[GRASS-user] inverting DEMs

[Michael Barton]

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 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,
>>
>