[GRASS-user] internal buffer of polygon

[Markus Metz]

On Thu, Apr 19, 2012 at 6:17 PM, Markus Neteler <neteler at osgeo.org> wrote:
> Hi all,
>
> does anyone have a new(er) trick for negative vector buffers (in GRASS 7)?

Internal buffers of areas are now (r51573) supported in trunk with
negative distances if GEOS support is enabled, i.e. v.buffer
distance=-1000 type=area works.

Markus M


>
> thanks
> Markus
>
> On Thu, Oct 29, 2009 at 4:59 PM, Milton Cezar Ribeiro
> <miltinho.astronauta at gmail.com> wrote:
>> 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 <emmanuel.sambale at gmail.com>
>>>
>>> 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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>>
>>
>>
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