[postgis-users] GEOSUnaryUnion: TopologyException: found non-noded intersection BUT geom is valid

[Birgit Laggner]

Dear discussion group, 

I am trying to ST_Union several polygons and get a TopologyException (GEOSUnaryUnion: TopologyException: found non-noded intersection between LINESTRING (3.56442e+06 5.42679e+06, 3.56442e+06 5.42679e+06) and LINESTRING (3.56442e+06 5.42679e+06, 3.56442e+06 5.42679e+06) at 3564420.7944701263 5426786.9800475985). 
I have tested with ST_Valid and all polygons in the datasets are valid. 

The dataset is pretty large (53.5 Mio. polygons) and will probably get grouped into around 8.7 Mio resulting geometries during ST_Union. 

If I try to ST_Union the geometries near the point ST_Union mentions in the error message (ST_Buffer with up to 100 metres), everything works fine. I am out of ideas how to find the problematic geometry or at least how to work around the TopologyException. 

My PostGIS version is: "POSTGIS="2.3.3 r15473" GEOS="3.5.1-CAPI-1.9.1 r4246" SFCGAL="1.2.2" PROJ="Rel. 4.9.2, 08 September 2015" GDAL="GDAL 1.11.3, released 2015/09/16" LIBXML="2.9.3" LIBJSON="0.11.99" TOPOLOGY RASTER" 


I would be very glad if anyone would come up with ideas how to solve my problem. 

Thanks a lot in advance! 

Regards, 
Birgit 


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