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Sailing reference
Clear explanations of the language used in navigation, pilotage, weather, safety and life under sail.
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Keeping check that the anchor is still holding
Maintained by taking beam and ahead transits or compass bearings of fixed marks and rechecking them regularly, backed by a GPS anchor alarm set to the swinging circle radius plus a margin for position error. Depth alarms are also useful, since dragging usually changes depth. Watchkeeping intervals should shorten as wind rises, tide turns, or when holding ground is known to be marginal.
Read definition →Marks showing where you may or must not drop the hook
A small anchor symbol indicates a recommended or charted anchorage, often within a dashed magenta limit line and sometimes lettered or numbered for berth allocation. An anchor crossed through by a diagonal line marks an area where anchoring is prohibited, typically over submarine cables, pipelines or in a fairway. Related symbols mark cable areas with a wavy line and the word Cable, and spoil grounds and dumping areas with dotted limits.
Read definition →How squarely two position lines cross each other
The reliability of a two-line fix depends on the angle between the lines. A cut near 90 degrees minimises the error ellipse, while a shallow cut converts a small bearing error into a large positional displacement along the bisector. For three objects, aim for roughly 60 degrees between adjacent bearings, spanning about 120 degrees of horizon. As a rule of thumb reject fixes where the cut falls below about 30 degrees unless nothing better is available.
Sailing reference
Clear explanations of the language used in navigation, pilotage, weather, safety and life under sail.