[postgis-users] GIS functions

[El Nico]

>  - Yes, the "selects" are redundant in this case. 
>  - No, exteriorring() is a very clever trick, which turns your polygons into
> the linestrings that represent their outer shells. The intersection of a
> linestring and a linestring is a... point. Which is exactly what you want. 
>  

Yes, sorry for this redundancy ! (was I so tired yesterday night ?)
I built the query by copying several "atomic" parts, first wanting to
get the polygons, then their buffers, then their exteriorRings, then
their intersection.

BTW, I'm very impressed by the performance and ease of use of the
latest postgis version.
The set of provided functions and operators allows very complex
geographic operations.
Thank you for this work !

Nicolas