Moin Robert,
thanks for your reply. I use this statement now:
create table atkisvegddis(oba integer, land character varying(2)) with oids;
select addgeometrycolumn('','atkisvegddis','geom','31467','MULTIPOLYGON',2);
insert into atkisvegddis
select oba, land, memgeomunion(geom) from atkisvegd
group by oba, land;
it seems this function takes some time.....atkisvegd has 7,2 million
polygons (postgis takes one hour so far and still working) or did i
something wrong?
hasta luego Andreas
Burgholzer,Robert schrieb:
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
[EMAIL PROTECTED]
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: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] 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
--
Dipl. Geoökologe Andreas Laggner
Institut für Ländliche Räume (LR)
Bundesforschungsanstalt für Landwirtschaft (FAL)
Institute of Rural Studies
Federal Agricultural Research Centre (FAL)
Bundesallee 50
D-38116 Braunschweig
Tel.: (+49) (0)531 596 5515
Fax: (+49) (0)531 596 5599
E-mail: [EMAIL PROTECTED]
Homepage: http://www.lr.fal.de/
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