static void test_geohash_precision(void)
{
GBOX bbox;
GBOX bounds;
int precision = 0;
gbox_init(&bbox);
gbox_init(&bounds);
bbox.xmin = 23.0;
bbox.xmax = 23.0;
bbox.ymin = 25.2;
bbox.ymax = 25.2;
precision = lwgeom_geohash_precision(bbox, &bounds);
//printf("\nprecision %d\n",precision);
CU_ASSERT_EQUAL(precision, 20);
bbox.xmin = 23.0;
bbox.ymin = 23.0;
bbox.xmax = 23.1;
bbox.ymax = 23.1;
precision = lwgeom_geohash_precision(bbox, &bounds);
//printf("precision %d\n",precision);
CU_ASSERT_EQUAL(precision, 3);
bbox.xmin = 23.0;
bbox.ymin = 23.0;
bbox.xmax = 23.0001;
bbox.ymax = 23.0001;
precision = lwgeom_geohash_precision(bbox, &bounds);
//printf("precision %d\n",precision);
CU_ASSERT_EQUAL(precision, 7);
}
/*
** Return a geohash string for the geometry. <http://geohash.org>
** Where the precision is non-positive, calculate a precision based on the
** bounds of the feature. Big features have loose precision.
** Small features have tight precision.
*/
char *lwgeom_geohash(const LWGEOM *lwgeom, int precision)
{
GBOX gbox;
GBOX gbox_bounds;
double lat, lon;
int result;
gbox_init(&gbox);
gbox_init(&gbox_bounds);
result = lwgeom_calculate_gbox(lwgeom, &gbox);
if ( result == LW_FAILURE ) return NULL;
/* Return error if we are being fed something outside our working bounds */
if ( gbox.xmin < -180 || gbox.ymin < -90 || gbox.xmax > 180 || gbox.ymax > 90 )
{
lwerror("Geohash requires inputs in decimal degrees.");
return NULL;
}
/* What is the center of our geometry bounds? We'll use that to
** approximate location. */
lon = gbox.xmin + (gbox.xmax - gbox.xmin) / 2;
lat = gbox.ymin + (gbox.ymax - gbox.ymin) / 2;
if ( precision <= 0 )
{
precision = lwgeom_geohash_precision(gbox, &gbox_bounds);
}
/*
** Return the geohash of the center, with a precision determined by the
** extent of the bounds.
** Possible change: return the point at the center of the precision bounds?
*/
return geohash_point(lon, lat, precision);
}
