[GRASSLIST:4844] 100KM raduis viewshed

Dan Jacobson jidanni at dman.ddts.net
Sat Oct 26 18:05:02 EDT 2002


Dear Sirs, what about curvature of the earth vs. line of sight?  The
r.cva man page mentions that it and r.los don't take curvature of the
earth into account.

You see, I'm trying to find out which mountains are visible from here
in a 100KM radius.  Mainly the ones on the first photo on
http://jidanni.org/location/view_en.html

I have a 40 meter DTM.  Shall I run it thru some mapcalc function of
radius to get curvature of the earth accounted for?

Tried r.los but I killed it after a half an hour of waiting.  I don't
care about the angle of sight (90 or 91 degrees usually), by the way.
I will try r.cva after I install the whole grass source just to get it
compiled, someday.

I want to concentrate on just 30 degrees of my horizon.  That means I
must use mapcalc to make a patt_map mask that any cell with the
azimuths I want to be =1. A pie slice shaped mask. Hmmm. How to
proceed?

http://www.directionsmag.com/features.php?feature_id=34 mentions a
"r.view" which I don't suppose exists.
-- 
http://jidanni.org/ Taiwan(04)25854780





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