[postgis-users] ST_Union (8.4) and TopologyException

[Simon Greener]

Kevin,

> I've found that such errors in the past are usually related to the
> precision of the coordinates.  Try putting your geometries through
> ST_SnapToGrid(), snapping them to some reasonable grid.  Ensure they are
> still valid and try ST_Union again.

I already put them data through FME Workbench's CoordinateRounder and Snapper functions
(and validate via FME's GeometryValidator function). So, the data goes in to PostGIS snapped 
and clean (isvalid etc all report everything OK in PostGIS).

> In any case, TopologyExceptions are getting fewer and farther between as
> the JTS and GEOS codebases are continually enhanced and improved upon.
> Can you provide a concrete example?

I'll see what I can do to isolate the offending polygons.

regards
Simon
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