PostGIS  2.4.9dev-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 846 of file lwalgorithm.c.

Referenced by ST_GeoHash(), and test_geohash().

847 {
848  GBOX gbox;
849  GBOX gbox_bounds;
850  double lat, lon;
851  int result;
852
853  gbox_init(&gbox);
854  gbox_init(&gbox_bounds);
855
856  result = lwgeom_calculate_gbox_cartesian(lwgeom, &gbox);
857  if ( result == LW_FAILURE ) return NULL;
858
859  /* Return error if we are being fed something outside our working bounds */
860  if ( gbox.xmin < -180 || gbox.ymin < -90 || gbox.xmax > 180 || gbox.ymax > 90 )
861  {
862  lwerror("Geohash requires inputs in decimal degrees, got (%g %g, %g %g).",
863  gbox.xmin, gbox.ymin,
864  gbox.xmax, gbox.ymax);
865  return NULL;
866  }
867
868  /* What is the center of our geometry bounds? We'll use that to
869  ** approximate location. */
870  lon = gbox.xmin + (gbox.xmax - gbox.xmin) / 2;
871  lat = gbox.ymin + (gbox.ymax - gbox.ymin) / 2;
872
873  if ( precision <= 0 )
874  {
875  precision = lwgeom_geohash_precision(gbox, &gbox_bounds);
876  }
877
878  /*
879  ** Return the geohash of the center, with a precision determined by the
880  ** extent of the bounds.
881  ** Possible change: return the point at the center of the precision bounds?
882  */
883  return geohash_point(lon, lat, precision);
884 }
double xmax
Definition: liblwgeom.h:293
int lwgeom_geohash_precision(GBOX bbox, GBOX *bounds)
Definition: lwalgorithm.c:750
#define LW_FAILURE
Definition: liblwgeom.h:79
char * geohash_point(double longitude, double latitude, int precision)
Definition: lwalgorithm.c:581
double ymin
Definition: liblwgeom.h:294
void gbox_init(GBOX *gbox)
Zero out all the entries in the GBOX.
Definition: g_box.c:51
double xmin
Definition: liblwgeom.h:292
uint8_t precision
Definition: cu_in_twkb.c:25
double ymax
Definition: liblwgeom.h:295
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:683
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