Ocean current chart

An ocean current chart shows the prevailing surface currents of an ocean area by direction and rate, usually as part of a pilot chart or routing atlas compiled from long-run observations and drift data. Navigators use it in passage planning to estimate set and drift over a leg, choosing a track that works the current rather than against it, the same reasoning behind ship-routeing services. It differs from a tidal stream chart, which gives periodic tidal flow keyed to the time of high water, and from real-time surface-current products now delivered under the IHO S-111 data standard. Pilot charts also carry winds, ice limits, and weather statistics.