Yachtmaster Offshore Standard: Chartwork

The RYA Yachtmaster Offshore examination includes navigation and safety, while the theory scope includes position fixing, course shaping and plotting, tidal knowledge, publications and electronic position equipment. At this level, a correct historic construction is not enough: the skipper must decide whether the current plan still works and issue a safe, understandable command.

Use the last position that the navigation team has accepted, with its time and uncertainty, as the start of the revised problem. Do not continue measuring from the departure point or chase an old track line after the evidence has changed. Recalculate distance and time remaining, compare actual progress and cross-track error with the briefed limits, then protect a holding, diversion or sea-room option before making a new route commitment.

Keep evidence classes visible. A timed visual or radar fix is an observation with identification and plotting uncertainty. DR and EP are estimates built from course, distance, leeway and stream assumptions. A chartplotter route is a planned geometry using chart, position and user-entered data. Agreement between displays that share those inputs is repetition, not independent confirmation.

All values in this lesson are fictional revision data, not a route or instruction for use aboard. A real plan requires current charts and publications, vessel-specific performance, applicable weather and tide, a suitable lookout and the skipper's live assessment.