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And if that won't do, consider exporting the data to a well known GIS
format and operate a join in the GIS. After joining, you can then
upload the data back into a table and perform joins and so with postGIS<br>
<br>
Burgholzer,Robert schreef:
<blockquote
cite="mid:6C097DA58429B743A67070F98BE73A37025DD65A@deqex01.deq.local"
type="cite">
<pre wrap="">Andreas,
I have used the following query with varying degrees of success (that is, sometimes the memory requirements seem to be too much, and it takes forever to complete). The resulting shape occasionally renders strangely in Qgis.
SELECT landuse_name, memgeomunion(the_geom)
GROUP BY landuse_name
Regular geomunion (instead of memGeomUnion) can also work, but seems to choke on larger collections.
r.b.
Robert W. Burgholzer
Surface Water Modeler
Office of Water Supply and Planning
Virginia Department of Environmental Quality
<a class="moz-txt-link-abbreviated" href="mailto:rwburgholzer@deq.virginia.gov">rwburgholzer@deq.virginia.gov</a>
804-698-4405
Open Source Modeling Tools:
<a class="moz-txt-link-freetext" href="http://sourceforge.net/projects/npsource/">http://sourceforge.net/projects/npsource/</a>
Web-Based Water Supply Planning Demo:
<a class="moz-txt-link-freetext" href="http://soulswimmer.dynalias.net/models/wsdemo/demo_hsi.php">http://soulswimmer.dynalias.net/models/wsdemo/demo_hsi.php</a>
-----Original Message-----
From: <a class="moz-txt-link-abbreviated" href="mailto:postgis-users-bounces@postgis.refractions.net">postgis-users-bounces@postgis.refractions.net</a> [<a class="moz-txt-link-freetext" href="mailto:postgis-users-bounces@postgis.refractions.net">mailto:postgis-users-bounces@postgis.refractions.net</a>] On Behalf Of Andreas Laggner
Sent: Wednesday, August 15, 2007 12:30 PM
To: PostGis_Mailinglist
Subject: [postgis-users] what function to "dissolve" data?
Hi,
i want to simplify my data by dissolving lines (borders) between
Polygons (the polygons share one line or at least one point) with the
same attributes to get a smaller dataset and i did not find a function
for that operation (so far). For example i have one million polygons
with the same landuse but a different polygon_number or what else and i
only want to distinguish between landuse in my data. Thus i can reduce
my dataset to same hundred polygons (or perhaps even one big polygon if
all polygons touches).
thanks for help Andreas
</pre>
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