[GRASS5] Angle of incidence in viewshed/line of sight

[Michael Barton]

Benjamin,

How are you coming on a way to install code like this without compiling or
recompiling GRASS?

Michael
____________________
C. Michael Barton, Professor of Anthropology
School of Human Evolution and Social Change
PO Box 872402
Arizona State University
Tempe, AZ  85287-2402
USA

Phone: 480-965-6262
Fax: 480-965-7671
www: <www.public.asu.edu/~cmbarton>


> From: Benjamin Ducke <benducke at compuserve.de>
> Organization: FU Berlin
> Date: Thu, 3 Mar 2005 21:33:12 +0100
> To: <grass5 at grass.itc.it>
> Subject: Re: [GRASS5] Angle of incidence in viewshed/line of sight
> 
> On Wed, 2 Mar 2005 13:28:14 +1300
> Hamish <hamish_nospam at yahoo.com> wrote:
> 
>>> Just so we don't re-invent the wheel, has anyone developed the code
>>> for evaluating the angle of incidence from a single point in the
>>> landscape (i.e. the point used for r.los) to cells within the
>>> viewshed? I am analyzing repeated historical topographic survey
>>> photographs (more on this later) and want to account for components of
>>> registration and classification error due to terrain (angle of
>>> incidence). I have looked at the code for r.los and r.sun and will be
>>> seeking help from some students in our new computer science/geomatics
>>> programme as I am not (yet) a programmer. Look forward to any
>>> suggestions...
>> 
>> 
>> Yes, I have done this some time ago.
>> 
>> I modified r.los to return horizontal angle to target instead of
>> vertical angle to target for the values in the resultant raster map. This
>> was for GRASS 5.0, but it should work for 6.0 just as well I think. If
>> you want I can supply the code.
>> 
>> r.los is a real mess and doesn't scale well to larger grid sizes.
>> 
>> Be sure to check out r.cva as well:
>>   http://www.ucl.ac.uk/~tcrnmar/GIS/r.cva.html
>> 
> 
> The GRASS 5 version of r.cva is currently broken due to a bug
> in the floating point raster code I introduced myself (ahem).
> I will have finished an updated version for GRASS 6 next week
> that fixes the bug, handles vector points for observer positions
> and introduces attributes for observer positions just
> like Argh!nfo's Spatial Analyst uses.
> I'll ask Mark Lake to update the file on his webpage then.
> 
> Regards,
> 
> Benjamin.
> 
> 
> 
>> 
>> r.sunmask with altitude and azimuth options might be another way.
>> 
>> 
>> 
>> Hamish
>> 
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>