I'm trying to work out least cost paths in QGIS. I have a DEM and a slope raster extracted from it, and a set of points, between which I want to find the least cost paths. I can find a SAGA plugin, but it needs a cost raster.
How do I go about making one of those, and then getting the least cost paths?
Best Answer
I am assuming that you already have some sort of friction surface, for instance slopes from the DEM.You can try two things. The first one involves use the procesing toolbox. Make sure it is on advanced interface. From the grass comands section yo can use use either r.cost or r.walk to define your cost surface. Then you can use r.drain to calculate the least cost path.
The second one is using the grass plugin with the same tool mentioned above. You will have to define the grass environment to use your data and "import" the rasters you want to use in to grass. Once you have the data in the grass format you can use r.cost r.wal and r.drain.
Look at the Wiki Evaluating Landscape Permeability in Quantum and you can see the implementation under QGIS.