Tools Astrocalculator Geodetic Coordinates module The Geodetic Coordinates calculator module Geodetic Coordinates The normal geographic coordinate system assumes that the Earth is a perfect sphere. This is nearly true, so for most purposes geographic coordinates are fine. If very high precision is required, then we must take the true shape of the Earth into account. The Earth is an ellipsoid; the distance around the equator is about 0.3% longer than a Great Circle that passes through the poles. The Geodetic Coordinate system takes this ellipsoidal shape into account, and expresses the position on the Earth's surface in Cartesian coordinates (X, Y and Z) or in Geographic coordinates (Longitude, Latitude and Elevation). To use the module, first select which coordinates you will use as input in the Select Input Coordinates section: Cartesian or Geographic radio buttons. Then select an ellipsoid model and fill in the input coordinates in either the Cartesian Coordinates section or the Geographic Coordinates section. When you press the Convert button, the corresponding coordinates will be filled in. The module contains a batch mode for converting several coordinate values at once. You must construct an input file in which each line contains up to three numbers: the input coordinate values (either Cartesian or Geographic). Then specify which coordinates you are using as input, and identify the input and output filenames. Finally, press the Run button to generate the output file, which will contain the converted coordinates (Cartesian or Geographic; the complement of what you chose as the input values).