PostGIS  2.5.7dev-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 856 of file lwalgorithm.c.

857 {
858  GBOX gbox;
859  GBOX gbox_bounds;
860  double lat, lon;
861  int result;
862
863  gbox_init(&gbox);
864  gbox_init(&gbox_bounds);
865
866  result = lwgeom_calculate_gbox_cartesian(lwgeom, &gbox);
867  if ( result == LW_FAILURE ) return NULL;
868
869  /* Return error if we are being fed something outside our working bounds */
870  if ( gbox.xmin < -180 || gbox.ymin < -90 || gbox.xmax > 180 || gbox.ymax > 90 )
871  {
872  lwerror("Geohash requires inputs in decimal degrees, got (%g %g, %g %g).",
873  gbox.xmin, gbox.ymin,
874  gbox.xmax, gbox.ymax);
875  return NULL;
876  }
877
878  /* What is the center of our geometry bounds? We'll use that to
879  ** approximate location. */
880  lon = gbox.xmin + (gbox.xmax - gbox.xmin) / 2;
881  lat = gbox.ymin + (gbox.ymax - gbox.ymin) / 2;
882
883  if ( precision <= 0 )
884  {
885  precision = lwgeom_geohash_precision(gbox, &gbox_bounds);
886  }
887
888  /*
889  ** Return the geohash of the center, with a precision determined by the
890  ** extent of the bounds.
891  ** Possible change: return the point at the center of the precision bounds?
892  */
893  return geohash_point(lon, lat, precision);
894 }
static uint8_t precision
Definition: cu_in_twkb.c:25
int lwgeom_calculate_gbox_cartesian(const LWGEOM *lwgeom, GBOX *gbox)
Calculate the 2-4D bounding box of a geometry.
Definition: g_box.c:678
void gbox_init(GBOX *gbox)
Zero out all the entries in the GBOX.
Definition: g_box.c:47
#define LW_FAILURE
Definition: liblwgeom.h:79
int lwgeom_geohash_precision(GBOX bbox, GBOX *bounds)
Definition: lwalgorithm.c:760
char * geohash_point(double longitude, double latitude, int precision)
Definition: lwalgorithm.c:591
void lwerror(const char *fmt,...)
Write a notice out to the error handler.
Definition: lwutil.c:190
double ymax
Definition: liblwgeom.h:298
double xmax
Definition: liblwgeom.h:296
double ymin
Definition: liblwgeom.h:297
double xmin
Definition: liblwgeom.h:295

Referenced by ST_GeoHash(), and test_geohash().

Here is the call graph for this function:
Here is the caller graph for this function: