PostGIS  2.5.0beta2dev-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 1283 of file lwgeodetic.c.

References distance(), FP_EQUALS, GEOGRAPHIC_POINT::lat, GEOGRAPHIC_POINT::lon, LW_FAILURE, and LW_SUCCESS.

Referenced by circ_center_spherical(), and test_sphere_project().

1284 {
1285  double d = distance;
1286  double lat1 = r->lat;
1287  double lon1 = r->lon;
1288  double lat2, lon2;
1289 
1290  lat2 = asin(sin(lat1)*cos(d) + cos(lat1)*sin(d)*cos(azimuth));
1291 
1292  /* If we're going straight up or straight down, we don't need to calculate the longitude */
1293  /* TODO: this isn't quite true, what if we're going over the pole? */
1294  if ( FP_EQUALS(azimuth, M_PI) || FP_EQUALS(azimuth, 0.0) )
1295  {
1296  lon2 = r->lon;
1297  }
1298  else
1299  {
1300  lon2 = lon1 + atan2(sin(azimuth)*sin(d)*cos(lat1), cos(d)-sin(lat1)*sin(lat2));
1301  }
1302 
1303  if ( isnan(lat2) || isnan(lon2) )
1304  return LW_FAILURE;
1305 
1306  n->lat = lat2;
1307  n->lon = lon2;
1308 
1309  return LW_SUCCESS;
1310 }
#define LW_SUCCESS
Definition: liblwgeom.h:79
#define LW_FAILURE
Definition: liblwgeom.h:78
Datum distance(PG_FUNCTION_ARGS)
#define FP_EQUALS(A, B)
Here is the call graph for this function:
Here is the caller graph for this function: