I am currently trying to reconstruct more or less convincing networks for the north-eastern part of Germany based on the EU-DEM using the tool r.walk in GRASS GIS. After showing talking about that during the last meeting, I tried out a data set of a more hilly region (around the nice mountain Brocken in central Germany).
I ran a few tests with several different start and stop points, trying to reconstruct a network between some of the larger settlements surrounding the mountain. The workflow was basically 1) r.walk with 1 of the points as the start and all the others as the targets iterated for all points and 2) r.drain on the resulting cost surfaces inverted, meaning the start point of r.walk is now the target point and vice versa. What I got is something like this.
My questions would be:
1) Is there a way to script this? I did not find a way to convince QGIS or GRASS GIS to select every point in a layer in an iterative process for the start points for r.walk and to invert this selection for the corresponding target points.
2) Since r.walk is nonisotropic, sometimes there are two paths connecting two points, according to which direction one walks. Is there a way to normalize this?
