[GRASS-user] Viewsheds

[Benjamin Ducke]

I would just like to add that the curvature correction feature
has never been tested extensively, so before you want to use
it in a production environment, give it some testing to see
if it gives plausible results (maybe compare with ArcGIS generated
viewsheds)

Benjamin

Mark Lake wrote:
> Paul,
> 
>> Before I recommend to my boss that we use GRASS for
>> this, I wanted to confirm that r.los does, in fact, account for the  
>> Earth's
>> curvature. Unfortunately, the online manpage makes no mention of  it, 
>> so I
>> was wondering if anyone can tell me if it does or doesn't.
> 
> 
> r.los does not correct for curvature of the earth.  The latest  version 
> of r.cva - upgraded by benjamin Ducke - does however have  this option.  
> You can get it from my site <http://www.ucl.ac.uk/ ~tcrnmar/> or 
> Benjamin's site <http://www.uni-kiel.de/ufg/ ufg_BerDucke.htm>.
> 
> Although r.cva is designed for multiple and cumulative viewshed  
> analysis, you can use it for calculating individual viewsheds if you  
> create a vector map containing the single viewpoint.  Note also that  
> whereas r.los returns a map containing the inclination at which  target 
> cells are visible, r.cva (when used to calculate one viewshed)  will 
> essentially just return a binary map (i.e. visible or not).  You  will 
> also need to invoke the -f flag (see the man page) to get the  effect 
> you want.
> 
> Mark
> 
> 
> -- 
> Dr Mark Lake
> 
> Institute of Archaeology
> University College London
> 31-34 Gordon Square
> London.  WC1H 0PY
> 
> Tel: +44 (0)207 679 7495
> Fax: +44 (0)207 383 2572
> 
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> 

-- 
Benjamin Ducke, M.A.
Archäoinformatik
(Archaeoinformation Science)
Institut für Ur- und Frühgeschichte
(Inst. of Prehistoric and Historic Archaeology)
Christian-Albrechts-Universität zu Kiel
Johanna-Mestorf-Straße 2-6
D 24098 Kiel
Germany

Tel.: ++49 (0)431 880-3378 / -3379
Fax : ++49 (0)431 880-7300
www.uni-kiel.de/ufg