Here how "Isochrone Variable Speed" from SAGA works:
First you need to load your filled DTM into SAGA
Then you need to run the "Slope, Aspect, Curvature" tool as shown in the two pictures below. (only the slope layer will be used in the "Isochrone" tool)
Then click on "Geoprocessing" ; "Find and run tool" ...
There's another trick you might try: You can invert the DEM, so that ridges become valleys and stream outlets become the peaks. Then run r.watershed, and the resulting flow accum should be highest at the original "upstream" mountains, and lowest at the original drainage points.
I now have the required output for the gullies, and can use the other landform classes from r.geomorphon to create shapefiles of the other features such as ridges and shoulders. The workflow is as follows:
Resample the DSM to 0.1m cell size;
Run r.geomorphon with these parameters: outer search radius: 35, inner search radius: 9, flatness threshold: 3.7, ...
It looks like the system does not know the path of your current GRASS installation. Have you checked that you have the GRASSBIN set to your current GRASS version?
You can do that in the commandline (assuming your grass version is 7.8) like:
grass --config path
or directly from within your script like
I faced this type of issue when importing and write ESA SNAP .dim images in R. Then after some research I tried to update the crs of the raster from here. It works for me.
try this for your case:
crs(raster_objects)<-CRS("+proj=utm +zone=19 +south +datum=WGS84 +units=m +no_defs")
then export your image. you can find the proj4string it here.
You can also use the Raster calculator to change certain values on the raster. For example, if you want to transform all values between 300 and 310 to 305, raster calculator can do that. The QGIS manual has some examples on this. The last 5 minutes of this YT video also has an example on this.