[postgis-users] Polygons: the unstable foundation of spatial modeling

David Blasby dblasby at refractions.net
Thu Mar 25 09:18:18 PST 2004

bartvde at xs4all.nl wrote:

> Hi list,
> the following article dating from October 2003 deals with a comparison of
> polygon definitions (and especially the boundary between valid and
> invalid) in several Spatial DBMS's, and also PostGIS 0.6.2.
> http://www.vz.geodan.nl/users/bart/17-VanOosterom_Polygons.pdf
> Any comments on this? I can imagine a lot has changed since version 0.6.2
> regarding this subject?

You should run the isvalid(<geometry>) function on the polygons.  You'll 
find its 100% OGC compliant, except it allows for repeated points on the 


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