Just complementing ... In my case there is no overlap in any of the layers, there really was no need ST_Union.
Thanks again for the help and the discussion. Regards, 2013/10/22 Pierre Racine <[email protected]> > > Won't that only yield the same answer if you can guarantee no overlapping > > geometries in the fazendas table? My understanding was that the other > > table was the raster table (which it is reasonable to assume has no > > overlaps), but we don't know if that's the case with this one. > > Right. But you generally have to have a minimal knowledge about the > topology of a layer when you query it. Querying a layer with overlaps is > never the same as querying a layer without. > > So if you know your fazendas layer has overlaps it is a good idea to use > ST_Union but that means you are getting stats about the global farming area > not about each farming area. What about areas overlapping? Should they > count twice? Do these overlaps make sense in reality? Maybe you have to fix > then first... > > Pierre > _______________________________________________ > postgis-users mailing list > [email protected] > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users > -- *Marcello Benigno B. de Barros Filho* Prof. do Curso Superior de Tecnologia em Geoprocessamento - IFPB Mestre em Ciências Geodésicas e Tecnologias da Geoinformação - UFPE Doutorando em Tecnologia Ambiental e Recursos Hídricos - UFPE http://profmarcello.blogspot.com http://about.me/marcello.benigno
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