[postgis-users] Intersection errors

Markus Schaber schabi at logix-tt.com
Thu Jun 9 00:31:55 PDT 2005

Hi, Carl,

Carl Anderson wrote:

>> If you need a really stable algorithm, current JTS releases contain a
>> polygonize function that converts arbitrary linework into polygons. This
>> should work without any dependencies on ring order or clockwise
>> ordinates, but I suspect this to be rather inefficient.
> Alternatively, the treatment of shapefile polygons the same as the
> accumulated symdifference of each ring.
> look at ESRI's handling of polygons which have parts that cross each
> other for how that works.
> If you can cast each ring to a PostGIS polygon you can use the
> symdifference function to assemble all the parts.
> It's still relatively expensive, but not as expensive as the polgonize
> function.

Good idea, I agree that this should be more efficient as my polygonize
method, and will work as good as my method, given that the rings
themselves do not contain any self-intersections.


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