[GRASS-user] V.generalize

[DAZIN Fabrice (SIRS)]

Hi,

Yes i try with other methods of v.generalize tool with same problems.
I realize that if the generalisation tool creates a topological error on a part of the vector then the tool does not treat this part and leaves it as it is.
I didn't succeed in forcing him to do it.

As a workaround i used https://mapshaper.org/   that implement the Visvalingam algo that work fine with a real time result!
(see https://gis.stackexchange.com/questions/87505/grass-v-generalize-method-douglas-not-working-as-expected)

My challenge is now to create a tool in grass with this Visvalingam algo.

Best regards
Fabrice Dazin
[cid:8590fe01-f45d-4f0d-8c6a-8ce2a9867149]
________________________________
De : Markus Neteler <neteler at osgeo.org>
Envoyé : mercredi 26 août 2020 16:27
À : DAZIN Fabrice (SIRS) <Fabrice.DAZIN at sirs-fr.com>
Cc : GRASS user list <grass-user at lists.osgeo.org>
Objet : Re: [GRASS-user] V.generalize

Hi,

On Mon, Aug 24, 2020 at 4:35 PM DAZIN Fabrice (SIRS)
<Fabrice.DAZIN at sirs-fr.com> wrote:
>
>
> Dear all,
>
> In the process of transforming a raster classification into a vector layer, I use among others the command V.GENERALIZE.
>
> v.generalize input=v_classif_ext at PERMANENT layer=1 type=area type=boundary  method=reduction threshold=4 alpha=0.5 iterations=4 output=v_classif_ext_redv.generalize input=v_classif_ext_red at PERMANENT layer=1 type=area type=boundary method=sliding_averaging threshold=100 alpha=0.5 iterations=4 output=v_smooth_1
>
> with
> grassversion=79
> srid=2154
>
> And I wonder why the smoothing result is not homogeneous, even sometimes for the same polygon.
> Any idea about the reason?

Not sure about this particular "reduction" method but did you already
try with a different method?

Best regards,
Markus

--
Markus Neteler, PhD
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