[GRASS-user] inverting DEMs

GRASS GRASS user
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,

–
BÜLENT ARIKAN
School of Human Evolution and Social Change
Arizona State University
Tempe - AZ
85287-2402

2

Multiply the DEM by -1

In r.mapcalc do:
dem_inv = dem * -1

On Sat, Nov 21, 2009 at 12:01 PM, Bulent Arikan <bulent.arikan@gmail.com> wrote:

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,

--
BÜLENT ARIKAN
School of Human Evolution and Social Change
Arizona State University
Tempe - AZ
85287-2402

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

3

Kind of a odd solution, but would it be possible to use the outputs of
r.param.scale to get the classed areas (i.e., peaks, pits, passes,
valleys) and then recode them as their opposite?

Alternatively, using r.mapcalc, can you multiply all the values by -1?

Mark

On Sat, Nov 21, 2009 at 9:01 AM, Bulent Arikan <bulent.arikan@gmail.com> wrote:

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,

--
BÜLENT ARIKAN
School of Human Evolution and Social Change
Arizona State University
Tempe - AZ
85287-2402

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

4

Daniel Victoria wrote:

Multiply the DEM by -1

In r.mapcalc do:
dem_inv = dem * -1

Or just negate it:

  dem_inv = -dem

This is more efficient, although I doubt that the difference would be
noticeable in practice; I would expect reading and writing the data to
dwarf the computation.

--
Glynn Clements <glynn@gclements.plus.com>