On Tue, Jul 26, 2011 at 03:16:09PM -0500, Mr. Puneet Kishor wrote: > So, as advised, I got a real pencil and paper, drew out all my options, > scanned them in, and discovered that I had a poor understanding on the > relationship of MULTIPOLYGONs and GEOMETRIES. Turns out, my MULTIPOLYGON has > 1 GEOMETRY, 4 rings, one being exterior and three interior rings. Hence, an > expression like the following works well > > ST_NumPoints(ST_InteriorRingN(ST_GeometryN(the_geom, 1), 2))
Good job ! > Now, here is where it gets interesting. My test feature in reality is a lot > more complicated, as can be seen in the attached image (see the blue bordered > multipoly). I took the shapefile and shp2pgsql-ed it, and now I get only 4 > rings in my query. My guess is that these four rings are the ones on the top > of the image. So, I thought maybe I have another GEOMETRY that I am missing > out on. But, no... ST_NumGeometries(the_geom) = 1. > > Can anyone theorize what happened to the rest of the feature? How did it get > lost in translation? Was it simply ignored, or was it made into a different > feature? Or, is it there, but I still haven't understood the > MULTIPOLYGON/GEOMETRY/POLYGON/LINERSTRING nexus really well. Could be a bug in shp2pgsql ... did it tell you anything interesting at load time ? Do you have the shapefile published somewhere to look at ? --strk; () Free GIS & Flash consultant/developer /\ http://strk.keybit.net/services.html _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
