[GRASSLIST:10828] Re: other methods for calculate profile and plan curvature

[Dylan Beaudette]

Hi Carlos,

This topic is one of my favorites, so I thought that I would chime in here.

Although the map derived from krigging may look similar to the RST map, subtle 
differences might only be apparent when higher order derivatives of the 
surfaces are calculated (i.e. for curvature estimates). It might be 
interesting to create a difference map of the two, or even a couple maps 
describing the standard deviation within a window for each map (r.neighbors). 
This might give you some insight on what exactly is "different" about the two 
maps. 

While I am by no means an expert on either command, I do believe that the 
curvatures are computed slightly differently in each algorithm. Do you have 
any samples that might be helpful in identifying the artifacts?

Cheers,

Dylan

On Wednesday 08 March 2006 08:27 am, Carlos "Guâno" Grohmann wrote:
> Hello all.
>
> I have just resampled a SRTM DEM using krigging (in R) and did the
> same with RST. The maps are very similar. When I resampled
> (interpolated) the DEM with RST, I can choose to derive maps for plan
> and tangencial curvature (among others) at the same time, and so I
> did.
> For the map interpolated with krigging, I have to derive curvatures
> using r.slope.aspect.
> While the DEMs are very similar, derivative maps don't. Curvature maps
> calculated with r.slope.aspect have lots of artifacts, while those
> from rst are much more smooth.
>
> So, I want to ask how I can calculate these curvatures in another way
> (r.mapcalc?)? I'd like to use the same method over both DEMs.
>
> thanks
>
> Carlos
>
>
> --
> +-----------------------------------------------------------+
>               Carlos Henrique Grohmann - Guano
>   Geologist M.Sc  - Doctorate Student at IGc-USP - Brazil
> Linux User #89721  - carlos dot grohmann at gmail dot com
> +-----------------------------------------------------------+
> _________________
> "Good morning, doctors. I have taken the liberty of removing Windows
> 95 from my hard drive."
> --The winning entry in a "What were HAL's first words" contest judged
> by 2001: A SPACE ODYSSEY creator Arthur C. Clarke

-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341