For a suitability analysis I need to define the suitability of slope from DEM values (in %) to build new trails.
Knowledges says that flat and rather steep areas are not suitable due to water runoff. Unfortunately, it is not possible to define threshold like
<5% nogo, 5%<x>60% go, >60% nogo.
So I was thinking about a fuzzy set. I use QGIS and do not want to install GRASS GIS (due to security settings on my macOS). SAGA GIS fuzzify allows to define gradients between 0 (fully flat) and 1, see
Basically, this works for me. But: For further calculations my output should be in the range from 1 to 5, whereas
0 - 1 = NoGo 1 - 2 = not good 2 - 3 = take care 3 - 4 = good 4 - 5 = must go
So I wanted to recalculate the 0 to 1 gradient from SAGA GIS into my gradient.
0 =! 1 ... 0.5 =! 3 ... 1 =! 4
How can I do this? Is there a better fuzzy logic algorithm available than this one from SAGA GIS (apart from GRASS GIS)?
If I didn't find any solution, I would probably create a discrete assignment between the slope and my categories.