Cartographic projection filter and library (datum package)

 Proj and invproj perform respective forward and inverse transformation
 of cartographic data to or from Cartesian data with a wide range of
 selectable projection functions (over 100 projections).
 .
 Geod and invgeod perform geodesic (Great Circle) computations for
 determining latitude, longitude and back azimuth of a terminus point given
 a initial point latitude, longitude, azimuth and distance (direct) or the
 forward and back azimuths and distance between an initial and terminus
 point latitudes and longitudes (inverse).
 .
 This package contains auxiliary projection datum grids used by the
 library and tools.