I am not a "computer person". So -- I don't know what this error message means. I found this question and answer for this same problem, but the solution did not work for me, dammit. GRASS algorithm r.los does not produce raster
I am using QGIS 2.0 (or maybe 2.0.1?). The computer is running Windows 7. I activated the menu Processing > Commander and got the command entry line above the map-area window -- no problem there. (The QGIS project I'm using has an elevation raster.) The computer program picks up just fine that I want to use the loaded raster. I copy and paste my coordinates for viewer location just fine. I tried leaving the default, temporary output file, and I also tried creating and entering into the GUI form a new file for this process. Each time, the following error message resulted.
Oooops! The following output layers could not be open Output raster layer: C:/Users/Cogreg/Documents/GIS, QGiS/Files_Greg_created_via_GIS/300_CountyRd_41_viewshed.tif The above files could not be opened, which probably indicates that they were not correctly produced by the executed algorithm Checking the log information might help you see why those layers were not created as expected This algorithm requires GRASS to be run. A test to check if GRASS is correctly installed and configured in your system has been performed, with the following result: GRASS seems to be correctly installed and configured