Join all your polygons into 1 multi-polygon. Run ST_Difference between your area (a rectangle for the whole world I guess) and the your multi-polygon. This should produce the expected results.
On Mon, Oct 5, 2009 at 3:00 PM, Kevin Kempfer <post...@kevinkempfer.de> wrote: > Hi, > > I am trying to punch holes into a polygon - can someone tell me how to > achieve this? > > I have a large database of polygon geometries. > I am now trying to "invert" these polygons area to receive a big > polygon, that covers everything that is *not* covered in my existing > polygons. > > The result should be a polygon covering the whole world but with holes > in the areas which are already covered by my source polygons. > > I successfully created a "positive" using geomunion() on all my geoms. > Now I need to invert the result to get a "negative". Hope I got the > idea across... > > Thanks for any advice, > > Kevin > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users > -- http://iap.md, The future is open _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
