Geodetic

A Geodetic Coordinate System is a three-dimensional coordinate system defined by an ellipsoid, the equatorial plane of the ellipsoidal and a plane defined along the polar axis (a meridional plane).

Coordinates in a Geodetic Coordinate System are given by a geodetic latitude (the angle between the normal to the ellipsoid at a location and the equatorial plane), a geodetic longitude (the angle between the meridional reference plane and a meridional plane containing the normal to the ellipsoid at a location) and a geodetic height (the perpendicular distance of a location from the ellipsoid).

A geodetic datum is the only required defining parameter for a Geodetic Coordinate System in the Geographic Calculator. A geodetic datum defines constants that relate a Geodetic Coordinate System to the physical earth, the dimensions of the reference ellipsoid, the location of the origin of the system, and the orientation of the system.

A geodetic coordinate is specified in the Geographic Calculator by latitude, longitude, and ellipsoidal height values. Any angular unit defined within the Geographic Calculator may be used to specify latitude and longitude coordinates.

The ellipsoidal height of a location is defined as the elevation of the location above the geoid (essentially a modeled surface representing mean sea level) and the separation of the geoid surface from the ellipsoidal surface. The Geographic Calculator assumes a value of 0.0 if the ellipsoidal height of a location is unknown. Any distance unit defined within the Geographic Calculator may be used to specify ellipsoidal height values.