Coastal Skipper Terminology

At Coastal Skipper and Yachtmaster Offshore level, precise navigational language becomes critical. Leeway is the sideways drift of a vessel to leeward caused by the wind acting on the hull and superstructure. Set is the direction in which a tidal stream or current moves, while drift is the speed of that stream measured in knots.

A Dead Reckoning position (DR) is an estimated position based solely on course steered, speed through the water, and time elapsed — it ignores tidal stream and leeway. An Estimated Position (EP) improves on the DR by also accounting for tidal set and drift and an allowance for leeway. Bearings can be expressed as true (referenced to true north), magnetic (referenced to magnetic north), or compass (as read from the vessel's compass, which includes deviation).

A transit (or range) is formed when two charted objects appear in line from the observer's position — this gives an exact position line without needing a compass. A clearing bearing is a bearing of a charted object that, if maintained, keeps the vessel clear of a specific danger. A tidal gate is a point or passage where the tidal stream is so strong that it can only be safely navigated at certain states of the tide.

A weather shore is one from which the wind is blowing — it provides sheltered water in its lee. A lee shore is one onto which the wind is blowing, pushing vessels towards it; this is dangerous because the wind and sea work to drive a vessel aground. Fetch is the unobstructed distance over water that the wind has been blowing — the greater the fetch, the larger the waves that can develop. Sea state descriptors such as 'slight', 'moderate', 'rough', and 'very rough' are standardised terms used in weather forecasts (the Douglas sea scale) to communicate wave heights consistently.