GRASS and Sextante

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Revision as of 15:22, 15 April 2011 by Neteler (talk | contribs) (updated)

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GRASS has been integrated into Sextante as extension. Sextante itself is commonly used within gvSIG. Through this integration, gvSIG users have access to the wealth of well tested algorithms provided by GRASS.

Note: the GDAL-GRASS plugin must be installed.

How to install (tuned OADE version)

  1. Download and install OADE gvSIG binaries from here

Since version gvSIG OA Digital Edition 2010 (1.0), Sextante 0.6 with integrated GRASS GIS support is included.

Alternative: How to install (original gvSIG version)

From gvSIG 1.10 onwards, Sextante with integrated GRASS GIS support is included:

  1. download gvSIG binaries from here (download the All-included version)
  2. run the installer
  3. start gvSIG

Activating GRASS GIS in Sextante

(modified after grass_sextante.html)

Configuring Sextante to use GRASS takes just a few easy steps. Once you have configured the system, you will be able to execute GRASS algorithms from any Sextante component like the toolbox or the graphical modeller, just like you do with any other Sextante geo-algorithm.

Only two parameters must be set, namely:

  • The path to the GRASS installation folder. It is needed by Sextante to execute GRASS commands.
  • The path to a GRASS mapset. The mapset doesn't have to contain any data at all, since data will be imported automatically each time you execute an algorithm. The only important part of the mapset is the location information, particularly the Coordinate Reference System. You must set the same CRS that is used by the layers that you want to process using GRASS algorithms. If, for instance, you have layers with data in the EPSG 23030 reference system, you must set the mapset to that same reference system. When data is imported into the mapset, no reprojection is performed, and layers are assumed to be in the same projection as the mapset itself.
  • Open the Sextante Toolbox icon
  • Go to Sextante settings (open icon -> right of the "Search" bar at bottom of the window)
  • Go to "GRASS"
  • Set therein
  GRASS folder: /path/to/grass-binary-installation/  (e.g., /usr/local/grass-6.4.0svn/ )
  GRASS mapset: /path/to/grassdata/location/mapset  (e.g., /home/neteler/grassdata/nc_spm_08/sextante ) The mapset doesn't have to contain any data at all!

Note: you need to create this mapset with GRASS

  grass64 -c /path/to/grassdata/location/mapset  (e.g., grass64 -c /home/neteler/grassdata/nc_spm_08/sextante )
  exit
  • Click on "Setup GRASS" to register the raster and vector commands
  • Now click on the "Help" button to know that it is there and what it contains
  • Finally click "OK" to leave the dialog. Now 5xx Sextante/GRASS commands should be available

How to use

Note that GRASS is used in an internal temporary session (you cannot open GRASS data but work on GeoTIFF, SHAPE files etc).

A sample dataset is available here (based on free North Carolina dataset, provided by B. Ducke):

  ftp://88.208.250.116/gvsig-ref-data-nc.zip

Unpack the data set. It contains raster and vector map files.

Sample session:

  1. Start a new project: "File" -> "New Project" -> Click on the new name -> "Open" button
  2. Set the projection of the View: "View" -> "Properties" -> "Current projection" -> "Type:" select "EPSG" -> Enter code: "32119" -> Click on "Search" -> Click on "OK" -> Accept Properties with "OK"
  3. Add raster/vector map(s) with the "Add layer" button (top menu, circa in the center): File -> "Add" -> Select file -> "OK"
  4. Zoom to map
  5. Open Sextante dialog
  6. Go to "Indices and other hydrological parameters"
  7. Start (double click) r.topidx, select as Input "Elevation", as output write "topidx.tif" (it will go into your current directory; check with browse button), click OK
  8. It should have generated a new map.

See also