Mapx is a coordinate transformation library developed at NSIDC. The C code was initially developed from equations given by Snyder (1982) and tested against the examples in his Appendix A. Additional projections have been added as needed. The C version of Mapx currently supports 11 common projections, in both spherical and ellipsoid forms when appropriate.
The Java version was ported from the C to simplify using the transforms in Java applets and applications. The Java lags behind the C somewhat and currently supports nine common projections, in both spherical and ellipsoid forms when appropriate.
The Mapx package is licensed under the GNU Lesser General Public License.
A poster describing some uses of the Mapx library.
Overview of mapping and gridding at NSIDC
Download the C library (mapx-x.x.tar.gz) or Java package (mapx-x.x.jar.gz), and/or a collection of grid parameter definition files (nsidc_maps.tar.gz) to use with the software.
Documentation for the Java package
Documentation for the C library