[R-sig-Geo] Proper algorithms for computing slopes for global/polar DEMs?

[Clint Bowman]

Have you thought about a Lambert Conformal projection?  I'd think you 
could adjust the projection parameters to get a pretty nice grid over 
Alaska.  I'm sure the mesoscale modelers at UA-Fairbanks have worked this 
out.

Clint

Clint Bowman			INTERNET:	clint at ecy.wa.gov
Air Quality Modeler		INTERNET:	clint at math.utah.edu
Department of Ecology		VOICE:		(360) 407-6815
PO Box 47600			FAX:		(360) 407-7534
Olympia, WA 98504-7600

         USPS:           PO Box 47600, Olympia, WA 98504-7600
         Parcels:        300 Desmond Drive, Lacey, WA 98503-1274

On Fri, 20 Feb 2015, Jonathan Greenberg wrote:

> r-sig-geo'ers:
>
> We're trying to figure out a good algorithm for computing topographic slope
> for Alaska, which is both huge and near the pole.  Our DEM is currently in
> geographic coordinates, but we need slope over a fixed distance (change in
> elevation vs. horizontal meters).  The issue is, there is no projection to
> switch this to to get an accurate set of slope calculations.  Of course
> with degrees, the X and Y distances change over the globe -- so the
> horizontal distances will be variables from one window to the next.  I have
> seen various solutions published, but I wanted to see if someone knows of a
> decent coded-up algorithm for this.  Thoughts?
>
> Some background:
> http://gis.stackexchange.com/questions/14750/how-to-use-srtm-global-dem-for-slope-calculation/40464#40464
>
> --j
>
> 	[[alternative HTML version deleted]]
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>