[postgis-users] what function to "dissolve" data?

[Milo van der Linden]

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

Burgholzer,Robert schreef:
> 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
> rwburgholzer at deq.virginia.gov
> 804-698-4405
> Open Source Modeling Tools:
> http://sourceforge.net/projects/npsource/
> Web-Based Water Supply Planning Demo:
> http://soulswimmer.dynalias.net/models/wsdemo/demo_hsi.php
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-bounces at postgis.refractions.net] 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
>
>
>
>   


-- 


	

Milo van der Linden
skype: milovanderlinden <skype:milovanderlinden?add>
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milo at 3dsite.nl <mailto:milo at 3dsite.nl>
http://www.3dsite.nl

	  	

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