14 91 154:00 120 2:00 AIR 10 26 35 413 486:40 4.5 EE: SurDO2 AIR/O2 10 26 18 101 173:00 180 1:40 AIR 3 23 47 68 593 736:20 7.5 EE: SurDO2 AIR/O2 3 23 47 34 159 298:40 120 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 15 4:00 AIR 0 4:00 0 F Normal AIR/O2 0 4:00 20 3:20 AIR 4 8:00 0.5 H Normal AIR/O2 2 6:00 25 3:20 AIR 9 13:00 0.5 J Normal AIR/O2 5 9:00 30 3:20 AIR 24 28:00 0.5 L SurDO2 Rec AIR/O2 13 17:00 35 3:20 AIR 38 42:00 1 N SurDO2 Rec AIR/O2 20 24:00 40 3:00 AIR 2 49 54:40 1 O SurDO2 Rec AIR/O2 1 26 30:40 45 3:00 AIR 3 71 77:40 1.5 Z SurDO2 Rec AIR/O2 2 31 36:40 50 3:00 AIR 10 85 98:40 1.5 Z EE: Air / O2 Req AIR/O2 5 33 46:40 55 3:00 AIR 19 116 138:40 2 Z EE: Air / O2 Req AIR/O2 10 35 53:40 60 3:00 AIR 27 142 172:40 2 Z EE: Air / O2 Req AIR/O2 14 39 61:40 70 2:40 AIR 13 28 190 234:20 2.5 EE: Air / O2 Req AIR/O2 13 14 51 86:40 80 2:40 AIR 24 28 246 301:20 3 EE: O2 Req AIR/O2 24 14 67 118:40 90 2:20 AIR 7 26 28 303 367:00 3.5 EE: O2 Req AIR/O2 7 26 14 80 140:20 100 2:20 AIR 15 25 28 372 443:00 4 EE: O2 Req AIR/O2 15 25 14 95 167:20 110 2:20 AIR 21 25 38 433 520:00 5 EE: SurDO2 AIR/O2 21 25 19 105 188:20 120 2:00 AIR 3 23 25 47 480 580:40 5.5 EE: SurDO2 AIR/O2 3 23 25 24 113 211:00 130 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 12 4:20 AIR 0 4:20 0 F Normal AIR/O2 0 4:20 15 3:40 AIR 3 7:20 0.5 G Normal AIR/O2 2 6:20 20 3:40 AIR 8 12:20 0.5 I Normal AIR/O2 5 9:20 25 3:40 AIR 17 21:20 0.5 K SurDO2 Rec AIR/O2 9 13:20 30 3:20 AIR 2 32 38:00 1 M SurDO2 Rec AIR/O2 1 17 22:00 35 3:20 AIR 5 44 53:00 1 O SurDO2 Rec AIR/O2 3 23 30:00 40 3:20 AIR 6 66 76:00 1.5 Z SurDO2 Rec AIR/O2 3 30 37:00 45 3:00 AIR 1 11 84 99:40 1.5 Z EE: Air / O2 Req AIR/O2 1 6 33 49:00 50 3:00 AIR 2 20 118 143:40 2 Z EE: Air / O2 Req AIR/O2 2 10 36 57:00 55 3:00 AIR 4 28 146 181:40 2 Z EE: Air / O2 Req AIR/O2 4 14 40 67:00 60 3:00 AIR 12 28 170 213:40 2.5 Z EE: Air / O2 Req AIR/O2 12 14 46 81:00 70 2:40 AIR 1 26 28 235 293:20 3 EE: O2 Req AIR/O2 1 26 14 63 117:40 80 2:40 AIR 12 26 28 297 366:20 3.5 EE: O2 Req AIR/O2 12 26 14 79 144:40 90 2:40 AIR 22 25 28 375 453:20 4 EE: O2 Req AIR/O2 22 25 14 95 174:40 100 2:20 AIR 6 23 26 38 444 540:00 5 EE: SurDO2 AIR/O2 6 23 26 20 106 204:20 120 2:20 AIR 17 24 27 57 534 662:00 6 EE: SurDO2 AIR/O2 17 24 27 29 130 255:20 180 2:00 AIR 13 21 45 57 94 658 890:40 9 EE: SurDO2 AIR/O2 13 21 45 57 46 198 418:00 140 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 10 4:40 AIR 0 4:40 0 E Normal AIR/O2 0 4:40 15 4:00 AIR 5 9:40 0.5 H Normal AIR/O2 3 7:40 20 4:00 AIR 13 17:40 0.5 J Normal AIR/O2 7 11:40 25 3:40 AIR 3 24 31:20 1 L SurDO2 Rec AIR/O2 2 12 18:20 30 3:40 AIR 7 37 48:20 1 N SurDO2 Rec AIR/O2 4 19 27:20 35 3:20 AIR 2 7 58 71:00 1.5 O SurDO2 Rec AIR/O2 2 4 26 36:20 40 3:20 AIR 4 7 82 97:00 1.5 Z EE: Air / O2 Req AIR/O2 4 4 33 50:20 45 3:20 AIR 5 18 114 141:00 2 Z EE: Air / O2 Req AIR/O2 5 9 36 59:20 50 3:20 AIR 8 27 145 184:00 2 Z EE: Air / O2 Req AIR/O2 8 14 39 70:20 55 3:00 AIR 1 15 29 171 219:40 2.5 Z EE: Air / O2 Req AIR/O2 1 15 15 45 85:00 60 3:00 AIR 2 23 28 209 265:40 3 EE: O2 Req AIR/O2 2 23 14 56 109:00 70 3:00 AIR 14 25 29 276 347:40 3.5 EE: O2 Req AIR/O2 14 25 15 74 142:00 80 2:40 AIR 2 24 25 29 362 445:20 4 EE: O2 Req AIR/O2 2 24 25 15 91 175:40 90 2:40 AIR 12 23 26 38 443 545:20 5 EE: SurDO2 AIR/O2 12 23 26 19 107 210:40 150 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 8 5:00 AIR 0 5:00 0 E Normal AIR/O2 0 5:00 10 4:20 AIR 2 7:00 0.5 F Normal AIR/O2 1 6:00 15 4:20 AIR 8 13:00 0.5 H Normal AIR/O2 5 10:00 20 4:00 AIR 2 15 21:40 0.5 K SurDO2 Rec AIR/O2 1 8 13:40 25 4:00 AIR 7 29 40:40 1 M SurDO2 Rec AIR/O2 4 14 22:40 30 3:40 AIR 4 7 45 60:20 1.5 O SurDO2 Rec AIR/O2 4 4 22 34:40 35 3:40 AIR 6 7 74 91:20 1.5 Z EE: Air / O2 Req AIR/O2 6 4 30 44:40 40 3:20 AIR 2 6 14 106 132:00 2 Z EE: Air / O2 Req AIR/O2 2 6 7 35 59:20 45 3:20 AIR 3 8 24 142 181:00 2 Z EE: Air / O2 Req AIR/O2 3 8 12 40 72:20 50 3:20 AIR 4 14 28 170 220:00 2.5 Z EE: Air / O2 Req AIR/O2 4 14 14 46 87:20 55 3:20 AIR 7 21 28 212 272:00 3 EE: O2 Req AIR/O2 7 21 14 57 113:20 60 3:20 AIR 11 26 28 248 317:00 3 EE: O2 Req AIR/O2 11 26 14 67 132:20 70 3:00 AIR 3 24 25 28 330 413:40 4 EE: O2 Req AIR/O2 3 24 25 14 85 170:00 80 3:00 AIR 15 23 26 35 430 532:40 4.5 EE: SurDO2 AIR/O2 15 23 26 18 104 205:00 90 2:40 AIR 3 22 23 26 47 496 620:20 5.5 EE: SurDO2 AIR/O2 3 22 23 26 24 118 239:40 120 2:20 AIR 3 20 22 23 50 75 608 804:00 8 EE: SurDO2 AIR/O2 3 20 22 23 50 37 168 356:20 180 2:00 AIR 2 19 20 42 48 79 121 694 1027:40 10.5 AIR/O2 2 19 20 42 48 79 58 222 538:00 160 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 7 5:20 AIR 0 5:20 0 E Normal AIR/O2 0 5:20 10 4:40 AIR 4 9:20 0.5 F Normal AIR/O2 2 7:20 15 4:20 AIR 2 10 17:00 0.5 I Normal AIR/O2 1 6 12:00 20 4:00 AIR 1 4 19 28:40 0.5 L SurDO2 Rec AIR/O2 1 2 10 18:00 25 4:00 AIR 4 7 35 50:40 1 N SurDO2 Rec AIR/O2 4 4 17 30:00 30 3:40 AIR 2 6 7 62 81:20 1.5 Z SurDO2 Rec AIR/O2 2 6 4 26 42:40 35 3:40 AIR 4 6 8 89 111:20 1.5 Z EE: Air / O2 Req AIR/O2 4 6 4 34 57:40 40 3:40 AIR 6 6 21 134 171:20 2 Z EE: Air / O2 Req AIR/O2 6 6 11 38 70:40 45 3:20 AIR 2 5 11 28 166 216:00 2.5 Z EE: Air / O2 Req AIR/O2 2 5 11 14 45 86:20 50 3:20 AIR 2 8 19 28 207 268:00 3 EE: O2 Req AIR/O2 2 8 19 15 55 113:20 55 3:20 AIR 3 11 26 28 248 320:00 3 EE: O2 Req AIR/O2 3 11 26 14 67 135:20 60 3:20 AIR 6 17 25 29 291 372:00 3.5 EE: O2 Req AIR/O2 6 17 25 15 77 154:20 70 3:20 AIR 15 23 26 29 399 496:00 4.5 EE: SurDO2 AIR/O2 15 23 26 15 99 197:20 80 3:00 AIR 6 21 24 25 44 482 605:40 5.5 EE: SurDO2 AIR/O2 6 21 24 25 23 114 237:00 170 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 6 5:40 AIR 0 5:40 0 D Normal AIR/O2 0 5:40 10 5:00 AIR 6 11:40 0.5 G Normal AIR/O2 3 8:40 15 4:40 AIR 3 13 21:20 0.5 J SurDO2 Rec AIR/O2 2 6 13:20 20 4:20 AIR 3 6 24 38:00 1 M SurDO2 Rec AIR/O2 3 3 12 23:20 25 4:00 AIR 1 7 7 41 60:40 1 O SurDO2 Rec AIR/O2 1 7 4 20 37:00 30 4:00 AIR 5 7 7 77 100:40 1.5 Z EE: Air / O2 Req AIR/O2 5 7 3 30 50:00 35 3:40 AIR 2 6 6 15 120 153:20 2 Z EE: Air / O2 Req AIR/O2 2 6 6 8 37 68:40 40 3:40 AIR 4 6 9 25 158 206:20 2.5 Z EE: Air / O2 Req AIR/O2 4 6 9 12 44 84:40 45 3:40 AIR 5 7 16 28 197 257:20 2.5 Z EE: O2 Req AIR/O2 5 7 16 14 53 109:40 50 3:20 AIR 1 5 11 23 28 244 316:00 3 EE: O2 Req AIR/O2 1 5 11 23 14 66 134:20 55 3:20 AIR 2 7 16 26 28 289 372:00 3.5 EE: O2 Req AIR/O2 2 7 16 26 14 77 156:20 60 3:20 AIR 2 11 21 26 28 344 436:00 4 EE: O2 Req AIR/O2 2 11 21 26 14 88 181:20 70 3:20 AIR 7 19 24 25 39 454 572:00 5 EE: SurDO2 AIR/O2 7 19 24 25 20 109 228:20 80 3:20 AIR 17 22 23 26 53 525 670:00 6 EE: SurDO2 AIR/O2 17 22 23 26 27 128 267:20 90 3:00 AIR 8 19 22 23 37 66 574 752:40 7 EE: SurDO2 AIR/O2 8 19 22 23 37 33 148 319:00 120 2:40 AIR 9 19 20 22 42 60 94 659 928:20 9 EE: SurDO2 AIR/O2 9 19 20 22 42 60 46 198 454:40 180 2:20 AIR 10 18 19 40 43 70 97 156 703 1159:00 11.5 AIR/O2 10 18 19 40 43 70 97 74 229 648:00 180 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 6 6:00 AIR 0 6:00 0 E Normal AIR/O2 0 6:00 10 5:20 AIR 8 14:00 0.5 G Normal AIR/O2 4 10:00 15 4:40 AIR 2 3 14 24:20 0.5 K SurDO2 Rec AIR/O2 2 2 7 16:40 20 4:20 AIR 1 5 7 29 47:00 1 M SurDO2 Rec AIR/O2 1 5 3 15 29:20 25 4:20 AIR 5 6 7 57 80:00 1.5 O SurDO2 Rec AIR/O2 5 6 4 24 44:20 30 4:00 AIR 3 6 6 7 95 121:40 1.5 Z EE: Air / O2 Req AIR/O2 3 6 6 4 34 63:00 35 3:40 AIR 1 5 6 6 22 144 188:20 2 Z EE: Air / O2 Req AIR/O2 1 5 6 6 11 41 79:40 40 3:40 AIR 2 6 5 13 28 178 236:20 2.5 EE: O2 Req AIR/O2 2 6 5 13 14 48 97:40 45 3:40 AIR 4 5 10 20 28 235 306:20 3 EE: O2 Req AIR/O2 4 5 10 20 14 63 130:40 50 3:40 AIR 4 8 13 25 29 277 360:20 3.5 EE: O2 Req AIR/O2 4 8 13 25 15 75 154:40 55 3:40 AIR 5 11 19 26 28 336 429:20 4 EE: O2 Req AIR/O2 5 11 19 26 14 87 181:40 60 3:20 AIR 1 8 13 23 25 31 406 511:00 4.5 EE: SurDO2 AIR/O2 1 8 13 23 25 16 100 205:20 70 3:20 AIR 4 12 21 24 25 48 499 637:00 5.5 EE: SurDO2 AIR/O2 4 12 21 24 25 24 119 253:20 190 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group Category 5 6:20 AIR 0 6:20 0 D Normal AIR/O2 0 6:20 10 5:20 AIR 2 8 16:00 0.5 H Normal AIR/O2 1 4 11:00 15 4:40 AIR 1 3 3 16 28:20 0.5 K SurDO2 Rec AIR/O2 1 3 2 8 19:40 20 4:20 AIR 1 2 6 7 34 55:00 1 N SurDO2 Rec AIR/O2 1 2 6 4 17 35:20 25 4:20 AIR 2 6 7 7 72 99:00 1.5 Z EE: Air / O2 Req AIR/O2 2 6 7 3 28 51:20 30 4:00 AIR 1 6 5 7 13 122 158:40 2 Z EE: Air / O2 Req AIR/O2 1 6 5 7 7 38 74:00 35 4:00 AIR 4 5 6 8 26 165 218:40 2.5 Z EE: O2 Req AIR/O2 4 5 6 8 13 45 91:00 40 3:40 AIR 1 5 5 8 17 28 217 285:20 3 EE: O2 Req AIR/O2 1 5 5 8 17 15 58 123:40 45 3:40 AIR 2 5 6 12 24 29 264 346:20 3.5 EE: O2 Req AIR/O2 2 5 6 12 24 15 71 149:40 50 3:40 AIR 3 5 10 17 26 28 324 417:20 4 EE: O2 Req AIR/O2 3 5 10 17 26 14 85 179:40 55 3:40 AIR 4 8 10 24 25 30 397 502:20 4.5 EE: SurDO2 AIR/O2 4 8 10 24 25 15 99 204:40 60 3:40 AIR 5 10 16 24 25 40 454 578:20 5 EE: SurDO2 AIR/O2 5 10 16 24 25 20 109 233:40 90 3:20 AIR 11 19 20 21 28 51 83 626 863:00 8.5 EE: SurDO2 AIR/O2 11 19 20 21 28 51 41 178 408:20 120 3:00 AIR 15 17 19 20 37 46 79 113 691 1040:40 10.5 EE: SurDO2 AIR/O2 15 17 19 20 37 46 79 55 219 551:00 Exceptional Exposure Depths (200-300 FSW) NOTE: All dives to 200 FSW and deeper on air are Exceptional Exposures.\n200 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group 5 6:40 AIR 0 6:40 0 E AIR/O2 0 6:40 10 5:40 AIR 3 8 17:20 0.5 H AIR/O2 2 4 12:20 15 5:00 AIR 2 3 5 19 34:40 0.5 L AIR/O2 2 3 3 9 23:00 20 4:40 AIR 2 4 6 7 43 67:20 1 O AIR/O2 2 4 6 4 20 41:40 25 4:20 AIR 1 5 6 6 7 85 115:00 1.5 Z AIR/O2 1 5 6 6 4 32 64:20 30 4:20 AIR 4 6 5 7 19 145 191:00 2 Z AIR/O2 4 6 5 7 10 42 84:20 35 4:00 AIR 2 5 5 6 13 28 188 251:40 2.5 AIR/O2 2 5 5 6 13 14 51 106:00 40 4:00 AIR 4 5 5 11 21 28 249 327:40 3.5 AIR/O2 4 5 5 11 21 14 68 143:00 45 3:40 AIR 1 4 5 10 14 25 28 306 397:20 3.5 AIR/O2 1 4 5 10 14 25 14 81 168:40 50 3:40 AIR 2 4 8 10 21 26 28 382 485:20 4.5 AIR/O2 2 4 8 10 21 26 14 97 201:40 210 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group 4 7:00 AIR 0 7:00 0 D AIR/O2 0 7:00 5 6:20 AIR 2 9:00 0.5 E AIR/O2 1 8:00 10 5:40 AIR 2 3 9 20:20 0.5 I AIR/O2 2 2 4 14:40 15 5:00 AIR 1 3 3 6 24 42:40 1 M AIR/O2 1 3 3 3 12 28:00 20 4:40 AIR 1 3 5 6 7 57 84:20 1 O AIR/O2 1 3 5 6 4 23 47:40 25 4:40 AIR 3 6 5 7 8 110 144:20 2 Z AIR/O2 3 6 5 7 4 38 73:40 30 4:20 AIR 2 5 6 6 6 26 163 219:00 2.5 Z AIR/O2 2 5 6 6 6 13 45 93:20 35 4:00 AIR 1 4 5 6 7 18 28 223 296:40 3 AIR/O2 1 4 5 6 7 18 14 60 130:00 40 4:00 AIR 2 5 5 7 11 26 28 278 366:40 3.5 AIR/O2 2 5 5 7 11 26 14 76 161:00 45 4:00 AIR 4 4 6 11 18 26 28 355 456:40 4 AIR/O2 4 4 6 11 18 26 14 91 194:00 50 3:40 AIR 1 4 5 10 12 23 26 36 432 553:20 5 AIR/O2 1 4 5 10 12 23 26 18 105 223:40 220 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group 4 7:20 AIR 0 7:20 0 E AIR/O2 0 7:20 5 6:40 AIR 3 10:20 0.5 E AIR/O2 2 9:20 10 6:00 AIR 3 4 10 23:40 0.5 J AIR/O2 3 2 5 17:00 15 5:20 AIR 3 2 4 7 28 50:00 1 AIR/O2 3 2 4 4 14 33:20 20 5:00 AIR 2 4 6 6 7 70 100:40 1.5 AIR/O2 2 4 6 6 4 26 54:00 25 4:40 AIR 1 5 6 6 6 14 133 176:20 2 AIR/O2 1 5 6 6 6 7 41 82:40 30 4:20 AIR 1 4 5 6 6 10 28 183 248:00 2.5 AIR/O2 1 4 5 6 6 10 14 50 106:20 35 4:20 AIR 3 5 5 5 10 22 28 251 334:00 3.5 AIR/O2 3 5 5 5 10 22 14 68 147:20 40 4:00 AIR 1 4 5 5 9 15 26 28 319 416:40 4 AIR/O2 1 4 5 5 9 15 26 14 84 183:00 250 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group 4 7:40 AIR 4 12:20 0.5 F AIR/O2 2 10:20 5 7:40 AIR 7 15:20 0.5 G AIR/O2 4 12:20 10 6:20 AIR 2 2 4 3 15 33:00 0.5 AIR/O2 2 2 4 2 7 24:20 15 5:40 AIR 2 2 3 4 6 7 53 83:20 AIR/O2 2 2 3 4 6 4 22 49:40 20 5:20 AIR 2 2 4 6 6 6 11 125 168:00 AIR/O2 2 2 4 6 6 6 6 39 82:20 25 5:00 AIR 1 4 4 5 6 6 10 28 189 258:40 AIR/O2 1 4 4 5 6 6 10 14 51 112:00 30 4:40 AIR 1 4 4 4 5 6 9 25 28 267 358:20 AIR/O2 1 4 4 4 5 6 9 25 15 72 160:40 35 4:40 AIR 3 4 4 5 5 10 19 26 28 363 472:20 AIR/O2 3 4 4 5 5 10 19 26 14 93 203:40 300 FSW Bottom Time (min) Time to 1st Stop (M:S) Gas 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Chamber O2 Rep Group 4 9:00 AIR 3 7 19:40 0.5 G AIR/O2 2 4 15:40 5 8:40 AIR 3 3 8 23:20 0.5 I AIR/O2 3 2 4 18:40 10 7:20 AIR 2 3 2 3 4 7 35 64:00 1 N AIR/O2 2 3 2 3 4 4 18 44:20 15 6:20 AIR 1 2 2 3 3 5 6 7 11 125 172:00 2 Z AIR/O2 1 2 2 3 3 5 6 7 6 39 86:20 20 6:00 AIR 2 2 2 4 5 5 5 6 16 28 219 300:40 3 AIR/O2 2 2 2 4 5 5 5 6 16 14 59 137:00 25 5:40 AIR 1 3 4 4 4 5 5 5 18 26 28 324 433:20 4 AIR/O2 1 3 4 4 4 5 5 5 18 26 14 85 195:40 Table 10-1. Equivalent Air Depth Table Purpose: For Decompression Table Selection Only. EAD values are rounded to the next greater standard depth.\nLegend:\nRegular values = Within 1.4 ata normal working limit Values with (max min) = Exceeds 1.4 ata normal working limit. Requires Commanding Officer\u0026rsquo;s authorization and surface-supplied equipment. Repetitive dives not authorized. Maximum allowable exposure time shown in parentheses. Blank cells = Depth exceeds safe limits of NITROX diving Notes:\nDepths not listed are considered beyond the safe limits of NITROX diving. The EAD, 1.4 ata Normal Working Limit Line and Maximum Allowable Exposure Time for dives deeper than the Normal Working Limit Line are calculated assuming the diver rounds the oxygen percentage in the gas mixture using the standard rounding rule discussed in paragraph 10-4.1. The calculations also take into account the allowable ± 0.5 percent error in gas analysis. Depth (fsw) 25% O2 26% O2 27% O2 28% O2 29% O2 30% O2 31% O2 32% O2 33% O2 34% O2 35% O2 36% O2 37% O2 38% O2 39% O2 40% O2 20 20 20 20 20 20 20 20 15 15 15 15 15 10 10 10 10 30 30 30 30 30 30 30 30 25 25 25 20 20 20 20 20 20 40 40 40 40 40 40 40 40 35 30 30 30 30 30 30 25 25 50 50 50 50 50 50 50 50 40 40 40 40 40 35 35 35 35 60 60 60 60 60 60 60 50 50 50 50 50 50 50 50 40 40 70 70 70 70 70 70 60 60 60 60 60 60 60 50 50 50 50 80 80 80 80 80 70 70 70 70 70 70 70 60 60 60 60 60 90 90 90 90 90 80 80 80 80 80 80 70 70 70 (107) 70 (80) 70 (61) 70 (47) 100 100 100 100 90 90 90 90 90 90 80 (113) 80 (82) 80 (61) 80 (46) 80 (36) 80 (29) 70 (23) 110 110 110 110 100 100 100 100 100 (96) 100 (69) 90 (51) 90 (39) 90 (30) 120 120 120 120 110 110 110 (91) 110 (64) 110 (47) 100 (35) 100 (27) 130 130 130 120 120 (95) 120 (65) 120 (47) 120 (35) 110 (26) 140 140 140 (109) 130 (73) 130 (50) 130 (36) 150 150 (89) 150 (59) 140 (41) 160 160 (50) 160 (35) Table 2A-1. No-Decompression Limits and Repetitive Group Designators for Shallow Water Air No-Decompression Dives Depths 30–50 FSW in 1-foot increments. Blank cells = Group not achievable at this depth.\nDepth (fsw) No-Stop Limit (min) A B C D E F G H I J K L M N O Z 30 371 17 27 38 50 62 76 91 107 125 145 167 193 223 260 307 371 31 334 16 26 37 48 60 73 87 102 119 138 158 182 209 242 282 334 32 304 15 25 35 46 58 70 83 98 114 131 150 172 197 226 261 304 33 281 15 24 34 45 56 67 80 94 109 125 143 163 186 212 243 281 34 256 14 23 33 43 54 65 77 90 104 120 137 155 176 200 228 256 35 232 14 23 32 42 52 63 74 87 100 115 131 148 168 190 215 232 36 212 14 22 31 40 50 61 72 84 97 110 125 142 160 180 204 212 37 197 13 21 30 39 49 59 69 81 93 106 120 136 153 172 193 197 38 184 13 21 29 38 47 57 67 78 90 102 116 131 147 164 184 39 173 12 20 28 37 46 55 65 76 87 99 112 126 141 157 173 40 163 12 20 27 36 44 53 63 73 84 95 108 121 135 151 163 41 155 12 19 27 35 43 52 61 71 81 92 104 117 130 145 155 42 147 11 19 26 34 42 50 59 69 79 89 101 113 126 140 147 43 140 11 18 25 33 41 49 58 67 76 87 98 109 122 135 140 44 134 11 18 25 32 40 48 56 65 74 84 95 106 118 130 134 45 125 11 17 24 31 39 46 55 63 72 82 92 102 114 125 46 116 10 17 23 30 38 45 53 61 70 79 89 99 110 116 47 109 10 16 23 30 37 44 52 60 68 77 87 97 107 109 48 102 10 16 22 29 36 43 51 58 67 75 84 94 102 49 97 10 16 22 28 35 42 49 57 65 73 82 91 97 50 92 9 15 21 28 34 41 48 56 63 71 80 89 92 Table 2A-2. Residual Nitrogen Time Table for Repetitive Shallow Water Air Dives This table has two parts:\nSurface Interval Credit — Identical to Table 9-8 Part 1 (see above). Use the same surface interval credit table to determine new repetitive group after surface interval. Residual Nitrogen Times — Minutes of residual nitrogen time for depths 30–50 FSW in 1-foot increments. * = Dives following surface intervals longer than the values shown in Table 9-8 Part 1 are not repetitive dives. Use actual bottom times in the Air Decompression Tables to compute decompression for such dives.\nResidual Nitrogen Times (Minutes) — Depths 30–50 FSW Enter with Dive Depth (rows) and Repetitive Group at End of Surface Interval (columns).\nDepth (fsw) Z O N M L K J I H G F E D C B A 30 372 308 261 224 194 168 146 126 108 92 77 63 51 39 28 18 31 334 282 243 210 183 159 139 120 103 88 74 61 49 38 27 17 32 305 262 227 198 173 151 132 115 99 85 71 59 47 36 26 17 33 282 244 213 187 164 144 126 110 95 81 69 57 46 35 25 16 34 262 229 201 177 156 138 121 105 91 78 66 55 44 34 25 16 35 245 216 191 169 149 132 116 101 88 75 64 53 43 33 24 15 36 231 204 181 161 143 126 111 98 85 73 62 51 41 32 23 15 37 218 194 173 154 137 122 107 94 82 70 60 50 40 31 23 14 38 207 185 165 148 132 117 103 91 79 68 58 48 39 30 22 14 39 197 177 158 142 127 113 100 88 77 66 56 47 38 29 21 14 40 188 169 152 136 122 109 97 85 74 64 55 45 37 29 21 13 41 180 163 146 132 118 105 93 82 72 62 53 44 36 28 20 13 42 173 156 141 127 114 102 91 80 70 61 52 43 35 27 20 13 43 166 150 136 123 110 99 88 78 68 59 50 42 34 26 19 12 44 160 145 131 119 107 96 85 75 66 57 49 41 33 26 19 12 45 154 140 127 115 104 93 83 73 64 56 48 40 32 25 18 12 46 149 136 123 111 101 90 81 71 63 54 46 39 32 25 18 12 47 144 131 119 108 98 88 78 70 61 53 45 38 31 24 18 11 48 139 127 116 105 95 85 76 68 60 52 44 37 30 24 17 11 49 135 123 112 102 92 83 74 66 58 51 43 36 30 23 17 11 50 131 120 109 99 90 81 73 65 57 49 42 35 29 23 17 11 Frequently Asked Questions What is the no-decompression limit at 60 feet for air diving? Per USN Table 9-7, the NDL at 60 FSW on air is 63 minutes (Group A diver). With residual nitrogen from previous dives, use Table 9-8 to calculate adjusted bottom time.\nWhat is the no-decompression limit at 100 feet? Per USN Table 9-7, the NDL at 100 FSW on air is 25 minutes (Group A diver). Decompression stops are required beyond this time.\nHow do I calculate a repetitive dive? Find your post-dive repetitive group from Table 9-7 (depth + bottom time) Use Table 9-8 Part 1 (previous group + surface interval) → new group Use Table 9-8 Part 2 (new group + next dive depth) → Residual Nitrogen Time (RNT) Add RNT to planned bottom time → Equivalent Single Dive Time (ESDT) If ESDT \u0026gt; NDL, use Table 9-9 for decompression schedule Use the interactive tool above to perform steps 1–4 automatically.\nWhat is the source of these tables? SS521-AG-PRO-010, U.S. Navy Diving Manual, Revision 7, 01 December 2016 Published by Direction of Commander, Naval Sea Systems Command (NAVSEA)\nAlways verify against the original publication before operational use.\nRelated Topics USN Helium-Oxygen Dive Tables — HeO2 and mixed gas tables Dive Planning \u0026amp; Risk Assessment Surface-Supplied Diving Systems Emergency Response Frameworks Dive Logs \u0026amp; Operational Records ","permalink":"/melon-wiki/commercial-diving/usn-air-dive-tables/","summary":"\u003ch1 id=\"us-navy-diving-manual--revision-7-air-dive-tables\"\u003eU.S. Navy Diving Manual — Revision 7 Air Dive Tables\u003c/h1\u003e\n\u003cp\u003e\u003cstrong\u003eSource:\u003c/strong\u003e SS521-AG-PRO-010, U.S. Navy Diving Manual, Revision 7, 01 December 2016\n\u003cstrong\u003eNAVSEA Reference:\u003c/strong\u003e Published by Direction of Commander, Naval Sea Systems Command\u003c/p\u003e\n\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eCRITICAL WARNING:\u003c/strong\u003e These tables are transcribed from the official USN Diving Manual Revision 7. \u003cstrong\u003eThey must be verified against the original publication before operational use.\u003c/strong\u003e Transcription errors, however unlikely, could be fatal. Always cross-reference with the official NAVSEA publication.\u003c/p\u003e","title":"USN Air Dive Tables — U.S. Navy Diving Manual Rev 7"},{"content":"USN Dive Tables CRITICAL WARNING: These tables are transcribed from the official U.S. Navy Diving Manual Revision 7 (SS521-AG-PRO-010, 01 December 2016). They must be verified against the original NAVSEA publication before operational use. Transcription errors, however unlikely, could be fatal. Always cross-reference with the official publication.\nThis section provides the complete U.S. Navy Diving Manual Revision 7 decompression tables for operational reference. These tables are the authoritative standard for U.S. Navy diving operations and are widely used in commercial diving operations worldwide.\nWhy This Exists The U.S. Navy dive tables are the foundation of decompression planning for air and mixed-gas diving operations. They provide:\nNo-decompression limits — Maximum bottom times at various depths without required decompression stops Decompression schedules — Required stops, times, and gas switches for decompression dives Repetitive dive procedures — Surface interval credits and residual nitrogen/helium times Altitude considerations — Procedures for diving at altitude or ascending to altitude after diving Mixed gas procedures — Helium-oxygen (HeO2) decompression tables for deeper operations Operational reality: These tables are used by dive supervisors, commercial divers, and operational personnel worldwide. They must be used correctly and verified against the original publication.\nWho This Is For Dive supervisors planning and overseeing diving operations Commercial divers executing dives requiring decompression Safety officers reviewing dive plans and procedures Training personnel teaching decompression procedures Operational planners developing dive procedures and standards Critical Safety Requirements Before using these tables operationally:\nVerify against original publication — Cross-reference all values with the official NAVSEA publication (SS521-AG-PRO-010) Proper training required — Users must be trained in decompression table procedures Medical clearance — Divers must be medically cleared for diving operations Equipment verification — All diving equipment must be verified and functional Supervisor oversight — All decompression dives require qualified supervisor oversight What can go wrong: Incorrect table use, transcription errors, missing updates, improper application. Each failure mode can result in decompression sickness, injury, or death.\nTable Categories USN Air Dive Tables Complete air decompression tables including an interactive NDL lookup tool:\nTable 9-5 — Repetitive Groups Associated with Initial Ascent to Altitude Table 9-6 — Required Surface Interval Before Ascent to Altitude After Diving Table 9-7 — No-Decompression Limits and Repetitive Group Designators (10–190 FSW) Table 9-8 — Residual Nitrogen Time Table for Repetitive Air Dives Table 9-9 — Air Decompression Table (descent 75 FPM, ascent 30 FPM) The air tables page includes an interactive lookup tool for Tables 9-7 and 9-8 — enter depth and bottom time to instantly determine NDL status, repetitive group, and residual nitrogen time for repetitive dives.\nUSN Helium-Oxygen Dive Tables Complete helium-oxygen (HeO2) decompression tables including:\nTable 12-4 — Surface-Supplied HeO2 Decompression Table (60–380+ FSW) Descent rate: 75 FPM | Ascent rate: 30 FPM Mandatory gas switches: HeO2 bottom mix → 50% O2 at 40 FSW → 100% O2 at 30 and 20 FSW MK 16 MOD 1 UBA tables — Closed-circuit rebreather procedures for various oxygen partial pressures Mixed gas procedures — Gas switching procedures and chamber oxygen requirements Source Information Official Source: SS521-AG-PRO-010, U.S. Navy Diving Manual, Revision 7, 01 December 2016 Publisher: Naval Sea Systems Command (NAVSEA) Publication Authority: Published by Direction of Commander, Naval Sea Systems Command\nOperational Use Before operational use:\nObtain official publication — Secure the official NAVSEA publication Verify all values — Cross-check all table values against the official publication Training verification — Ensure all personnel are properly trained Medical clearance — Verify all divers are medically cleared Equipment check — Verify all equipment is functional and calibrated Supervisor approval — Obtain qualified supervisor approval for all dives Responsibility: The dive supervisor is responsible for ensuring correct table use. Incorrect application can result in serious injury or death.\nFrequently Asked Questions What are the U.S. Navy dive tables used for? The USN dive tables are the primary reference for decompression planning in air and mixed-gas diving. They determine the maximum no-decompression bottom time at any depth, the repetitive group accumulated after surfacing, the required surface interval before a second dive, the residual nitrogen time to add to a repetitive dive, and the full decompression schedule (stops, times, gas) when decompression is required.\nWhat edition is current? Revision 7 (SS521-AG-PRO-010, 01 December 2016) is the current edition. Always confirm you are using Revision 7 and obtain the official NAVSEA publication before operational use.\nWhere is the interactive lookup tool? The USN Air Dive Tables page includes a JavaScript-powered NDL lookup tool for Tables 9-7 and 9-8. Enter depth and bottom time for instant NDL and repetitive group lookup, and enter your surface interval for repetitive dive RNT calculations.\nRelated Topics Dive Planning \u0026amp; Risk Assessment Surface-Supplied Diving Systems Emergency Response Frameworks Dive Logs \u0026amp; Operational Records ","permalink":"/melon-wiki/commercial-diving/usn-dive-tables/","summary":"\u003ch1 id=\"usn-dive-tables\"\u003eUSN Dive Tables\u003c/h1\u003e\n\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eCRITICAL WARNING:\u003c/strong\u003e These tables are transcribed from the official U.S. Navy Diving Manual Revision 7 (SS521-AG-PRO-010, 01 December 2016). \u003cstrong\u003eThey must be verified against the original NAVSEA publication before operational use.\u003c/strong\u003e Transcription errors, however unlikely, could be fatal. Always cross-reference with the official publication.\u003c/p\u003e\u003c/blockquote\u003e\n\u003cp\u003eThis section provides the complete U.S. Navy Diving Manual Revision 7 decompression tables for operational reference. These tables are the authoritative standard for U.S. Navy diving operations and are widely used in commercial diving operations worldwide.\u003c/p\u003e","title":"USN Dive Tables — U.S. Navy Diving Manual Revision 7"},{"content":"U.S. Navy Diving Manual — Revision 7 HeO2 and Mixed Gas Dive Tables Source: SS521-AG-PRO-010, U.S. Navy Diving Manual, Revision 7, 01 December 2016 NAVSEA Reference: Published by Direction of Commander, Naval Sea Systems Command\nCRITICAL WARNING: These tables are transcribed from the official USN Diving Manual Revision 7. They must be verified against the original publication before operational use. Transcription errors, however unlikely, could be fatal. Always cross-reference with the official NAVSEA publication.\nDownload Tables as PDF Opens print dialog — choose \"Save as PDF\" to download About These Tables These tables apply to helium-oxygen (HeO2) and mixed gas diving using surface-supplied equipment (SSDS) and the MK 16 MOD 1 closed-circuit UBA. HeO2 is the standard breathing gas for deep commercial and naval diving operations where nitrogen narcosis and extended air decompression would be limiting factors.\nKey differences from air tables:\nNo nitrogen narcosis at depth (helium is narcosis-free) Faster uptake and elimination kinetics than nitrogen Gas switches during decompression (HeO2 → 50% O2 → 100% O2) dramatically shorten decompression time Chamber oxygen periods required post-dive Commanding Officer authorization required for exceptional exposure bottom times Table 12-4. Surface-Supplied Helium-Oxygen Decompression Table (DESCENT RATE 75 FPM — ASCENT RATE 30 FPM)\nGas Switches:\nBottom Mix (HeO2): All stops at 50 FSW and deeper 50% O2: Stop at 40 FSW 100% O2: Stops at 30 and 20 FSW Notes:\nStop times (min) include travel time, except first HeO2 stop and first O2 stop \u0026ldquo;Chamber O2 Periods\u0026rdquo; indicates required post-dive chamber oxygen breathing periods (each period = 30 minutes) Bottom times listed after \u0026ldquo;Exceptional Exposure\u0026rdquo; line require Commanding Officer\u0026rsquo;s authorization 60 FSW Max O2 = 40.0% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 40 ft 30 ft 20 ft Chamber O2 Periods 10 2:00 0 0 20 2:00 0 0 30 2:00 0 0 40 2:00 0 0 60 0:40 10 11 16 1 80 0:40 10 13 22 2 100 0:40 10 16 27 2 120 0:40 10 17 28 2 70 FSW Max O2 = 40.0% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 40 ft 30 ft 20 ft Chamber O2 Periods 10 2:20 0 0 20 2:20 0 0 30 2:20 0 0 40 1:00 10 10 16 1 60 1:00 10 14 24 2 80 1:00 10 18 30 2 100 1:00 10 19 34 2 120 1:00 10 21 37 2 80 FSW Max O2 = 38.0% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 40 ft 30 ft 20 ft Chamber O2 Periods 10 2:40 0 0 20 2:40 0 0 25 2:40 0 0 30 1:20 10 11 16 1 40 1:20 10 13 21 2 60 1:20 10 18 32 2 80 1:20 10 21 38 2 100 1:20 10 24 42 3 120 1:20 10 25 45 3 90 FSW Max O2 = 34.9% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods 10 3:00 0 0 20 3:00 0 0 25 1:40 10 10 15 1 30 1:40 10 12 19 2 40 1:40 10 15 25 2 60 1:40 10 20 37 2 80 1:40 10 23 43 3 100 1:40 10 27 50 3 120 1:40 10 10 29 54 3 100 FSW Max O2 = 40.0% | Min O2 = 16.0%\nBottom Time (min) Time to 1st Stop (M:S) 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods 10 3:20 0 0 20 1:40 10 10 14 1 25 1:40 10 11 17 1 30 1:40 10 13 22 2 40 1:40 10 17 29 2 60 1:40 10 10 22 41 3 80 1:40 10 10 27 50 3 100 1:40 10 10 30 56 4 120 1:40 10 10 32 60 4 110 FSW Max O2 = 30.0% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 2:20 10 8 11 1 Normal 20 2:20 10 12 20 1 Normal 30 2:20 10 17 28 2 Normal 40 2:20 10 20 36 2 Normal 60 2:20 10 27 49 3 Normal 80 2:20 10 31 58 3 Normal 100 2:20 10 33 62 4 Normal 120 2:20 10 35 64 4 EE 120 FSW Max O2 = 28.0% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 2:40 10 9 13 1 Normal 20 2:40 10 14 23 2 Normal 30 2:40 10 19 33 2 Normal 40 2:40 10 23 42 3 Normal 60 2:40 10 30 55 3 Normal 80 2:40 10 34 63 4 Normal 100 2:40 10 36 66 4 Normal 120 2:20 10 10 35 65 4 EE 130 FSW Max O2 = 26.3% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 2:40 10 10 6 8 1 Normal 20 2:40 10 10 12 19 1 Normal 30 2:40 10 10 18 30 2 Normal 40 2:20 7 10 10 22 40 3 Normal 60 2:20 7 10 10 29 52 3 Normal 80 2:20 7 10 10 33 60 3 Normal 100 2:20 7 10 10 35 64 4 EE 120 2:20 7 11 11 35 66 4 EE 140 FSW Max O2 = 24.8% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 3:00 10 10 6 8 1 Normal 20 3:00 10 10 12 19 1 Normal 30 3:00 10 10 18 30 2 Normal 40 2:40 7 10 10 22 40 2 Normal 60 2:40 7 10 10 29 52 3 Normal 80 2:40 7 10 10 33 60 3 Normal 100 2:40 7 10 10 35 64 4 EE 120 2:40 7 11 11 35 66 4 EE 150 FSW Max O2 = 23.4% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 3:20 10 10 7 8 1 Normal 20 3:00 7 10 10 14 22 2 Normal 30 3:00 7 10 10 19 34 2 Normal 40 3:00 7 10 10 24 44 3 Normal 60 3:00 7 10 10 31 56 3 Normal 80 3:00 7 10 10 35 64 4 Normal 100 3:00 7 13 13 36 66 4 EE 120 3:00 9 16 16 36 66 5 EE 160 FSW Max O2 = 22.2% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 3:20 7 10 10 8 10 1 Normal 20 3:20 7 10 10 15 24 2 Normal 30 3:20 7 10 10 21 37 2 Normal 40 3:20 7 10 10 26 47 3 Normal 60 3:00 7 6 10 10 30 56 3 Normal 80 3:00 7 9 10 10 35 66 4 EE 100 3:00 7 13 14 14 35 66 5 EE 120 3:00 7 17 17 17 36 66 5 EE 170 FSW Max O2 = 21.1% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 3:20 7 0 10 10 8 12 1 Normal 20 3:20 7 0 10 10 16 28 2 Normal 30 3:20 7 1 10 10 23 42 3 Normal 40 3:20 7 4 10 10 28 52 3 Normal 60 3:20 7 10 10 10 33 62 4 Normal 80 3:20 9 14 14 14 35 66 4 EE 100 3:00 7 5 18 18 18 36 66 5 EE 120 3:00 7 9 21 21 21 36 66 5 EE 180 FSW Max O2 = 20.1% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 3:40 7 0 10 10 9 14 1 Normal 20 3:40 7 0 10 10 17 30 2 Normal 30 3:40 7 4 10 10 25 45 3 Normal 40 3:20 7 0 8 10 10 30 54 3 Normal 60 3:20 7 5 11 11 11 35 64 4 Normal 80 3:20 7 9 15 15 15 36 66 4 EE 100 3:20 7 13 19 19 19 36 66 5 EE 120 3:20 7 17 23 23 23 36 66 6 EE 190 FSW Max O2 = 19.2% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 4:00 7 0 10 10 10 15 1 Normal 20 3:40 7 0 2 10 10 19 34 2 Normal 30 3:40 7 0 7 10 10 26 46 3 Normal 40 3:40 7 4 9 10 10 31 56 3 Normal 60 3:40 7 9 13 13 13 34 62 4 EE 80 3:20 7 3 13 18 18 18 36 66 5 EE 100 3:20 7 6 16 21 21 21 36 66 6 EE 120 3:20 7 8 20 23 23 23 36 66 7 EE 200 FSW Max O2 = 18.4% | Min O2 = 14.0%\nBottom Time (min) Time to 1st Stop (M:S) 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 4:00 7 0 0 10 10 11 17 1 Normal 20 4:00 7 0 4 10 10 20 36 2 Normal 30 3:40 7 0 3 7 10 10 27 50 3 Normal 40 3:40 7 0 7 10 10 10 31 58 3 Normal 60 3:40 7 4 10 14 14 14 35 66 4 EE 80 3:40 7 8 14 18 18 18 36 66 5 EE 100 3:40 7 12 17 23 23 23 36 66 6 EE 120 3:40 8 15 21 23 23 23 36 66 7 EE 210 FSW Max O2 = 17.7% | Min O2 = 10.0%\nBottom Time (min) Time to 1st Stop (M:S) 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 4:20 7 0 0 10 10 12 19 1 Normal 20 4:00 7 0 1 6 10 10 22 38 2 Normal 30 4:00 7 0 6 7 10 10 29 53 3 Normal 40 4:00 7 3 9 10 10 10 33 60 3 Normal 60 3:40 7 0 9 11 17 17 17 35 66 5 EE 80 3:40 7 3 11 15 20 20 20 36 66 6 EE 100 3:40 7 6 14 19 23 23 23 36 66 7 EE 120 3:40 7 8 18 23 23 23 23 36 66 7 EE 220 FSW Max O2 = 17.0% | Min O2 = 10.0%\nBottom Time (min) Time to 1st Stop (M:S) 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 4:40 7 0 2 10 10 13 20 1 Normal 20 4:20 7 0 3 7 10 10 23 41 3 Normal 30 4:20 7 2 6 9 10 10 30 54 3 Normal 40 4:00 7 0 6 9 11 11 11 34 62 4 Normal 60 4:00 7 4 9 12 18 18 18 36 66 5 EE 80 4:00 7 8 12 17 21 21 21 36 66 6 EE 100 4:00 7 12 15 20 23 23 23 36 66 7 EE 120 4:00 8 14 19 23 23 23 23 36 66 8 EE 230 FSW Max O2 = 16.3% | Min O2 = 10.0%\nBottom Time (min) Time to 1st Stop (M:S) 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 4:40 7 0 0 3 10 10 14 22 2 Normal 20 4:20 7 0 0 3 4 7 10 24 44 3 Normal 30 4:20 7 0 0 5 7 10 10 31 57 3 Normal 40 4:00 7 0 3 7 9 13 13 13 34 64 4 Normal 60 4:00 7 0 8 10 14 18 18 18 36 66 6 EE 80 4:00 7 3 10 14 18 23 23 23 36 66 7 EE 100 4:00 7 6 12 17 23 23 23 23 36 66 8 EE 120 4:00 7 7 16 19 23 23 23 23 36 66 8 EE 240 FSW Max O2 = 15.7% | Min O2 = 10.0%\nBottom Time (min) Time to 1st Stop (M:S) 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 4:40 7 0 0 3 4 10 14 24 2 Normal 20 4:40 7 0 0 3 5 7 10 25 46 3 Normal 30 4:20 7 0 0 3 6 7 10 10 32 58 3 Normal 40 4:20 7 0 5 8 9 14 14 14 35 64 4 Normal 60 4:20 7 4 8 11 14 19 19 19 36 66 6 EE 80 4:20 7 7 11 16 18 23 23 23 36 66 7 EE 100 4:20 7 10 14 19 23 23 23 23 36 66 8 EE 120 4:00 7 3 12 17 19 23 23 23 23 36 66 8 250 FSW Max O2 = 15.2% | Min O2 = 10.0%\nBottom Time (min) Time to 1st Stop (M:S) 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 5:00 7 0 0 3 4 10 10 15 25 2 Normal 20 4:40 7 0 0 0 3 6 7 10 26 47 3 Normal 30 4:40 7 0 0 0 4 6 8 10 10 32 60 4 Normal 40 4:40 7 0 2 5 9 9 14 14 14 35 64 4 Normal 60 4:20 7 0 7 9 12 16 21 21 21 36 66 6 EE 80 4:20 7 3 9 13 15 21 23 23 23 36 66 7 EE 100 4:20 7 6 11 14 19 23 23 23 23 36 66 8 EE 120 4:20 7 8 13 19 20 23 23 23 23 36 66 8 EE 260 FSW Max O2 = 14.6% | Min O2 = 10.0%\nBottom Time (min) Time to 1st Stop (M:S) 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 5:00 7 0 0 0 4 4 10 16 27 2 Normal 20 5:00 7 0 0 2 3 4 6 7 27 50 3 Normal 30 4:40 7 0 0 2 5 6 9 10 10 33 62 4 Normal 40 4:40 7 0 3 8 9 10 15 15 15 35 64 5 Normal 60 4:40 7 3 7 10 14 16 21 21 21 36 66 6 EE 80 4:40 7 6 10 13 17 23 23 23 23 36 66 7 EE 100 4:20 7 2 9 13 16 20 23 23 23 23 36 66 8 120 4:20 7 4 11 14 19 20 23 23 23 23 36 66 8 270 FSW Max O2 = 14.2% | Min O2 = 10.0%\nBottom Time (min) Time to 1st Stop (M:S) 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 5:20 7 0 0 0 3 3 4 18 28 2 Normal 20 5:00 7 0 0 0 0 3 6 6 8 17 29 2 Normal 30 5:00 7 0 0 2 5 5 9 13 13 34 62 4 Normal 40 4:40 7 0 2 5 8 8 12 16 16 16 35 66 5 EE 60 4:40 7 0 6 8 10 14 19 23 23 23 36 66 6 EE 80 4:40 7 3 8 11 14 17 23 23 23 23 36 66 7 EE 100 4:40 7 5 11 13 16 20 23 23 23 23 36 66 8 EE 120 4:40 7 8 12 16 19 20 23 23 23 23 36 66 8 EE 280 FSW Max O2 = 13.7% | Min O2 = 10.0%\nBottom Time (min) Time to 1st Stop (M:S) 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 5:40 7 0 0 0 3 3 4 18 31 2 Normal 20 5:20 7 0 0 0 0 4 6 7 7 30 54 2 Normal 30 5:00 7 0 1 5 5 9 9 12 12 12 35 64 4 Normal 40 5:00 7 0 4 6 8 9 12 17 17 17 35 66 5 EE 60 5:00 7 4 6 8 12 15 18 23 23 23 36 66 7 EE 80 4:40 7 0 7 9 11 15 17 23 23 23 23 36 66 8 100 4:40 7 2 9 11 15 17 20 23 23 23 23 36 66 8 120 4:40 7 4 11 13 16 19 20 23 23 23 23 36 66 8 290 FSW Max O2 = 13.3% | Min O2 = 10.0%\nBottom Time (min) Time to 1st Stop (M:S) 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods Exposure 10 5:40 7 0 0 0 4 3 4 19 33 2 Normal 20 5:20 7 0 0 0 2 0 6 6 9 30 56 2 Normal 30 5:20 7 0 0 2 5 5 9 9 14 14 34 63 5 Normal 40 5:20 7 0 5 7 8 11 13 17 17 17 35 66 5 EE 60 5:00 7 0 6 7 9 12 15 20 23 23 23 36 66 7 EE 80 5:00 7 2 8 10 12 16 19 23 23 23 23 36 66 8 EE 100 5:00 7 5 10 12 15 19 20 23 23 23 23 36 66 8 EE 120 5:00 7 8 11 16 17 19 20 23 23 23 23 36 66 8 EE 300 FSW Max O2 = 12.9% | Min O2 = 10.0%\nAll bottom times are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods 10 6:00 7 0 0 0 4 3 4 10 10 19 33 2 20 5:40 7 0 0 2 6 6 6 9 10 10 30 56 3 30 5:40 7 0 2 5 5 9 9 14 14 14 34 63 5 40 5:40 7 0 5 7 8 11 13 17 17 17 35 66 6 60 5:20 7 0 6 7 9 12 15 20 23 23 23 36 66 7 80 5:20 7 2 8 10 12 16 19 23 23 23 23 36 66 8 100 5:20 7 5 10 12 15 19 20 23 23 23 23 36 66 8 120 5:20 7 8 11 16 17 19 20 23 23 23 23 36 66 8 310 FSW Max O2 = 12.5% | Min O2 = 10.0%\nAll bottom times are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 150 ft 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods 10 6:00 7 0 0 0 3 3 3 7 10 10 21 36 2 20 5:40 7 0 0 2 4 5 6 7 10 10 10 31 57 4 30 5:40 7 0 2 4 5 7 8 11 15 15 15 35 66 5 40 5:20 7 0 1 4 6 7 8 12 15 19 19 19 36 66 7 60 5:20 7 0 5 6 9 11 13 17 20 23 23 23 36 66 8 80 5:20 7 3 7 9 11 13 17 20 23 23 23 23 36 66 8 100 5:20 7 5 9 11 13 17 19 20 23 23 23 23 36 66 8 120 5:20 7 7 12 13 16 17 19 20 23 23 23 23 36 66 8 320 FSW Max O2 = 12.2% | Min O2 = 10.0%\nAll bottom times are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 160 ft 150 ft 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods 10 6:20 7 0 0 0 4 3 3 7 10 10 21 38 2 20 6:00 7 0 0 3 5 5 6 8 10 10 10 32 59 4 30 5:40 7 0 0 4 4 6 7 9 11 17 17 17 35 66 5 40 5:40 7 0 4 4 6 7 9 12 16 20 20 20 36 66 6 60 5:20 7 0 2 6 8 9 11 14 17 23 23 23 23 36 66 8 80 5:20 7 0 6 8 8 13 14 19 20 23 23 23 23 36 66 8 100 5:20 7 2 7 10 13 16 17 19 20 23 23 23 23 36 66 8 120 5:20 7 4 9 12 13 16 17 19 20 23 23 23 23 36 66 8 330 FSW Max O2 = 11.8% | Min O2 = 10.0%\nAll bottom times are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 170 ft 160 ft 150 ft 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods 10 6:20 7 0 0 0 2 3 3 4 7 10 10 22 40 2 20 6:00 7 0 0 2 3 4 6 5 10 10 10 10 33 60 4 30 6:00 7 0 1 4 5 6 8 8 13 17 17 17 35 66 6 40 5:40 7 0 1 4 5 7 7 10 12 17 22 22 22 36 66 7 60 5:40 7 0 5 6 8 9 11 15 20 23 23 23 23 36 66 8 80 5:40 7 2 7 8 10 13 15 19 20 23 23 23 23 36 66 8 100 5:40 7 5 9 9 13 16 17 19 20 23 23 23 23 36 66 8 120 5:20 7 1 7 10 13 15 16 17 19 20 23 23 23 23 36 66 8 340 FSW Max O2 = 11.5% | Min O2 = 10.0%\nAll bottom times are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 170 ft 160 ft 150 ft 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods 10 6:40 7 0 0 0 3 3 3 4 7 10 10 23 41 3 20 6:20 7 0 0 2 4 5 7 8 9 10 10 10 33 60 5 30 6:00 7 0 0 3 5 5 6 8 9 13 18 18 18 35 66 6 40 6:00 7 0 2 4 6 7 8 10 13 16 22 22 22 36 66 7 60 5:40 7 0 3 5 6 9 10 13 16 18 21 23 23 23 36 66 8 80 5:40 7 0 7 7 8 11 13 15 19 20 23 23 23 23 36 66 8 100 5:40 7 2 8 8 12 13 16 17 19 20 23 23 23 23 36 66 8 120 5:40 7 4 9 11 13 15 16 17 19 20 23 23 23 23 36 66 8 350 FSW Max O2 = 11.2% | Min O2 = 10.0%\nAll bottom times are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 180 ft 170 ft 160 ft 150 ft 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods 10 6:40 7 0 0 0 2 2 3 3 5 7 10 10 24 43 3 20 6:20 7 0 0 0 4 4 5 5 7 9 13 13 13 33 63 5 30 6:20 7 0 1 4 4 5 7 8 11 13 18 18 18 36 66 6 40 6:00 7 0 1 3 5 6 7 8 11 14 17 23 23 23 36 66 7 60 6:00 7 0 5 5 8 8 11 12 16 19 23 23 23 23 36 66 8 80 6:00 7 2 7 7 10 11 13 17 19 20 23 23 23 23 36 66 8 100 5:40 7 0 6 8 9 11 15 16 17 19 20 23 23 23 23 36 66 8 120 5:40 7 1 7 9 12 14 15 16 17 19 20 23 23 23 23 36 66 8 360 FSW Max O2 = 10.9% | Min O2 = 10.0%\nAll bottom times are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 180 ft 170 ft 160 ft 150 ft 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods 10 7:00 7 0 0 0 2 2 3 3 7 7 10 10 25 44 3 20 6:40 7 0 0 2 3 4 5 5 8 10 13 13 13 34 63 5 30 6:20 7 0 0 3 3 5 6 7 8 11 13 19 19 19 36 66 7 40 6:20 7 0 2 4 5 7 7 9 10 14 20 23 23 23 36 66 8 60 6:20 7 2 5 6 7 9 11 14 16 19 23 23 23 23 36 66 8 80 6:00 7 0 6 6 8 11 12 14 16 19 20 23 23 23 23 36 66 100 6:00 7 2 7 8 11 13 13 16 17 19 20 23 23 23 23 36 66 120 6:00 7 4 8 10 12 14 15 16 17 19 20 23 23 23 23 36 66 370 FSW Max O2 = 10.6% | Min O2 = 10.0%\nAll bottom times are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 190 ft 180 ft 170 ft 160 ft 150 ft 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods 10 7:00 7 0 0 0 0 3 3 3 3 7 7 10 10 25 46 3 20 6:40 7 0 0 0 3 4 4 5 5 8 10 13 13 13 34 63 5 30 6:20 7 0 0 2 3 4 4 7 7 8 11 16 19 19 19 36 66 7 40 6:20 7 0 0 4 4 5 6 8 10 11 14 20 23 23 23 36 66 8 60 6:20 7 0 4 5 7 8 9 11 13 17 20 23 23 23 23 36 66 8 80 6:00 7 0 3 6 7 9 10 12 15 17 19 20 23 23 23 23 36 66 100 6:00 7 0 6 7 9 10 14 15 16 17 19 20 23 23 23 23 36 66 120 6:00 7 1 7 9 11 13 14 15 16 17 19 20 23 23 23 23 36 66 380 FSW Max O2 = 10.4% | Min O2 = 10.0%\nAll bottom times are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 190 ft 180 ft 170 ft 160 ft 150 ft 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Chamber O2 Periods 10 7:20 7 0 0 0 0 3 3 3 3 7 7 10 10 25 46 3 20 7:00 7 0 0 0 3 4 4 5 5 8 10 13 13 13 34 63 6 30 6:40 7 0 0 2 3 4 4 7 7 8 11 16 19 19 19 36 66 7 40 6:40 7 0 0 4 4 5 6 8 10 11 14 20 23 23 23 36 66 8 60 6:40 7 0 4 5 7 8 9 11 13 17 20 23 23 23 23 36 66 8 80 6:20 7 0 3 6 7 9 10 12 15 17 19 20 23 23 23 23 36 66 100 6:20 7 0 6 7 9 10 14 15 16 17 19 20 23 23 23 23 36 66 120 6:20 7 1 7 9 11 13 14 15 16 17 19 20 23 23 23 23 36 66 MK 16 MOD 1 Closed-Circuit UBA Tables (1.3 ata ppO2) (DESCENT RATE 60 FPM — ASCENT RATE 30 FPM)\nThe following tables apply to the MK 16 MOD 1 closed-circuit underwater breathing apparatus operating at a constant partial pressure of oxygen of 1.3 ata.\nTable 15-8. No Decompression Limits and Repetitive Group Designators for 1.3 ata ppO2 N2O2 Dives Notes:\n– Diver does not acquire a repetitive group designator during dives to these depths * Highest repetitive group that can be achieved at this depth regardless of bottom time Depths at 160 FSW and deeper are Exceptional Exposure (require CO authorization) Depth (fsw) No-Stop Limit A B C D E F G H I J K L M N O Z 10 Unlimited – – – – – – – – – – – – – – – – 15 Unlimited – – – – – – – – – – – – – – – – 20 Unlimited 153 420 * 25 Unlimited 51 87 133 196 296 557 * 30 Unlimited 31 50 72 98 128 164 210 273 372 629 * 35 Unlimited 22 35 50 66 84 103 126 151 181 217 263 326 425 680 * 40 Unlimited 89 168 318 * 50 Unlimited 27 44 63 84 108 136 169 210 265 344 496 * 60 297 16 25 36 46 58 70 83 97 113 130 149 170 194 222 255 297 70 130 11 18 25 32 39 47 55 64 73 83 93 103 115 127 130 80 70 9 14 19 24 30 36 42 48 54 61 68 70 90 50 7 11 15 20 24 29 33 38 43 48 50 100 39 6 9 13 16 20 24 28 32 36 39 110 32 5 8 11 14 17 20 24 27 30 32 120 27 4 7 9 12 15 18 20 23 26 27 130 23 3 6 8 11 13 16 18 21 23 140 21 3 5 7 9 12 14 16 18 21 150 17 3 5 6 8 10 12 15 17 Exceptional Exposure 160 15 3 4 6 8 9 11 13 15 170 13 4 5 7 9 10 12 13 180 12 3 5 6 8 9 11 12 190 10 4 6 7 9 10 Table 15-9. Residual Nitrogen Timetable for 1.3 ata ppO2 N2O2 Dives This table has two parts:\nSurface Interval Credit Table — Determines new repetitive group after a surface interval Residual Nitrogen Times — Minutes of residual nitrogen time for the repetitive dive Part 1: Surface Interval Credit Table Locate your previous repetitive group designation. Read horizontally to find the column where your surface interval falls. Read down to find your new repetitive group.\n* = Dives following surface intervals longer than this are not repetitive dives. Use actual bottom times in the Tables 15-8 and 15-10 to compute decompression for such dives.\nAll times in h:mm format.\nPrevious Group New Group: Z O N M L K J I H G F E D C B A Not Rep (\u0026gt;) Z 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:50 7:51–8:42 8:43–9:34 9:35–10:27 10:28–11:19 11:20–12:13 12:14–13:30 13:31–15:50 15:50 O 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:50 7:51–8:42 8:43–9:34 9:35–10:27 10:28–11:21 11:22–12:37 12:38–14:58 14:58 N 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:50 7:51–8:42 8:43–9:34 9:35–10:29 10:30–11:45 11:46–14:05 14:05 M 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:50 7:51–8:42 8:43–9:37 9:38–10:53 10:54–13:13 13:13 L 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:50 7:51–8:44 8:45–10:01 10:02–12:21 12:21 K 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–6:58 6:59–7:52 7:53–9:09 9:10–11:29 11:29 J 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:06 6:07–7:00 7:01–8:16 8:17–10:36 10:36 I 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:13 5:14–6:08 6:09–7:24 7:25–9:44 9:44 H 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:21 4:22–5:16 5:17–6:32 6:33–8:52 8:52 G 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:29 3:30–4:23 4:24–5:40 5:41–8:00 8:00 F 0:10–0:52 0:53–1:44 1:45–2:37 2:38–3:31 3:32–4:48 4:49–7:08 7:08 E 0:10–0:52 0:53–1:44 1:45–2:39 2:40–3:55 3:56–6:15 6:15 D 0:10–0:52 0:53–1:47 1:48–3:03 3:04–5:23 5:23 C 0:10–0:55 0:56–2:11 2:12–4:31 4:31 B 0:10–1:16 1:17–3:36 3:36 A 0:10–2:20 2:20 Note: The Surface Interval Credit intervals for 1.3 ata ppO2 N2O2 are identical to those for Air (Table 9-8 Part 1), since both use the same nitrogen offgassing model.\nPart 2: Residual Nitrogen Times (Minutes) Enter with Dive Depth (rows) and Repetitive Group at End of Surface Interval (columns).\n** = Residual Nitrogen Time cannot be determined using this table. See paragraph 9-9.1 subparagraph 8 for guidance. Substitute the ** depths in this table for those in the instructions. – = Repetitive dives to these depths are equivalent to remaining on the surface. Add the bottom time of the dive to the preceding surface interval. Use the Surface Interval Credit Table (SICT) to determine the repetitive group at the end of the dive.\nDepth (fsw) Z O N M L K J I H G F E D C B A 10 – – – – – – – – – – – – – – – – 15 – – – – – – – – – – – – – – – – 20 ** ** ** ** ** ** ** ** ** ** ** ** ** ** 420 153 25 ** ** ** ** ** ** ** ** ** ** 556 296 196 134 88 51 30 ** ** ** ** ** ** 626 372 273 211 165 129 99 73 51 31 35 ** ** 671 423 325 263 218 181 152 126 104 84 67 51 36 22 40 ** ** ** ** ** ** ** ** ** ** ** ** ** 311 166 88 50 ** ** ** ** ** 481 339 262 209 168 135 107 84 63 44 27 60 293 252 220 192 168 148 129 112 97 83 70 58 46 36 26 16 70 153 139 126 114 103 92 82 73 64 56 47 40 32 25 18 12 80 107 98 90 82 75 68 61 54 48 42 36 30 25 19 14 9 90 82 76 70 64 59 54 48 43 38 34 29 25 20 16 12 8 100 67 62 58 53 49 44 40 36 32 28 24 21 17 13 10 7 110 57 53 49 45 41 38 34 31 28 24 21 18 15 12 9 6 120 49 46 42 39 36 33 30 27 24 21 19 16 13 10 8 5 130 43 40 38 35 32 29 27 24 22 19 17 14 12 9 7 5 140 39 36 34 31 29 26 24 22 19 17 15 13 11 8 6 4 150 35 33 31 28 26 24 22 20 18 16 14 12 10 8 6 4 160 32 30 28 26 24 22 20 18 16 14 13 11 9 7 5 4 170 30 28 26 24 22 20 19 17 15 13 12 10 8 7 5 3 180 27 26 24 22 21 19 17 16 14 12 11 9 8 6 5 3 190 25 24 22 21 19 18 16 15 13 12 10 9 7 6 4 3 Table 15-10. 1.3 ata ppO2 N2O2 Decompression Tables (DESCENT RATE 60 FPM — ASCENT RATE 30 FPM)\nStop times (min) include travel time, except first stop.\n60 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 ft Total Ascent (M:S) Rep Group 297 2:00 0 2:00 Z 300 1:20 1 3:00 Z 310 1:20 2 4:00 Z 320 1:20 3 5:00 Z 330 1:20 4 6:00 Z Exceptional Exposure 340 1:20 5 7:00 350 1:20 6 8:00 360 1:20 7 9:00 370 1:20 8 10:00 380 1:20 9 11:00 390 1:20 10 12:00 70 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 ft Total Ascent (M:S) Rep Group 130 2:20 0 2:20 O 140 1:40 3 5:20 O 150 1:40 6 8:20 O 160 1:40 8 10:20 Z 170 1:40 10 12:20 Z 180 1:40 12 14:20 Z 190 1:40 14 16:20 Z 200 1:40 16 18:20 Z 210 1:40 19 21:20 Z 220 1:40 22 24:20 Z 230 1:40 24 26:20 Z Exceptional Exposure 240 1:40 26 28:20 250 1:40 29 31:20 260 1:40 31 33:20 270 1:40 33 35:20 280 1:40 35 37:20 290 1:40 37 39:20 300 1:40 38 40:20 310 1:40 40 42:20 320 1:40 42 44:20 340 1:40 47 49:20 350 1:40 49 51:20 80 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 ft Total Ascent (M:S) Rep Group 70 2:40 0 2:40 L 75 2:00 2 4:40 L 80 2:00 4 6:40 M 85 2:00 5 7:40 M 90 2:00 6 8:40 N 95 2:00 7 9:40 N 100 2:00 9 11:40 N 110 2:00 12 14:40 O 120 2:00 16 18:40 O 130 2:00 20 22:40 Z 140 2:00 24 26:40 Z 150 2:00 27 29:40 Z 160 2:00 30 32:40 Z 170 2:00 34 36:40 Z Exceptional Exposure 180 2:00 39 41:40 190 2:00 43 45:40 200 2:00 47 49:40 210 2:00 50 52:40 220 2:00 54 56:40 230 2:00 57 59:40 240 2:00 60 62:40 250 2:00 63 65:40 260 2:00 67 69:40 270 2:00 70 72:40 280 2:00 74 76:40 290 2:00 77 79:40 300 2:00 81 83:40 310 2:00 84 86:40 320 2:00 87 89:40 90 FSW Bottom Time (min) Time to 1st Stop (M:S) 30 ft 20 ft Total Ascent (M:S) Rep Group 50 3:00 0 3:00 K 55 2:20 3 6:00 K 60 2:20 6 9:00 L 65 2:20 8 11:00 L 70 2:20 11 14:00 M 75 2:20 13 16:00 M 80 2:20 14 17:00 N 85 2:20 16 19:00 N 90 2:20 18 21:00 O 95 2:20 21 24:00 O 100 2:20 24 27:00 O 110 2:20 30 33:00 O 120 2:20 35 38:00 Z 130 2:20 40 43:00 Z Exceptional Exposure 140 2:20 45 48:00 150 2:20 51 54:00 160 2:20 57 60:00 170 2:00 1 62 65:40 180 2:00 2 66 70:40 190 2:00 2 71 75:40 100 FSW Bottom Time (min) Time to 1st Stop (M:S) 30 ft 20 ft Total Ascent (M:S) Rep Group 39 3:20 0 3:20 J 40 2:40 1 4:20 J 45 2:40 5 8:20 K 50 2:40 9 12:20 L 55 2:40 12 15:20 L 60 2:40 15 18:20 M 65 2:40 18 21:20 M 70 2:40 21 24:20 N 75 2:40 23 26:20 N 80 2:40 26 29:20 O 85 2:40 30 33:20 O 90 2:40 34 37:20 O 95 2:20 1 37 41:00 O 100 2:20 3 39 45:00 O Exceptional Exposure 110 2:20 6 43 52:00 120 2:20 8 47 58:00 110 FSW Bottom Time (min) Time to 1st Stop (M:S) 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 32 3:40 0 3:40 J 35 3:00 3 6:40 J 40 3:00 8 11:40 K 45 3:00 13 16:40 L 50 3:00 17 20:40 L 55 3:00 21 24:40 M 60 3:00 25 28:40 M 65 3:00 28 31:40 N 70 2:40 1 30 34:20 O 75 2:40 4 32 39:20 O 80 2:40 7 34 44:20 O Exceptional Exposure 85 2:40 9 37 49:20 90 2:40 11 39 53:20 95 2:40 13 42 58:20 100 2:40 15 44 62:20 110 2:20 3 15 49 70:00 120 2:20 6 15 56 80:00 120 FSW Bottom Time (min) Time to 1st Stop (M:S) 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 27 4:00 0 4:00 J 30 3:20 4 8:00 J 35 3:20 10 14:00 K 40 3:20 16 20:00 L 45 3:20 21 25:00 L 50 3:20 26 30:00 M 55 3:20 30 34:00 M 60 3:00 4 31 38:40 N 65 3:00 8 30 41:40 O Exceptional Exposure 70 3:00 12 32 47:40 75 3:00 15 35 53:40 80 2:40 3 15 38 59:20 85 2:40 6 15 41 65:20 90 2:40 8 15 44 70:20 95 2:40 10 15 47 75:20 100 2:40 12 15 51 81:20 130 FSW Bottom Time (min) Time to 1st Stop (M:S) 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 23 4:20 0 4:20 I 25 3:40 2 6:20 J 30 3:40 10 14:20 K 35 3:40 17 21:20 K 40 3:40 23 27:20 L 45 3:40 29 33:20 M 50 3:20 4 30 38:00 N 55 3:20 9 30 43:00 N Exceptional Exposure 60 3:20 14 30 48:00 65 3:00 3 15 33 54:40 70 3:00 7 15 36 61:40 75 3:00 11 15 39 68:40 80 3:00 14 15 42 74:40 140 FSW Bottom Time (min) Time to 1st Stop (M:S) 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 21 4:40 0 4:40 I 25 4:00 7 11:40 J 30 4:00 16 20:40 K 35 4:00 23 27:40 L 40 3:40 2 29 35:20 L 45 3:40 7 30 41:20 M Exceptional Exposure 50 3:20 1 12 30 47:00 55 3:20 4 15 30 53:00 60 3:20 9 15 33 61:00 65 3:20 13 15 36 68:00 70 3:00 3 15 15 40 76:40 75 3:00 7 15 15 44 84:40 80 3:00 10 15 15 50 93:40 150 FSW Bottom Time (min) Time to 1st Stop (M:S) 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 17 5:00 0 5:00 H 20 4:20 3 8:00 I 25 4:20 13 18:00 J 30 4:20 22 27:00 K 35 4:00 3 27 34:40 L 40 4:00 8 30 42:40 M Exceptional Exposure 45 3:40 4 11 30 49:20 50 3:40 7 15 30 56:20 55 3:20 2 11 15 33 65:00 60 3:20 4 14 15 37 74:00 65 3:20 8 15 15 40 82:00 70 3:20 13 15 15 46 93:00 75 3:00 2 15 15 15 52 102:40 80 3:00 6 15 15 15 59 113:40 160 FSW Bottom Time (min) Time to 1st Stop (M:S) 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group Exceptional Exposure 15 5:20 0 5:20 H 20 4:40 7 12:20 J 25 4:20 1 17 23:00 K 30 4:20 3 25 33:00 L 35 4:00 1 8 28 41:40 M 40 4:00 5 10 30 49:40 45 3:40 2 7 14 30 57:20 50 3:40 5 10 15 33 67:20 55 3:40 8 14 15 36 77:20 60 3:20 3 10 15 15 41 88:00 65 3:20 5 13 15 15 48 100:00 70 3:20 8 15 15 15 55 112:00 75 3:20 13 15 15 15 61 123:00 80 3:00 3 15 15 15 15 68 134:40 170 FSW Bottom Time (min) Time to 1st Stop (M:S) 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group Exceptional Exposure 13 5:40 0 5:40 H 15 5:00 2 7:40 I 20 5:00 12 17:40 J 25 4:40 3 20 28:20 K 30 4:20 3 5 26 39:00 L 35 4:00 1 5 8 30 48:40 40 4:00 4 7 12 30 57:40 45 4:00 8 8 15 32 67:40 50 3:40 4 7 13 15 36 79:20 55 3:40 7 9 15 15 41 91:20 60 3:20 2 7 14 15 15 48 105:00 180 FSW Bottom Time (min) Time to 1st Stop (M:S) 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group Exceptional Exposure 12 6:00 0 6:00 H 15 5:20 4 10:00 I 20 5:00 2 14 21:40 K 25 4:40 3 3 23 34:20 L 30 4:20 2 4 7 27 45:00 35 4:00 1 3 8 9 30 55:40 40 4:00 2 7 8 14 30 65:40 45 4:00 6 7 11 15 35 78:40 50 3:40 2 8 8 15 15 40 92:20 55 3:40 5 8 12 15 15 49 108:20 60 3:20 1 7 9 15 15 15 57 123:00 190 FSW Bottom Time (min) Time to 1st Stop (M:S) 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group Exceptional Exposure 10 6:20 0 6:20 G 15 5:40 6 12:20 J 20 5:00 1 4 16 26:40 K 25 4:40 2 4 4 24 39:20 L 30 4:20 2 3 5 8 29 52:00 35 4:20 4 5 8 11 30 63:00 40 4:00 2 5 8 8 15 34 76:40 45 4:00 4 8 7 14 15 39 91:40 50 3:40 1 7 8 11 15 15 47 108:20 55 3:40 4 8 8 15 15 15 56 125:20 60 3:40 7 7 13 15 15 15 65 141:20 MK 16 MOD 1 Closed-Circuit UBA Tables — 1.3 ata ppO2 HeO2 The following tables apply to the MK 16 MOD 1 closed-circuit underwater breathing apparatus operating at a constant partial pressure of oxygen of 1.3 ata, using helium-oxygen (HeO2) as the breathing gas.\nTable 15-11. No Decompression Limits and Repetitive Group Designators for 1.3 ata ppO2 HeO2 Dives Notes:\n– Diver does not acquire a repetitive group designator during dives to these depths * Highest repetitive group that can be achieved at this depth regardless of bottom time Blank cells = Group not achievable at this depth Depth (fsw) No-Stop Limit A B C D E F G H I J K L M N O Z 10 Unlimited – – – – – – – – – – – – – – – – 15 Unlimited – – – – – – – – – – – – – – – – 20 Unlimited 129 269 * 25 Unlimited 45 72 106 146 200 278 425 * 30 332 27 43 60 78 100 124 152 185 227 281 332 35 190 19 30 41 54 67 81 97 114 133 154 178 190 40 Unlimited 122 246 * 50 325 27 43 59 78 99 123 150 183 223 276 325 60 134 15 23 32 41 51 61 71 83 95 108 123 134 70 86 11 16 22 28 34 41 47 54 61 69 77 85 86 80 63 8 12 17 21 26 30 35 40 45 51 56 62 63 90 44 6 10 13 17 20 24 28 32 36 40 44 100 31 5 8 11 14 17 20 23 26 30 31 110 24 4 7 9 12 14 17 20 22 24 120 20 4 6 8 10 13 15 17 19 20 130 17 3 5 7 9 11 13 15 17 140 15 3 4 6 8 10 12 13 15 150 13 3 4 6 7 9 10 12 13 160 12 3 5 6 8 9 11 12 170 11 3 4 6 7 9 10 11 180 10 3 4 5 6 8 9 10 190 9 4 5 6 7 8 9 200 8 4 5 7 8 Table 15-12. Residual Helium Timetable for 1.3 ata ppO2 HeO2 Dives Part 1: Surface Interval Credit Table (Helium) Locate the diver\u0026rsquo;s repetitive group designation from his previous dive in the \u0026ldquo;Previous Group\u0026rdquo; column. Read across to find the interval in which the diver\u0026rsquo;s surface interval lies. The column header shows the new repetitive group designation.\nMinimum surface interval for a repetitive dive is 0:10 (hours:minutes). Surface intervals less than 0:10 are not permitted. Intervals beyond the last value marked with * are not repetitive \u0026ndash; use actual bottom times with Tables 15-11 and 15-13. Previous Group Z O N M L K J I H G F E D C B A Not Rep (\u0026gt;) A 0:10-2:01 2:01 B 0:10-1:10 1:11-3:11 3:11 C 0:10-0:50 0:51-2:00 2:01-4:01 4:01 D 0:10-0:42 0:43-1:32 1:33-2:43 2:44-4:44 4:44 E 0:10-0:42 0:43-1:25 1:26-2:15 2:16-3:25 3:26-5:26 5:26 F 0:10-0:42 0:43-1:25 1:26-2:07 2:08-2:57 2:58-4:08 4:09-6:08 6:08 G 0:10-0:42 0:43-1:25 1:26-2:07 2:08-2:49 2:50-3:39 3:40-4:50 4:51-6:51 6:51 H 0:10-0:42 0:43-1:25 1:26-2:07 2:08-2:49 2:50-3:32 3:33-4:22 4:23-5:32 5:33-7:33 7:33 I 0:10-0:42 0:43-1:25 1:26-2:07 2:08-2:49 2:50-3:32 3:33-4:14 4:15-5:04 5:05-6:15 6:16-8:15 8:15 J 0:10-0:42 0:43-1:25 1:26-2:07 2:08-2:49 2:50-3:32 3:33-4:14 4:15-4:56 4:57-5:46 5:47-6:57 6:58-8:58 8:58 K 0:10-0:42 0:43-1:25 1:26-2:07 2:08-2:49 2:50-3:32 3:33-4:14 4:15-4:56 4:57-5:39 5:40-6:29 6:30-7:39 7:40-9:40 9:40 L 0:10-0:42 0:43-1:25 1:26-2:07 2:08-2:49 2:50-3:32 3:33-4:14 4:15-4:56 4:57-5:39 5:40-6:21 6:22-7:11 7:12-8:22 8:23-10:22 10:22 M 0:10-0:42 0:43-1:25 1:26-2:07 2:08-2:49 2:50-3:32 3:33-4:14 4:15-4:56 4:57-5:39 5:40-6:21 6:22-7:03 7:04-7:53 7:54-9:04 9:05-11:05 11:05 N 0:10-0:42 0:43-1:25 1:26-2:07 2:08-2:49 2:50-3:32 3:33-4:14 4:15-4:56 4:57-5:39 5:40-6:21 6:22-7:03 7:04-7:46 7:47-8:36 8:37-9:46 9:47-11:47 11:47 O 0:10-0:42 0:43-1:25 1:26-2:07 2:08-2:49 2:50-3:32 3:33-4:14 4:15-4:56 4:57-5:39 5:40-6:21 6:22-7:03 7:04-7:46 7:47-8:28 8:29-9:18 9:19-10:29 10:30-12:29 12:29 Z 0:10-0:42 0:43-1:25 1:26-2:07 2:08-2:49 2:50-3:32 3:33-4:14 4:15-4:56 4:57-5:39 5:40-6:21 6:22-7:03 7:04-7:46 7:47-8:28 8:29-9:10 9:11-10:00 10:01-11:11 11:12-13:12 13:12 Note: All surface intervals are in hours:minutes format. The \u0026ldquo;Not Rep (\u0026gt;)\u0026rdquo; column shows the threshold beyond which the dive is no longer considered repetitive.\nPart 2: Residual Helium Times (Minutes) After determining the new repetitive group designation from Part 1, read down the appropriate column to the row matching the repetitive dive depth to find the Residual Helium Time (RHT) in minutes. Add the RHT to the planned bottom time of the repetitive dive to obtain the equivalent single dive time for decompression planning.\nDepth (fsw) Z O N M L K J I H G F E D C B A 10 \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; 15 \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; 20 ** ** ** ** ** ** ** ** ** ** ** ** ** ** 269 129 25 ** ** ** ** ** ** ** ** ** 425 279 201 147 106 73 45 30 + + + + 515 361 281 227 186 152 124 100 79 60 43 28 35 420 338 283 241 207 179 155 133 114 97 82 68 54 42 31 20 40 ** ** ** ** ** ** ** ** ** ** ** ** ** ** 240 120 50 + + + + 474 345 272 220 181 149 122 98 78 59 42 27 60 217 194 173 154 137 122 108 95 83 71 61 51 41 32 24 16 70 122 112 102 93 85 77 69 61 54 47 41 34 28 22 17 11 80 86 80 73 68 62 56 51 46 40 36 31 26 22 17 13 9 90 67 62 57 53 49 44 40 36 32 29 25 21 17 14 10 7 100 55 51 47 44 40 37 33 30 27 24 21 18 15 12 9 6 110 46 43 40 37 34 31 29 26 23 20 18 15 13 10 8 5 120 40 37 35 32 30 27 25 23 20 18 16 13 11 9 7 5 130 35 33 31 29 27 24 22 20 18 16 14 12 10 8 6 4 140 32 30 28 26 24 22 20 18 16 14 13 11 9 7 6 4 150 29 27 25 23 22 20 18 17 15 13 12 10 8 7 5 4 160 26 25 23 21 20 18 17 15 14 12 11 9 8 6 5 3 170 24 23 21 20 18 17 15 14 13 11 10 8 7 6 4 3 180 22 21 20 18 17 16 14 13 12 10 9 8 7 5 4 3 190 21 20 18 17 16 15 13 12 11 10 9 7 6 5 4 3 200 20 18 17 16 15 14 13 11 10 9 8 7 6 5 4 3 Table Notes \u0026ndash; Repetitive dives to these depths are equivalent to remaining on the surface. Add the bottom time of the dive to the preceding surface interval. Use the Surface Interval Credit Table (SICT) to determine the repetitive group at the end of the dive. ** Residual Helium Time cannot be determined using this table. See paragraph 9-9.1 subparagraph 8 for guidance. Substitute the ** depths in this table for those in the instructions. + Read vertically down to the 35 or 60 fsw repetitive dive depth to obtain the RHT. Decompress on the 35 or 60 fsw table. Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (DESCENT RATE 60 FPM — ASCENT RATE 30 FPM)\nStop times (min) include travel time, except first stop.\n30 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 ft Total Ascent (M:S) Rep Group 332 1:00 0 1:00 340 0:20 4 5:00 360 0:20 13 14:00 420 0:20 34 35:00 480 0:20 48 49:00 540 0:20 59 60:00 600 0:20 70 71:00 660 0:20 87 88:00 720 0:20 101 102:00 35 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 ft Total Ascent (M:S) Rep Group 190 1:10 0 1:10 L 200 0:30 12 13:10 L 210 0:30 23 24:10 220 0:30 33 34:10 230 0:30 42 43:10 240 0:30 50 51:10 270 0:30 71 72:10 300 0:30 89 90:10 330 0:30 103 104:10 360 0:30 115 116:10 390 0:30 126 127:10 420 0:30 145 146:10 450 0:30 162 163:10 480 0:30 177 178:10 50 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 ft Total Ascent (M:S) Rep Group 325 1:40 0 1:40 K 330 1:00 1 2:40 K 340 1:00 2 3:40 K 350 1:00 3 4:40 K 360 1:00 5 6:40 K 420 1:00 11 12:40 480 1:00 15 16:40 540 1:00 18 19:40 600 1:00 21 22:40 660 1:00 25 26:40 720 1:00 29 30:40 60 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 ft Total Ascent (M:S) Rep Group 134 2:00 0 2:00 L 140 1:20 3 5:00 L 150 1:20 8 10:00 L 160 1:20 12 14:00 L 170 1:20 16 18:00 L 180 1:20 20 22:00 190 1:20 24 26:00 200 1:20 27 29:00 210 1:20 31 33:00 220 1:20 34 36:00 230 1:20 37 39:00 240 1:20 40 42:00 250 1:20 42 44:00 260 1:20 45 47:00 270 1:20 47 49:00 280 1:20 49 51:00 290 1:20 51 53:00 300 1:20 53 55:00 310 1:20 55 57:00 320 1:20 57 59:00 330 1:20 59 61:00 340 1:20 61 63:00 350 1:20 64 66:00 360 1:20 66 68:00 70 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 ft Total Ascent (M:S) Rep Group 86 2:20 0 2:20 M 90 1:40 3 5:20 M 95 1:40 8 10:20 100 1:40 12 14:20 110 1:40 19 21:20 120 1:40 26 28:20 130 1:40 33 35:20 140 1:40 39 41:20 150 1:40 45 47:20 160 1:40 50 52:20 170 1:40 55 57:20 180 1:40 60 62:20 190 1:40 64 66:20 200 1:40 68 70:20 210 1:40 72 74:20 220 1:40 76 78:20 80 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 ft Total Ascent (M:S) Rep Group 63 2:40 0 2:40 M 65 2:00 2 4:40 M 70 2:00 8 10:40 75 2:00 14 16:40 80 2:00 19 21:40 85 2:00 24 26:40 90 2:00 29 31:40 95 2:00 34 36:40 100 2:00 39 41:40 110 2:00 48 50:40 120 2:00 56 58:40 130 2:00 63 65:40 140 2:00 70 72:40 150 2:00 76 78:40 160 2:00 82 84:40 170 2:00 88 90:40 180 2:00 93 95:40 190 2:00 98 100:40 90 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 ft Total Ascent (M:S) Rep Group 44 3:00 0 3:00 K 45 2:20 1 4:00 K 50 2:20 2 5:00 L 55 2:20 7 10:00 M 60 2:20 15 18:00 65 2:20 22 25:00 70 2:20 29 32:00 75 2:20 35 38:00 80 2:20 41 44:00 85 2:20 47 50:00 90 2:20 53 56:00 95 2:20 58 61:00 100 2:20 63 66:00 110 2:20 73 76:00 120 2:20 82 85:00 130 2:20 90 93:00 140 2:20 97 100:00 150 2:20 105 108:00 160 2:20 112 115:00 100 FSW Bottom Time (min) Time to 1st Stop (M:S) 30 ft 20 ft Total Ascent (M:S) Rep Group 31 3:20 0 3:20 J 35 2:40 2 5:20 K 40 2:40 4 7:20 L 45 2:40 6 9:20 M 50 2:40 16 19:20 55 2:40 24 27:20 60 2:40 33 36:20 65 2:40 41 44:20 70 2:40 48 51:20 75 2:40 55 58:20 80 2:40 62 65:20 85 2:40 68 71:20 90 2:40 74 77:20 95 2:40 80 83:20 100 2:40 85 88:20 110 2:40 96 99:20 120 2:40 105 108:20 130 2:20 1 114 118:00 140 2:20 1 124 128:00 110 FSW Bottom Time (min) Time to 1st Stop (M:S) 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 24 3:40 0 3:40 I 25 3:00 1 4:40 I 30 3:00 4 7:40 J 35 3:00 7 10:40 L 40 3:00 10 13:40 M 45 3:00 21 24:40 50 3:00 31 34:40 55 3:00 40 43:40 60 2:40 1 49 53:20 65 2:40 2 57 62:20 70 2:40 3 64 70:20 75 2:40 4 71 78:20 80 2:40 5 77 85:20 85 2:40 5 84 92:20 90 2:40 6 89 98:20 95 2:40 6 95 104:20 100 2:40 6 101 110:20 110 2:40 7 112 122:20 EXCEPTIONAL EXPOSURE 120 2:40 7 123 133:20 130 2:40 7 136 146:20 140 2:20 1 7 149 160:00 120 FSW Bottom Time (min) Time to 1st Stop (M:S) 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 20 4:00 0 4:00 I 25 3:20 4 8:00 J 30 3:20 8 12:00 K 35 3:20 12 16:00 M 40 3:20 23 27:00 45 3:00 2 34 39:40 50 3:00 4 43 50:40 55 3:00 6 52 61:40 60 3:00 7 60 70:40 65 2:40 2 7 68 80:20 70 2:40 3 7 76 89:20 75 2:40 3 8 83 97:20 80 2:40 4 7 91 105:20 85 2:40 5 7 97 112:20 90 2:40 5 8 103 119:20 95 2:40 6 7 110 126:20 EXCEPTIONAL EXPOSURE 100 2:40 6 7 117 133:20 110 2:40 7 7 131 148:20 120 2:40 7 7 145 162:20 130 FSW Bottom Time (min) Time to 1st Stop (M:S) 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 17 4:20 0 4:20 H 20 3:40 3 7:20 I 25 3:40 8 12:20 K 30 3:40 13 17:20 L 35 3:20 2 21 27:00 L 40 3:20 5 32 41:00 L 45 3:00 1 7 43 54:40 L 50 3:00 3 7 53 66:40 55 3:00 5 7 63 78:40 60 3:00 6 8 71 88:40 65 2:40 1 7 7 81 99:20 70 2:40 2 7 7 89 108:20 75 2:40 3 7 7 97 117:20 80 2:40 3 8 7 104 125:20 85 2:40 4 8 7 111 133:20 EXCEPTIONAL EXPOSURE 90 2:40 5 7 7 119 141:20 95 2:40 5 8 7 127 150:20 100 2:40 6 7 7 136 159:20 110 2:40 6 8 7 152 176:20 120 2:40 7 7 18 159 194:20 140 FSW Bottom Time (min) Time to 1st Stop (M:S) 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 15 4:40 0 4:40 H 20 4:00 7 11:40 J 25 4:00 12 16:40 K 30 3:40 3 16 23:20 M 35 3:40 7 29 40:20 40 3:20 3 7 42 56:00 45 3:20 6 7 53 70:00 50 3:00 1 8 7 64 83:40 55 3:00 3 8 7 74 95:40 60 3:00 5 8 7 84 107:40 65 3:00 7 7 7 93 117:40 70 2:40 1 7 8 7 101 127:20 75 2:40 2 7 8 7 110 137:20 EXCEPTIONAL EXPOSURE 80 2:40 3 7 8 7 118 146:20 85 2:40 4 7 7 8 127 156:20 90 2:40 4 8 7 7 137 166:20 95 2:40 5 7 7 8 146 176:20 100 2:40 5 8 7 8 155 186:20 150 FSW Bottom Time (min) Time to 1st Stop (M:S) 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 13 5:00 0 5:00 H 15 4:20 3 8:00 H 20 4:20 10 15:00 J 25 4:00 2 14 20:40 L 30 4:00 7 24 35:40 L 35 3:40 4 8 37 53:20 L 40 3:20 1 7 8 50 70:00 45 3:20 4 8 7 63 86:00 50 3:20 7 7 8 74 100:00 55 3:00 2 8 7 7 86 113:40 60 3:00 4 8 7 7 96 125:40 65 3:00 6 7 7 8 105 136:40 70 3:00 7 7 8 7 114 146:40 EXCEPTIONAL EXPOSURE 75 2:40 1 8 7 7 8 124 158:20 80 2:40 2 8 7 7 8 135 170:20 85 2:40 3 7 8 7 7 146 181:20 90 2:40 4 7 7 8 9 155 193:20 160 FSW Bottom Time (min) Time to 1st Stop (M:S) 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 12 5:20 0 5:20 H 15 4:40 5 10:20 I 20 4:40 13 18:20 K 25 4:20 6 16 27:00 M 30 4:00 4 8 31 47:40 35 3:40 2 7 8 46 67:20 40 3:40 6 8 7 60 85:20 45 3:20 3 7 7 8 73 102:00 50 3:20 6 7 7 8 85 117:00 55 3:00 1 7 8 7 7 97 130:40 60 3:00 3 7 8 7 8 107 143:40 EXCEPTIONAL EXPOSURE 65 3:00 5 7 8 7 7 118 155:40 70 3:00 6 8 7 7 8 130 169:40 75 3:00 8 7 7 8 7 142 182:40 80 2:40 2 7 7 8 7 7 154 195:20 85 2:40 2 8 7 8 7 16 158 209:20 90 2:40 3 8 7 7 8 25 161 222:20 170 FSW Bottom Time (min) Time to 1st Stop (M:S) 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 11 5:40 0 5:40 H 15 5:00 8 13:40 I 20 4:40 2 15 22:20 K 25 4:20 2 8 22 37:00 L 30 4:00 2 7 7 39 59:40 L 35 4:00 7 7 8 55 81:40 40 3:40 4 8 7 7 70 100:20 45 3:20 1 7 8 7 7 84 118:00 50 3:20 4 7 8 7 8 96 134:00 55 3:20 7 7 7 8 7 108 148:00 EXCEPTIONAL EXPOSURE 60 3:00 2 7 8 7 7 8 120 162:40 65 3:00 4 7 8 7 7 8 134 178:40 70 3:00 5 8 7 8 7 7 148 193:40 75 3:00 7 7 8 7 7 12 157 208:40 80 2:40 1 7 8 7 7 8 22 160 223:20 180 FSW Bottom Time (min) Time to 1st Stop (M:S) 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 10 6:00 0 6:00 H 15 5:20 11 17:00 J 20 5:00 6 14 25:40 L 25 4:40 6 8 29 48:20 L 30 4:20 6 7 8 47 73:00 35 4:00 4 8 7 8 64 95:40 40 3:40 2 8 7 7 8 80 116:20 45 3:40 6 8 7 7 8 94 134:20 50 3:20 3 7 7 8 7 7 108 151:00 EXCEPTIONAL EXPOSURE 55 3:20 5 8 7 8 7 7 121 167:00 60 3:00 1 7 8 7 7 8 7 136 184:40 65 3:00 3 7 8 7 7 8 7 151 201:40 70 3:00 5 7 7 8 7 7 16 158 218:40 190 FSW Bottom Time (min) Time to 1st Stop (M:S) 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 9 6:20 0 6:20 H 10 5:40 2 8:20 H 15 5:40 14 20:20 J 20 4:40 1 1 8 16 31:20 M 25 3:20 1 0 0 0 4 7 7 38 61:00 30 3:00 1 0 0 2 2 7 7 8 57 87:40 35 2:40 1 0 0 2 0 8 7 8 7 75 111:20 40 2:20 1 0 0 0 2 6 8 7 7 8 91 133:00 45 2:20 1 0 0 0 5 7 8 7 7 8 105 151:00 50 2:20 1 0 0 0 8 8 7 8 7 7 120 169:00 EXCEPTIONAL EXPOSURE 55 2:20 1 0 0 4 8 7 7 8 7 7 138 190:00 60 2:20 1 0 0 7 7 8 7 7 8 7 153 208:00 65 2:20 1 0 2 7 7 8 7 7 8 19 159 228:00 70 2:20 1 0 3 8 7 8 7 7 8 31 164 247:00 200 FSW Bottom Time (min) Time to 1st Stop (M:S) 170 ft 160 ft 150 ft 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 8 6:40 0 6:40 G 10 6:00 5 11:40 H 15 5:20 1 1 15 23:00 K 20 3:20 1 0 0 2 0 0 5 7 25 44:00 L 25 2:00 1 0 0 0 2 0 1 0 1 7 7 7 47 75:40 L 30 1:20 1 0 0 2 0 0 0 2 0 1 7 7 8 7 69 106:00 35 1:20 1 0 1 1 0 0 2 0 0 7 7 7 8 7 87 130:00 40 1:00 1 0 1 1 0 0 2 0 0 5 8 7 7 8 7 104 152:40 45 1:00 1 0 1 1 0 0 2 0 2 7 8 7 8 7 7 120 172:40 EXCEPTIONAL EXPOSURE 50 1:00 1 0 1 1 0 1 0 1 6 7 7 8 7 8 7 139 195:40 55 1:00 1 0 1 1 0 1 0 2 8 7 7 8 7 8 8 155 215:40 60 1:00 1 0 1 1 0 1 0 5 7 8 7 7 8 7 22 161 237:40 210 FSW Bottom Time (min) Time to 1st Stop (M:S) 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 5 7:00 0 7:00 10 6:20 5 12:00 15 6:00 7 5 18:40 20 5:00 5 3 2 2 28 45:40 25 4:20 3 3 3 2 3 3 57 79:00 30 4:20 6 3 2 2 6 12 76 112:00 35 3:40 3 3 3 2 3 5 12 12 95 142:20 40 3:20 3 2 3 2 3 5 12 11 12 113 170:00 EXCEPTIONAL EXPOSURE 45 3:20 4 2 3 2 4 11 12 12 11 131 196:00 50 3:20 4 3 2 3 10 11 12 12 11 149 221:00 55 3:00 3 2 3 2 7 11 11 12 11 12 165 242:40 60 3:20 5 3 2 11 12 11 11 12 21 173 265:00 220 FSW Bottom Time (min) Time to 1st Stop (M:S) 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 5 7:20 0 7:20 10 6:40 5 12:20 15 5:40 4 3 2 6 21:20 20 5:00 4 3 2 3 2 37 56:40 25 5:00 7 3 3 2 8 65 93:40 30 4:00 3 3 2 3 3 3 10 12 84 127:40 35 4:20 8 2 3 2 12 12 11 106 161:00 40 4:20 9 3 2 12 11 12 11 126 191:00 EXCEPTIONAL EXPOSURE 45 3:40 6 2 3 2 10 12 11 12 11 144 217:20 50 4:00 8 3 8 11 12 11 11 12 164 244:40 55 4:00 9 4 12 11 12 11 11 18 177 269:40 230 FSW Bottom Time (min) Time to 1st Stop (M:S) 150 ft 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 5 7:40 0 7:40 10 7:00 6 13:40 15 6:00 5 3 2 9 25:40 20 5:00 3 3 2 3 3 2 46 67:40 25 4:40 5 2 3 3 2 3 12 71 106:20 30 4:00 3 3 2 3 2 3 6 12 12 93 143:40 35 4:00 5 3 2 3 2 8 12 12 11 116 178:40 EXCEPTIONAL EXPOSURE 40 3:20 2 3 2 3 2 3 8 12 11 12 11 137 210:00 45 4:00 8 2 3 7 12 11 11 12 11 159 240:40 50 3:20 4 3 2 3 5 11 13 11 11 11 16 174 268:00 55 3:00 2 3 2 4 2 12 11 11 11 11 11 38 172 293:40 240 FSW Bottom Time (min) Time to 1st Stop (M:S) 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 5 8:00 0 8:00 10 7:20 8 16:00 15 6:00 4 3 2 4 15 34:40 20 5:20 5 2 3 2 3 3 54 78:00 25 5:20 9 3 2 2 8 12 80 122:00 30 4:20 5 3 2 2 3 3 11 12 12 103 161:00 35 4:20 7 3 2 3 4 12 11 12 12 127 198:00 EXCEPTIONAL EXPOSURE 40 4:20 8 3 3 4 12 12 11 12 12 150 232:00 45 4:20 10 2 4 12 12 11 12 11 12 173 264:00 50 3:40 6 3 2 3 12 11 11 12 11 11 32 174 292:20 250 FSW Bottom Time (min) Time to 1st Stop (M:S) 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 5 8:20 0 8:20 10 7:40 9 17:20 15 6:20 5 3 3 2 24 44:00 20 5:40 6 3 2 3 3 6 61 90:20 25 5:00 6 3 2 2 3 3 12 12 87 135:40 30 4:20 4 3 3 2 3 2 8 11 12 12 112 177:00 EXCEPTIONAL EXPOSURE 35 4:40 9 2 3 2 10 12 12 11 12 139 217:20 40 4:20 8 3 2 3 11 12 11 11 12 11 164 253:00 45 4:00 7 3 3 2 11 11 12 11 11 12 25 175 287:40 50 3:40 6 2 3 3 9 12 11 11 12 11 11 49 175 319:20 260 FSW Bottom Time (min) Time to 1st Stop (M:S) 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 5 8:40 0 8:40 10 8:00 11 19:40 15 6:20 4 3 3 2 3 31 53:00 20 5:40 5 3 3 2 3 3 10 67 102:20 25 5:20 8 3 2 2 3 7 13 12 96 152:00 30 4:40 6 3 2 3 2 3 12 12 13 11 123 195:20 EXCEPTIONAL EXPOSURE 35 4:40 8 3 3 2 6 12 12 11 12 11 151 236:20 40 4:20 8 3 2 3 7 12 12 11 11 12 14 175 275:00 45 4:00 7 3 2 3 8 12 11 11 11 12 11 42 173 310:40 270 FSW Bottom Time (min) Time to 1st Stop (M:S) 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 5 8:20 5 14:00 10 8:20 13 22:00 15 6:20 3 3 3 2 3 3 39 63:00 20 6:20 9 3 2 3 5 12 75 116:00 25 5:40 9 3 2 3 3 12 11 12 105 166:20 EXCEPTIONAL EXPOSURE 30 5:00 8 3 2 3 2 9 11 12 11 12 134 212:40 35 4:40 8 3 2 3 3 11 12 12 11 11 12 163 256:20 40 4:20 8 3 3 1 5 12 12 11 11 11 12 30 174 298:00 45 4:20 9 3 2 5 12 13 10 11 11 12 11 56 176 336:00 280 FSW Bottom Time (min) Time to 1st Stop (M:S) 150 ft 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 5 8:40 5 14:20 10 8:40 14 23:20 15 7:00 7 3 2 3 3 47 72:40 20 6:20 9 2 3 2 3 9 12 82 129:00 25 5:20 6 3 3 2 3 2 7 12 12 12 114 182:00 EXCEPTIONAL EXPOSURE 30 5:20 10 3 2 3 3 12 12 11 12 12 145 231:00 35 4:40 8 2 3 2 3 8 12 12 11 11 11 13 176 277:20 40 4:40 10 2 3 2 11 12 11 12 12 10 12 45 174 321:20 45 4:40 11 3 3 11 11 12 11 11 11 12 11 72 178 362:20 290 FSW Bottom Time (min) Time to 1st Stop (M:S) 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 5 9:00 5 14:40 10 8:00 4 4 2 6 24:40 15 7:00 6 3 2 3 3 2 55 81:40 20 6:20 8 2 3 2 3 4 12 12 88 141:00 25 5:40 8 3 2 3 3 2 12 12 11 12 122 196:20 EXCEPTIONAL EXPOSURE 30 5:00 7 3 2 3 3 2 9 12 12 11 11 12 156 248:40 35 5:00 10 2 3 2 5 12 11 12 11 11 12 28 176 300:40 40 5:00 12 2 3 7 12 11 12 11 11 11 12 59 177 345:40 45 5:00 13 3 9 11 12 11 11 11 11 11 18 82 180 388:40 300 FSW Bottom Time (min) Time to 1st Stop (M:S) 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 5 9:20 5 15:00 10 8:20 6 3 2 9 29:00 15 7:00 5 3 2 3 2 3 5 61 91:40 20 6:20 7 3 2 3 2 4 6 12 12 96 154:00 25 5:20 5 3 2 3 3 2 3 7 12 11 12 11 132 212:00 EXCEPTIONAL EXPOSURE 30 5:20 9 3 2 3 2 5 12 12 11 11 12 12 169 269:00 35 5:20 12 2 3 2 10 12 11 12 11 11 12 41 176 321:00 40 5:20 14 2 4 12 12 11 11 12 11 11 11 74 180 371:00 310 FSW All schedules at this depth are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 10 8:20 5 2 3 3 14 36:00 15 7:20 6 3 3 2 3 2 9 66 102:00 20 6:20 6 3 2 3 2 3 3 12 11 12 103 167:00 25 6:00 9 3 2 3 3 2 12 11 12 12 11 142 228:40 30 5:40 11 3 2 2 3 10 12 11 11 12 12 17 176 288:20 35 5:40 14 2 3 6 12 11 12 11 11 11 12 55 178 344:20 40 5:40 16 2 10 12 11 12 11 11 11 11 19 83 182 397:20 320 FSW All schedules at this depth are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 140 ft 130 ft 120 ft 110 ft 100 ft 90 ft 80 ft 70 ft 60 ft 50 ft 40 ft 30 ft 20 ft Total Ascent (M:S) Rep Group 10 8:20 4 2 3 3 2 21 44:00 15 7:40 8 3 2 3 2 3 12 71 112:20 20 6:20 6 2 3 2 3 2 4 5 12 12 12 111 181:00 25 6:20 11 3 2 2 3 7 12 11 12 11 12 153 246:00 30 6:00 13 2 3 2 6 12 11 12 11 11 12 30 177 308:40 35 6:00 15 3 3 11 12 11 12 11 11 11 12 68 182 368:40 40 6:00 18 7 11 12 11 11 11 12 11 11 35 83 185 424:40 MK 16 MOD 1 Closed-Circuit UBA Tables (0.75 ata ppO2) (DESCENT RATE 60 FPM — ASCENT RATE 30 FPM)\nThe following tables apply to the MK 16 MOD 1 closed-circuit underwater breathing apparatus operating at a constant partial pressure of oxygen of 0.75 ata.\nTable 15-14. No-Decompression Limits and Repetitive Group Designators for 0.75 ata ppO2 N2O2 Dives Notes:\n– Diver does not acquire a repetitive group designator during dives to these depths * Highest repetitive group that can be achieved at this depth regardless of bottom time Blank cells = Group not achievable at this depth Depths at 160 FSW and deeper are Exceptional Exposure (require CO authorization) Depth (fsw) No-Stop Limit A B C D E F G H I J K L M N O Z 10 Unlimited – – – – – – – – – – – – – – – – 15 Unlimited – – – – – – – – – – – – – – – – 20 Unlimited 154 425 * 30 Unlimited 31 50 73 98 128 165 211 274 375 643 * 40 369 17 27 38 50 63 76 91 107 125 144 167 192 223 259 305 369 50 143 12 19 26 33 41 50 59 68 78 88 99 111 123 137 143 60 74 9 14 19 25 31 37 43 50 56 63 71 74 70 51 7 11 15 20 25 29 34 39 44 50 51 80 40 6 9 13 16 20 24 28 32 36 40 90 32 5 8 11 14 17 20 24 27 31 32 100 27 4 7 9 12 15 18 21 24 27 110 23 3 6 8 11 13 16 18 21 23 120 20 3 5 7 9 12 14 16 18 20 130 16 4 6 8 10 12 14 16 140 14 4 6 7 9 11 13 14 150 11 3 5 7 8 10 11 Exceptional Exposure 160 10 3 4 6 8 9 10 170 9 3 4 5 7 8 9 Table 15-15. Residual Nitrogen Timetable for Repetitive 0.75 ata Constant ppO2 N2O2 Dives Part 1: Surface Interval Credit Table Note: The Surface Interval Credit intervals for 0.75 ata ppO2 N2O2 are identical to those for Air (Table 9-8 Part 1), since both use the same nitrogen offgassing model.\nLocate the diver\u0026rsquo;s repetitive group designation from his previous dive in the left column. Read horizontally to the interval in which the diver\u0026rsquo;s surface interval lies. Read vertically downward to the new repetitive group designation.\nPrevious Group Z O N M L K J I H G F E D C B A Not Rep (\u0026gt;) Z 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:37 2:38\u0026ndash;3:29 3:30\u0026ndash;4:21 4:22\u0026ndash;5:13 5:14\u0026ndash;6:06 6:07\u0026ndash;6:58 6:59\u0026ndash;7:50 7:51\u0026ndash;8:42 8:43\u0026ndash;9:34 9:35\u0026ndash;10:27 10:28\u0026ndash;11:19 11:20\u0026ndash;12:13 12:14\u0026ndash;13:30 13:31\u0026ndash;15:50 15:50 O 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:37 2:38\u0026ndash;3:29 3:30\u0026ndash;4:21 4:22\u0026ndash;5:13 5:14\u0026ndash;6:06 6:07\u0026ndash;6:58 6:59\u0026ndash;7:50 7:51\u0026ndash;8:42 8:43\u0026ndash;9:34 9:35\u0026ndash;10:27 10:28\u0026ndash;11:21 11:22\u0026ndash;12:37 12:38\u0026ndash;14:58 14:58 N 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:37 2:38\u0026ndash;3:29 3:30\u0026ndash;4:21 4:22\u0026ndash;5:13 5:14\u0026ndash;6:06 6:07\u0026ndash;6:58 6:59\u0026ndash;7:50 7:51\u0026ndash;8:42 8:43\u0026ndash;9:34 9:35\u0026ndash;10:29 10:30\u0026ndash;11:45 11:46\u0026ndash;14:05 14:05 M 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:37 2:38\u0026ndash;3:29 3:30\u0026ndash;4:21 4:22\u0026ndash;5:13 5:14\u0026ndash;6:06 6:07\u0026ndash;6:58 6:59\u0026ndash;7:50 7:51\u0026ndash;8:42 8:43\u0026ndash;9:37 9:38\u0026ndash;10:53 10:54\u0026ndash;13:13 13:13 L 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:37 2:38\u0026ndash;3:29 3:30\u0026ndash;4:21 4:22\u0026ndash;5:13 5:14\u0026ndash;6:06 6:07\u0026ndash;6:58 6:59\u0026ndash;7:50 7:51\u0026ndash;8:44 8:45\u0026ndash;10:01 10:02\u0026ndash;12:21 12:21 K 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:37 2:38\u0026ndash;3:29 3:30\u0026ndash;4:21 4:22\u0026ndash;5:13 5:14\u0026ndash;6:06 6:07\u0026ndash;6:58 6:59\u0026ndash;7:52 7:53\u0026ndash;9:09 9:10\u0026ndash;11:29 11:29 J 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:37 2:38\u0026ndash;3:29 3:30\u0026ndash;4:21 4:22\u0026ndash;5:13 5:14\u0026ndash;6:06 6:07\u0026ndash;7:00 7:01\u0026ndash;8:16 8:17\u0026ndash;10:36 10:36 I 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:37 2:38\u0026ndash;3:29 3:30\u0026ndash;4:21 4:22\u0026ndash;5:13 5:14\u0026ndash;6:08 6:09\u0026ndash;7:24 7:25\u0026ndash;9:44 9:44 H 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:37 2:38\u0026ndash;3:29 3:30\u0026ndash;4:21 4:22\u0026ndash;5:16 5:17\u0026ndash;6:32 6:33\u0026ndash;8:52 8:52 G 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:37 2:38\u0026ndash;3:29 3:30\u0026ndash;4:23 4:24\u0026ndash;5:40 5:41\u0026ndash;8:00 8:00 F 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:37 2:38\u0026ndash;3:31 3:32\u0026ndash;4:48 4:49\u0026ndash;7:08 7:08 E 0:10\u0026ndash;0:52 0:53\u0026ndash;1:44 1:45\u0026ndash;2:39 2:40\u0026ndash;3:55 3:56\u0026ndash;6:15 6:15 D 0:10\u0026ndash;0:52 0:53\u0026ndash;1:47 1:48\u0026ndash;3:03 3:04\u0026ndash;5:23 5:23 C 0:10\u0026ndash;0:55 0:56\u0026ndash;2:11 2:12\u0026ndash;4:31 4:31 B 0:10\u0026ndash;1:16 1:17\u0026ndash;3:36 3:36 A 0:10\u0026ndash;2:20 2:20 * Dives following surface intervals longer than the \u0026ldquo;Not Rep\u0026rdquo; time are not repetitive dives. Use actual bottom times in Tables 15-14 and 15-16 to compute decompression for such dives.\nPart 2: Residual Nitrogen Times (Minutes) Using the new repetitive group designation from Part 1, read down the column to the row representing the depth of the repetitive dive. The time at the intersection is the Residual Nitrogen Time (RNT) in minutes to be applied to the repetitive dive.\nDepth (fsw) Z O N M L K J I H G F E D C B A 10 \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; 15 \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; \u0026ndash; 20 ** ** ** ** ** ** ** ** ** ** ** ** ** ** 420 153 30 ** ** ** ** ** ** 626 372 273 211 165 129 99 73 51 31 40 365 303 258 222 192 167 144 125 107 91 77 63 51 39 28 18 50 167 151 137 123 111 99 88 78 68 59 50 42 34 27 19 12 60 113 104 95 87 79 71 64 57 50 44 38 32 26 20 15 10 70 86 79 73 67 61 56 50 45 40 35 30 25 21 16 12 8 80 69 64 60 55 50 46 41 37 33 29 25 21 18 14 10 7 90 58 54 50 46 43 39 35 32 28 25 22 18 15 12 9 6 100 50 47 44 40 37 34 31 28 25 22 19 16 13 11 8 5 110 44 41 38 36 33 30 27 25 22 19 17 14 12 9 7 5 120 39 37 34 32 29 27 25 22 20 18 15 13 11 9 6 4 130 36 33 31 29 27 24 22 20 18 16 14 12 10 8 6 4 140 33 30 28 26 24 22 20 18 17 15 13 11 9 7 5 4 150 30 28 26 24 22 21 19 17 15 14 12 10 8 7 5 3 160 28 26 24 23 21 19 18 16 14 13 11 9 8 6 5 3 170 26 24 23 21 19 18 16 15 13 12 10 9 7 6 4 3 Notes \u0026ndash; Repetitive dives to these depths are equivalent to remaining on the surface. Add the bottom time of the dive to the preceding surface interval. Use the Surface Interval Credit Table (SICT) to determine the repetitive group at the end of the dive.\n** Residual Nitrogen Time cannot be determined using this table. See paragraph 9-9.1 subparagraph 8 for guidance. Substitute the ** depths in this table for those in the instructions.\nTable 15-16. 0.75 ata ppO2 N2O2 Decompression Tables (DESCENT RATE 60 FPM — ASCENT RATE 30 FPM)\nStop times (min) include travel time, except first stop.\n40 FSW Bottom Time (min) Time to 1st Stop (M:S) 10 Total Ascent (M:S) Rep Group 369 1:20 0 1:20 Z 370 1:00 1 2:20 Z 380 1:00 2 3:20 Z 390 1:00 3 4:20 Z 50 FSW Bottom Time (min) Time to 1st Stop (M:S) 10 Total Ascent (M:S) Rep Group 143 1:40 0 1:40 O 150 1:20 3 4:40 O 160 1:20 8 9:40 O 170 1:20 12 13:40 O 180 1:20 15 16:40 Z 190 1:20 19 20:40 Z 200 1:20 22 23:40 Z 210 1:20 25 26:40 Z 220 1:20 29 30:40 Z 230 1:20 33 34:40 Z 240 1:20 37 38:40 Z 250 1:20 42 43:40 Z 260 1:20 45 46:40 Z 270 1:20 49 50:40 Z 280 1:20 52 53:40 Z 290 1:20 56 57:40 Z 300 1:20 59 60:40 Z 310 1:20 61 62:40 Z 320 1:20 64 65:40 Z 330 1:20 67 68:40 Z Exceptional Exposure 340 1:20 69 70:40 350 1:20 73 74:40 360 1:20 77 78:40 370 1:20 80 81:40 380 1:20 83 84:40 390 1:20 87 88:40 60 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 10 Total Ascent (M:S) Rep Group 74 2:00 0 2:00 L 75 1:40 1 3:00 L 80 1:40 3 5:00 L 90 1:40 8 10:00 M 100 1:40 12 14:00 N 110 1:40 16 18:00 O 120 1:40 24 26:00 O 130 1:40 32 34:00 O 140 1:40 38 40:00 Z 150 1:40 44 46:00 Z 160 1:40 50 52:00 Z 170 1:40 55 57:00 Z 180 1:20 3 60 64:40 Z 190 1:20 8 62 71:40 Z 200 1:20 12 65 78:40 Z 210 1:20 15 69 85:40 Z 220 1:20 19 71 91:40 Z 230 1:20 22 74 97:40 Z 240 1:20 25 76 102:40 Z 250 1:20 27 80 108:40 Z Exceptional Exposure 260 1:20 30 82 113:40 270 1:20 32 85 118:40 280 1:20 35 88 124:40 290 1:20 40 90 131:40 300 1:20 43 93 137:40 310 1:20 47 94 142:40 320 1:20 51 96 148:40 330 1:20 54 98 153:40 340 1:20 57 100 158:40 350 1:20 60 102 163:40 360 1:20 63 105 169:40 370 1:20 65 109 175:40 380 1:20 68 112 181:40 390 1:20 70 115 186:40 70 FSW Bottom Time (min) Time to 1st Stop (M:S) 30 20 10 Total Ascent (M:S) Rep Group 51 2:20 0 2:20 K 55 2:00 4 6:20 K 60 2:00 9 11:20 K 70 2:00 17 19:20 L 80 2:00 24 26:20 M 90 1:40 2 29 33:00 N 100 1:40 7 34 43:00 O 110 1:40 12 39 53:00 O 120 1:40 15 46 63:00 O 130 1:40 18 52 72:00 Z 140 1:40 21 57 80:00 Z 150 1:40 29 58 89:00 Z 160 1:40 36 62 100:00 Z 170 1:40 42 66 110:00 Z 180 1:40 48 70 120:00 Z Exceptional Exposure 190 1:20 1 53 73 128:40 200 1:20 2 57 77 137:40 210 1:20 6 57 81 145:40 220 1:20 10 57 84 152:40 230 1:20 14 59 87 161:40 240 1:20 18 62 89 170:40 250 1:20 21 66 91 179:40 260 1:20 24 69 94 188:40 270 1:20 26 72 97 196:40 280 1:20 29 75 99 204:40 290 1:20 31 78 102 212:40 300 1:20 33 81 105 220:40 310 1:20 35 83 110 229:40 320 1:20 37 86 113 237:40 330 1:20 41 86 118 246:40 340 1:20 45 86 124 256:40 350 1:20 49 88 127 265:40 80 FSW Bottom Time (min) Time to 1st Stop (M:S) 40 30 20 10 Total Ascent (M:S) Rep Group 40 2:40 0 2:40 J 45 2:20 8 10:40 K 50 2:20 15 17:40 K 55 2:20 21 23:40 L 60 2:20 27 29:40 L 70 2:00 9 28 39:20 M 80 2:00 17 29 48:20 N 90 2:00 24 36 62:20 O 100 1:40 2 29 43 76:00 O 110 1:40 7 29 50 88:00 Z 120 1:40 12 29 57 100:00 Z Exceptional Exposure 130 1:40 15 37 58 112:00 140 1:40 18 43 62 125:00 150 1:40 21 49 67 139:00 160 1:40 23 56 70 151:00 170 1:40 29 57 75 163:00 180 1:40 36 57 80 175:00 190 1:40 42 57 85 186:00 200 1:20 1 48 60 86 196:40 210 1:20 2 52 64 90 209:40 220 1:20 2 57 68 93 221:40 230 1:20 6 57 73 96 233:40 240 1:20 10 57 77 100 245:40 250 1:20 14 57 81 104 257:40 260 1:20 18 56 85 110 270:40 270 1:20 21 59 86 116 283:40 280 1:20 24 63 85 124 297:40 290 1:20 26 67 86 129 309:40 300 1:20 29 70 88 134 322:40 310 1:20 31 73 92 137 334:40 320 1:20 33 76 95 141 346:40 90 FSW Bottom Time (min) Time to 1st Stop (M:S) 50 40 30 20 10 Total Ascent (M:S) Rep Group 32 3:00 0 3:00 J 35 2:40 5 8:00 J 40 2:40 14 17:00 K 45 2:40 23 26:00 K 50 2:20 3 28 33:40 L 55 2:20 10 28 40:40 L 60 2:20 17 28 47:40 M 70 2:20 28 29 59:40 N 80 2:00 10 29 34 75:20 O 90 2:00 18 29 44 93:20 Z Exceptional Exposure 100 2:00 25 29 52 108:20 110 1:40 3 29 33 56 123:00 120 1:40 8 29 41 62 142:00 130 1:40 12 29 49 67 159:00 140 1:40 16 29 56 73 176:00 150 1:40 19 36 57 76 190:00 160 1:40 21 43 57 81 204:00 170 1:40 23 50 57 89 221:00 180 1:40 25 56 62 91 236:00 190 1:40 31 57 67 95 252:00 100 FSW Bottom Time (min) Time to 1st Stop (M:S) 50 40 30 20 10 Total Ascent (M:S) Rep Group 27 3:20 0 3:20 I 30 3:00 6 9:20 J 35 3:00 18 21:20 J 40 3:00 28 31:20 K 45 2:40 10 28 41:00 L 50 2:40 19 28 50:00 M 55 2:40 27 29 59:00 M 60 2:20 7 28 28 65:40 N 65 2:20 14 28 28 72:40 O Exceptional Exposure 70 2:20 20 28 32 82:40 75 2:20 26 28 37 93:40 80 2:00 3 28 29 42 104:20 90 2:00 12 29 28 53 124:20 100 2:00 20 29 34 61 146:20 110 2:00 27 28 44 66 167:20 110 FSW Bottom Time (min) Time to 1st Stop (M:S) 50 40 30 20 10 Total Ascent (M:S) Rep Group 23 3:40 0 3:40 I 25 3:20 4 7:40 J 30 3:20 18 21:40 J 35 3:00 3 28 34:20 K 40 3:00 14 29 46:20 L 45 3:00 25 29 57:20 L 50 2:40 7 29 28 67:00 M 55 2:40 16 29 28 76:00 N Exceptional Exposure 60 2:40 25 28 29 85:00 65 2:20 4 29 28 33 96:40 70 2:20 11 29 28 40 110:40 80 2:20 24 28 29 52 135:40 90 2:00 6 29 28 34 65 164:20 120 FSW Bottom Time (min) Time to 1st Stop (M:S) 50 40 30 20 10 Total Ascent (M:S) Rep Group 20 4:00 0 4:00 I 25 3:40 14 18:00 J 30 3:20 3 27 33:40 J 35 3:20 15 29 47:40 K 40 3:00 4 25 28 60:20 L 45 3:00 12 29 28 72:20 M Exceptional Exposure 50 2:40 1 23 28 28 83:00 55 2:40 5 29 28 29 94:00 60 2:40 15 28 28 35 109:00 70 2:20 3 28 29 28 50 140:40 80 2:20 17 28 29 31 68 175:40 130 FSW Bottom Time (min) Time to 1st Stop (M:S) 50 40 30 20 10 Total Ascent (M:S) Rep Group 16 4:20 0 4:20 H 20 4:00 5 9:20 I 25 3:40 4 20 28:00 J 30 3:20 2 11 28 44:40 K 35 3:20 7 21 29 60:40 L Exceptional Exposure 40 3:00 1 14 28 28 74:20 45 3:00 7 21 28 29 88:20 50 3:00 12 28 28 29 100:20 55 2:40 3 20 28 29 34 117:00 60 2:40 7 26 28 29 43 136:00 70 2:40 23 28 28 29 67 178:00 140 FSW Bottom Time (min) Time to 1st Stop (M:S) 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 14 4:40 0 4:40 H 15 4:20 1 5:40 H 20 4:00 3 11 18:20 J 25 3:40 3 7 24 38:00 K 30 3:20 1 7 17 28 56:40 L Exceptional Exposure 35 3:20 4 13 24 29 73:40 40 3:20 11 18 28 28 88:40 45 3:00 4 14 25 29 28 103:20 50 3:00 10 18 28 29 35 123:20 60 2:40 5 18 28 29 28 61 172:00 70 2:40 14 28 29 28 36 80 218:00 150 FSW Bottom Time (min) Time to 1st Stop (M:S) 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 11 5:00 0 5:00 G 15 4:40 6 11:00 H 20 4:00 2 7 14 27:20 J 25 3:40 2 7 9 27 49:00 K 30 3:40 7 9 20 28 68:00 M Exceptional Exposure 35 3:20 3 10 14 28 28 86:40 40 3:20 7 14 22 28 29 103:40 45 3:00 1 14 15 29 28 35 125:20 50 3:00 7 14 23 29 28 49 153:20 60 2:40 3 14 24 29 28 32 76 209:00 70 2:40 10 24 28 29 28 52 91 265:00 160 FSW All bottom times are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 10 5:20 0 5:20 15 4:40 3 7 15:00 20 4:20 6 8 17 35:40 25 4:00 7 7 12 29 59:20 30 3:40 6 7 12 23 28 80:00 35 3:20 3 7 12 17 29 28 99:40 40 3:20 5 13 14 25 29 35 124:40 45 3:20 12 14 19 29 28 49 154:40 50 3:00 4 15 14 28 28 29 65 186:20 170 FSW All bottom times are Exceptional Exposure.\nBottom Time (min) Time to 1st Stop (M:S) 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 9 5:40 0 5:40 10 5:20 2 7:40 15 4:40 2 6 7 20:00 20 4:20 5 7 7 21 44:40 25 4:00 6 7 7 17 28 69:20 30 3:40 5 7 8 14 26 29 93:00 35 3:20 2 7 9 14 21 28 35 119:40 40 3:20 5 9 14 15 28 29 46 149:40 45 3:20 8 15 14 24 28 29 65 186:40 50 3:00 2 14 14 19 28 29 36 76 221:20 Table 15-17. 0.75 ata ppO2 HeO2 Decompression Tables (DESCENT RATE 60 FPM — ASCENT RATE 30 FPM)\nStop times (min) include travel time, except first stop.\n40 FSW Bottom Time (min) Time to 1st Stop (M:S) 10 Total Ascent (M:S) Rep Group 390 1:20 0 1:20 50 FSW Bottom Time (min) Time to 1st Stop (M:S) 10 Total Ascent (M:S) Rep Group 205 1:40 0 1:40 210 1:20 3 4:40 220 1:20 9 10:40 230 1:20 14 15:40 240 1:20 20 21:40 250 1:20 24 25:40 Exceptional Exposure 260 1:20 29 30:40 270 1:20 33 34:40 280 1:20 37 38:40 290 1:20 41 42:40 300 1:20 45 46:40 310 1:20 48 49:40 320 1:20 52 53:40 330 1:20 55 56:40 340 1:20 58 59:40 350 1:20 60 61:40 360 1:20 63 64:40 370 1:20 65 66:40 380 1:20 68 69:40 390 1:20 70 71:40 60 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 10 Total Ascent (M:S) Rep Group 133 2:00 0 2:00 140 1:40 8 10:00 150 1:40 20 22:00 160 1:40 30 32:00 170 1:40 40 42:00 Exceptional Exposure 180 1:40 50 52:00 190 1:40 59 61:00 200 1:40 67 69:00 210 1:40 75 77:00 220 1:40 82 84:00 230 1:40 90 92:00 240 1:40 96 98:00 250 1:40 103 105:00 260 1:40 109 111:00 270 1:20 1 113 115:40 280 1:20 7 113 121:40 290 1:20 12 113 126:40 300 1:20 16 114 131:40 310 1:20 21 113 135:40 320 1:20 25 113 139:40 330 1:20 29 113 143:40 340 1:20 33 113 147:40 350 1:20 36 113 150:40 360 1:20 40 113 154:40 370 1:20 43 113 157:40 380 1:20 46 113 160:40 390 1:20 49 113 163:40 70 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 10 Total Ascent (M:S) Rep Group 82 2:20 0 2:20 85 2:00 2 4:20 90 2:00 6 8:20 95 2:00 9 11:20 100 2:00 12 14:20 110 2:00 19 21:20 120 2:00 35 37:20 130 2:00 51 53:20 140 2:00 65 67:20 Exceptional Exposure 150 2:00 79 81:20 160 2:00 92 94:20 170 2:00 104 106:20 180 1:40 7 109 118:00 190 1:40 14 113 129:00 200 1:40 24 113 139:00 210 1:40 34 113 149:00 220 1:40 43 113 158:00 230 1:40 52 113 167:00 240 1:40 60 113 175:00 250 1:40 68 113 183:00 260 1:40 75 113 190:00 270 1:40 82 113 197:00 80 FSW Bottom Time (min) Time to 1st Stop (M:S) 20 10 Total Ascent (M:S) Rep Group 52 2:40 0 2:40 55 2:20 2 4:40 60 2:20 5 7:40 65 2:20 8 10:40 70 2:20 14 16:40 75 2:20 19 21:40 80 2:20 24 26:40 85 2:20 29 31:40 90 2:20 33 35:40 95 2:20 36 38:40 100 2:00 3 44 49:20 110 2:00 9 58 69:20 120 2:00 14 73 89:20 Exceptional Exposure 130 2:00 18 87 107:20 140 2:00 22 100 124:20 150 2:00 33 105 140:20 160 2:00 43 111 156:20 170 2:00 55 113 170:20 180 2:00 69 113 184:20 190 2:00 82 113 197:20 90 FSW Bottom Time (min) Time to 1st Stop (M:S) 30 20 10 Total Ascent (M:S) Rep Group 37 3:00 0 3:00 40 2:40 4 7:00 45 2:40 10 13:00 50 2:40 15 18:00 55 2:40 19 22:00 60 2:20 1 23 26:40 65 2:20 4 27 33:40 70 2:20 6 32 40:40 75 2:20 8 36 46:40 80 2:20 12 38 52:40 85 2:20 17 38 57:40 90 2:20 22 44 68:40 95 2:20 26 53 81:40 100 2:20 30 61 93:40 110 2:20 38 77 117:40 120 2:00 6 38 94 140:20 Exceptional Exposure 130 2:00 11 46 102 161:20 140 2:00 15 55 109 181:20 150 2:00 19 66 113 200:20 160 2:00 22 81 113 218:20 100 FSW Bottom Time (min) Time to 1st Stop (M:S) 40 30 20 10 Total Ascent (M:S) Rep Group 29 3:20 0 3:20 30 3:00 1 4:20 35 3:00 11 14:20 40 3:00 19 22:20 50 2:40 9 22 34:00 60 2:40 18 27 48:00 70 2:20 2 22 38 64:40 80 2:20 7 31 41 81:40 90 2:20 11 38 59 110:40 100 2:20 21 38 78 139:40 Exceptional Exposure 110 2:20 29 39 96 166:40 120 2:20 36 50 103 191:40 130 2:00 4 38 61 111 216:20 140 2:00 9 38 76 113 238:20 110 FSW Bottom Time (min) Time to 1st Stop (M:S) 50 40 30 20 10 Total Ascent (M:S) Rep Group 23 3:40 0 3:40 25 3:20 2 5:40 30 3:20 14 17:40 35 3:00 3 22 28:20 40 3:00 11 22 36:20 50 2:40 3 22 22 50:00 60 2:40 13 22 33 71:00 70 2:40 20 28 37 88:00 80 2:20 3 23 37 55 120:40 90 2:20 7 31 38 76 154:40 100 2:20 11 38 39 96 186:40 Exceptional Exposure 110 2:20 20 38 52 103 215:40 120 2:20 28 38 64 111 243:40 130 2:20 34 40 80 113 269:40 140 2:00 2 38 51 89 113 295:20 120 FSW Bottom Time (min) Time to 1st Stop (M:S) 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 18 4:00 0 4:00 20 3:40 2 6:00 25 3:40 13 17:00 30 3:20 5 22 30:40 35 3:20 16 22 41:40 40 3:00 4 22 22 51:20 50 3:00 19 23 24 69:20 60 2:40 9 22 22 37 93:00 70 2:40 16 22 34 52 127:00 80 2:40 22 29 38 72 164:00 Exceptional Exposure 90 2:20 4 24 37 38 95 200:40 100 2:20 7 32 38 50 104 233:40 110 2:20 12 37 38 65 112 266:40 120 2:20 20 38 41 83 113 297:40 130 FSW Bottom Time (min) Time to 1st Stop (M:S) 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 15 4:20 0 4:20 20 4:00 8 12:20 25 3:40 6 18 28:00 30 3:20 2 16 22 43:40 35 3:20 8 22 22 55:40 40 3:20 19 22 22 66:40 50 3:00 14 22 22 28 89:20 60 2:40 4 22 22 26 48 125:00 70 2:40 12 22 24 38 70 169:00 Exceptional Exposure 80 2:40 18 22 36 38 93 210:00 90 2:20 1 22 32 37 46 107 247:40 100 2:20 4 26 38 37 64 113 284:40 110 2:20 6 35 38 40 84 113 318:40 120 2:20 12 38 38 55 93 113 351:40 140 FSW Bottom Time (min) Time to 1st Stop (M:S) 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 12 4:40 0 4:40 15 4:20 4 8:40 20 4:00 5 12 21:20 25 3:40 4 10 22 40:00 30 3:40 10 20 22 56:00 35 3:20 4 18 22 22 69:40 40 3:20 12 22 22 22 81:40 50 3:00 8 22 22 22 35 112:20 60 3:00 21 22 22 31 66 165:20 70 2:40 9 22 22 29 38 93 216:00 Exceptional Exposure 80 2:40 15 22 27 38 40 113 258:00 90 2:40 20 23 38 38 63 113 298:00 100 2:20 1 22 35 38 37 88 113 336:40 150 FSW Bottom Time (min) Time to 1st Stop (M:S) 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 10 5:00 0 5:00 15 4:20 2 7 13:40 20 4:00 2 10 15 31:20 25 3:40 2 9 15 22 52:00 30 3:40 7 14 22 22 69:00 35 3:20 3 11 22 22 22 83:40 40 3:20 6 21 22 22 22 96:40 45 3:20 15 22 22 22 33 117:40 50 3:00 2 23 22 22 22 56 150:20 55 3:00 10 22 22 22 27 74 180:20 60 3:00 16 22 23 22 35 88 209:20 Exceptional Exposure 70 2:40 5 22 22 22 35 40 113 262:00 80 2:40 12 22 22 34 38 65 113 309:00 90 2:40 17 22 31 38 38 90 113 352:00 155 FSW Bottom Time (min) Time to 1st Stop (M:S) 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 9 5:10 0 5:10 10 4:50 1 6:10 15 4:30 3 9 16:50 20 4:10 5 10 17 36:30 25 3:50 5 9 17 22 57:10 30 3:30 2 9 17 22 22 75:50 35 3:30 6 15 22 22 22 90:50 40 3:30 12 22 22 22 22 103:50 45 3:10 3 20 22 22 22 44 136:30 50 3:10 10 23 22 22 22 68 170:30 55 3:10 18 22 22 22 30 84 201:30 60 2:50 3 22 22 22 22 38 100 232:10 Exceptional Exposure 70 2:50 14 22 22 22 38 52 113 286:10 80 2:50 21 22 22 38 37 77 113 333:10 90 2:30 5 22 22 35 38 37 103 113 377:50 160 FSW Bottom Time (min) Time to 1st Stop (M:S) 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 9 5:20 0 5:20 10 5:00 2 7:20 15 4:20 1 4 10 19:40 20 4:00 1 8 9 19 41:20 25 4:00 8 10 19 22 63:20 30 3:40 5 10 19 22 22 82:00 35 3:20 1 9 18 22 22 22 97:40 40 3:20 4 15 22 22 23 27 116:40 45 3:20 9 22 22 22 22 55 155:40 50 3:20 18 22 23 22 22 79 189:40 Exceptional Exposure 55 3:00 5 22 22 22 22 31 97 224:20 60 3:00 12 22 22 22 24 38 113 256:20 70 2:40 1 22 22 22 25 38 64 113 310:00 80 2:40 8 22 23 25 37 38 91 113 360:00 90 2:40 14 22 24 37 38 43 111 113 405:00 165 FSW Bottom Time (min) Time to 1st Stop (M:S) 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 8 5:30 0 5:30 10 5:10 3 8:30 15 4:30 2 6 9 21:50 20 4:10 2 10 9 21 46:30 25 3:50 2 10 9 22 22 69:10 30 3:50 9 9 22 22 22 88:10 35 3:30 5 9 21 22 22 22 104:50 40 3:30 8 19 22 22 22 39 135:50 45 3:10 1 16 22 22 22 22 66 174:30 50 3:10 5 22 22 22 22 24 92 212:30 Exceptional Exposure 55 3:10 13 22 22 22 22 34 108 246:30 60 3:10 20 22 22 22 27 48 113 277:30 70 2:50 10 22 22 22 28 38 79 113 337:10 80 2:50 18 22 22 28 38 38 105 113 387:10 170 FSW Bottom Time (min) Time to 1st Stop (M:S) 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 8 5:40 0 5:40 10 5:00 1 3 9:20 15 4:40 4 7 9 25:00 20 4:20 5 10 10 22 51:40 25 4:00 6 9 11 22 22 74:20 30 3:40 3 10 12 22 22 22 95:00 35 3:40 8 12 22 22 22 22 112:00 40 3:20 3 9 22 22 22 22 50 153:40 45 3:20 5 19 22 23 22 22 78 194:40 50 3:20 13 22 22 22 22 26 104 234:40 Exceptional Exposure 55 3:20 21 23 22 22 22 42 113 268:40 60 3:00 7 22 22 22 22 29 62 113 302:20 70 3:00 19 22 22 22 31 38 92 113 362:20 80 2:40 5 22 22 22 32 38 43 113 113 413:00 175 FSW Bottom Time (min) Time to 1st Stop (M:S) 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 7 5:50 0 5:50 10 5:10 2 4 11:30 15 4:30 1 4 8 10 27:50 20 4:10 1 7 10 12 22 56:30 25 4:10 9 9 14 22 22 80:30 30 3:50 7 9 15 22 22 22 101:10 35 3:30 3 9 15 22 22 22 31 127:50 40 3:30 7 13 22 22 22 22 62 173:50 Exceptional Exposure 45 3:30 10 22 22 22 22 22 91 214:50 50 3:10 2 19 22 22 22 22 30 113 255:30 55 3:10 8 22 22 22 22 22 58 113 292:30 60 3:10 16 22 22 22 22 31 76 113 327:30 65 3:10 22 22 22 22 25 38 90 113 357:30 70 2:50 6 22 22 22 22 34 38 106 113 388:10 75 2:50 10 22 22 23 27 37 45 113 113 415:10 80 2:50 14 22 22 22 36 38 58 113 113 441:10 180 FSW Bottom Time (min) Time to 1st Stop (M:S) 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 7 6:00 0 6:00 10 5:20 3 4 12:40 15 4:40 3 4 9 11 32:00 20 4:20 3 8 10 14 22 61:40 25 4:00 3 9 10 16 22 22 86:20 30 3:40 1 10 9 17 22 22 23 108:00 35 3:40 7 9 17 22 23 22 41 145:00 40 3:20 1 10 16 22 22 22 22 73 191:40 Exceptional Exposure 45 3:20 4 14 22 22 22 22 22 105 236:40 50 3:20 7 22 22 22 22 22 44 113 277:40 55 3:20 16 22 22 22 22 24 70 113 314:40 60 3:00 3 22 22 22 22 22 33 90 113 352:20 65 3:00 9 22 22 22 22 28 38 105 113 384:20 70 3:00 15 22 22 22 22 37 45 113 113 414:20 185 FSW Bottom Time (min) Time to 1st Stop (M:S) 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 6 6:10 0 6:10 10 5:30 4 4 13:50 15 4:50 4 5 10 12 36:10 20 4:10 1 4 10 9 16 22 66:30 25 4:10 6 10 9 19 22 22 92:30 30 3:50 5 9 10 20 22 22 22 114:10 35 3:30 1 10 9 21 22 22 22 52 162:50 40 3:30 5 10 19 22 22 22 22 86 211:50 Exceptional Exposure 45 3:30 8 18 22 22 22 22 28 113 258:50 50 3:10 1 14 22 22 22 22 22 58 113 299:30 55 3:10 3 22 22 22 22 22 26 84 113 339:30 60 3:10 11 22 22 22 22 22 36 103 113 376:30 65 3:10 18 22 22 22 22 30 44 113 113 409:30 70 2:50 2 22 22 22 22 24 38 60 113 113 441:10 190 FSW Bottom Time (min) Time to 1st Stop (M:S) 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 6 6:20 0 6:20 10 5:20 1 4 5 15:40 15 4:40 2 4 6 9 15 41:00 20 4:20 2 6 10 9 18 22 71:40 25 4:00 1 9 9 10 20 23 22 98:20 30 4:00 8 10 10 22 22 22 27 125:20 35 3:40 5 9 11 22 22 22 22 63 180:00 40 3:40 9 11 22 22 22 22 22 99 233:00 Exceptional Exposure 45 3:20 3 9 22 22 22 22 22 41 113 279:40 50 3:20 5 18 22 22 22 22 22 73 113 322:40 55 3:20 11 22 22 22 22 22 28 99 113 364:40 60 3:20 20 22 22 22 22 22 42 114 113 402:40 65 3:00 5 22 22 22 22 22 33 59 113 113 436:20 70 3:00 11 22 22 22 22 27 38 76 113 113 469:20 195 FSW Bottom Time (min) Time to 1st Stop (M:S) 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 6 6:30 0 6:30 10 5:30 3 3 6 17:50 15 4:50 3 4 8 9 16 45:10 20 4:30 4 7 10 9 20 22 76:50 25 4:10 4 9 10 10 22 22 22 103:30 30 3:50 3 9 10 12 22 23 22 37 142:10 35 3:50 9 9 14 22 22 22 22 75 199:10 40 3:30 4 9 14 22 22 22 22 22 112 252:50 Exceptional Exposure 45 3:30 7 12 22 22 22 22 22 55 113 300:50 50 3:30 9 22 22 22 22 22 22 88 113 345:50 55 3:10 1 19 22 22 22 22 22 30 113 113 389:30 60 3:10 6 22 22 22 22 22 26 55 113 113 426:30 200 FSW Bottom Time (min) Time to 1st Stop (M:S) 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 6 6:40 0 6:40 10 5:40 4 4 6 20:00 15 4:40 1 4 4 8 10 17 49:00 20 4:20 2 4 9 9 9 22 22 81:40 25 4:20 7 10 9 13 22 22 22 109:40 30 4:00 6 10 9 16 22 22 22 48 159:20 35 3:40 3 10 9 17 22 22 22 22 87 218:00 Exceptional Exposure 40 3:40 7 10 17 22 22 22 22 34 113 273:00 45 3:20 1 10 16 22 22 22 22 22 70 113 323:40 50 3:20 4 14 22 22 22 22 22 22 106 113 372:40 55 3:20 6 22 22 22 22 22 22 46 113 113 413:40 60 3:20 15 22 22 22 22 22 27 72 113 114 454:40 205 FSW Bottom Time (min) Time to 1st Stop (M:S) 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 6:50 0 6:50 10 5:30 1 4 4 8 22:50 15 4:50 2 4 5 9 9 19 53:10 20 4:30 3 5 9 10 11 22 22 86:50 25 4:10 2 9 9 10 15 22 22 22 115:30 30 3:50 1 9 10 9 18 22 22 22 59 176:10 35 3:50 7 9 10 20 22 22 22 22 100 238:10 Exceptional Exposure 40 3:30 2 10 9 21 22 22 22 22 48 113 294:50 45 3:30 5 10 20 22 22 22 22 22 85 113 346:50 50 3:30 8 18 22 22 22 22 22 30 113 113 395:50 55 3:30 14 22 22 22 22 22 22 62 113 113 437:50 60 3:10 2 22 22 22 22 22 22 30 87 113 113 480:30 210 FSW Bottom Time (min) Time to 1st Stop (M:S) 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 7:00 0 7:00 10 5:40 2 4 4 9 25:00 15 5:00 4 3 6 10 9 20 57:20 20 4:20 1 4 6 10 9 13 22 22 91:40 25 4:20 5 9 9 10 17 22 22 26 124:40 30 4:00 4 10 9 9 21 22 23 22 68 192:20 35 3:40 1 10 9 11 22 22 22 22 22 112 257:00 Exceptional Exposure 40 3:40 6 9 12 22 22 22 22 22 61 113 315:00 45 3:40 9 11 22 23 22 22 22 22 100 113 370:00 50 3:20 2 10 22 22 22 22 22 22 45 113 113 418:40 55 3:20 4 19 22 22 22 22 22 22 81 113 113 465:40 60 3:20 10 22 22 22 22 22 22 32 103 113 113 506:40 215 FSW Bottom Time (min) Time to 1st Stop (M:S) 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 7:10 0 7:10 10 5:50 3 4 4 10 27:10 15 4:50 1 4 4 7 9 10 22 62:10 20 4:30 2 4 8 10 9 15 22 22 96:50 25 4:10 1 7 10 9 9 20 22 22 36 140:30 30 4:10 8 9 10 11 22 22 22 22 81 211:30 Exceptional Exposure 35 3:50 5 10 9 14 22 22 22 22 35 113 278:10 40 3:30 1 9 10 15 22 22 22 22 22 77 113 338:50 45 3:30 4 9 15 22 22 22 23 22 24 113 113 392:50 50 3:30 6 14 22 22 22 22 22 22 62 113 114 444:50 55 3:30 9 22 22 22 22 22 22 23 97 113 113 490:50 60 3:30 19 22 22 22 22 22 22 41 112 113 113 533:50 220 FSW Bottom Time (min) Time to 1st Stop (M:S) 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 7:20 0 7:20 10 5:40 1 4 4 5 9 29:00 15 5:00 3 3 4 9 9 11 22 66:20 20 4:40 4 4 9 10 9 17 22 22 102:00 25 4:20 3 8 10 9 10 22 22 22 45 155:40 30 4:00 2 10 9 9 14 22 22 22 22 93 229:20 Exceptional Exposure 35 4:00 9 9 10 17 22 22 22 22 48 113 298:20 40 3:40 5 9 9 19 22 22 22 22 22 92 113 361:00 45 3:40 8 9 19 22 22 22 22 22 41 113 113 417:00 50 3:20 1 10 17 22 22 22 22 22 22 80 113 113 469:40 55 3:20 3 15 22 22 22 22 22 22 30 108 113 113 517:40 225 FSW Bottom Time (min) Time to 1st Stop (M:S) 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 4 7:30 0 7:30 5 7:10 1 8:30 10 5:50 2 4 4 6 9 31:10 15 5:10 4 4 4 9 10 12 22 70:30 20 4:30 2 4 5 10 9 9 19 22 22 106:50 25 4:10 1 5 9 9 10 12 22 22 22 56 172:30 30 4:10 6 9 9 10 16 22 22 23 22 104 247:30 Exceptional Exposure 35 3:50 3 10 9 10 20 22 22 22 22 61 113 318:10 40 3:50 8 10 9 22 22 22 22 22 22 106 113 382:10 45 3:30 3 9 10 22 22 22 22 22 22 56 113 113 439:50 50 3:30 5 10 21 22 22 22 22 22 22 97 113 113 494:50 55 3:30 7 19 22 22 22 22 22 22 42 113 113 114 543:50 230 FSW Bottom Time (min) Time to 1st Stop (M:S) 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 4 7:40 0 7:40 5 7:20 2 9:40 10 6:00 3 4 4 7 9 33:20 15 5:00 2 4 3 6 9 9 14 22 74:20 20 4:40 3 4 7 9 10 9 21 22 22 112:00 25 4:20 2 7 9 10 9 14 22 22 22 66 187:40 30 4:20 9 10 9 9 20 22 22 22 26 113 266:40 Exceptional Exposure 35 4:00 7 9 10 10 22 22 22 22 22 74 113 337:20 40 3:40 3 9 10 13 22 22 22 22 22 31 113 113 406:00 45 3:40 7 9 14 22 22 22 22 22 22 74 113 113 466:00 50 3:40 9 13 22 22 22 22 22 22 27 109 113 113 520:00 55 3:20 2 10 22 22 22 23 22 22 22 60 113 113 113 569:40 235 FSW Bottom Time (min) Time to 1st Stop (M:S) 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 4 7:50 0 7:50 5 7:30 3 10:50 10 5:50 1 4 3 4 8 10 36:10 15 5:10 3 4 4 6 10 9 15 22 78:30 20 4:30 1 4 4 8 10 9 10 22 22 22 116:50 25 4:30 4 8 9 10 9 17 22 22 22 76 203:50 30 4:10 4 9 9 10 9 22 22 22 22 38 113 284:30 Exceptional Exposure 35 3:50 2 9 9 10 13 22 22 23 22 22 88 113 359:10 40 3:50 7 9 10 16 22 22 22 22 22 46 113 113 428:10 45 3:30 1 10 9 17 23 22 22 22 22 22 90 113 113 489:50 50 3:30 4 9 17 22 22 22 22 22 22 40 113 113 113 544:50 240 FSW Bottom Time (min) Time to 1st Stop (M:S) 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 4 8:00 0 8:00 5 7:40 3 11:00 10 6:00 2 4 4 3 9 10 38:20 15 5:00 1 4 4 3 8 9 10 17 22 83:20 20 4:40 3 3 5 9 10 9 12 22 22 32 132:00 25 4:20 2 4 10 9 9 10 19 22 22 22 87 220:40 Exceptional Exposure 30 4:20 7 9 10 9 12 22 22 22 22 51 113 303:40 35 4:00 5 10 9 10 16 22 22 22 22 22 104 113 381:20 40 3:40 1 10 9 10 19 22 22 22 22 22 60 113 113 449:00 45 3:40 5 10 9 21 22 22 22 22 22 22 107 113 113 514:00 50 3:40 8 9 21 22 22 22 22 22 22 58 113 113 113 571:00 245 FSW Bottom Time (min) Time to 1st Stop (M:S) 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 7:30 1 4 12:50 10 6:10 3 4 4 4 9 11 41:30 15 5:10 2 4 4 4 9 9 9 19 22 87:30 20 4:50 4 4 6 9 10 9 14 22 22 41 146:10 25 4:30 3 6 10 9 10 9 21 22 22 22 98 236:50 Exceptional Exposure 30 4:10 1 10 9 10 9 15 22 22 22 22 64 113 323:30 35 4:10 9 9 10 9 20 22 22 22 22 27 113 113 402:30 40 3:50 5 10 9 11 22 22 22 22 22 22 77 114 113 475:10 45 3:50 9 10 12 22 22 22 22 22 22 33 113 113 113 539:10 50 3:30 3 9 12 22 22 22 22 22 23 22 75 113 114 113 597:50 250 FSW Bottom Time (min) Time to 1st Stop (M:S) 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 7:40 1 4 13:00 10 6:20 4 4 4 5 9 12 44:40 15 5:20 3 4 4 5 9 9 10 20 22 91:40 20 4:40 2 4 4 7 9 10 9 16 22 22 50 160:00 25 4:20 1 4 8 9 10 9 11 22 22 22 22 110 254:40 Exceptional Exposure 30 4:20 5 9 10 9 10 17 22 22 22 22 78 113 343:40 35 4:00 4 9 9 10 10 22 22 22 22 22 41 113 114 424:20 40 4:00 9 9 10 14 22 22 22 22 22 22 94 113 113 498:20 45 3:40 4 9 10 16 22 22 22 22 22 22 51 113 113 113 565:00 50 3:40 7 9 16 22 22 22 22 22 22 22 95 113 113 113 624:00 255 FSW Bottom Time (min) Time to 1st Stop (M:S) 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 7:50 2 4 14:10 10 6:10 1 4 4 4 6 10 12 47:30 15 5:10 1 4 4 4 5 10 9 10 22 22 96:30 20 4:50 3 4 4 9 9 10 9 18 22 22 59 174:10 25 4:30 3 4 9 10 9 10 13 22 22 22 31 113 272:50 Exceptional Exposure 30 4:10 1 8 9 10 9 9 21 22 22 22 22 91 113 363:30 35 4:10 7 10 9 9 14 22 22 22 22 22 56 113 113 445:30 40 3:50 4 9 10 9 17 22 22 22 22 22 25 107 113 113 521:10 45 3:50 8 9 10 19 22 22 22 22 22 22 68 113 113 113 589:10 50 3:30 2 9 10 20 22 22 22 22 22 22 32 104 113 113 113 651:50 260 FSW Bottom Time (min) Time to 1st Stop (M:S) 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 8:00 3 4 15:20 10 6:20 2 4 4 4 7 10 14 51:40 15 5:20 2 4 4 4 7 9 10 11 22 22 100:40 20 4:40 1 4 4 5 9 10 9 9 20 22 22 69 189:00 25 4:20 1 4 5 10 9 10 9 16 22 22 22 43 113 290:40 Exceptional Exposure 30 4:20 3 9 10 9 9 11 22 22 22 22 22 105 113 383:40 35 4:00 2 9 10 9 9 17 22 22 22 22 22 72 113 113 468:20 40 4:00 8 9 9 10 20 22 22 23 22 22 34 113 113 113 544:20 45 3:40 3 9 9 11 22 22 22 22 22 22 22 86 113 113 113 615:00 265 FSW Bottom Time (min) Time to 1st Stop (M:S) 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 8:10 4 4 16:30 10 6:30 4 3 4 4 8 10 15 54:50 15 5:30 4 4 3 4 9 9 9 13 22 22 104:50 20 4:50 3 4 3 7 9 10 9 9 22 22 22 78 203:10 25 4:30 2 4 8 9 10 9 9 18 22 22 22 55 113 307:50 Exceptional Exposure 30 4:30 6 10 9 9 10 13 22 22 22 22 27 113 113 402:50 35 4:10 5 10 9 10 9 19 22 23 22 22 22 87 113 113 490:30 40 3:50 2 10 9 10 11 22 22 22 22 22 22 52 113 113 113 569:10 45 3:50 7 9 9 15 22 22 22 22 22 22 26 100 113 113 113 641:10 270 FSW Bottom Time (min) Time to 1st Stop (M:S) 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 8:00 1 4 4 17:20 10 6:20 1 4 4 4 4 9 9 16 57:40 15 5:20 1 4 4 4 4 9 10 9 15 22 22 109:40 20 5:00 4 4 4 8 9 9 10 11 22 22 22 88 218:20 25 4:40 4 4 9 9 10 9 10 20 22 22 22 66 113 325:00 Exceptional Exposure 30 4:20 2 8 9 10 9 10 16 22 22 22 22 41 113 113 423:40 35 4:20 9 9 10 9 10 22 22 22 22 22 22 102 113 113 511:40 40 4:00 6 9 10 9 15 22 22 22 22 22 22 69 113 113 113 593:20 45 3:40 1 10 9 10 18 22 22 22 22 22 22 37 107 113 113 113 667:00 275 FSW Bottom Time (min) Time to 1st Stop (M:S) 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 8:10 2 4 4 18:30 10 6:30 2 4 4 4 4 10 9 18 61:50 15 5:30 3 4 3 4 5 10 9 10 16 22 24 115:50 20 4:50 2 4 4 4 9 9 10 9 14 22 22 22 99 235:10 Exceptional Exposure 25 4:30 2 4 5 9 10 9 10 10 22 22 22 22 79 113 343:50 30 4:30 4 9 10 9 10 9 19 22 22 22 22 55 113 113 443:50 35 4:10 4 9 9 10 9 13 22 22 22 22 22 32 108 113 113 534:30 40 3:50 1 9 10 9 9 19 22 22 22 22 22 22 86 113 113 114 619:10 45 3:50 5 10 9 9 22 22 22 22 22 22 22 48 113 113 113 113 691:10 280 FSW Bottom Time (min) Time to 1st Stop (M:S) 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 8:20 3 4 3 18:40 10 6:40 3 4 4 4 5 10 9 19 65:00 15 5:40 4 4 4 4 6 9 10 9 18 22 32 128:00 20 5:00 3 4 4 5 10 9 10 9 15 23 22 22 109 250:20 Exceptional Exposure 25 4:40 3 4 7 10 9 10 9 12 22 22 22 22 92 113 362:00 30 4:20 2 6 9 10 9 10 9 21 22 22 22 22 70 113 113 464:40 35 4:20 7 10 9 9 10 16 22 22 22 22 22 43 113 113 113 557:40 40 4:00 4 10 9 10 9 22 22 22 22 22 22 26 99 113 113 113 642:20 45 4:00 9 9 10 13 22 22 22 22 22 22 22 68 113 113 113 113 719:20 285 FSW Bottom Time (min) Time to 1st Stop (M:S) 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 8:30 3 4 4 19:50 10 6:30 1 4 4 3 4 7 9 10 20 68:50 15 5:30 2 4 4 3 4 8 9 10 9 21 22 40 141:50 20 4:50 1 4 4 4 7 9 9 10 9 18 22 22 29 113 266:10 Exceptional Exposure 25 4:30 1 4 4 9 9 10 9 10 14 22 22 22 23 104 113 380:50 30 4:30 3 8 10 9 10 9 11 22 22 22 22 22 84 113 113 484:50 35 4:10 2 9 10 9 9 10 19 22 22 22 22 22 59 113 113 113 580:30 40 4:10 8 10 9 10 12 22 22 22 22 22 22 38 104 113 113 113 666:30 45 3:50 4 9 10 9 17 22 22 22 22 22 22 22 87 113 113 113 113 746:10 290 FSW Bottom Time (min) Time to 1st Stop (M:S) 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 8:20 1 4 3 5 21:40 10 6:40 2 4 4 4 3 8 9 10 22 73:00 15 5:40 3 4 4 4 4 8 10 9 10 22 22 48 154:00 20 5:00 3 4 3 4 9 9 9 10 9 20 22 22 40 113 282:20 Exceptional Exposure 25 4:40 3 4 5 9 9 10 9 10 17 22 22 22 31 109 113 400:00 30 4:20 1 5 9 10 9 9 10 14 22 22 22 22 23 99 113 113 507:40 35 4:20 5 10 9 10 9 10 22 22 22 22 22 22 76 113 113 113 604:40 40 4:00 3 9 10 9 10 15 22 23 22 22 22 22 49 111 113 113 113 692:20 45 4:00 8 9 10 9 20 22 22 22 22 22 22 31 95 113 113 113 113 770:20 295 FSW Bottom Time (min) Time to 1st Stop (M:S) 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 8:30 1 4 4 5 22:50 10 6:50 3 4 4 4 3 9 9 11 22 76:10 15 5:30 1 4 4 3 4 5 9 10 9 12 22 22 56 166:50 20 4:50 1 3 4 4 4 10 9 10 9 10 22 22 22 50 113 298:10 Exceptional Exposure 25 4:30 1 4 4 6 10 9 9 10 9 20 22 22 22 41 112 113 418:50 30 4:30 3 6 10 9 9 10 9 17 22 22 22 22 33 103 113 113 527:50 35 4:30 9 9 10 9 10 12 22 22 22 22 22 23 91 113 113 113 626:50 40 4:10 7 9 10 9 9 20 22 22 22 22 22 22 66 113 113 113 113 718:30 45 3:50 2 10 9 10 11 22 22 22 22 22 22 22 43 102 113 113 113 113 797:10 300 FSW Bottom Time (min) Time to 1st Stop (M:S) 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group 5 8:40 2 4 4 6 25:00 10 7:00 4 4 4 4 4 9 9 12 22 79:20 15 5:40 2 4 4 4 4 5 10 9 10 14 22 22 64 180:00 20 5:00 2 4 4 4 5 10 9 10 9 12 22 22 22 62 113 315:20 Exceptional Exposure 25 4:40 2 4 4 8 10 9 10 9 9 22 22 23 22 51 113 113 436:00 30 4:20 1 4 8 9 10 9 10 9 20 22 22 22 22 43 108 113 113 549:40 35 4:20 4 9 9 10 9 10 15 22 22 22 22 23 32 97 113 113 113 649:40 40 4:00 1 10 9 10 9 10 22 22 22 22 22 22 22 83 113 113 113 113 742:20 310 FSW Bottom Time (min) Time to 1st Stop (M:S) 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group Exceptional Exposure 6 8:20 1 4 4 4 6 9 36:40 10 7:00 2 4 4 4 4 6 9 10 15 22 87:20 15 5:40 1 4 4 4 4 4 8 9 9 10 18 22 22 81 206:00 20 5:00 1 4 4 4 4 8 10 9 10 9 17 22 22 22 85 113 349:20 25 4:40 2 4 3 7 9 10 9 9 10 14 22 22 22 22 81 113 113 477:00 30 4:40 4 6 10 9 10 9 10 12 22 22 22 22 22 69 113 113 113 593:00 35 4:20 2 9 10 9 9 10 9 22 22 22 22 22 22 54 109 113 113 113 696:40 40 4:20 9 9 10 9 10 16 22 22 22 22 23 22 41 98 113 113 113 113 791:40 320 FSW Bottom Time (min) Time to 1st Stop (M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 Total Ascent (M:S) Rep Group Exceptional Exposure 6 8:40 3 4 4 4 7 10 41:00 10 7:00 1 4 4 4 4 4 7 10 9 19 22 95:20 15 6:00 4 3 4 4 4 5 10 9 9 10 22 22 22 98 232:20 20 5:20 4 4 4 4 6 9 10 9 9 10 22 22 22 28 102 113 383:40 25 4:40 1 4 4 4 9 10 9 10 9 10 19 22 22 22 34 96 113 113 516:00 30 4:40 3 5 10 9 9 10 9 10 18 22 22 22 22 31 91 113 113 113 637:00 35 4:20 1 8 10 9 10 9 9 16 22 22 22 22 22 24 84 113 113 113 113 746:40 40 4:20 7 10 9 10 9 11 22 22 22 22 22 22 22 66 112 113 113 113 113 844:40 Frequently Asked Questions Why use helium-oxygen instead of air at depth? Air causes nitrogen narcosis at depths beyond ~100 FSW (individual variation), which impairs diver judgment and performance. Helium does not cause narcosis, making HeO2 the preferred gas for deep operations. HeO2 also has faster decompression kinetics than air at equivalent depths due to helium\u0026rsquo;s lower solubility.\nWhat are the gas switch requirements? USN Table 12-4 mandates specific gas switches during ascent:\nBottom mix (HeO2) — all bottom time and stops at 50 FSW and deeper 50% O2 — stop at 40 FSW 100% O2 — stops at 30 and 20 FSW These switches are non-optional and dramatically reduce total decompression time.\nWhat does \u0026ldquo;Chamber O2 Periods\u0026rdquo; mean? Each chamber O2 period is 30 minutes of 100% oxygen breathing in a deck recompression chamber (DRC) after surfacing. This surface decompression (SurDO2) completes the decompression obligation started in the water. The number of periods required increases with bottom time and depth.\nRelated Topics USN Air Dive Tables — Air decompression tables with interactive NDL lookup USN Dive Tables Overview — Complete index of all USN tables Surface-Supplied Diving Systems Dive Planning \u0026amp; Risk Assessment Emergency Response Frameworks ","permalink":"/melon-wiki/commercial-diving/usn-heo2-dive-tables/","summary":"\u003ch1 id=\"us-navy-diving-manual--revision-7-heo2-and-mixed-gas-dive-tables\"\u003eU.S. Navy Diving Manual — Revision 7 HeO2 and Mixed Gas Dive Tables\u003c/h1\u003e\n\u003cp\u003e\u003cstrong\u003eSource:\u003c/strong\u003e SS521-AG-PRO-010, U.S. Navy Diving Manual, Revision 7, 01 December 2016\n\u003cstrong\u003eNAVSEA Reference:\u003c/strong\u003e Published by Direction of Commander, Naval Sea Systems Command\u003c/p\u003e\n\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eCRITICAL WARNING:\u003c/strong\u003e These tables are transcribed from the official USN Diving Manual Revision 7. \u003cstrong\u003eThey must be verified against the original publication before operational use.\u003c/strong\u003e Transcription errors, however unlikely, could be fatal. Always cross-reference with the official NAVSEA publication.\u003c/p\u003e","title":"USN Helium-Oxygen Dive Tables — U.S. Navy Diving Manual Rev 7"},{"content":"USN No-Decompression Limits — Air Diving Source: SS521-AG-PRO-010, U.S. Navy Diving Manual, Revision 7, 01 December 2016\nCRITICAL WARNING: These tables are transcribed from the official USN Diving Manual Revision 7. They must be verified against the original NAVSEA publication before operational use. Transcription errors, however unlikely, could be fatal.\nDownload NDL Tables as PDF Opens print dialog — choose \"Save as PDF\" to download Interactive NDL Lookup — Tables 9-7 \u0026amp; 9-8 Enter depth and bottom time to instantly find your no-decompression status and repetitive group. Enter a surface interval for repetitive dive calculations.\nSingle Dive Repetitive Dive Enter depth and bottom time to find your no-decompression status and repetitive group (Table 9-7).\nDepth (FSW) Select… 101520 253035 404550 556070 8090100 110120130 140150160 170180190 Bottom Time (min) Look Up Plan a second dive using Table 9-8. Enter your post-dive group, surface interval, and next dive depth.\nStep 1 — Surface interval credit (Table 9-8, Part 1) Post-Dive Group Select… ZONM LKJI HGFE DCBA Surface Interval : Next Depth (FSW) Select… 101520 253035 404550 556070 8090100 110120130 140150160 170180190 Look Up Verify before operational use. These values are transcribed from USN Diving Manual Rev 7 (SS521-AG-PRO-010). Cross-reference with the official NAVSEA publication before any dive. Transcription errors, however unlikely, can be fatal. Table 9-7. No-Decompression Limits and Repetitive Group Designators For standard depths 10–190 FSW. The No-Stop Limit column shows the maximum bottom time (minutes) without required decompression stops. The lettered columns show the repetitive group accumulated at that bottom time.\n* = Highest repetitive group achievable at this depth regardless of bottom time. Blank cells = Group not achievable at this depth.\nDepth (fsw) No-Stop Limit (min) A B C D E F G H I J K L M N O Z 10 Unlimited 57 101 158 245 426 * 15 Unlimited 36 60 88 121 163 217 297 449 * 20 Unlimited 26 43 61 82 106 133 165 205 256 330 461 * 25 1102 20 33 47 62 78 97 117 140 166 198 236 285 354 469 992 1102 30 371 17 27 38 50 62 76 91 107 125 145 167 193 223 260 307 371 35 232 14 23 32 42 52 63 74 87 100 115 131 148 168 190 215 232 40 163 12 20 27 36 44 53 63 73 84 95 108 121 135 151 163 45 125 11 17 24 31 39 46 55 63 72 82 92 102 114 125 50 92 9 15 21 28 34 41 48 56 63 71 80 89 92 55 74 8 14 19 25 31 37 43 50 56 63 71 74 60 63 7 12 17 22 28 33 39 45 51 57 63 70 48 6 10 14 19 23 28 32 37 42 47 48 80 39 5 9 12 16 20 24 28 32 36 39 90 33 4 7 11 14 17 21 24 28 31 33 100 25 4 6 9 12 15 18 21 25 110 20 3 6 8 11 14 16 19 20 120 15 3 5 7 10 12 15 130 12 2 4 6 9 11 12 140 10 2 4 6 8 10 150 8 3 5 7 8 160 7 3 5 6 7 170 6 4 6 180 6 4 5 6 190 5 3 5 Dives to 200 FSW and deeper have no no-decompression option — decompression stops are mandatory. Use Table 9-9 for required decompression schedules.\nTable 2A-1. Shallow Water NDL — 30 to 50 FSW (1-Foot Increments) For precise planning at non-standard depths within the 30–50 FSW range. Same repetitive group designators as Table 9-7.\nBlank cells = Group not achievable at this depth.\nDepth (fsw) No-Stop Limit (min) A B C D E F G H I J K L M N O Z 30 371 17 27 38 50 62 76 91 107 125 145 167 193 223 260 307 371 31 334 16 26 37 48 60 73 87 102 119 138 158 182 209 242 282 334 32 304 15 25 35 46 58 70 83 98 114 131 150 172 197 226 261 304 33 281 15 24 34 45 56 67 80 94 109 125 143 163 186 212 243 281 34 256 14 23 33 43 54 65 77 90 104 120 137 155 176 200 228 256 35 232 14 23 32 42 52 63 74 87 100 115 131 148 168 190 215 232 36 212 14 22 31 40 50 61 72 84 97 110 125 142 160 180 204 212 37 197 13 21 30 39 49 59 69 81 93 106 120 136 153 172 193 197 38 184 13 21 29 38 47 57 67 78 90 102 116 131 147 164 184 39 173 12 20 28 37 46 55 65 76 87 99 112 126 141 157 173 40 163 12 20 27 36 44 53 63 73 84 95 108 121 135 151 163 41 155 12 19 27 35 43 52 61 71 81 92 104 117 130 145 155 42 147 11 19 26 34 42 50 59 69 79 89 101 113 126 140 147 43 140 11 18 25 33 41 49 58 67 76 87 98 109 122 135 140 44 134 11 18 25 32 40 48 56 65 74 84 95 106 118 130 134 45 125 11 17 24 31 39 46 55 63 72 82 92 102 114 125 46 116 10 17 23 30 38 45 53 61 70 79 89 99 110 116 47 109 10 16 23 30 37 44 52 60 68 77 87 97 107 109 48 102 10 16 22 29 36 43 51 58 67 75 84 94 102 49 97 10 16 22 28 35 42 49 57 65 73 82 91 97 50 92 9 15 21 28 34 41 48 56 63 71 80 89 92 For residual nitrogen times at these depths in 1-foot increments, see Table 2A-2 on the full air tables page.\nHow to Use These Tables Single Dive (no prior dives within 12 hours) Find your planned depth in the Depth column Read across to find the No-Stop Limit — your maximum bottom time Find the column matching your actual bottom time to read your Repetitive Group on surfacing If your planned bottom time exceeds the No-Stop Limit, decompression stops are required — use Table 9-9 Repetitive Dive (prior dive within 12 hours) Note your Repetitive Group from the previous dive (Table 9-7) Find your surface interval in Table 9-8 Part 1 to determine your new group Use Table 9-8 Part 2 with your new group and next dive depth → Residual Nitrogen Time (RNT) Add RNT to planned bottom time → Equivalent Single Dive Time (ESDT) If ESDT exceeds the NDL, use Table 9-9 for the required decompression schedule Use the interactive tool at the top of this page to perform repetitive dive calculations automatically.\nRelated Tables USN Air Decompression Table (Table 9-9) — Required stops when the NDL is exceeded; also contains Tables 9-7, 9-8, 9-5, 9-6, 2A-1, and 2A-2 USN HeO2 Dive Tables (Table 12-4) — Helium-oxygen mixed gas decompression Dive Planning \u0026amp; Risk Assessment Dive Logs \u0026amp; Operational Records ","permalink":"/melon-wiki/commercial-diving/usn-ndl-table/","summary":"\u003ch1 id=\"usn-no-decompression-limits--air-diving\"\u003eUSN No-Decompression Limits — Air Diving\u003c/h1\u003e\n\u003cp\u003e\u003cstrong\u003eSource:\u003c/strong\u003e SS521-AG-PRO-010, U.S. Navy Diving Manual, Revision 7, 01 December 2016\u003c/p\u003e\n\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eCRITICAL WARNING:\u003c/strong\u003e These tables are transcribed from the official USN Diving Manual Revision 7. \u003cstrong\u003eThey must be verified against the original NAVSEA publication before operational use.\u003c/strong\u003e Transcription errors, however unlikely, could be fatal.\u003c/p\u003e\u003c/blockquote\u003e\n\u003cdiv class=\"pdf-dl-bar\" id=\"pdf-dl-bar-0\"\u003e\n  \u003cbutton class=\"pdf-dl-btn\" id=\"pdf-dl-btn-0\"\u003e\n    \u003csvg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2.5\" stroke-linecap=\"round\" stroke-linejoin=\"round\" aria-hidden=\"true\"\u003e\u003cpath d=\"M21 15v4a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2v-4\"/\u003e\u003cpolyline points=\"7 10 12 15 17 10\"/\u003e\u003cline x1=\"12\" y1=\"15\" x2=\"12\" y2=\"3\"/\u003e\u003c/svg\u003e\n    Download NDL Tables as PDF\n  \u003c/button\u003e\n  \u003cspan class=\"pdf-dl-hint\"\u003eOpens print dialog — choose \"Save as PDF\" to download\u003c/span\u003e\n\u003c/div\u003e\n\n\u003cscript\u003e\n(function() {\n  var btn = document.getElementById('pdf-dl-btn-0');\n  if (!btn) return;\n\n  btn.addEventListener('click', function() {\n    var contentEl = document.querySelector('.post-content');\n    if (!contentEl) { window.print(); return; }\n\n    \n    var clone = contentEl.cloneNode(true);\n\n    \n    ['.ndl-lookup', '.dlf-wrap', '.pdf-dl-bar'].forEach(function(sel) {\n      clone.querySelectorAll(sel).forEach(function(el) { el.remove(); });\n    });\n\n    \n    var titleEl = document.querySelector('.post-title') || document.querySelector('h1');\n    var pageTitle = titleEl ? 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Enter a surface interval for repetitive dive calculations.\u003c/p\u003e","title":"USN No-Decompression Limits — Table 9-7 \u0026 2A-1 (Air Diving)"},{"content":"Vehicle Classes \u0026amp; Capabilities Subsea vehicles are classified by their operational role, level of autonomy, depth rating, and intervention capability. Understanding the classification helps in matching the right vehicle type to a specific mission requirement and understanding the operational constraints that apply.\nWhy This Exists \u0026ldquo;Subsea vehicle\u0026rdquo; covers everything from a shallow-water inspection drone to a full-ocean-depth survey AUV. The operational, safety, and regulatory requirements differ dramatically across these categories. Clear classification prevents misapplication of capability or operating requirements.\nWho This Is For Project managers specifying vehicle requirements for operations Engineers selecting or designing vehicles for specific missions Safety officers understanding the risk profile of different vehicle types Regulators and auditors assessing operational compliance Classification by Level of Autonomy Remotely Operated Vehicles (ROVs) Tethered, operator-controlled vehicles:\nControl: Continuous real-time operator control via umbilical Communication: High-bandwidth copper or fibre umbilical (video, commands, telemetry) Endurance: Unlimited while tethered; limited by consumables and personnel rotation Safety: Tether provides physical recovery mechanism; immediate operator response to anomalies Semi-Autonomous Underwater Vehicles (SAUVs) Vehicles with both tethered and autonomous modes, or with significant autonomous stabilisation and task execution:\nControl: Operator provides high-level commands; vehicle executes autonomously Communication: Tethered or acoustic (for extended range) Applications: Hover-capable AUVs that can be remotely supervised when acoustic comms are available Autonomous Underwater Vehicles (AUVs) Untethered, self-navigating vehicles executing pre-programmed missions:\nControl: Operator-defined before deployment; autonomous during mission Communication: Acoustic (low bandwidth, high latency) or none during mission Endurance: Limited by battery; typically hours to days Safety: No immediate intervention capability; must have built-in fail-safe behaviours See AUV Platforms Overview for AUV categories.\nClassification by Operational Role Observation-Class ROVs Light vehicles for observation and inspection:\nDepth rating: Typically 100–1000m Payload: Cameras, basic sensors; limited or no manipulators Launch system: Can be deployed from small vessels; some man-portable Applications: Shallow inspection, scientific observation, aquaculture monitoring Work-Class ROVs Heavy vehicles with significant intervention capability:\nDepth rating: Typically 2000–4000m; some rated to 6000m Payload: Multiple cameras, manipulators (2×), heavy tooling, large sensor payloads Launch system: Requires dedicated handling system (LARS) and large support vessel Thrust: 100–400+ kg bollard pull Applications: Offshore construction and installation, subsea infrastructure maintenance, pipeline intervention Survey AUVs AUVs optimised for large-area mapping:\nForm factor: Torpedo/streamlined Depth rating: Shallow (100m) to full ocean depth (6000m+) Payload: MBES, SSS, SBP, CTD Applications: Route surveys, environmental baseline, geohazard assessment Inspection AUVs AUVs optimised for detailed inspection of specific targets:\nForm factor: Hovering/multi-thruster Depth rating: Mission-specific Payload: Cameras, laser scanners, NDT sensors Applications: Pipeline and riser inspection, structure inspection Gliders Low-power, long-endurance oceanographic platforms:\nForm factor: Winged, buoyancy-driven Depth rating: 200–1000m typically Payload: Oceanographic sensors (CTD, ADCP, fluorometer) Endurance: Weeks to months Applications: Sustained oceanographic monitoring Classification by Depth Rating Depth rating is a fundamental vehicle characteristic that limits where it can operate:\nClass Depth Rating Typical Applications Shallow \u0026lt;100m Harbour, aquaculture, diver support Mid-water 100–1000m Continental shelf inspection Deep 1000–3000m Deep shelf and upper slope Deep-water 3000–4000m Standard offshore deepwater Ultra-deep 4000–6000m Deepwater oil and gas Full ocean 6000m+ Scientific research, deep trench Operational rule: Never deploy a vehicle beyond its rated depth. Safety factors for pressure housings do not accommodate arbitrary additional depth.\nInspection Qualification Standards Work-class ROVs and inspection AUVs used for safety-critical inspections (structural, pipeline integrity) may require certification:\nClass society acceptance — DNV, Bureau Veritas, Lloyd\u0026rsquo;s Register inspection and documentation Client qualification — Asset operators may have specific qualification requirements National regulations — Some jurisdictions require approved vehicle types for specific applications Related Topics ROV Systems Overview AUV Platforms Overview Sensor Payloads Power Systems \u0026amp; Endurance Failure Modes \u0026amp; Recovery ","permalink":"/melon-wiki/subsea-robotics/vehicle-classes/","summary":"\u003ch1 id=\"vehicle-classes--capabilities\"\u003eVehicle Classes \u0026amp; Capabilities\u003c/h1\u003e\n\u003cp\u003eSubsea vehicles are classified by their operational role, level of autonomy, depth rating, and intervention capability. Understanding the classification helps in matching the right vehicle type to a specific mission requirement and understanding the operational constraints that apply.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003e\u0026ldquo;Subsea vehicle\u0026rdquo; covers everything from a shallow-water inspection drone to a full-ocean-depth survey AUV. The operational, safety, and regulatory requirements differ dramatically across these categories. Clear classification prevents misapplication of capability or operating requirements.\u003c/p\u003e","title":"Vehicle Classes \u0026 Capabilities"},{"content":"Why Auditability Matters More Than Raw Autonomy As subsea systems become more autonomous, the ability to audit what happened becomes more important than the raw capability to operate autonomously. This page explains why auditability is the critical requirement for trusted autonomous operations.\nWhy This Exists Autonomous systems can operate without human oversight, but this creates a trust problem. How do we know what the system did? Why did it make certain decisions? What went wrong when something fails? Auditability answers these questions and enables trust in autonomous systems.\nWho This Is For System architects designing autonomous systems Regulators reviewing autonomous operations Operators deploying autonomous systems Auditors verifying autonomous operations Incident investigators reconstructing autonomous system behavior The Autonomy-Auditability Tradeoff Raw Autonomy Raw autonomy focuses on:\nCapability — What can the system do? Performance — How well does it perform? Independence — How independently can it operate? Operational reality: Raw autonomy is necessary but not sufficient. A system that can operate autonomously but cannot be audited is not trustworthy.\nAuditability Auditability focuses on:\nObservability — Can we observe what the system is doing? Explainability — Can we explain why the system made decisions? Traceability — Can we trace system behavior to causes? Verifiability — Can we verify system behavior after the fact? Operational reality: Auditability enables trust. Without auditability, autonomous systems cannot be trusted for critical operations.\nWhy Auditability Matters Regulatory Compliance Regulators require auditability:\nIncident investigation — Regulators must be able to investigate incidents Compliance verification — Regulators must be able to verify compliance Accountability — Someone must be accountable for autonomous system behavior Legal requirement: Autonomous systems must be auditable for regulatory compliance. Non-auditable systems may not be permitted.\nInsurance Underwriting Insurers require auditability:\nRisk assessment — Insurers must assess risk of autonomous operations Claims investigation — Insurers must investigate claims Loss prevention — Insurers must understand what went wrong Operational reality: Insurers may not cover non-auditable autonomous systems, or may charge higher premiums.\nIncident Investigation Incident investigation requires auditability:\nWhat happened — Investigators must understand what happened Why it happened — Investigators must understand why it happened How to prevent — Investigators must understand how to prevent recurrence What can go wrong: Non-auditable systems make incident investigation impossible. This creates legal and operational risk.\nOperational Trust Operators require auditability:\nDecision confidence — Operators must trust autonomous system decisions Failure understanding — Operators must understand failures Continuous improvement — Operators must improve systems based on audit data Operational reality: Operators will not trust non-auditable autonomous systems for critical operations.\nAuditability Requirements Observability System must be observable:\nState visibility — Can we see system state? Decision visibility — Can we see system decisions? Action visibility — Can we see system actions? Sensor visibility — Can we see sensor data? What can go wrong: System not observable, critical information not logged, logs not accessible. Observability must be designed in.\nExplainability System must be explainable:\nDecision explanation — Can we explain why decisions were made? Action explanation — Can we explain why actions were taken? Failure explanation — Can we explain why failures occurred? Operational reality: Explainability is difficult for complex systems (e.g., neural networks), but essential for trust.\nTraceability System must be traceable:\nData traceability — Can we trace data to source? Decision traceability — Can we trace decisions to inputs? Action traceability — Can we trace actions to decisions? Audit requirement: Traceability enables auditors to verify system behavior and identify causes.\nVerifiability System must be verifiable:\nPost-facto verification — Can we verify behavior after the fact? Independent verification — Can independent parties verify behavior? Cryptographic verification — Can we cryptographically verify records? Legal requirement: Verifiability enables legal defense and regulatory compliance.\nAuditability vs. Performance The Tradeoff There is often a tradeoff between auditability and performance:\nLogging overhead — Logging adds computational and storage overhead Explanation complexity — Explanation may require additional computation Design constraints — Auditability may constrain system design Operational reality: Tradeoffs must be made, but auditability should not be sacrificed for performance in critical systems.\nThe Solution Design for auditability from the start:\nBuilt-in logging — Logging designed into system architecture Efficient logging — Efficient logging to minimize overhead Selective logging — Log what matters, not everything Compression — Compress logs to reduce storage What can go wrong: Auditability added as afterthought, logging too expensive, logging incomplete. Auditability must be designed in.\nImplementation Approaches Comprehensive Logging Log everything:\nSystem state — Log all system state changes Decisions — Log all decisions and reasoning Actions — Log all actions taken Sensor data — Log all sensor data Advantages: Complete audit trail, no gaps.\nDisadvantages: High storage and computational overhead, difficult to analyze.\nSelective Logging Log what matters:\nCritical decisions — Log critical decisions and reasoning State changes — Log significant state changes Anomalies — Log anomalies and exceptions Periodic snapshots — Periodic full state snapshots Advantages: Lower overhead, easier to analyze.\nDisadvantages: May miss important information, gaps in audit trail.\nEvent Sourcing Log events, reconstruct state:\nEvent log — Log all events that change state State reconstruction — Reconstruct state from event log Immutable log — Event log is immutable Advantages: Complete audit trail, state reconstruction, time travel.\nDisadvantages: Requires event sourcing architecture, may be complex.\nRelated Topics Data Provenance \u0026amp; Chain-of-Custody Audit Logs \u0026amp; Immutability Dive Logs \u0026amp; Operational Records ","permalink":"/melon-wiki/open-standards/auditability/","summary":"\u003ch1 id=\"why-auditability-matters-more-than-raw-autonomy\"\u003eWhy Auditability Matters More Than Raw Autonomy\u003c/h1\u003e\n\u003cp\u003eAs subsea systems become more autonomous, the ability to audit what happened becomes more important than the raw capability to operate autonomously. This page explains why auditability is the critical requirement for trusted autonomous operations.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eAutonomous systems can operate without human oversight, but this creates a trust problem. How do we know what the system did? Why did it make certain decisions? What went wrong when something fails? Auditability answers these questions and enables trust in autonomous systems.\u003c/p\u003e","title":"Why Auditability Matters More Than Raw Autonomy"},{"content":"Why Simulation Matters Offshore Simulation enables safe testing, training, and validation before real-world deployment. This page covers why simulation is essential for modern subsea operations and how it is used in practice.\nWhy This Exists Offshore operations are expensive, risky, and difficult to test. Simulation provides a way to:\nTest safely — Test systems and procedures without risk to personnel or equipment Train effectively — Train operators in realistic scenarios without operational cost Validate before deployment — Validate systems and procedures before real-world use Plan missions — Rehearse missions and identify issues before execution Investigate incidents — Reconstruct incidents and test hypotheses What can go wrong: Simulation not used, simulation results not validated, over-reliance on simulation, simulation not representative of reality.\nWho This Is For Robotics engineers developing autonomous systems Operations managers planning missions Training coordinators developing training programs Safety officers validating procedures Incident investigators reconstructing events Simulation Applications System Development Simulation during system development:\nAlgorithm testing — Test control algorithms in simulation before hardware Failure mode testing — Test system behavior under failure conditions Performance validation — Validate system performance against requirements Integration testing — Test system integration before deployment Operational reality: Simulation accelerates development and reduces risk. However, simulation results must be validated against hardware.\nOperator Training Simulation for operator training:\nBasic skills — Train basic vehicle control and operation Emergency procedures — Train emergency response in safe environment Mission scenarios — Train mission execution in realistic scenarios Failure response — Train response to failures and degraded operations What can go wrong: Training not realistic, training scenarios not representative, operators not prepared for real operations. Training must be validated.\nMission Planning Simulation for mission planning:\nMission rehearsal — Rehearse mission execution in simulation Hazard identification — Identify potential hazards and issues Procedure validation — Validate procedures before execution Resource planning — Plan resources (time, power, equipment) based on simulation Operational reality: Mission rehearsal in simulation identifies issues before real-world execution. However, simulation must be representative.\nIncident Investigation Simulation for incident investigation:\nIncident reconstruction — Reconstruct incident in simulation Hypothesis testing — Test hypotheses about what happened Root cause analysis — Understand root causes through simulation Preventive measures — Test preventive measures in simulation What can go wrong: Simulation not representative of actual conditions, incorrect assumptions, simulation results misinterpreted. Simulation must be validated against actual data.\nSimulation Benefits Safety Simulation improves safety:\nRisk reduction — Test systems and procedures without risk Failure testing — Test failure modes safely Emergency training — Train emergency response safely Procedure validation — Validate procedures before use Operational reality: Simulation cannot eliminate all risk, but it reduces risk by enabling safe testing and training.\nCost Reduction Simulation reduces cost:\nDevelopment cost — Test in simulation before building hardware Training cost — Train in simulation without operational cost Mission cost — Identify issues before execution, reducing mission time Failure cost — Identify failures before deployment, reducing failure cost What can go wrong: Simulation cost exceeds benefit, simulation not used effectively, over-investment in simulation. Cost-benefit must be assessed.\nEfficiency Simulation improves efficiency:\nFaster development — Develop and test faster in simulation Better training — Train more effectively in simulation Better planning — Plan more effectively with simulation Faster validation — Validate faster in simulation Operational reality: Simulation accelerates development and operations, but only if used effectively.\nSimulation Limitations Fidelity Limitations Simulation is not reality:\nModel accuracy — Simulation models are approximations Unknown unknowns — Simulation cannot model everything Environmental variability — Real environment is more variable than simulation System complexity — Real systems are more complex than simulation What can go wrong: Over-confidence in simulation, simulation not validated, simulation results not representative. Simulation must be validated.\nValidation Requirements Simulation must be validated:\nAgainst hardware — Validate simulation against real hardware Against operations — Validate simulation against real operations Against data — Validate simulation against operational data Continuous validation — Validation is ongoing, not one-time Responsibility: Simulation developers must validate simulation. Operators must understand simulation limitations.\nOver-Reliance Risk Over-reliance on simulation:\nFalse confidence — Simulation may create false confidence Reality gaps — Simulation may not capture reality Validation gaps — Simulation may not be validated Operational gaps — Operators may not be prepared for reality What can go wrong: Over-reliance on simulation, insufficient real-world testing, operators not prepared. Simulation complements, but does not replace, real-world testing.\nOperational Integration Simulation in Operations Simulation integrated into operations:\nPre-mission rehearsal — Rehearse missions in simulation Real-time simulation — Use simulation for real-time decision support Post-mission analysis — Analyze missions using simulation Continuous improvement — Use simulation for continuous improvement Operational reality: Simulation is most valuable when integrated into operations, not just used for development.\nSimulation Infrastructure Simulation requires infrastructure:\nComputing resources — Simulation requires computing power Software — Simulation software and licenses Models — Simulation models and data Expertise — Simulation expertise and training What can go wrong: Infrastructure not available, infrastructure not maintained, expertise not available. Simulation infrastructure must be maintained.\nRelated Topics Physics vs Control Realism Confidence Calibration Digital Twins Pre-Mission Rehearsal ","permalink":"/melon-wiki/simulation-training/why-simulation/","summary":"\u003ch1 id=\"why-simulation-matters-offshore\"\u003eWhy Simulation Matters Offshore\u003c/h1\u003e\n\u003cp\u003eSimulation enables safe testing, training, and validation before real-world deployment. This page covers why simulation is essential for modern subsea operations and how it is used in practice.\u003c/p\u003e\n\u003ch2 id=\"why-this-exists\"\u003eWhy This Exists\u003c/h2\u003e\n\u003cp\u003eOffshore operations are expensive, risky, and difficult to test. Simulation provides a way to:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eTest safely\u003c/strong\u003e — Test systems and procedures without risk to personnel or equipment\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eTrain effectively\u003c/strong\u003e — Train operators in realistic scenarios without operational cost\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eValidate before deployment\u003c/strong\u003e — Validate systems and procedures before real-world use\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003ePlan missions\u003c/strong\u003e — Rehearse missions and identify issues before execution\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eInvestigate incidents\u003c/strong\u003e — Reconstruct incidents and test hypotheses\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eWhat can go wrong:\u003c/strong\u003e Simulation not used, simulation results not validated, over-reliance on simulation, simulation not representative of reality.\u003c/p\u003e","title":"Why Simulation Matters Offshore"}]