GCTPC is a software library for geolocation written by the USGS

gctpc adds:
           (1) support for ellipsoidal models of the earth 
           (2) support for new projections
           (3) transformations:  (lat,lon) -> (X, Y)
                                 (X, Y) -> (lat, lon)

           (1) is necessary as grid approach 1 km.
           (3) is necessary if you want to replace the grib1-centric IPOLATES library
                (limited to spherical earth, 0.001 degrees lat/lon precision)


location:  http://edcftp.cr.usgs.gov/pub/software/gctpc/     (no longer available from this location)
status: public domain

Changes of the source code as distributed by USGS.

 Fixed formats Orion Poplawski 9/2013
 Set files pointers to NULL Orion Poplawski 9/2013
 fixed name collisions  sincos() and sign() Wesley Ebisuzaki 9/2013
 added makefile Wesley Ebisuzaki 2012
 note: stplnfor and stplninv (state plate) which is not used has a problem
 result gctpc20.tar.Z -> gctpc20a.tgz