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

[Michael Barton]

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 at lists.osgeo.org wrote:

> Date: Sat, 21 Nov 2009 07:01:37 -0700
> From: Bulent Arikan <bulent.arikan at gmail.com>
> Subject: [GRASS-user] inverting DEMs
> To: grass-user at lists.osgeo.org
> Message-ID:
> 	<f3d3690d0911210601j2679db9bh91e39960a4eb9206 at 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,