PostGIS  3.0.0dev-r@@SVN_REVISION@@

◆ lwgeom_geohash()

char* lwgeom_geohash ( const LWGEOM lwgeom,
int  precision 
)

Calculate the GeoHash (http://geohash.org) string for a geometry.

Caller must free.

Definition at line 848 of file lwalgorithm.c.

References gbox_init(), geohash_point(), LW_FAILURE, lwerror(), lwgeom_calculate_gbox_cartesian(), lwgeom_geohash_precision(), GBOX::xmax, GBOX::xmin, GBOX::ymax, and GBOX::ymin.

Referenced by ST_GeoHash(), and test_geohash().

849 {
850  GBOX gbox;
851  GBOX gbox_bounds;
852  double lat, lon;
853  int result;
854 
855  gbox_init(&gbox);
856  gbox_init(&gbox_bounds);
857 
858  result = lwgeom_calculate_gbox_cartesian(lwgeom, &gbox);
859  if ( result == LW_FAILURE ) return NULL;
860 
861  /* Return error if we are being fed something outside our working bounds */
862  if ( gbox.xmin < -180 || gbox.ymin < -90 || gbox.xmax > 180 || gbox.ymax > 90 )
863  {
864  lwerror("Geohash requires inputs in decimal degrees, got (%g %g, %g %g).",
865  gbox.xmin, gbox.ymin,
866  gbox.xmax, gbox.ymax);
867  return NULL;
868  }
869 
870  /* What is the center of our geometry bounds? We'll use that to
871  ** approximate location. */
872  lon = gbox.xmin + (gbox.xmax - gbox.xmin) / 2;
873  lat = gbox.ymin + (gbox.ymax - gbox.ymin) / 2;
874 
875  if ( precision <= 0 )
876  {
877  precision = lwgeom_geohash_precision(gbox, &gbox_bounds);
878  }
879 
880  /*
881  ** Return the geohash of the center, with a precision determined by the
882  ** extent of the bounds.
883  ** Possible change: return the point at the center of the precision bounds?
884  */
885  return geohash_point(lon, lat, precision);
886 }
double xmax
Definition: liblwgeom.h:295
int lwgeom_geohash_precision(GBOX bbox, GBOX *bounds)
Definition: lwalgorithm.c:752
#define LW_FAILURE
Definition: liblwgeom.h:78
char * geohash_point(double longitude, double latitude, int precision)
Definition: lwalgorithm.c:591
double ymin
Definition: liblwgeom.h:296
void gbox_init(GBOX *gbox)
Zero out all the entries in the GBOX.
Definition: g_box.c:47
double xmin
Definition: liblwgeom.h:294
uint8_t precision
Definition: cu_in_twkb.c:25
double ymax
Definition: liblwgeom.h:297
void lwerror(const char *fmt,...)
Write a notice out to the error handler.
Definition: lwutil.c:190
int lwgeom_calculate_gbox_cartesian(const LWGEOM *lwgeom, GBOX *gbox)
Calculate the 2-4D bounding box of a geometry.
Definition: g_box.c:678
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