Hi Luciano:
(Returning to the maillist - maybe this will help others...)
On 05/11/2012 18:29, Luciano La Sala wrote:
Two simple questions
Thank you Micha, I found the icons right under my nose.
To tell you the truth I am kind of lost here. I am trying to do the
interpolation from within QGIS using the raster map of risk I did
following your instructions (JPEG attached).
Pixel values, as calculated using the “r.mapcalculator” module in
GRASS, are (from the lightest yellow to the darkest red):
0.0406
0.1422
0.4268
0.5284
0.7154
0.8983
I first used the module “r.surf.idw” module (Screen_01) which runs
successfully but produces an entirely black raster map as output
(Screen_02). All the pixels of this raster contain a value of 1.
There is obviously something wrong here. Any tips? Should I use
“v.surf.idw” instead?
I found on an old maillist post that r.surf.idw works only with integer
values. That's why you're getting everything "rounded" to 1. To work
around this, you can try two options:
* revert back to vectors, as you suggest. (v.surf.idw accepts decimal
values)
r.to.vect -z in=risk_raster out=risk_vector feature=point
v.surf.idw in=risk_vector out=risk_idw layer=0
OR
* multiply your risk raster by some constant, say 1000, to get integer
values. Then run r.surf.idw on that, and divide the result by the same
1000 again to get back to your normalized values.
r.mapcalc risk_integer=risk_raster*1000
r.surf.idw in=risk_integer out=risk_idw_tmp
r.mapcalc risk_idw=risk_idw_tmp/1000.0
# Use the decimal value 1000.0 to insure that the result is
floating point.
Regards,
Micha
Thank you so very much for your time Micha.
Luciano
*De:*Micha Silver [mailto:[email protected] <mailto:[email protected]>]
*Enviado el:* Monday, November 05, 2012 4:01 AM
*Para:* Luciano La Sala
*Asunto:* [Bulk] Re: Two simple questions
On 05/11/2012 04:42, Luciano La Sala wrote:
Hello Micha,
Where do you access the
modules///v.surf.idw/and///r.surf.idw/from?I just can’t seem to
find them!
If you run GRASS on its own (not the QGIS plugin), these modules are
under the "Raster->Interpolate Surfaces"menu. In addition, all GRASS
commands can be run straight from the command line.
Thanks!
Luciano
This mail was received via Mail-SeCure System.
--
Micha Silver
GIS Consulting
052-3665918
http://www.surfaces.co.il
This mail was received via Mail-SeCure System.
--
Micha Silver
GIS Consulting
052-3665918
http://www.surfaces.co.il
_______________________________________________
grass-user mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/grass-user
