October 22, 2020

Currents and tidal streams

Nature of currents. Currents are permanent or seasonal horizontal movement of water flowing in a certain direction and in the oceans caused by differences in temperature, salinity, density and wind.  Information concerning their direction and strength is given on charts, in Sailing Directions and various current atlases.  The net result […]
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October 22, 2020

Definitions

The following terminology is used with currents and tidal streams: Set – we speak about the set of the current/tidal stream when referring to its direction of flow. It is expressed in degrees (°). Rate – this is the speed of the current/tidal stream expressed in knots. Drift – this […]
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October 22, 2020

Plotting symbols

When plotting courses of vessels and the set of a current/tidal stream, the direction of travel is indicated by arrow heads pointing in the direction of travel. The number of arrow heads differentiate between courses steered, courses made good and the set of a current/tidal stream: One arrow head = […]
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October 22, 2020

Finding the set, rate and drift of a current

The best way of demonstrating how to find the set, rate and drift of a current is by using a practical example: Problem: From an observed position at 1200 a vessel steers 110° (T) at 12 knots. At 1330 another fix is obtained. Determine the set rate and drift of […]
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