[GRASSLIST:58] Re: other methods for calculate profile and plan curvature

[Carlos "Guâno" Grohmann]

Roger,
thanks for your help. I found the references you mentioned, and wrote
a script for calculate slope, aspect, profile and plan curvatures.
The results are not what I expected, so I am thinking I might not have
fully understood your previous post. You said I need to make a shifted
array, why? because the way GRASS deals with coordinates of cells? I
don't know how to do it.

The script is attached, in case you want to take a look at it.

thanks again

Carlos




On 3/8/06, Roger Bivand <Roger.Bivand at nhh.no> wrote:
> On Wed, 8 Mar 2006, 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.
>
> You can use the Zevenbergen and Thorne (1987) recipe given by Burrough and
> McDonnell, 1998, p. 191 - do you have access to that? You do r.mapcalc
> using raster array indexing to make 8 shifted arrays, then more r.mapcalc
> to get slope, aspect, plan and profile curvature.
>
> Roger
>
>
> >
> > 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
> >
>
> --
> 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
>
>


--
+-----------------------------------------------------------+
              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
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