David Jantzen a écrit :
Hi again,
I'm trying to ST_Union multipolygons from the Zillow neighborhood data.
When I do this I occasionally see:
NOTICE: TopologyException: found non-noded intersection between
-73.812....
This appears to be due to invalid geometries, as the following query
returns over a hundred rows:
select * from neighborhoods where not ST_IsValid(the_geom)
Can anyone suggest a workaround here? The resulting geometry needs to
be a multipolygon. Also, what is ST_Is_valid actually testing for? The
documentation isn't very explicity about the definition of validity.
Most of time, invalid polygons are polygons with a self intersecting
boundaries (as in the number '8') or self-touching boundary (two non
contiguous points of the boundary are touching each other)
The best solution is to correct those geometries if you can.
Another solution which *may* work is to replace the geometry by a buffer
of size 0 around the geometry in your select statement (using a 0-buffer
is a work-around which generally works with JTS library from which
postgis functions are derived).
Michaël
Thanks,
David
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