DragonFly On-Line Manual Pages

GEODESIC(3)           DragonFly Library Functions Manual           GEODESIC(3)

NAME
       geod_init - initialize an ellipsoid
       geod_lineinit - initialize a geodesic line
       geod_position - a position on a geodesic line
       geod_direct - the direct geodesic problem
       geod_inverse - the inverse geodesic problem
       geod_polygonarea - the area of a polygon

SYNOPSIS
       #include <geodesic.h>
       and link against the proj library.

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,
       where f is the flattening.  Note that the geodesic routines measure
       angles (latitudes, longitudes, and azimuths) in degrees, unlike the
       rest of the proj library, 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/1.40/C

EXAMPLE
       The following program reads in lines with the coordinates for two
       points in decimal degrees (lat1, lon1, lat2, lon2) and prints out azi1,
       azi2, s12 for the geodesic line between each pair of points on the
       WGS84 ellipsoid.  (N.B. azi2 is 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 for geodesic(3),
       http://geographiclib.sf.net/1.40/C

       geod(1)

       GeographicLib, http://geographiclib.sf.net

       The GeodesicExact class in GeographicLib solves the geodesic problems
       in terms of elliptic integrals; the results are accurate for arbitrary
       f.

       C. F. F. Karney, Algorithms for Geodesics,
       J. Geodesy 87, 43-55 (2013);
       DOI: http://dx.doi.org/10.1007/s00190-012-0578-z
       http://geographiclib.sf.net/geod-addenda.html

       The online geodesic bibliography,
       http://geographiclib.sf.net/geodesic-papers/biblio.html

HOME PAGE
       http://proj.osgeo.org

                             2014/12/17 Rel. 4.9.0                 GEODESIC(3)