[GRASSLIST:4973] Re: 100KM raduis viewshed

Dan Jacobson jidanni at dman.ddts.net
Fri Nov 15 23:50:18 EST 2002

Actually by trial and error I found I had to use
r.mapcalc "pie=eval(heading=360+90-atan(x()-$xc,y()-$yc),heading>140&&heading<170)"
to make the 30 degree pie shaped mask in the SE quadrant like I wanted.

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.

It seems that nice parameters for r.los might be starting_azimuth and
ending_azimuth, but I was told r.los is set in stone and will not be

And r.los doesn't have a switch to turn off the computing the angles
of sight for each cell if one does not need them.

And r.cva is not in GRASS officially etc. and it and grass 5.0.0
itself are not ready in a .deb ...

Some mail:
>> I'm happy for you to include r.cva if you think it's appropriate.
>> But how urgent is this?  A couple of months back I converted r.los to
>> make proper use of INT, FCELL or DCELL and so should be able to do
>> something similar for r.cva over Christmas (incidentally, you might
>> also like the revised r.los code - let me know?).

Markus> Yes, the revised r.los code is interesting for us/me :-)
Markus> Whenever the r.cva is updated, please let me know.
http://jidanni.org/ Taiwan(04)25854780

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