[postgis-users] Question to canonical form and SRID

[Kai Behncke]

> --- Ursprüngliche Nachricht ---
> Von: Markus Schaber <schabi at logix-tt.com>
> An: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
> Betreff: Re: [postgis-users] Question to canonical form and SRID
> Datum: Mon, 10 Apr 2006 11:16:53 +0200
> 
> Hi, Kai Behncke,
> 
> Kai Behncke wrote:
> > I know, that I can use "SELECT AsText(the_geom) from xyz",
> > but I would like to see the text-from directly.
> 
> This will not work on psql or driver level, PostGIS currently has the
> machine readable format as default, because the text formats introduced
> precision loss / coordinate shifts due to rounding errors in the
> floating point parsing.
> 
> The exact issues were discussed on postgis-users@/postgis-devel@, you
> can search it in the archives.
> 
> > And a second question please:
> > How do I need to insert the geometry to get back an entry like:
> > 
> > "SRID=32632;POINT(3455632 6787989)".
> 
> try
> 
> INSERT table (the_geom, ...) VALUES (
> 'SRID=32632;POINT(3455632 6787989)'::geometry, ...)
> 
> or
> 
> INSERT table (the_geom, ...) VALUES (setsrid(
> 'POINT(3455632 6787989)'::geometry,4326), ...)
> 
> or
> 
> INSERT table (the_geom, ...) VALUES (GeomFromText(
> 'POINT(3455632 6787989)',4326), ...)
> 
> This insert the geometry with a set SRID.
> 
> 
> asText() will not show the SRID, as the OpenGIS standard does not define
> the SRID to be a part of the geometry representation.
> 
> For OpenGIS, you need to use the srid(the_geom) function to get the
> SRID, separately from using asText() or asBinary() for getting the
> geometry itsself. Also note that OpenGIS currently does not allow
> Measures (4th dimension), and is somehow weak on 3 dimensional geometries.
> 
> If you want the above notation using OpenGIS functions only, you can use
> 'SRID=4326' || srid(the_geom) || ';' || asText(the_geom)
> 
> An alternative is the PostGIS function asEWKT, which outputs the
> 'SRID=4326;POINT(3455632 6787989)' format directly.
> 
> 
> HTH,
> Markus
> 
> 
Hello Markus,
thank you very< much for answering. 
Kai Behncke

-- 
GMX Produkte empfehlen und ganz einfach Geld verdienen!
Satte Provisionen für GMX Partner: http://www.gmx.net/de/go/partner