Viewshed analysis in GRASS and Jupyter

A colleague asked me if the speed of the ESRI viewshed calculation could be improved. It took them 10.5 hours to compute 1620 viewsheds.

This was the first time I looked into GRASS GIS 1 and the grass.jupyter package 2. Computing time is now down to 30 minutes for 1620 viewsheds (16 threads parallel processing, 32GB memory). See the notebook for my example walkthrough 3.