[postgis-users] Invalid geometry? (and side location conflict)

Rob Tester robtester at gmail.com
Mon Nov 6 06:19:38 PST 2006

I receive an error when getting the area for an intersection of two geometry objects. One is large containing several hundered points the other was much smaller. 

I get:

NOTICE:  TopologyException: side location conflict (-84.4858,33.6872,33.6872)

ERROR:  GEOS Intersection() threw an error!

(note that geomunion with the same geometry objects works fine)

After reading the email lists I saw that invalid geometry objects are often the cause this error, so I checked them with isValid(). Sure enough the large geometry returns false. My question is what really makes a geometry invalid? Is it the invalid geometry that is really causing this issue or something related to the intersection (since geomunion works fine)?

I have tried the intersection with other polygons and have had no problems, but one table that contains these very large polygons always causes this problem.

Any help is greatly appreciated.


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