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<div class="moz-cite-prefix">On 26-01-17 08:40, Markus Metz wrote:<br>
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On Wed, Jan 25, 2017 at 5:19 PM, Paulo van Breugel <<a
moz-do-not-send="true"
href="mailto:p.vanbreugel@gmail.com"><a class="moz-txt-link-abbreviated" href="mailto:p.vanbreugel@gmail.com">p.vanbreugel@gmail.com</a></a>>
wrote:<br>
><br>
><br>
><br>
> On 25-01-17 16:57, Markus Metz wrote:<br>
><br>
><br>
><br>
> On Wed, Jan 25, 2017 at 12:31 PM, Paulo van Breugel
<<a moz-do-not-send="true"
href="mailto:p.vanbreugel@gmail.com">p.vanbreugel@gmail.com</a>>
wrote:<br>
> ><br>
> > Dear all,<br>
> ><br>
> > 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:<br>
> ><br>
> > Warning 1: Ring Self-intersection at or near point<br>
> > 88.100626640406631 27.668444701473838<br>
> > ERROR 6: Invalid polygon<br>
> > Warning 1: Ring Self-intersection at or near point<br>
> ><br>
> > 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.<br>
> ><br>
> > When I import the layer in Spatialite and check
the geometries I am getting similar warnings / error
messages, e.g.,:<br>
> ><br>
> > 27 Ring Self-intersection at or near point
82.397900772562522 29.707213605319616<br>
> ><br>
> ><br>
> > 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.<br>
><br>
> Did you try<br>
> v.clean -c type=boundary tool=rmsa,break,rmdangle
threshold=0,0,-1<br>
> ?<br>
><br>
> Yes, I tried<br>
><br>
> Also try v.build -e<br>
><br>
><br>
> Tried that too, it does not report any error.<br>
><br>
> 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.<br>
><br>
> +-----+ +<br>
> | | / \<br>
> | A |+ A +<br>
> | | \ /<br>
> +-----+ +<br>
><br>
OK. In some cases, the vertex is not exactly on the line but
just slightly off. It depends on how floating point
precision is handled if this is regarded as an intersection
or not. If GRASS assumes a smaller floating point precision
error than GEOS, GRASS treats it as no intersection while
GEOS might recognize an intersection. A solution could be to
snap boundaries with a very small threshold.<br>
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That did help me to get rid of many of the reported errors, thanks!<br>
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Just a guess.<br>
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Markus M<br>
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> 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.<br>
><br>
> Markus M<br>
><br>
> ><br>
> > Paulo<br>
> > _______________________________________________<br>
> > grass-dev mailing list<br>
> > <a moz-do-not-send="true"
href="mailto:grass-dev@lists.osgeo.org">grass-dev@lists.osgeo.org</a><br>
> > <a moz-do-not-send="true"
href="https://lists.osgeo.org/mailman/listinfo/grass-dev">https://lists.osgeo.org/mailman/listinfo/grass-dev</a><br>
><br>
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