Iulian, Oops I forgot one important point. DO NOT simplify In longlat projection. You get somewhat bizarre results and that may be perhaps what you are experiencing.
I think you will want to reproject to a planar project and then project back So SELECT ST_Transform(ST_SimpilfyPreserverTopology(ST_Transform(the_geom,2163), 100),4326) As newsimpgeom FROM zipcode; (2163 is US National Atlas meters so you may need to change that, and 4326 is WGS 84 longlat. If you got zips from census you may need to change that to 4269 NAD 83 long lat). You'll also need to play around with the simplification metric. Hope that helps, Regina -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Iulian Margarintescu Sent: Tuesday, November 04, 2008 10:16 AM To: [email protected] Subject: [postgis-users] gis noob question Hi, I have a collection of shapefiles for a number of zipcodes witch i already imported to postgres, and with i need to use them to create a map with ThinkGeo. Loading all the data in ThinkGeo (the same in uDig) works but really slow ( also slow when loading shapefiles directly ). After some research i've found out about simplification algorithms and at first tried to simplify every shape for every zipcode but when displayed there are a lot of gaps between shapes. Than i've found out about topology preserving simplification but i does not make a lot of sense to apply the algorithm for each shape, and if applyed for a collection of shapes it would be nice if after the simplification i still have a shape for each zipcode since i have data attached to the zipcodes. Now my question is how should i apply this topology preserving simplification? Is it sane to do something like this (with a lot of zipcodes): select geom(st_dump( (select ST_SimplifyPreserveTopology ( st_collect(the_geom),0.01) from zipcodes ))) Any other ideas on how should i approach this ? _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
