It is possible to do by groupping : the idea is : you group small polygons by the coordinate of there centroid, rounded (or snapped ot grid) so that polygon less than XX meter are in the same group.
Example : SELECT ST_Union(poly.geom ) FROM my_poly AS poly GROUP BY ST_SnapToGrid(ST_Centroid(poly.geom),XX) Please note that this code doesn't enforce the fact that polygons are touching to merge, but you don"t really need this, because separate polygons will get merged into a multipolygons, which is easy to deal with by dump . Cheers, Rémi-C 2014-01-28 Morten Sickel <mor...@sickel.net> > I never used it, but it should be along the lines discussed here: > http://gis.stackexchange.com/questions/49650/merge-polygons-in-postgis > > if it is just a few, it should be doable to do manually - I don't know if > it is possible to do automatically in SQL > > For each poly with area < some_limit{ > find largest neighboring poly > // or smallest, or whatever were you are sure you'll get a > well-defined answer > join the two polys > } > > Morten > > > Astrid Bjørnerød skrev: > > Is there anyone you have written some sql-code for removing the small > > polygons onto one of the neighbor-polygons ? > > Any stabil functions for this task? > > > > Astrid > > > > -----Opprinnelig melding----- > > Fra: postgis-users-boun...@lists.osgeo.org > > [mailto:postgis-users-boun...@lists.osgeo.org] På vegne av Tom McCallum > > Sendt: 27. januar 2014 20:48 > > Til: mor...@sickel.net; PostGIS Users Discussion > > Emne: Re: [postgis-users] Removing tiny polygons > > > > Thanks Morten. I wanted the first case, so that helps. > > > > On Mon, 27 Jan 2014 19:15:18 -0000, Morten Sickel <mor...@sickel.net> > > wrote: > > > >> It depends on what you mean with "remove" - do you want to just have > >> the large polygons without the area that is covered by the small ones > >> or do you want to add the area of the small polygons onto one or more > >> of the larges? (e.g. how one typically wants to handle shiver > >> polygons) > >> > >> In the first case it is as easy as a query like > >> > >> select the_geom where ST_area(the_geom) > ... > >> > >> Morten > >> > >> > >> Tom McCallum skrev: > >>> Hi all, > >>> > >>> If I have a polygon geometry field which seems to be made up of a > >>> large number of tiny polygons and some larger ones, what is the best > >>> way to remove polygons below a certain size? Would I need to > >>> preprocess this and save in a new table/record or can I dynamically > >>> do it? > >>> > >>> Thanks > >>> > >>> Tom > >>> _______________________________________________ > >>> postgis-users mailing list > >>> postgis-users@lists.osgeo.org > >>> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users > >>> > >> > >> > >> _______________________________________________ > >> postgis-users mailing list > >> postgis-users@lists.osgeo.org > >> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users > > _______________________________________________ > > postgis-users mailing list > > postgis-users@lists.osgeo.org > > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users > > _______________________________________________ > > postgis-users mailing list > > postgis-users@lists.osgeo.org > > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users > > > > > _______________________________________________ > postgis-users mailing list > postgis-users@lists.osgeo.org > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >
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