Definition
Derived by GNSS from successive fixes or from Doppler measurement against the bottom. It is the speed to use for estimated time of arrival, for tidal gate calculations and for closing rates on fixed hazards. Vectorially, ground track and speed over ground result from combining water track and speed through the water with the set and drift of the tidal stream. Short term GNSS speed can be noisy in a seaway, so use an averaged value.
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