GCTP - General Cartographic Transformation Package GCTP is software designed to permit the transformation of coordinate pairs from one map projection to another. The GCTP is used by the National Mapping Division for map projection computations. Unix/Win32 (Apr 2001)
GEOTRANS - Geographic Translator GEOTRANS is an application program which allows users to easily convert geographic coordinates among a wide variety of coordinate systems, map projections, and datums. Supports Win32/Unix (Apr 2002)
GMT - Generic Mapping Tools GMT is a free, open source collection of ~60 UNIX style tools that allow users to manipulate (x,y) and (x,y,z) data sets (including filtering, trend fitting, gridding, projecting, etc.) and produce PostScript. Unix/Win32. (Apr 2001)
PROJ.4 - Cartographic transformation library PROJ.4 is a cartographic projections and datum shifting library written in C. Support many (100+) projections, including Transverse Mercator and Lambert Conformal Conic. Unix/Win32. Open Source. (Apr 2001)
Zipdy - library calculates ZIP code distances Zipdy performs great circle distance calculations between two US zip codes. A database of longitude and latitude points for zip codes created by the US Census is distributed with zipdy. It is available in C, PHP, and Perl, GPL (Sep 2002)
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