[GRASSLIST:7906] Re: Hutchinson's Adaptive Alogrithm for sound DEMs?

[Dylan Beaudette]

On Monday 15 August 2005 06:58 am, Maciek Sieczka wrote:
> From: "Dylan Beaudette" <dylan at iici.no-ip.org>
>
> <snip>
>
> > I think that it  would be great if the pooled efforts of the GRASS
> > community could be  used to make GRASS the premier DEM creation /
> > modification environment.
>
> <snip>
>
> > Currently v.surf.rst provides a very flexible means to produce  elevation
> > surfaces from point and contour data.
>
> I fully agree. Unfortunatelly, these are the only data it supports...

Good point...

> > The recent work by  Tomas Cebecauer and others (See "Processing digital
> > terrain models by  regularized spline with tension: tuning interpolation
> > parameters for  different input datasets" from the proceedings to the
> > 2002 GRASS  conference.) shows how v.surf.rst can be used in a method
> > similar to  ANUDEM to enforce proper drainage networks, by adding a
> > "terrain skeleton".
>
> I'm affraid the method described in Cebecauer's paper is *completely*
> diffferent from the one used in ANUDEM. ANUDEM supports watercourse *lines*
> and elevation fault *lines*. While for v.surf.rst you have to digitise them
> as *points*. What's really bad, each such point has to be labelled for
> elevation before you feed it into v.surf.rst. So actually you have to do
> the interpolation of fault lines, ridges and watercourses manually, before
> you can make v.surf.rst use this crucial information. I find it strange,
> because a DEM interpolation program should be able to do it alone. At least
> that's the way I see it.

Indeed. Perhaps my wording was a bit ambiguous, i meant to say that while 
functionally different, this method can be used to obtain realistic drainage 
networks.

[snip]
> I'm no programmer, so I don't know if that is hard to
> implement and I can't offer any help. But I don't want to taken for a pain
> in the back only. Might I be really the only one intersted indeed? 
[/snip]

I am in the boat there, so you are certainly not the only one interested. 

> So why 
> does ANUDEM even exist? Or CatchmentSIM, SURGE? And why does ANUDEM sell at
> such a high price and is included in ESRI software? Having an equal
> competitor for ANUDEM could be really a tremendous benefit for GRASS IMHO.
> Currently v.surf.rst is excellent for homogenous data, like LIDAR. 

Good point. 

> But such 
> datasets are rare, which makes v.surf.rst usefull for limited amount of
> users. Who could make v.surf.rst really usefull for data derived from topo
> maps - the most available kind of elevation data?
>
> P.S.
> I'm CCing to grass devel as advised by Markus so Helena could read this
> all. Let's continue there.
>
> Helena,
> There's been some discussion on grass user list on this toppic. I don't
> want to crowd your box or grass devel forwarding it all, so please take a
> look at the archive if you can.
>
> All hail GRASS!
> Maciek

For us non programmers, lets put together a list of things that we can 
accomplish to facilitate the developers. Possible tasks might include:
1. writing of good documentation with figures and references
2. testing for bugs with known datasets
3. literature search and review of methods -> passing on the information to 
the developers.

any others ideas?


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