[GRASS-dev] vector layer contains error not detected by v.build nor cleaned in v.clean

[Paulo van Breugel]

Dear all,

I have a vector layer which I cleaned up using v.clean. It all appears 
to be fine, but when trying to export using the libkml in v.out.ogr and 
the type=area option, I am getting the warning and error messages like 
below:

Warning 1: Ring Self-intersection at or near point
88.100626640406631 27.668444701473838
ERROR 6: Invalid polygon
Warning 1: Ring Self-intersection at or near point

In the resulting kml file, some of the polygons are missing. If I use 
the kml output in v.out.ogr, I am not getting any warnings, but 
similarly, some of the polygons are missing.

When I import the layer in Spatialite and check the geometries I am 
getting similar warnings / error messages, e.g.,:

27 Ring Self-intersection at or near point 82.397900772562522 29.707213605319616


How can I identify and clean these issues in GRASS? Checking for 
topological errors with v.build does not result in any error, and I 
tried the various tools in v.clean to no avail.

Paulo