[GRASS-user] internal buffer of polygon

GRASS GRASS user
1

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/
------------------------------------------------------

2

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@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

“Freedom is still the most radical idea of all” -N.Branden
wiki: http://esambale.wikispaces.com/
blog: http://epsg4253.wordpress.com/

grass-user mailing list
grass-user@lists.osgeo.org
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3

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

4

Hi all,

does anyone have a new(er) trick for negative vector buffers (in GRASS 7)?

thanks
Markus

On Thu, Oct 29, 2009 at 4:59 PM, Milton Cezar Ribeiro
<miltinho.astronauta@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@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
------------------------------------------------------
"Freedom is still the most radical idea of all" -N.Branden
wiki: http://esambale.wikispaces.com/
blog: http://epsg4253.wordpress.com/
------------------------------------------------------
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

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5

v.in.region + v.overlay to do the inversion.

H

--- On Thu, 4/19/12, Markus Neteler <neteler@osgeo.org> wrote:

From: Markus Neteler <neteler@osgeo.org>
Subject: Re: [GRASS-user] internal buffer of polygon
To: "Milton Cezar Ribeiro" <miltinho.astronauta@gmail.com>
Cc: "GRASS user list" <grass-user@lists.osgeo.org>
Date: Thursday, April 19, 2012, 9:17 AM
Hi all,

does anyone have a new(er) trick for negative vector buffers
(in GRASS 7)?

thanks
Markus

On Thu, Oct 29, 2009 at 4:59 PM, Milton Cezar Ribeiro
<miltinho.astronauta@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@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
>>
------------------------------------------------------
>> "Freedom is still the most radical idea of all"
-N.Branden
>> wiki: http://esambale.wikispaces.com/
>> blog: http://epsg4253.wordpress.com/
>>
------------------------------------------------------
>> _______________________________________________
>> grass-user mailing list
>> grass-user@lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/grass-user
>
>
>
> _______________________________________________
> grass-user mailing list
> grass-user@lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-user
>
_______________________________________________
grass-user mailing list
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6

On Thu, Apr 19, 2012 at 6:17 PM, Markus Neteler <neteler@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@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@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
------------------------------------------------------
"Freedom is still the most radical idea of all" -N.Branden
wiki: http://esambale.wikispaces.com/
blog: http://epsg4253.wordpress.com/
------------------------------------------------------
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

_______________________________________________
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grass-user@lists.osgeo.org
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7

Hi,

2012/4/29 Markus Metz <markus.metz.giswork@googlemail.com>:

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.

cool, thanks! Martin

--
Martin Landa <landa.martin gmail.com> * http://geo.fsv.cvut.cz/~landa

8

On Sun, Apr 29, 2012 at 7:11 PM, Markus Metz
<markus.metz.giswork@googlemail.com> wrote:

On Thu, Apr 19, 2012 at 6:17 PM, Markus Neteler <neteler@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

I tried, phantastic! thanks so much,

Markus