[Qgis-user] Validate geometries with QGis

[Carson Farmer]

Hi Felix,
> Hello,
>
> I have a postgis table with large polygons. For some of them postgis' isvalid function returns false
> Is there a way to spot these self-intersection places easily?
>   
One roundabout way to do this would be to use the 'polygons to lines' 
tool in fTools to convert your polygons to lines, then use the 
'intersect lines' tool (in fTools) to find intersections between the new 
line layer (use the line layer as both input and intersect layer).

I haven't tested this myself, but in theory in should work...

Carson

-- 
Carson J. Q. Farmer
ISSP Doctoral Fellow
National Centre for Geocomputation (NCG),
National University of Ireland, Maynooth,
Email: Carson.Farmer at gmail.com
Web:   http://www.carsonfarmer.com/
       http://www.ftools.ca/