fyi taken from http://lists.maptools.org/pipermail/proj/2013-May/006602.html
--------------------------------------------------------------------------------------------- geod and invgeod, programs for performing geodesic calculations, have been part of proj.4 since at least 1995. There are several problems with them: * the overall accuracy is limited; * the results of inverse calculations are sometimes wildly wrong; * there's no documented API for the geodesic capabilities; * there's no provision from computing various quantities associated with geodesics (in particular the area of a geodesic polygon). These problems will be addressed in the next release of proj.4 with the inclusion of the algorithms for geodesics from GeographicLib. These are documented in C. F. F. Karney, Algorithms for geodesics, J. Geodesy 87(1), 43-55 (Jan. 2013) http://dx.doi.org/10.1007/s00190-012-0578-z Addenda: http://geographiclib.sf.net/geod-addenda.html Points to note: [...] * Several libraries that depend on proj.4, e.g., GRASS, use approximate methods for computing polygonal areas. They can now use proj.4 to compute areas accurately. ----- best regards Helmut -- View this message in context: http://osgeo-org.1560.x6.nabble.com/Proj-Improvements-to-geod-and-invgeod-tp5055773.html Sent from the Grass - Dev mailing list archive at Nabble.com. _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
