internal buffer of polygon

[maning sambale]

I tried using a negative values as
buffer=-3000 in v.buffer but it doesn't give me internal buffer in a
polygon layer.

Any hints?

--
cheers,
maning
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[Milton Cezar Ribeiro]

Hi Maning,

 

Sometimes I have the same issue, but I don't solve this on vector.

Just supose you have a map where 1 is your raster-based-polygon

and NULL is outside of polygon. You can use r.mapcalc to

invert it, in the maner that 1 come to be your non-polygon, and

NULL your polygon. So you can run r.buffer with positive value

and at the end may be you need to do some kind of crossing

between original and output maps.

 

Bests.

 

miltinho

2009/10/29 maning sambale <[hidden email]>

I tried using a negative values as
buffer=-3000 in v.buffer but it doesn't give me internal buffer in a
polygon layer.

Any hints?

--
cheers,
maning
------------------------------------------------------
"Freedom is still the most radical idea of all" -N.Branden
wiki: http://esambale.wikispaces.com/
blog: http://epsg4253.wordpress.com/
------------------------------------------------------
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[hidden email]
http://lists.osgeo.org/mailman/listinfo/grass-user

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[hamish-2]

Milton:
> Sometimes I have the same issue, but I don't solve
> this on vector.


in the past I have created a negative vector mask with v.in.region (infinite
area as the inverse of a closed polygon is not really possible) and then run
'v.overlay op=not'.

but perhaps v.buffer + the original area fed to 'v.overlay op=and' does the
trick. ?

I can't quite remember the method I used, but it is possible using something like the above method.


Hamish



     
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