Provided by: libproj-dev_4.9.2-2_amd64

**NAME**

geod_init- initialize an ellipsoidgeod_lineinit- initialize a geodesic linegeod_position- a position on a geodesic linegeod_direct- the direct geodesic problemgeod_inverse- the inverse geodesic problemgeod_polygonarea- the area of a polygon

**SYNOPSIS**

#include <geodesic.h> and link against theprojlibrary.

**DESCRIPTION**

This library is a port of the geodesic routines in the C++ library, GeographicLib, to C. It solves the direct and inverse geodesic problems on an ellipsoid of revolution. In addition, the reduced length of a geodesic and the area between a geodesic and the equator can be computed. The results are accurate to round off for |f| < 1/50, wherefis the flattening. Note that the geodesic routines measure angles (latitudes, longitudes, and azimuths) in degrees, unlike the rest of theprojlibrary, which uses radians. The documentation for this library is included in geodesic.h. A formatted version of the documentation is available at http://geographiclib.sf.net/1.44/C

**EXAMPLE**

The following program reads in lines with the coordinates for two points in decimal degrees (lat1,lon1,lat2,lon2) and prints outazi1,azi2,s12for the geodesic line between each pair of points on the WGS84 ellipsoid. (N.B.azi2is the forward azimuth at point 2.) #include <stdio.h> #include <geodesic.h> int main() { double a = 6378137, f = 1/298.257223563; /* WGS84 */ double lat1, lon1, azi1, lat2, lon2, azi2, s12; struct geod_geodesic g; geod_init(&g, a, f); while (scanf("%lf %lf %lf %lf\n", &lat1, &lon1, &lat2, &lon2) == 4) { geod_inverse(&g, lat1, lon1, lat2, lon2, &s12, &azi1, &azi2); printf("%.8f %.8f %.3f\n", azi1, azi2, s12); } return 0; }

**LIBRARY**

libproj.a - library of projections and support procedures

**SEE** **ALSO**

Full online documentation forgeodesic(3), http://geographiclib.sf.net/1.44/Cgeod(1)GeographicLib, http://geographiclib.sf.net TheGeodesicExactclass in GeographicLib solves the geodesic problems in terms of elliptic integrals; the results are accurate for arbitraryf. C. F. F. Karney,AlgorithmsforGeodesics, J. Geodesy87, 43-55 (2013); DOI: http://dx.doi.org/10.1007/s00190-012-0578-z http://geographiclib.sf.net/geod-addenda.html Theonlinegeodesicbibliography, http://geographiclib.sf.net/geodesic-papers/biblio.html

**HOME** **PAGE**

https://github.com/OSGeo/proj.4/wiki 2014/12/17 Rel. 4.9.0 GEODESIC(3)