[postgis-users] how to create ouline of multiple objects

[Paragon Corporation]

Ge,

What do you mean by outline of all objects?  You mean  if you have a bunch
of polygons you just want one record with all boundaries dissolved?

Maybe you are looking for ST_Union

SELECT ST_Union(the_geom)
FROM sometable

That will dissolve boundaries.
http://postgis.refractions.net/documentation/manual-svn/ST_Union.html

or you mean you have a polygon and you want the linestring outline.

For that use ST_Boundary(the_geom) or ST_ExteriorRing
http://postgis.refractions.net/documentation/manual-svn/ST_Boundary.html

http://postgis.refractions.net/documentation/manual-svn/ST_ExteriorRing.html



Leo 

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of G. van
Es
Sent: Thursday, August 13, 2009 2:48 PM
To: PostGIS Users Discussion
Subject: [postgis-users] how to create ouline of multiple objects

Hi All,

Maybe a stupid question but I have a shape imported in PG of wich I want to
determine the outline of all objects. The result should be a LINE or just
one POLYGON.

Does anyone know if this is possible in PG.

Thanks,

Ge


      
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