[GRASS-dev] Re: Line of Sight Update

[Markus Neteler]

On Wed, Jul 23, 2008 at 12:21 PM, Benjamin Ducke
<benjamin.ducke at oxfordarch.co.uk> wrote:
> Markus Neteler wrote:
>>
>> It is important - please, if not too hard (I ported it from r.cva to
>> r.los, wasn't
>> so hard) add it. It makes a difference... I have an ongoing "batlle" with
>> an ex colleague if we can see the sea from our mountain here or not,
>> r.los and his algorithm do not agree. :)
>
> Interesting, I remember putting that into r.cva years ago (I used the
> approximation in the paper I mailed about before), but never really
> had any time to test it very well (which is why I marked it as
> untested in the HTML page for r.cva).
>
> Does it produce plausible results with your data?

Good question:
http://www.grassbook.org/neteler/tmp/

- r.los from two adjacent mountain peaks (LAEA projection, SRTM 250m)
- "marmota" [1] algorithm from one of the peaks (the viewshed I don't
have, LatLong,
    SRTM 250m)

Additionally:
- "Sitting" in Google Earth on Monte Bondone does *not* show the sea
   near Venice (but they use a sphere). If I increase the flight height a bit,
   I see the sea...

It's rather complicated (for me).

Markus

[1] http://tev.fbk.eu/TeV/Research/vem.html   <- very cool