The earthdistance module provides two different approaches to calculating great circle distances on the surface of the Earth. The one described first depends on the cube module. The second one is based on the built-in point data type, using longitude and latitude for the coordinates.
In this module, the Earth is assumed to be perfectly spherical. (If that's too inaccurate for you, you might want to look at the PostGIS project.)
The cube module must be installed before earthdistance can be installed (although you can use the CASCADE option of CREATE EXTENSION to install both in one command).
It is strongly recommended that earthdistance and cube be installed in the same schema, and that that schema be one for which CREATE privilege has not been and will not be granted to any untrusted users. Otherwise there are installation-time security hazards if earthdistance's schema contains objects defined by a hostile user. Furthermore, when using earthdistance's functions after installation, the entire search path should contain only trusted schemas.
Data is stored in cubes that are points (both corners are the same) using 3 coordinates representing the x, y, and z distance from the center of the Earth. A