[postgis-users] Polygon validity

[strk]

On Tue, Mar 30, 2010 at 08:38:55PM +0400, Rykov Denis wrote:
> There is following polygon:
> POLYGON((317371.62563763 5731575.49932608,
> 317028.110300846 5731043.43103426,
> 317028.110300846 5731043.43103426,
> 316389.822682815 5731138.79331604,
> 316478.209591618 5731705.00321977,
> 316478.209591619 5731705.00321977,
> 317350.223258488 5731584.46661525,
> 317371.62563763 5731575.49932608))
> 
> with two duplicate nodes. When I try to check it with ST_IsValidReason
> function I get message
> that it is Valid Geometry. Is this OGC compliant? When I try to check
> it with QGIS, ArcView or
> ArcGIS - I get notice about self intersection. Please explain this situation.

My guess is that when transferring the data from postgis to QGIS,
ArcView or ArcGis you're loosing precision (using WKT ?) thus introducing
self intersections.

--strk;

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