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List: grass-user
Subject: Re: [GRASS-user] Remove islands with v.extract problem (again)
From: "Blumentrath, Stefan" <Stefan.Blumentrath () nina ! no>
Date: 2014-06-29 21:18:47
Message-ID: 2C5F82DA3EE3E449BD473075F2C290BF991112A0 () NINSRV05 ! nina ! no
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Hi Sotiris,
Thanks for your answer. The second workaround you propose should work, but is a bit \
complicated. Does removal of islands with v.extract work for others? Am I doing \
something wrong?
Cheers
Stefan
From: S. Koukoulas (listes) [mailto:sotkouklistes@gmail.com]
Sent: 21. juni 2014 21:59
To: Blumentrath, Stefan; grass-user@lists.osgeo.org
Subject: Re: [GRASS-user] Remove islands with v.extract problem (again)
I don't know how your file looks like, but one of the following should work,
try
v.clean and remove small areas
or
make the internal islands polygons, and using the same attributes (add them), use \
v.dissolve to get rid of internal polygons.
regards,
sotiris
On 06/12/2014 12:35 PM, Blumentrath, Stefan wrote:
Hi,
I am trying to remove islands (here also in the topological sense) from a set of lake \
polygons.
The polygon layer contains only the water bodies (means islands within the lakes have \
no category).
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).
In all tests the layer did not get modified as expected and islands were still \
present.
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):
http://lists.osgeo.org/pipermail/grass-user/2006-January/032016.html
I am wondering what the problem might be?
Any idea? I can provide sample data if that might help...
I am now using ST_ExteriorRing from PostGIS \
(http://postgis.net/docs/manual-2.1/ST_ExteriorRing.html) to achieve what I want, but \
it would be nice to have a GRASS solution...
Cheers
Stefan
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<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi \
Sotiris,<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks \
for your answer. The second workaround you propose should work, but is a bit \
complicated.<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Does \
removal of islands with v.extract work for others? Am I doing something \
wrong?<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Cheers<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Stefan
<o:p></o:p></span></p>
<p class="MsoNormal"><span \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US" \
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span \
lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"> \
S. Koukoulas (listes) [mailto:sotkouklistes@gmail.com] <br>
<b>Sent:</b> 21. juni 2014 21:59<br>
<b>To:</b> Blumentrath, Stefan; grass-user@lists.osgeo.org<br>
<b>Subject:</b> Re: [GRASS-user] Remove islands with v.extract problem \
(again)<o:p></o:p></span></p> </div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">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<o:p></o:p></p>
<div>
<p class="MsoNormal">On 06/12/2014 12:35 PM, Blumentrath, Stefan \
wrote:<o:p></o:p></p> </div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">Hi,<o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">I \
am trying to remove islands (here also in the topological sense) from a set of lake \
polygons.<o:p></o:p></span></p> <p><span \
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">The \
polygon layer contains only the water bodies (means islands within the lakes have no \
category).<o:p></o:p></span></p> <p><span \
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">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).<o:p></o:p></span></p> <p><span \
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">In \
all tests the layer did not get modified as expected and islands were \
still present.<o:p></o:p></span></p> <p><span \
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">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):<o:p></o:p></span></p> <p><span \
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""><a \
href="http://lists.osgeo.org/pipermail/grass-user/2006-January/032016.html">http://lis \
ts.osgeo.org/pipermail/grass-user/2006-January/032016.html</a><o:p></o:p></span></p> \
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">I \
am wondering what the problem might be?<o:p></o:p></span></p> <p><span \
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">Any \
idea? I can provide sample data if that might help...<o:p></o:p></span></p> <p><span \
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">I \
am now using ST_ExteriorRing from PostGIS (<a \
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... <o:p></o:p></span></p> <p><span \
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">Cheers<o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">Stefan<o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <o:p></o:p></span></p>
</div>
<p class="MsoNormal"><br>
<br>
<br>
<o:p></o:p></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>grass-user mailing list<o:p></o:p></pre>
<pre><a href="mailto:grass-user@lists.osgeo.org">grass-user@lists.osgeo.org</a><o:p></o:p></pre>
<pre><a href="http://lists.osgeo.org/mailman/listinfo/grass-user">http://lists.osgeo.org/mailman/listinfo/grass-user</a><o:p></o:p></pre>
</blockquote>
<p class="MsoNormal"><o:p> </o:p></p>
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