There is no spoon. Why do you need ST_Expand()? If you're doing a distance query, ST_DWIthin(thisgeog, thatgeog, radiusdouble) will create a fully indexed query for you and return the right answers. You can look at its definition under the covers to see what it's up to.
http://trac.osgeo.org/postgis/browser/trunk/postgis/geography.sql.in.c#L612 If you're working with geometry in 4326, well then, you're in a tough spot, yes? That's why geography was invented. There's some hacks available for you here: http://trac.osgeo.org/postgis/wiki/UsersWikiExamplesFindNearbyLatLon P. On Wed, Jul 7, 2010 at 11:51 PM, Stefan Priess <[email protected]> wrote: > > Hey Paul, > > i need the ST_Expand() function with a radius/expand of 10 Meters, how i will > do that? > The Point to expand is in SRID 4326 . > > Thanks > > Stefan > > > > Paul Ramsey <[email protected]> > Gesendet von: [email protected] > > 07.07.2010 23:13 > > Bitte antworten an > PostGIS Users Discussion <[email protected]> > An > PostGIS Users Discussion <[email protected]> > Kopie > Thema > Re: [postgis-users] Projection(s) for global point-and-radius searches > > > > > No, because the functions on Geometry(4326) don't return metric answers. > > SELECT > ST_Distance('SRID=4326;POINT(0 0)'::geometry, 'SRID=4326;POINT(1 > 1)'::geometry) as geom, > ST_Distance('POINT(0 0)'::geography, 'POINT(1 1)'::geography) as geog; > > Geography understands that it's on a sphere and does the Right Thing. > Geometry(4326) still operates on a cartesian plane, it just has > "units" of degrees (which is pretty nonsensical for any kind of > measurement calculation). > > P > > On Wed, Jul 7, 2010 at 2:03 PM, David Jantzen <[email protected]> wrote: > > Ok, interesting. Is it equivalent then to using a GEOMETRY type with SRID > > 4326? > > > > On Jul 7, 2010, at 12:25 PM, Paul Ramsey wrote: > > > >> On Wed, Jul 7, 2010 at 12:25 PM, Paul Ramsey <[email protected]> wrote: > >>> ST_Buffer(geography, float8) returns geography > >>> ST_Intersection(geography, geography) returns geography > >> > >> These last two actually *do* carry out projections under the covers, > >> so watch out. > >> > >> P > >> _______________________________________________ > >> postgis-users mailing list > >> [email protected] > >> http://postgis.refractions.net/mailman/listinfo/postgis-users > > > > _______________________________________________ > > postgis-users mailing list > > [email protected] > > http://postgis.refractions.net/mailman/listinfo/postgis-users > > > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > > > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
