[GRASS-user] Remove islands with v.extract problem (again)

[Blumentrath, Stefan]

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 at gmail.com]
Sent: 21. juni 2014 21:59
To: Blumentrath, Stefan; grass-user at 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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