A circle on the earth's surface formed by the intersection of a plane parallel to the equator. Each parallel represents a line of constant latitude, with the equator being the largest parallel at 0 degrees.
Category: Navigation & Seamanship
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LongitudeThe angular distance of a point east or west of the Prime Meridian at Greenwich, measured in degrees from 0 to 180.Magnetic NorthThe direction indicated by a magnetic compass needle toward the earth's magnetic north pole, which differs from true north by an angle called magnetic variation or declination.Nautical MileA unit of distance used in maritime and air navigation equal to approximately 1,852 metres or 1.151 statute miles.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.Speed Over GroundThe speed of a vessel relative to the earth's surface, as measured by GPS or other positioning systems.
Back to DictionaryEntry updated May 2026