[GRASS-user] Euclidean distance (grow.distance) on raster to certain extent?

GRASS GRASS user
1

Hello,

I am trying to run the grow.distance command to create a raster that displays the euclidean distance from an ‘orchard’ outward to 1108m. I am not trying to measure the distance between 2 non-null features, but simply wish to have the euclidean distance extend out from the orchard to 1108m. I recognize this tool does not allow a distance to be included so I created a buffer around my orchard (1108m) and intended to run grow.distance on that, however it outputs the distance as if it includes the full raster extent (so I have an output raster of 1108m that is all yellow as opposed to a range of values displaying varying distances) and not limited to my buffer. I want it to assume the buffer extent is the raster extent, so to speak. Is there another way to do this?
Any ideas would be much appreciated.

Best,

Tanya

2

Tanya wrote:

I am trying to run the grow.distance command to create a raster that displays the euclidean distance from an ‘orchard’ outward to 1108m. I am not trying to measure the distance between 2 non-null features, but simply wish to have the euclidean distance extend out from the orchard to 1108m.

I don´t know r.grow.distance or why it is not working for you, but every time I need distance rasters, I use the procedure found in the GRASS book, as follows:

r.mapcalc area1=1

r.cost -k in=area1 out=distance_to_orchard start_rast=orchard_location --o --q
r.mapcalc “distance_to_orchard=distance_to_orchard * (ewres() + nsres())/2.”

It is an approximate measure, but you can evolve this idea for a better solution for your case. Then you only need to use your buffer as a mask to get the final raster you want or simply use:

r.mapcalc “final_raster=if(distance_to_orchard<=1108,distance_to_orchard,null())”

Hope it helps.
Cheers,
Marcello.

3

Hi Tanya,

I would use r.distance rather than r.grow.distance and then reclassify the results to include only areas with <=1108 m distance - that should be a lot easier.

Best,
Daniel

–

B.Sc. Daniel Lee
Geschäftsführung für Forschung und Entwicklung
ISIS - International Solar Information Solutions GbR
Vertreten durch: Daniel Lee, Nepomuk Reinhard und Nils Räder

Softwarecenter 3
35037 Marburg
Festnetz: +49 6421 379 6256
Mobil: +49 176 6127 7269
E-Mail: Lee@isi-solutions.org
Web: http://www.isi-solutions.org

2012/5/7 Tanya Dyck <tanya.dyck@hotmail.com>

Hello,

I am trying to run the grow.distance command to create a raster that displays the euclidean distance from an ‘orchard’ outward to 1108m. I am not trying to measure the distance between 2 non-null features, but simply wish to have the euclidean distance extend out from the orchard to 1108m. I recognize this tool does not allow a distance to be included so I created a buffer around my orchard (1108m) and intended to run grow.distance on that, however it outputs the distance as if it includes the full raster extent (so I have an output raster of 1108m that is all yellow as opposed to a range of values displaying varying distances) and not limited to my buffer. I want it to assume the buffer extent is the raster extent, so to speak. Is there another way to do this?
Any ideas would be much appreciated.

Best,

Tanya

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

4

On 07/05/12 16:36, Daniel Lee wrote:

Hi Tanya,

I would use r.distance rather than r.grow.distance and then reclassify
the results to include only areas with <=1108 m distance - that should
be a lot easier.

I don't think r.distance gives what you want, however r.grow.distance should be exactly your tool:

As a starting point you need a raster map with all pixels in the orchard non-null and all other pixels null Let's call that raster map 'orchard'. Then you can do the following:

r.grow.distance input=orchard distance=distance_map

Then, if you only want to see the distance from the orchard to 1108m, then you can use r.mapcalc:

r.mapcalc "final_distance_map=if(distance_map>1108, null(), distance_map)"

All this keeping in mind that I don't understand what you mean by "I recognize this tool does not allow a distance to be included".

If this means that you also want to measure a distance _within_ the orchard, then instead of using a raster map of the orchard, use as input to r.grow.distance a raster map with only the center pixel of the orchard non-null.

Moritz

2012/5/7 Tanya Dyck <tanya.dyck@hotmail.com <mailto:tanya.dyck@hotmail.com>>

    Hello,

    I am trying to run the grow.distance command to create a raster that
    displays the euclidean distance from an 'orchard' outward to 1108m.
      I am not trying to measure the distance between 2 non-null
    features, but simply wish to have the euclidean distance extend out
    from the orchard to 1108m. I recognize this tool does not allow a
    distance to be included so I created a buffer around my orchard
    (1108m) and intended to run grow.distance on that, however it
    outputs the distance as if it includes the full raster extent (so I
    have an output raster of 1108m that is all yellow as opposed to a
    range of values displaying varying distances) and not limited to my
    buffer. I want it to assume the buffer extent is the raster extent,
    so to speak. Is there another way to do this?
    Any ideas would be much appreciated.

    Best,

    Tanya

    _______________________________________________
    grass-user mailing list
    grass-user@lists.osgeo.org <mailto: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

5

Thank you Moritz, this worked beautifully!

Date: Mon, 7 May 2012 18:00:01 +0200
From: mlennert@club.worldonline.be
To: lee@isi-solutions.org
CC: tanya.dyck@hotmail.com; grass-user@lists.osgeo.org
Subject: Re: [GRASS-user] Euclidean distance (grow.distance) on raster to certain extent?

On 07/05/12 16:36, Daniel Lee wrote:

Hi Tanya,

I would use r.distance rather than r.grow.distance and then reclassify
the results to include only areas with <=1108 m distance - that should
be a lot easier.

I don’t think r.distance gives what you want, however r.grow.distance
should be exactly your tool:

As a starting point you need a raster map with all pixels in the orchard
non-null and all other pixels null Let’s call that raster map
‘orchard’. Then you can do the following:

r.grow.distance input=orchard distance=distance_map

Then, if you only want to see the distance from the orchard to 1108m,
then you can use r.mapcalc:

r.mapcalc “final_distance_map=if(distance_map>1108, null(), distance_map)”

All this keeping in mind that I don’t understand what you mean by “I
recognize this tool does not allow a distance to be included”.

If this means that you also want to measure a distance within the
orchard, then instead of using a raster map of the orchard, use as input
to r.grow.distance a raster map with only the center pixel of the
orchard non-null.

Moritz

2012/5/7 Tanya Dyck <tanya.dyck@hotmail.com mailto:tanya.dyck@hotmail.com>

Hello,

I am trying to run the grow.distance command to create a raster that
displays the euclidean distance from an ‘orchard’ outward to 1108m.
I am not trying to measure the distance between 2 non-null
features, but simply wish to have the euclidean distance extend out
from the orchard to 1108m. I recognize this tool does not allow a
distance to be included so I created a buffer around my orchard
(1108m) and intended to run grow.distance on that, however it
outputs the distance as if it includes the full raster extent (so I
have an output raster of 1108m that is all yellow as opposed to a
range of values displaying varying distances) and not limited to my
buffer. I want it to assume the buffer extent is the raster extent,
so to speak. Is there another way to do this?
Any ideas would be much appreciated.

Best,

Tanya

grass-user mailing list
grass-user@lists.osgeo.org mailto: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