[postgis-devel] (Bug?) Strange Behavior with ST_SymDifference (line, surface)

[Sandro Santilli]

On Fri, Sep 27, 2013 at 06:11:53PM +0200, Rémi Cura wrote:
> another food for thought :
> ST_SymDifference produces polygon with no area (ie lines), and polygon with
> self intersecting boundary.
> 
> First image shows result of a buffer and SYmDifference based processing
> Second image : I moved manually things to expose errors, I added no points.
> 
> It surely is a precision issue I'll try to solve with snapping.
> 
> Yet all the geometries passes ST_IsValid, but are invalid for QGIS

Are you saying ST_IsValid is wrong ?
If that's the case please provide HEXWKB of the geometry you think
is invalid. Best if in a ticket.

A line from overlay involving areas is an expected possibility.

--strk;