The closest thing we have to a table is in the special index of the help. I think it covers all the functions that support this though we were focusing more on Z coordiante than M. So probably M we missed and should be more specific about.
http://postgis.refractions.net/documentation/manual-svn/ch08.html#PostGIS_3D _Functions I like the idea of a chart though. Have to think about a way to automate that. Thanks, Regina -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Paul Ramsey Sent: Wednesday, August 05, 2009 1:52 PM To: PostGIS Users Discussion Subject: Re: [postgis-users] ST_UNION drops M coordinate No, sorry no table. In general: "interesting" things (containment tests, calculations of new derived shapes) only take X and Y into account. constructive functions (buffer, union, difference) that make new geometries pass Z through and for new points try to interpolate a "reasonable" Z value from the inputs constructive functions do not pass M through So the most you can expect from higher dimension handling is that they are not stripped and are hopefully correctly interpolated on introduced vertices. P. On Wed, Aug 5, 2009 at 10:46 AM, Satish Murthy<[email protected]> wrote: > Thanks Paul. > > I also noticed that some other functions too have this limitation > (such as ST_CONTAINS). Is there a table/matrix somewhere that lists > which function supports XYZM? > > Satish > >> Date: Wed, 5 Aug 2009 10:36:46 -0700 >> From: [email protected] >> To: [email protected] >> Subject: Re: [postgis-users] ST_UNION drops M coordinate >> >> Yes, we just don't support the higher dimension in the operation. >> GEOS was extended to 3 dimensional handling some time ago, but never >> got pushed farther when we added M at postgis 1.0. Probably fixable, >> but with a reasonable amount of careful work to catch every case. >> >> P >> >> On Wed, Aug 5, 2009 at 10:22 AM, Satish Murthy<[email protected]> >> wrote: >> > >> > When I do this (notice the second ST_COLLECT): >> > select ST_AsEWKT (ST_COLLECT (geom)) from ( select >> > (ST_DUMP(geom)).geom from (select p_geom as geom from ( select >> > ST_COLLECT (geom_col, st_GeomFromEWKT('Point(1 -1 0 10)')) as >> > p_geom from tab) a )as b ) as c I get: >> > "MULTIPOINT(71.1 -42.31 10 10,1 -1 0 10,1 -1 0 10)" >> > This is fine, except that "1 -1 0 10" gets repeated. >> > >> > BUT--- >> > When I do (I use ST_UNION here): >> > select ST_AsEWKT (ST_COLLECT (geom)) from ( select >> > (ST_DUMP(geom)).geom from (select p_geom as geom from ( select >> > ST_UNION (geom_col, st_GeomFromEWKT('Point(1 -1 0 10)')) as p_geom >> > from tab) a )as b ) as c I get this: >> > "MULTIPOINT(1 -1 0,71.1 -42.31 10)" >> > No repetition, but the M coordinate is missing. >> > >> > Any pointers on what's going wrong here? >> > >> > >> > ________________________________ >> > Are you an untamed, bizarre or daring explorer? Find out now! Drag n' >> > drop >> > _______________________________________________ >> > 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 > > ________________________________ > Date India's Teen Diva. Find out if you hit it off with her or are her > fiery opposite. Drag n' drop > _______________________________________________ > 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
