proj.4 is a standard UNIX filter function which converts geographic longitude and latitude coordinates into cartesian coordinates (and vice versa), and it is a C API for software developers to include coordinate transformation in their own software. proj.4 is maintained on GitHub.

Platform Test Status and Coverage
Travis travis
AppVeyor appveyor
Coverage coverals

Full documentation is available as a single PDF at

Mailing List

The Proj.4 mailing list can be found at

Indices and tables