[GRASS-user] select only patches with 1-cell width

Blumentrath, Stefan Stefan.Blumentrath at nina.no
Thu Apr 20 11:47:42 PDT 2017

Sorry, forgot to mention, that water has to be NULL and everything else NOT NULL before you run 1) (r.grow.distance), and in 3) (r.mapcalc) the value has to be below or equal the resolution…


From: Blumentrath, Stefan
Sent: torsdag 20. april 2017 20.14
To: 'Giuseppe Amatulli' <giuseppe.amatulli at gmail.com>; GRASS user list <grass-user at lists.osgeo.org>
Subject: RE: [GRASS-user] select only patches with 1-cell width

Hi Giuseppe,

Not a single command, but you could:

1.       run r.grow.distance, then

2.       r.neighbors with 5 pixels circular neighborhood and maximum statistics

3.       r.mapcalc expression=”result=max_nbh_5<=1,1,null()”

If you want to get a vector lines result you might need r.thin and v.to.rast after that.

Hope that helps!


From: grass-user [mailto:grass-user-bounces at lists.osgeo.org] On Behalf Of Giuseppe Amatulli
Sent: torsdag 20. april 2017 18.06
To: GRASS user list <grass-user at lists.osgeo.org<mailto:grass-user at lists.osgeo.org>>
Subject: [GRASS-user] select only patches with 1-cell width

I have a huge streams/lakes dataset and I want to be able to select only water bodies (streams) with 1-cell width.
In other words if i have this raster

[Inline images 1]

I want to select only this streams

[Inline images 2]

Any suggestion or grass command that does such operation.
Thank you
Giuseppe Amatulli, Ph.D.

Research scientist at
Yale School of Forestry & Environmental Studies
Yale Center for Research Computing
Center for Science and Social Science Information
New Haven, 06511
Teaching: http://spatial-ecology.org
Work:  https://environment.yale.edu/profile/giuseppe-amatulli/
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