DB2 Version 9.7 for Linux, UNIX, and Windows

Geodetic latitude and longitude

DB2® Geodetic Data Management Feature's coordinate reference system uses geodetic latitude and longitude to describe locations relative to the Earth. Geodetic latitude and longitude are always based on a specific datum.

Geodetic latitude: The geodetic latitude of a point is the angle between the equatorial plane and the perpendicular line that intersects the normal line at the point on the surface of the Earth.
Geodetic longitude: Geodetic longitude is the angle in the equatorial plane between the line a that connects the Earth's center with the prime meridian and the line b that connects the center with the meridian on which the point lies. A meridian is a direct path on the surface of the datum that is the shortest distance between the poles.

The ellipsoid in Figure 1 shows the angles that represent geodetic latitude and longitude. The angle for the geodetic latitude does not start at the very center because of the Earth's ellipsoidal shape.

Figure 1. Geodetic latitude and longitude angles

The figure shows the angles that form the longitude and latitude of point p.

Latitude and longitude coordinates are expressed in degrees with a decimal fraction. There are 360 degrees of longitude, starting at the prime meridian (0° longitude) and proceeding eastward in a positive direction through 180° and west in negative values through –180°. Latitude degrees begin at the equator (0° latitude) and proceed to the North Pole (90° latitude) and South Pole (–90° latitude).