[GRASS-user] Re: grass-user Digest, Vol 43, Issue 47

GRASS GRASS user
1

Hi Bulent,

I had a chance to mess around with the inverted DEM idea tonight. Here's what seemed to produce the best results for identifying peaks.

r.mapcalc 'inverted.DEM = -DEM'

Then I ran r.terraflow on the inverted DEM to get a filled, inverted DEM

r.terraflow elevation=inverted.DEM filled=terraflow.filled direction=<required> swatershed=<required> accumulation=<required> tci=<required>

(note that you will have to specify the other output maps too, even if you don't use them)

In the terraflow.filled map, I set the cells with value=0 to null (places where the flow went off the edge of the map).
Then I subtracted the filled map from the inverted DEM to find the sinks (=peaks of the original DEM)

r.mapcalc 'fill.difference =inverted.DEM-terraflow.filled'

If desired, these could then be inverted so that the larger the number, the closer to the peak.

r.mapcalc 'peaks = -fill.difference'

The result is draped over a relief map.

http://www.public.asu.edu/~cmbarton/files/temp/peaks_from_terraflow.jpg

Compare with the minic peaks map from r.param.scale

http://www.public.asu.edu/~cmbarton/files/temp/peaks.jpg

Michael

____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University

Phone: 480-965-6262
Fax: 480-965-7671
www: www.public.asu.edu/~cmbarton, http://csdc.asu.edu

On Nov 21, 2009, at 10:00 AM, grass-user-request@lists.osgeo.org wrote:

Date: Sat, 21 Nov 2009 07:01:37 -0700
From: Bulent Arikan <bulent.arikan@gmail.com>
Subject: [GRASS-user] inverting DEMs
To: grass-user@lists.osgeo.org
Message-ID:
  <f3d3690d0911210601j2679db9bh91e39960a4eb9206@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi,

I am trying to invert a DEM (i.e., make peaks basins and vice versa) but
there does not seem to be a module for this. I am assuming this can be done
through ' r.mapcalc ' which I have very limited experience.

I also want to get ' r.prominence ' from the Add-ons site but the
text file is not downloadable. Should I copy and paste to create a text
file that contains the script?

Thank you for all the suggestions,

2

Compare

http://www.public.asu.edu/~cmbarton/files/temp/peaks_from_terraflow.jpg

with

http://www.public.asu.edu/~cmbarton/files/temp/peaks_from_rparamscale_minic.jpg

(new version of the r.param.scale minic output)

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University

Phone: 480-965-6262
Fax: 480-965-7671
www: www.public.asu.edu/~cmbarton, http://csdc.asu.edu

On Nov 21, 2009, at 9:38 PM, Michael Barton wrote:

Hi Bulent,

I had a chance to mess around with the inverted DEM idea tonight.
Here's what seemed to produce the best results for identifying peaks.

r.mapcalc 'inverted.DEM = -DEM'

Then I ran r.terraflow on the inverted DEM to get a filled, inverted DEM

r.terraflow elevation=inverted.DEM filled=terraflow.filled
direction=<required> swatershed=<required> accumulation=<required>
tci=<required>

(note that you will have to specify the other output maps too, even if
you don't use them)

In the terraflow.filled map, I set the cells with value=0 to null
(places where the flow went off the edge of the map).
Then I subtracted the filled map from the inverted DEM to find the
sinks (=peaks of the original DEM)

r.mapcalc 'fill.difference =inverted.DEM-terraflow.filled'

If desired, these could then be inverted so that the larger the
number, the closer to the peak.

r.mapcalc 'peaks = -fill.difference'

The result is draped over a relief map.

http://www.public.asu.edu/~cmbarton/files/temp/peaks_from_terraflow.jpg

Compare with the minic peaks map from r.param.scale

http://www.public.asu.edu/~cmbarton/files/temp/peaks.jpg

Michael

____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University

Phone: 480-965-6262
Fax: 480-965-7671
www: www.public.asu.edu/~cmbarton, http://csdc.asu.edu

On Nov 21, 2009, at 10:00 AM, grass-user-request@lists.osgeo.org wrote:

Date: Sat, 21 Nov 2009 07:01:37 -0700
From: Bulent Arikan <bulent.arikan@gmail.com>
Subject: [GRASS-user] inverting DEMs
To: grass-user@lists.osgeo.org
Message-ID:
  <f3d3690d0911210601j2679db9bh91e39960a4eb9206@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi,

I am trying to invert a DEM (i.e., make peaks basins and vice versa)
but
there does not seem to be a module for this. I am assuming this can
be done
through ' r.mapcalc ' which I have very limited experience.

I also want to get ' r.prominence ' from the Add-ons site but the
text file is not downloadable. Should I copy and paste to create a
text
file that contains the script?

Thank you for all the suggestions,

3

Here are nviz versions of the 2 peaks maps for comparison:

http://www.public.asu.edu/~cmbarton/files/temp/peaks_from_terraflow_nviz.jpg
http://www.public.asu.edu/~cmbarton/files/temp/peaks_from_rparamscale_minic_nviz.jpg

It seems like the inverted DEM/hydrology method identifies major peak *regions*, while the r.param.scale minic method finds individual topographic highs. This makes sense given the way that both find peaks differently.

Michael

____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University

Phone: 480-965-6262
Fax: 480-965-7671
www: www.public.asu.edu/~cmbarton, http://csdc.asu.edu

On Nov 21, 2009, at 9:48 PM, Michael Barton wrote:

Compare

http://www.public.asu.edu/~cmbarton/files/temp/
peaks_from_terraflow.jpg

with

http://www.public.asu.edu/~cmbarton/files/temp/peaks_from_rparamscale_minic.jpg

(new version of the r.param.scale minic output)

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University

Phone: 480-965-6262
Fax: 480-965-7671
www: www.public.asu.edu/~cmbarton, http://csdc.asu.edu

On Nov 21, 2009, at 9:38 PM, Michael Barton wrote:

Hi Bulent,

I had a chance to mess around with the inverted DEM idea tonight.
Here's what seemed to produce the best results for identifying peaks.

r.mapcalc 'inverted.DEM = -DEM'

Then I ran r.terraflow on the inverted DEM to get a filled, inverted
DEM

r.terraflow elevation=inverted.DEM filled=terraflow.filled
direction=<required> swatershed=<required> accumulation=<required>
tci=<required>

(note that you will have to specify the other output maps too, even if
you don't use them)

In the terraflow.filled map, I set the cells with value=0 to null
(places where the flow went off the edge of the map).
Then I subtracted the filled map from the inverted DEM to find the
sinks (=peaks of the original DEM)

r.mapcalc 'fill.difference =inverted.DEM-terraflow.filled'

If desired, these could then be inverted so that the larger the
number, the closer to the peak.

r.mapcalc 'peaks = -fill.difference'

The result is draped over a relief map.

http://www.public.asu.edu/~cmbarton/files/temp/
peaks_from_terraflow.jpg

Compare with the minic peaks map from r.param.scale

http://www.public.asu.edu/~cmbarton/files/temp/peaks.jpg

Michael

____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University

Phone: 480-965-6262
Fax: 480-965-7671
www: www.public.asu.edu/~cmbarton, http://csdc.asu.edu

On Nov 21, 2009, at 10:00 AM, grass-user-request@lists.osgeo.org
wrote:

Date: Sat, 21 Nov 2009 07:01:37 -0700
From: Bulent Arikan <bulent.arikan@gmail.com>
Subject: [GRASS-user] inverting DEMs
To: grass-user@lists.osgeo.org
Message-ID:
  <f3d3690d0911210601j2679db9bh91e39960a4eb9206@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi,

I am trying to invert a DEM (i.e., make peaks basins and vice versa)
but
there does not seem to be a module for this. I am assuming this can
be done
through ' r.mapcalc ' which I have very limited experience.

I also want to get ' r.prominence ' from the Add-ons site but the
text file is not downloadable. Should I copy and paste to create a
text
file that contains the script?

Thank you for all the suggestions,