[R-sig-Geo] Calculation of geographical slope

[Roger Bivand]

On Wed, 7 May 2008, May, Roel wrote:

> Hi all,
>
> Does anyone know if there exists a function in R that can calculate
> geographical slope and aspect (i.e. like elevational slope/aspect) on
> grid values?

I'd suggest pushing the DEM out to GRASS, and using the module there. It 
could be done by creating new columns in a SpatialGridDataFrame for the 
eight neighbours and just doing the math - Zevenbergen and Thorne (1987) 
algorithm (for a reasonable sized DEM), but we don't have a function for 
grid shifting yet, contributions welcome!

Roger

> I've looked around on the R-sites but could not find anything on this.
> I hope can help a simple soul...
>
> Cheers, Roel
>
> Roel May
> Norwegian Institute for Nature Research
> Tungasletta 2, NO-7089 Trondheim
> Norway
>
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-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no