I think there’s an error in the docs of the r.viewshed addon. It states that the default output raster contains vertical angle relative to the observer and that the values are:
“a value in [0, 180] representing the vertical angle with regard to the viewpoint, in degrees, if the point is visible. 0 degrees: directly above the observer, 180 degrees: directly below the observer” [1]
It’s the opposite of r.los, where 0 is below and 180 right above.
The resulting maps are equivalent, and looking to my results r.los interpretion is right.
giovanni
[1] https://svn.osgeo.org/grass/grass-addons/grass6/raster/r.viewshed/r.viewshed.html
–
Giovanni Allegri
http://about.me/giovanniallegri
Twitter: https://twitter.com/giohappy
blog: http://blog.spaziogis.it
GEO+ geomatica in Italia http://bit.ly/GEOplus
(sorry for slow)
On Tue, Jul 1, 2014 at 3:47 PM, G. Allegri <giohappy@gmail.com> wrote:
I think there's an error in the docs of the r.viewshed addon. It states that
the default output raster contains vertical angle relative to the observer
and that the values are:
"a value in [0, 180] representing the vertical angle with regard to the
viewpoint, in degrees, if the point is visible. 0 degrees: directly above
the observer, 180 degrees: directly below the observer" [1]
It's the opposite of r.los, where 0 is below and 180 right above.
The resulting maps are equivalent, and looking to my results r.los
interpretion is right.
In r61669 I have slightly polished the manual and added an example + screenshot.
And subsequently in r61670.[2] also added that 1.75 is the default
observer height and a correction to the text snippet you mentioned.
Thanks for catching, hope it is more clear now.
Markus
[2] for those not familiar with this rBLA stuff: it is the actual
revision number:
http://trac.osgeo.org/grass/changeset/61670
giovanni
[1]
https://svn.osgeo.org/grass/grass-addons/grass6/raster/r.viewshed/r.viewshed.html
--
Giovanni Allegri
http://about.me/giovanniallegri
Twitter: https://twitter.com/_giohappy_
blog: http://blog.spaziogis.it
GEO+ geomatica in Italia http://bit.ly/GEOplus
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