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I don't know how your file looks like, but one of the following
should work,<br>
<br>
try <br>
v.clean and remove small areas<br>
or <br>
make the internal islands polygons, and using the same attributes
(add them), use v.dissolve to get rid of internal polygons.<br>
<br>
regards,<br>
sotiris<br>
<br>
<div class="moz-cite-prefix">On 06/12/2014 12:35 PM, Blumentrath,
Stefan wrote:<br>
</div>
<blockquote
cite="mid:2C5F82DA3EE3E449BD473075F2C290BF9903E20F@NINSRV05.nina.no"
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<p>Hi,</p>
<p> </p>
<p>I am trying to remove islands (here also in the topological
sense) from a set of lake polygons.</p>
<p> </p>
<p>The polygon layer contains only the water bodies (means
islands within the lakes have no category).</p>
<p> </p>
<p>I tryed v.extract -d as well as v.extract
list/cats=1-99999999 both in GRASS 6 and 7 (on Ubuntu 12.04
LTS).</p>
<p> </p>
<p>In all tests the layer did not get modified as expected and
islands were still present.</p>
<p> </p>
<p>This topic has been (repeatedly) discussed earlier. But the
proposed solution (also in the manual of v.extract) did not
work for others as well (quite some time ago):</p>
<p><a moz-do-not-send="true"
href="http://lists.osgeo.org/pipermail/grass-user/2006-January/032016.html">http://lists.osgeo.org/pipermail/grass-user/2006-January/032016.html</a></p>
<p> </p>
<p>I am wondering what the problem might be?</p>
<p>Any idea? I can provide sample data if that might help...</p>
<p> </p>
<p>I am now using ST_ExteriorRing from PostGIS (<a
moz-do-not-send="true"
href="http://postgis.net/docs/manual-2.1/ST_ExteriorRing.html">http://postgis.net/docs/manual-2.1/ST_ExteriorRing.html</a>)
to achieve what I want, but it would be nice to have a GRASS
solution... </p>
<p> </p>
<p>Cheers</p>
<p>Stefan</p>
<p> </p>
</div>
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