[GRASSLIST:7902] Re: Hutchinson's Adaptive Alogrithm for sound DEMs?

[Carlos Guâno Grohmann]

Regarding this discussion on which features GRASS should have for
DEM/surface creation, I'd like to give my two cents and add one more
to the list, that is the possibility of using fault lines. This is not
so useful for general terrain analysis, but if one wants to
interpolate a stratigraphic level, for instance, it really makes a
difference.
There are several proprietary software that does it (eg, Surfer), you
give a vector file of fault lines as a secondary input of data points
for interpolation, and the mathematical function will understand the
lines as "barriers", that is, values in one side of a line won't be
taken into account when calculating interpolated values on the other
side of the line.

Carlos


On 8/14/05, Maciek Sieczka <werchowyna at epf.pl> wrote:
> Helena, Markus,
> 
> Since improving v.surf.rst is discussed, I would like to ad a few notes from
> a simple user, who doesn't understand all the maths of DEM interpolation but
> who would like to obtain decent results. Sorry for any naiveness. Please let
> me know what you think and if any of my wishes you find worthy of adding to
> v.surf.rst.
> 
> From: "Markus Neteler" <neteler at itc.it>
> 
> > Here a FWD from Helena Mitasova:
> >
> > On Tue, Aug 02, 2005 at 07:01:33PM -0400, Helena Mitasova wrote:
> 
> >> We are currently testing different interpolation methods including
> >> topogrid (or whatever its current name is)
> 
> I gues we should call it ANUDEM - after Hutchinson. The TOPOGRID is an
> ArcInfo program, which is an implementation of ANUDEM v. 4.5 or 4.6.3,
> depending ArcInfo/ArcGIS version
> http://support.esri.com/index.cfm?fa=knowledgebase.techarticles.articleShow&d=20779.
> 
> >> and v.surf.rst along with other methods and we
> >> plan to implement modifications/improvements that we find beneficial.
> 
> If I may point 4 features I find very usefull in ANUDEM (and two other
> tools) for creating DEMs from data extracted from topo maps. It would be
> great if v.surf.rst could provide them.
> 
> ANUDEM is able to utilize following data besides elevation points and
> contours:
> 
> 1. watercourses, including their flow direction
> I used it in TOPOGRID. At little effort - only digitise the watercourses in
> the direction needed - it is possible to obtain a DEM where the water flows
> exactly the way you want it.
> 
> 2. elevation discontinuity lines, called 'cliffs' in ANUDEM
> This was introduced in version 5.1. I haven't had an occasion to use it,
> since it is not available in TOPOGRID and I never had the original ANUDEM at
> hand. I only read it's supported in new version
> http://cres.anu.edu.au/outputs/anudem.php and think it is a great feature.
> Often elevation contour lines and points alone simply can't express all the
> complexity of terrain when gullies, scarps, embakments, walls, other
> breaklines are involved. That's due to these are not parallel to elevation
> isolines, thus cannot be presented as elevation isolines. Trying to
> represent them as points, although in theory doable in *some* cases, would
> require a lot of work to digitise points dense enough and to correctly
> estimate each point elevation manually. Yet utilising elevation
> discontinuity lines, digitised from topo maps, could greatly improve DEM
> accuracy - at very little effort. Especially in areas of land slides,
> erosion drived by river or flooding, land deformation due to mining, cliff
> shoreline - to name those I can think of right now.
> 
> Such a functionality is also present in SURGE interpolation software.
> http://www.geocities.com/miroslavdressler/surgemain.htm
> But it's only freeware/shareware for Windows, not free software, is very
> limited as to amount of data it can handle in one turn and the input data
> format is non standard and pretty complex.
> 
> 3. waterbodies
> I used it in TOPOGRID. The elevation of waterbodies interpolated agreed very
> well with their actual elevation as seen on topo maps and they are flat like
> they should be. I bet many folks would find it usefull for accurate
> elevation representation in lakelands, visualisation of areas in the
> vicinity of water bodies etc.
> 
> The other feature, not supported in ANUDEM but practical I think, are
> ridges. I found it supported in another DEM interpolation software,
> CatchmentSIM (again freeware for Windows, sigh), as "Interpolation Training
> Lines". The user can digitise them from topo maps and inlude during
> interpolation to model the mountain ridges in his DEM as he wishes
> http://www.toolkit.net.au/catchsim/.
> 
> Maciek
> 
> 


-- 
+-----------------------------------------------------------+
              Carlos Henrique Grohmann - Guano   
  Geologist M.Sc  - Doctorate Student at IGc-USP - Brazil
Linux User #89721  - carlos dot grohmann at gmail dot com
+-----------------------------------------------------------+