My impression is that working topologies is slow, especially with large datasets - lots of computation involved.
How effective would this be with hundreds of thousands or millions or small polygons? Just running ST_Union() takes hours to days. Thanks Brent Wood --- On Fri, 10/26/12, Sandro Santilli <s...@keybit.net> wrote: From: Sandro Santilli <s...@keybit.net> Subject: Re: [postgis-users] How to eliminate small gaps produced by ST_union? To: "PostGIS Users Discussion" <postgis-users@postgis.refractions.net> Date: Friday, October 26, 2012, 6:04 AM You may try to construct a topology within PostGIS-2.0, using a small tolerance, and then get the geometries back. --strk; On Thu, Oct 25, 2012 at 05:54:05PM +0100, Alexandre Neto wrote: > I'm trying to Aggregate\Dissolve a set of adjacent, but not touching > polygons in Postgis. The geometries were created editing the Postgis table > in QGIS created, with snapping and avoid overlap in the layer. > > I used ST_Union like this: > > SELECT ST_Union(the_geom) > FROM table; > > Small gaps similar to lines appear in the result. This happens when the > adjacent polygons do not share the exact same vertices. > > [image: Inline image 2] > Is there a way to eliminate this "gaps" or "small angles" within Postgis? > > I know that v.clean in GRASS can eliminate small angles, and correct > topology, but that would mean I needed to copy the features to GRASS, > correct them and copy it back to Postgis. > > Thanks in advance, > > Alexandre Neto _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
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