[GRASSLIST:4982] Re: 100KM raduis viewshed

[H. Bowman]

> But even using a 2 degree wide sliver still didn't stop r.los from
> taking hours and hours.  So I had to put r.los out of its misery.
> 
> Apparently if you use small square masks, r.los might even finish sooner
> or later, But the man page gives no strategies, and the program gives no
> progress indications.

I've been playing around with r.los lately, namely modifying it to return 
horizontal compass heading, rather than vertical angle to target. This is 
for for a simple wave exposure index along a coastline. (No refraction or 
reflection of waves for now, just direction * known wave stats from that 
direction, iterated over 360 degrees)


As far as I can tell, the r.los in GRASS 5.0.0 totally ignores a null 
MASK. This is a pain.
Setting the region/window to a smaller area does speed things up of course.
Setting max_dist= just bigger than your area of interest may or may not 
speed things up as well. I'm not sure.

If you thing r.los is slow, try r.sunmask!