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An expression sometimes used to indicate the direc- tion intended to be made good over the ground. The preferred term is TRACK, definition 1. This is a misnomer in that courses are directions steered or intended to be steered through the water with respect to a reference meridian.



Related Terms

COURSE OVER GROUND

The direction of the path over the ground actually followed by a vessel. The preferred term is TRACK, definition 1. It is normally a somewhat irregular line. This is a misnomer in that courses are directions steered or intended to be steered through the water with respect to a reference meridian.

TIDAL DIFFERENCE

Difference in time or height of a high or low water at a subordinate station and at a reference station for which predictions are given in the Tide Tables. The difference, when applied accord- ing to sign to the prediction at the reference station, gives the corresponding time or height for the subordinate station.

HYDROGRAPHIC SURVEY

The survey of a water area, with particular reference to submarine relief, and any adjacent land

MEAN RISE OF TIDE

The height of mean high water above the reference or chart sounding datum.

TIDAL CURRENT TABLES

  1. Tables which give the predicted times of slack water and the predicted times and velocities of maximum current flood and ebb for each day of the year at a number of reference stations, together with time differences and velocity ratios for obtain- ing predictions at subordinate stations. 2. Tidal Current Tables, published annually by the National Ocean Survey.

NEAP RISE

The height of neap high water above the elevation of reference or datum of chart.

CURRENT DIFFERENCE

The difference between the time of slack water (or minimum current) or strength of current in any locality and the time of the corresponding phase of the tidal current at a reference station, for which predictions are given in the Tidal Current Tables.

CHART SOUNDING DATUM

The tidal datum to which soundings and drying heights on a chart are referred. It is usually taken to correspond to a low water stage of the tide. Often shortened to CHART DATUM, especially when it is clear that reference is not being made to a geodetic datum.

PILOTING

Navigation involving frequent or continuous determination of position relative to observed geographical points, to a high order of accuracy; directing the movements of a vessel near a coast by means of terrestrial reference points is called coast piloting. Some- times called PILOTAGE. See also PILOTAGE, definition 1.

TIDE TABLES

Tables which give the predicted times and heights of high and low water for every day in the year for a number of reference stations, and tidal differences and ratios by which additional predictions can be obtained for subordinate stations. From these values it is possible to interpolate by a simple procedure the height of the tide at any hour of the day.

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