PostGIS  2.4.9dev-r@@SVN_REVISION@@

## ◆ sphere_project()

 int sphere_project ( const GEOGRAPHIC_POINT * r, double distance, double azimuth, GEOGRAPHIC_POINT * n )

Given a starting location r, a distance and an azimuth to the new point, compute the location of the projected point on the unit sphere.

Definition at line 1310 of file lwgeodetic.c.

Referenced by circ_center_spherical(), and test_sphere_project().

1311 {
1312  double d = distance;
1313  double lat1 = r->lat;
1314  double lon1 = r->lon;
1315  double lat2, lon2;
1316
1317  lat2 = asin(sin(lat1)*cos(d) + cos(lat1)*sin(d)*cos(azimuth));
1318
1319  /* If we're going straight up or straight down, we don't need to calculate the longitude */
1320  /* TODO: this isn't quite true, what if we're going over the pole? */
1321  if ( FP_EQUALS(azimuth, M_PI) || FP_EQUALS(azimuth, 0.0) )
1322  {
1323  lon2 = r->lon;
1324  }
1325  else
1326  {
1327  lon2 = lon1 + atan2(sin(azimuth)*sin(d)*cos(lat1), cos(d)-sin(lat1)*sin(lat2));
1328  }
1329
1330  if ( isnan(lat2) || isnan(lon2) )
1331  return LW_FAILURE;
1332
1333  n->lat = lat2;
1334  n->lon = lon2;
1335
1336  return LW_SUCCESS;
1337 }
#define LW_SUCCESS
Definition: liblwgeom.h:80
#define LW_FAILURE
Definition: liblwgeom.h:79
Datum distance(PG_FUNCTION_ARGS)
#define FP_EQUALS(A, B)
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