[Qgis-user] Running v.clean on a QGIS vector layer (Polygon) through Sextante

[Victor Olaya]

Bernd,

there is no v.in.ogr, because it is used *always* when you use a
vector layer with SEXTANTE and GRASS, to import the layer into GRASS,
and then produce a result.

Maybe a wrapper of v.in.ogr can be added, to do just import (which
includes cleaning), and then export the cleaned layer. Would that make
sense to you?

Thanks for your help!

2013/4/30 Bernd Vogelgesang <bernd.vogelgesang at gmx.de>:
> Hi,
> don't know if i understand the matter correctly, but what i extracted from
> Stefans initial question is, that there is no v.in.ogr accessible in
> Sextante, and therefore no advanced options for snapping and minimum areas
> to import from e.g. shape files.
> Especially for badly digitized polygon layers, this one-time import into
> GRASS with the advanced options cures almost all errors for me in 99% of the
> cases.
>
> v.clean.snap, as it was suggested by Paolo, is no alternative for that,
> cause snap seems not to handly polygons but only lines! ("snap: snap lines
> to vertex in threshold" from grass manual).
> So, i never found an easy way for topologically cleaning polygon layers
> through other v.clean functions as easy as with v.in.ogr, but as long as
> it's not accessible in Sextante, i still have to manually import it in GRASS
> (with all the mapset and location hokuspokus, most people do not understand)
>
> Maybe i'm completely on the wrong track. In this case: Please direct me ;)
>
> Cheers
> Bernd
>
> Am 30.04.2013, 17:02 Uhr, schrieb Paolo Cavallini <cavallini at faunalia.it>:
>
>
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>> Il 30/04/2013 13:46, SBL ha scritto:
>>
>>> What I did not understand completely was: Do you mean that the default
>>> settings of v.in.ogr are being used (snapping disabled and min_area set
>>> to
>>> 0.0001) or is the topology cleaning completely disabled in the
>>> v.in.ogr-part
>>> of Sextante?
>>
>>
>> The first one.
>>
>>> So maybe importing and exporting to and from GRASS could be used to
>>> perform
>>> a quick, simple and beginner-friendly "lightweight-cleaning"?
>>
>>
>> You can use v.clean for this
>>
>>> I see this also as a solution for  Bug #2921
>>> <http://hub.qgis.org/issues/2921>  , which furthermore offers additional
>>> quality checks...
>>> Actually, before I learned about the possibility in Sextante I considered
>>> creating a plugin for that...
>>
>>
>> Never reinvent the wheel; but you're always welcome to come and help
>> improving
>> Sextante, e.g. adding unit tests - it's easy, Victor can explain how.
>> All the best.
>> - --
>> Paolo Cavallini - Faunalia
>> www.faunalia.eu
>> Full contact details at www.faunalia.eu/pc
>> Nuovi corsi QGIS e PostGIS: http://www.faunalia.it/calendario
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>
>
> --
> Bernd Vogelgesang * Siedlerstrasse 2 * 91083 Baiersdorf * +49-9133-825374
>
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