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 861 of file lwalgorithm.c.

{
        GBOX gbox;
        GBOX gbox_bounds;
        double lat, lon;
        int result;
 
        gbox_init(&gbox);
        gbox_init(&gbox_bounds);
 
        result = lwgeom_calculate_gbox_cartesian(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, got (%g %g, %g %g).",
                         gbox.xmin, gbox.ymin,
                         gbox.xmax, gbox.ymax);
                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);
}

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

Referenced by ST_GeoHash(), and test_geohash().

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