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

[Clint Bowman]

Also Roland Stull at U British Columbia is doing high resolution numerical 
weather prediction in the Canadian Arctic.  Again, I'm sure he has worked 
out the topographic issues.

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
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On Fri, 20 Feb 2015, Clint Bowman wrote:

> 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]]
>>
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