# Polar Definitions for Land Surveyors

**polar area**—A stereographic grid extending to 79°30′ N from the South Pole and to 79°30′ S from the North Pole, thus providing a 30′ overlap on the Universal Transverse Mercator grid.

**polar axis**—The primary axis of direction in a system of polar or spherical coordinates.

**polar bearing**—In a system of polar or spherical coordinates, the angle formed by the intersection of the reference meridional plane and the meridional plane containing the point.

**polar coordinates**—See *coordinates, polar.*

**polar distance-**^{1} The astronomical coordinate (0° to 180°) measured from the pole of a planet or a star to a point along an hour circle; usually limited in actual use to mean codeclination. ^{2} The complement of the declination (co-declination) or 90° minus the declination. Polar distance forms one side of the astronomical triangle.

**polar map projection**—See *map projection, polar*

**polar motion**—^{1} The irregularly varying motion of the Earth’s pole of rotation with respect to the Earth’s crust. ^{2} The movement of the Earth’s instantaneous axis or rotation with respect to the axis of the figure of the Earth; wobble, wander.

**polar planimeter**—See *planimeter; polar.*

**polar symmetry**—Symmetry in which parts are equal and interchangeable in all directions in planes perpendicular to a central axis but not in both directions from these planes.

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Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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