# Geodetic Definitions for Land Surveyors

**geodesy—** The science concerned with the determination of the size and shape of the Earth. The term is often used to include both the science, which must depend on the determinations of the shape and size of the Earth from direct measurements made on its surface (triangulation, leveling, astronomic, and gravity determinations), and the art, which utilizes the scientific determinations in a practical way, and is usually known as geodetic surveying or geodetic engineering.

**geodesy, astronomical—**The determination of longitudes, latitudes, and azimuths by observations of the directions of stars, planets, the Moon, or other celestial bodies.

**geodetic—**Signifies the basic relationship to the Earth in which the curvature of its sea-level surface is taken into account.

**geodetic azimuth—**See *azimuth, geodetic. *

**geodetic bearing—**See *bearing; azimuth, geodetic. *

**geodetic control—**See *control, geodetic.*

**geodetic coordinates—**See *coordinates, geodetic.*

**geodetic distance—**An arc distance on a reference ellipsoid.

**geodetic height—**The height of a point above or below the surface of reference ellipsoid; ellipsoidal height. The geodetic height is equal to the sum of the geoidal height and the orthometric height.

**geodetic latitude**—See *latitude, geodetic.*

**geodetic leveling—**See *leveling, geodetic.*

**geodetic line**—See *line, geodetic.*

**geodetic** **longitude—**See *longitude, geodetic.*

**geodetic meridian—**See *meridian, geodetic.*

**ge****odetic north **[PLSS]**—**The direction of the pole of the Earth ellipsoid of reference.

**geodetic parallel**—See *parallel, geodetic.*

**geodetic position—**See *position, geodetic.*

**Geodetic Reference** **System 1967 **(GRS 67)—The following set of numbers adopted in 1967 by the International Union of Geodesy and Geophysics:

where *a *is the length of the semi-major axis of an equipotential, rotational ellipsoid; *GM *is the product of the gravitational constant *G *by the mass *M *of the Earth; and J_{2}is the dynamic form factor.

**Geodetic Reference System 1980 **(GRS 80)—The following set of numbers

adopted in 1979 by the International Union of Geodesy and Geophysics:

where ω is the angular rate of rotation of the ellipsoidal body; the other symbols have the same meanings as those used for the Geodetic Reference System 1967.

**geodetic survey—**See *survey, geodetic. *

**geodetic surveying**—See *surveying, geodetic.*

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

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