GRASS GIS line of sight but permeable
My Data
I have a digital terrain model (brown), a height model for buildings (grey), a height model for trees (green).
My goal
For light pollution and ecology issues, I'd like to compute light emission on each cell of my digital terrain model from lamp poles.
My approach
A lamp pole can be compared to an observer who will look at each cell of the digital terrain model.
A typical viewshed approach is ok when light traverses buildings because light can't go through it. A binary approach (see/not see) can do the job.
trees and permeability
But for trees, a typical viewshed approach is not ok. There is an absorbance factor, which can be a function of the number of tree cells that are traversed by the beam of light.
Is there a GRASS GIS function, like r.los, that drawes a line from an observer to each cell of a raster of a digital terrain model and that sees how many cells of a digital height model are traversed ?
I'm also open to R stat approaches.
