[GRASS-user] Densify vertices in polygon

[Robert Nuske]

Moin Markus

thanks for your helpful answer. v.split is what I was looking for and 
couldn't find.

I did see the v.generalize tutorial in the wiki. That's where I found 
the great description of in- and circumscribing smoothing ;-) But I did 
not find any information on the parameter of snakes, neither on the 
manual page nor the tutorial. alpha and beta seem to influence somehow 
the smoothness. But I could not figure out what the paramter threshold 
does. Seems to have no effect.

Thanks
   Robert


Am 19.06.19 um 18:01 schrieb Markus Metz:
> Hi Robert,
>
> On Wed, Jun 19, 2019 at 4:26 PM Robert Nuske 
> <rsn.mailinglists at gmail.com <mailto:rsn.mailinglists at gmail.com>> wrote:
> >
> > Dear Listers,
> >
> > I would like to smooth polygons coming from a raster via r.to.vect using
> > v.generalize methods=snakes.
> >
> > If I understood the documentation correctly, snakes is the only method
> > that tries to go the middle ground: neither entirely circumscribing
> > (larger than original polygon) nor inscribing (smaller than original
> > polygon) the polygon. I love that behavior. But snakes only works with
> > the available vertices and does not generate new vertices => quite rough
> > outlines.
> >
> > So i thought it would be a good idea to densify the vertices of the
> > polygon before the generalization. Create new vertices with distance x
> > on the boundary of the polygon. But couldn't find a function in GRASS
> > doing that.
>
> v.split -n should do exactly this: add new vertices with distance x: 
> length=x
> The -n flag causes new vertices to be added with splitting the 
> lines/boundaries.
>
> >
> > I would love any hints on generalization in general and on how to
> > densify my vertices.
>
> Apart from the manual of v.generalize, there is a tutorial at
> https://grasswiki.osgeo.org/wiki/V.generalize_tutorial
> (maybe not completely up to date)
>
> HTH,
>
> Markus M
>

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