Module 14 - Passage Planning
Monitor
Monitor the vessel's position and progress closely and continuously against the plan. Use the planned primary and independent position evidence, safe-water limits, depth, cross-track error, speed and ETA at critical points. The frequency and method should match the risk: open water and a constrained approach do not justify the same interval or evidence.
Also monitor the conditions that made the plan acceptable: forecast versus observed weather, tide, visibility, traffic, equipment, usable fuel, crew fatigue or seasickness, and the continuing suitability of the destination and alternative. A single on-track position cannot compensate for a closing tidal gate, deteriorating crew or an exposed arrival that has moved outside its limit.
Use decision points and triggers written during planning. If progress is late, visibility deteriorates, independent positions disagree or the crew loses capacity, decide while waiting, turning back, shortening or diverting is still feasible. After any accepted change, update the plan, log and brief, then monitor the new plan rather than continuing to compare against the obsolete one.
| Observed change | Question | Possible trigger response |
|---|---|---|
| Position evidence conflicts | Is safe water still assured and which source is independent? | Create sea room, slow or stop as appropriate, then verify |
| ETA slips | Does the gate, daylight or refuge margin still hold? | Recalculate, hold, shorten or divert |
| Weather differs from forecast | Which exposed leg or arrival assumption changes? | Reef, update, change route or return |
| Crew capacity falls | Can critical navigation and handling roles still be performed? | Rest, redistribute, shorten or seek refuge |
| Equipment degrades | Does the remaining navigation method retain adequate independence? | Change method, route, destination or passage |
Optional quick check
Section 5 of 6
ETA is before the gate, but the planned 45-minute margin has fallen to 15 minutes. What is the sound interpretation?
Sources and factual review
Reviewed 19 August 2026 - Day Skipper Revision.
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