From what you've described maybe ST_ConvexHull() is what you are after?
cheers
Ben
On 14/08/2009, at 3:11 AM, G. van Es wrote:
Leo/Paul,
Indeed, a bunch of polygons (900) of wich I need the outline. In
fact drawing one line around the objects.
I tried st_union but this returns an empty result.
st_exteriorRing returns lines from polygons but still the same
number of objects.
Might be close to it but I'm still struggling with it.
Ge
--- On Thu, 8/13/09, Paragon Corporation <[email protected]> wrote:
From: Paragon Corporation <[email protected]>
Subject: Re: [postgis-users] how to create ouline of multiple objects
To: "'PostGIS Users Discussion'" <[email protected]
>
Date: Thursday, August 13, 2009, 11:54 AM
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: [email protected]
[mailto:[email protected]]
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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