I am trying to use r.cost and r.walk and r.drain to calculate the shortest path from an archaeological site to the nearest basalt source. I am using all this algorithms with the processing toolbox (I have no grass experience...). I am able to run both r.cost and r.walk but when I try to use r.drain I have a python error. I thought I can use the rasters created to obtain the path in another program (Yes, like ArcMap). In order to do so I need the "movement direction raster" that you are suppose to get either from r.walk or r. cost. Nevertheless, when I use r.cost or r.walk from the processing toolbox and I can only visualize the cumulative costs rasters and not the direction ones. I also looked for an option to define a name and a path for the movement direction raster showing advanced parameters, but I have no luck either. ¿Does somebody know how to produce this movement direction raster? (if possible from the processing toolbox). I am using Dufour 64bits on win7 16mb of ram (standalone install and osGeo4w install)

Thanks in advance


PS. This is the Python error: An error has occured while executing Python code:

Traceback (most recent call last): File "C:\Users\IIAMaps/.qgis2/python/plugins\processing\gui\AlgorithmExecutionDialog.py", line 208, in accept self.setParamValues() File "C:\Users\IIAMaps/.qgis2/python/plugins\processing\gui\AlgorithmExecutionDialog.py", line 143, in setParamValues self.paramTable.valueItems[param.name]): File "C:\Users\IIAMaps/.qgis2/python/plugins\processing\gui\AlgorithmExecutionDialog.py", line 189, in setParamValue value.append(options[index]) IndexError: list index out of range

Python version: 2.7.5 (default, May 15 2013, 22:44:16) [MSC v.1500 64 bit (AMD64)]

QGIS version: 2.0.1-Dufour Dufour, d94c044

Python path: ['C:\Users\IIAMaps/.qgis2/python/plugins\processing', 'C:/PROGRA~1/QGISDU~1/apps/qgis/./python', 'C:\Users\IIAMaps/.qgis2/python', 'C:\Users\IIAMaps/.qgis2/python/plugins', 'C:/PROGRA~1/QGISDU~1/apps/qgis/./python/plugins', 'C:\Program Files (x86)\ArcGIS\bin', 'C:\PROGRA~1\QGISDU~1\bin\python27.zip', 'C:\PROGRA~1\QGISDU~1\apps\Python27\DLLs', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\plat-win', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\lib-tk', 'C:\PROGRA~1\QGISDU~1\bin', 'C:\PROGRA~1\QGISDU~1\apps\Python27', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\site-packages', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\site-packages\PIL', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\site-packages\win32', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\site-packages\win32\lib', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\site-packages\Pythonwin', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\site-packages\Shapely-1.2.18-py2.7-win-amd64.egg', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\site-packages\six-1.3.0-py2.7.egg', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\site-packages\wx-2.8-msw-unicode', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\site-packages\xlrd-0.9.2-py2.7.egg', 'C:\PROGRA~1\QGISDU~1\apps\Python27\lib\site-packages\xlwt-0.7.5-py2.7.egg', 'C:\Users\IIAMaps\.qgis2\python\plugins\mmqgis/forms', 'C:\PROGRA~1\QGISDU~1\apps\qgis\python\plugins\fTools\tools']

  • Please consider to post the r.drain python error...
    – markusN
    Commented Nov 10, 2013 at 5:42
  • @MarkusN I included the Python error in my question. I have no way to put it as acomment (too long) Commented Nov 10, 2013 at 15:39
  • To me that looks like a QGIS error (looking at your message)..."qgis2/python/plugins\processing\gui\AlgorithmExecutionDialog.py"
    – markusN
    Commented Nov 12, 2013 at 22:14

1 Answer 1


yo can obtain a "movement direction raster" or simply "direction raster" with the tool "watershed", selecting only the correct output.

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