[postgis-users] help with overlapping polygon query

[Brent Wood]

I need to identify cells which lie partly outside the area covered by the
polygons returned in a query in another table. A spatial overlay of two tables
with polygon geometries.

I had assumed I could use the overlap function to identify such polygons, ie:
partially contained.

The problem is that the specified area includes neighbouring polygons. A cell
which overlaps two or more of these, is entirely within the overall area, but
is still returned by the overlap function.

So, using Postgis to identify a polygon set, I need to identify cells
overlapping only the exterior boundaries of the set of polygons.



Can anyone give me some pointers so I can do this in PostGIS?


Thanks
  
  Brent Wood