The reference level from which depths on a nautical chart are measured, typically the lowest astronomical tide (LAT). All soundings shown on a chart indicate the depth of water below this datum under normal conditions.
Category: Navigation & Seamanship
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BeamThe width of a vessel at its widest point, measured at the midship section.BearingThe horizontal direction of one point from another, measured clockwise from true north, magnetic north, or the heading of a vessel.BowThe forward-most part of a vessel's hull, designed to reduce the resistance of the hull cutting through water.Compass RoseA graduated circle printed on nautical charts showing both true and magnetic north, used to determine bearings and courses.CourseThe intended horizontal direction of travel measured as an angle from north.Course Over GroundThe actual direction of a vessel's movement over the earth's surface, as determined by GPS or other positioning systems.
Back to DictionaryEntry updated May 2026