The speed of a vessel relative to the earth's surface, as measured by GPS or other positioning systems. SOG may differ from the vessel's speed through the water due to the effects of current and tidal streams.
Category: Navigation & Seamanship
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ParallelA circle on the earth's surface formed by the intersection of a plane parallel to the equator.Port (Direction)The left-hand side of a vessel when facing forward (toward the bow).Rhumb LineA line on the earth's surface that crosses all meridians at the same angle, appearing as a straight line on a Mercator projection chart.StarboardThe right-hand side of a vessel when facing forward (toward the bow).SternThe rear-most part of a vessel's hull where the rudder and propeller are typically located.TransitThe passage of a vessel through a canal, strait, or narrow waterway.
Back to DictionaryEntry updated May 2026