[GRASS5] [bug #2061] (grass) r.los needs FP update

[Greg Sepesi]

> The algorithm in PE&RS is from the US Army CERL so it would be especially
> appropriate for it to go into the latest GRASS. I would hope some of the
> Vectlib and dglib functions could be used for determining the crossing
> points and distances between the cells but I will have to learn about
> them first.
> 
> Paul

Hi Paul,

What is the definition of "crossing points" in the algorithm?

The directed graph library I've been writing maintains a table of graph
intersection points.  There are also some well known geometric
algorithms, although I haven't attempted to put any into the directed
graph library yet, for finding the intersections among a set of line
segments.

Greg