[OSGeo-Discuss] Iteration and supercomputing with GRASS GIS

[Markus Neteler]

Hi Johannes,

On Fri, Jan 14, 2011 at 12:34 PM, Johannes Radinger <JRadinger at gmx.at> wrote:
> Hello,
>
> I am very new to GRASS GIS!

welcome!
Please note that this is the general OSGeo list but see for
some answers below. Perhaps we switch to the GRASS users list
for further discussion: http://lists.osgeo.org/mailman/listinfo/grass-user

More below:

> At the moment I am working with ArcGIS10 to develop a dispersal model
> (raster based) which
> involves single calculations for each raster cell (around 20 000
> calculations) conducted by an iteration process over the cells of the input
> raster.
> As this takes quite long, a change to a Linux based software and  the use of
> a supercomputer (mulitcore) is considered. Therefore especially GRASS GIS
> sounds interesting to me for the soltution.

Yes, it should offer what you need.

> How are iterations (like in the ArcGIS10 modelbuilder) solved in GRASS GIS?

You can use for example (besides other module), the raster map algebra
calculator
for this:
http://grass.osgeo.org/grass64/manuals/html64_user/r.mapcalc.html

Especially the eval() function may be of interest to simplify the coding.
See for example the script of
http://svn.osgeo.org/grass/grass/branches/releasebranch_6_4/scripts/r.shaded.relief/

for an example.

> Is that possible?

I would say "yes". Again, best discussed in the GRASS list.

> Is it possible to perform the single calculation in parallel mode and use a
> multicore Linux supercomputer e.g.?

Also yes. I have processed > 11.000 MODIS Land Surface Temperature maps
using a 128 node Linux cluster. See for references

* http://grass.osgeo.org/wiki/Parallel_GRASS_jobs
  -> Grid Engine

* Neteler, M. (2010): Estimating daily Land Surface Temperatures in mountainous
   environments by reconstructed MODIS LST data. Remote Sensing 2(1), 333-351.
   Abstract + free PDF: http://www.mdpi.com/2072-4292/2/1/333

I can give you more indications if you need.

Best
Markus

-- 
Markus Neteler, PhD
Fondazione Edmund Mach (FEM) - IASMA Research and Innovation Centre
Department of Biodiversity and Molecular Ecology
Head of GIS and Remote Sensing Unit
Via E. Mach, 1 - 38010 S. Michele all'Adige (TN), Italy
Web:   http://gis.cri.fmach.it  -   http://grass.osgeo.org