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

[SBL]

Hi

Hope I am not too bothersome with that topic...

Unfortunately, Sextante 1.09 was hidden in my OSGeo4W installation behind
the old 1.07, so it took me a while to find the "advanced parameters".
Actually, both Sextante versions were installed in parallel, which I was not
aware of (neither the fact that allways only the old version was loaded).

Now I reinstalled QGIS and QGIS-dev with Sextante 1.1, created a polygon
layer with overlapping and not adjacent digitised boundaries (to be
snapped), and ran some tests:

Indeed, the advanced import parameters in Sextante 1.1 do the trick.

However, I can confirm Bernds findings in that sense, that the advanced
import parameters (especially snapping) in the v.in.ogr-part worked well,
while using the default settings for v.in.ogr combined with snapping with
exactly the same distance as in the earlier test in v.clean did not (though
that is maybe a GRASS issue). 

Furthermore, different from what I and Paolo expected overlapping areas are
beeing preserved in the Sextante output. I guess that is because Sextante
uses "type=auto" in the v.out.ogr-part.
Would it be possible to have "advanced parameters" also for exporting from
GRASS, where for example selective export of geometry-types or layers could
be choosen?

Though it may be trivial to chain several v.clean steps in a Sextante model,
this solution has definately some drawbacks. Because, as far as I can see
from the log, there is allways export, location creation and import
(including building of topology along with more or less cleaning) between
two model-steps... This affects both behavior of a chain of v.clean-tools
and performance...

Cheers
Stefan



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