[postgis-users] Decomposing Multiploygon

strk strk at keybit.net
Tue Dec 16 00:15:48 PST 2003

See the Intersects(geometry, geometry) function.
You need GEOS support compiled in.


ralph.mason wrote:
> I am new to postgis and spatial data so I apologies in advance if this 
> is covered already.  Google didn't turn up anything.
> I have a shape file of country outlines, each country is a multipolygon.
> I imported this using shp2postgis and created an index on the geometry 
> column.  So far so good.
> However, as the a search is done on the bounding box of the multi 
> polygon I get more than one country returned to many searches.  Eg 
> querying in canada will return Canada, USA (because of the alaska , 
> mainland box), and Russia.
> So - Is there a way to query for records that contain the point in one 
> of the polygons in the multipolygon?  Or do I need to decompose the 
> multipolygon to a polygons?
> Assuming I need to decompose, is there a utility that can do this (I 
> guess one could write a postgres function to do it)
> Thanks for any help
> Ralph
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