This appears to be an implementation of the R3 Viewshed algorithm
from [1].
1. Franklin, Wm Randolph, and Clark Ray.
"Higher isn’t necessarily better: Visibility algorithms and experiments."
Advances in GIS research: sixth international symposium on spatial data handling. Vol. 2.
Taylor & Francis Edinburgh, 1994.
Created by jchien on 4/24/14.
This appears to be an implementation of the R3 Viewshed algorithm from [1].
1. Franklin, Wm Randolph, and Clark Ray. "Higher isn’t necessarily better: Visibility algorithms and experiments." Advances in GIS research: sixth international symposium on spatial data handling. Vol. 2. Taylor & Francis Edinburgh, 1994.