Calculate rumple index as a raster

[ncorroyez]

Hello,

I've calculated a CHM of a LAS catalog. Now I want to extract the rumple index from this CHM. Or, when I do:

rumple_index <- rumple_index(chm)
I get a single numerical value: one value for the whole raster. I would like to get a full raster of same dimensions and resolution than my CHM. I looked at terra focal and app but didn't manage to make them work. Any ideas on that ?

Cheers

[Jean-Romain]

rumple index requires to aggregate many cells. You cannot get a rumple index with the same resolution than the CHM. Or maybe with a moving windows. You could take 20 x 20 cells on a moving windows and assign the value to the central pixel. then move the windows by one pixel. This is what focal does but focal does not not keep track of the spatial arrangement (XY coordinates) of the pixels, thus won't be able to process rumple_index. Thus you have to code it yourself.