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SOG The actual speed of a vessel relative to the fixed ground displayed in a GPS unit. This is basically a SMG over a very short period, sometimes less than a second. It is always a speed in the direction of the COG. It is an instantaneous realtime measure of your progress, as is COG. We distinguish this from SMG (speed made good), which describes the average speed from any two points in the past (regardless of the course between them). SMG can be also used to describe speeds that are planned to be achieved in the future.

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