Yachtmaster Offshore Standard: Position

The RYA theory scope includes position fixing, course shaping and plotting and electronic position-finding equipment; the Yachtmaster Offshore examination assesses navigation and skippering. A defensible update therefore says more than ‘we are doing five knots east’. It identifies the accepted position and time, intended ground track, heading reference, water-track or ground-track evidence, speed frame, uncertainty, monitoring limit and next action.

Heading is where the fore-and-aft line points. Course is a selected direction. Water track describes movement through the water after effects such as leeway. Ground track and COG describe movement over the ground; SOG is the corresponding rate. A log commonly supplies speed through water, while GNSS derives movement over the ground. None of those pairs can be substituted silently in an ETA or DR/EP construction.

A COG and SOG sustained over a stated interval form a ground-movement vector. If COG differs from the intended track, not all of the travelled distance advances the route: one component is along track and another is cross track. A plot can show those components directly; the trigonometry below makes the same geometry explicit for revision.

Treat the calculation as a monitored estimate rather than an automatic helm order. Verify the position and time behind the vector, check whether the motion was steady, compare depth, radar, visual and other suitable evidence, and protect a hold, diversion or sea-room option before a danger-side action limit is exceeded.

All numbers in this lesson are fictional revision data. They do not prescribe a live course, speed, passing side or clearance, and written work cannot demonstrate practical Yachtmaster command or instrument competence.