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

[Paulo van Breugel]

On 25-01-17 16:57, Markus Metz wrote:
>
>
> On Wed, Jan 25, 2017 at 12:31 PM, Paulo van Breugel 
> <p.vanbreugel at gmail.com <mailto:p.vanbreugel at gmail.com>> wrote:
> >
> > 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.
>
> Did you try
> v.clean -c type=boundary tool=rmsa,break,rmdangle threshold=0,0,-1
> ?
>
Yes, I tried

> Also try v.build -e

Tried that too, it does not report any error.

Generally where the boundaries of two polygons with the same category 
touch each other by one point (illustrated below), Spatialite and QGIS 
(both using geos) seem to report an error for that point.

+-----+   +
|     | /   \
|  A  |+  A  +
|     | \   /
+-----+   +


I am not sure yet if that is what is causing the problem (missing 
polygons) when exporting to kml. I am cleaning a layer now for export. 
Will report how that worked out.

> Markus M
>
> >
> > Paulo
> > _______________________________________________
> > grass-dev mailing list
> > grass-dev at lists.osgeo.org <mailto:grass-dev at lists.osgeo.org>
> > https://lists.osgeo.org/mailman/listinfo/grass-dev
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/grass-dev/attachments/20170125/8c31edd6/attachment-0001.html>