A forward from Helena Mitasova:
On Thu, Jan 10, 2002 at 11:01:13AM -0500, Helena Mitasova wrote:
Markus
I do not subscribe to grassusers list.
Quick answer is - use s.surf.rst, substantially reduce the number of
points on contours - they are oversampled (choose dmin at least 1.5 times
resolution and dmax a BIG number so that the program does not add
additional points to contours). If you still get the segments - run
r.random on your new DEM in the area where you have the visible segments
to generate few additional points and add them to your contours and
reinterpolate. And use smoothing at least 0.1 (you can use variable
smoothing with s.surf.rst - set it zero for the peaks and higher value for
the flat areas).I am thinking about taking out v.surf.rst from the distribution as it
needs all kinds of fixes (it gives seg fault if you compute the curvatures
- there is a bug in writing the color tables, but it computes everything
OK, also the default tension is too high, and overall I am not sure what
it is doing - what was updated and what not - e.g. how could it run with
npmin=2000 - it has a 400 or 700 limit).Also I have the fix for s.surf.rst for preventing it to run forever when
it gets dense points (such as LIDAR), just 2 lines of code, but I am
hesitating to include it for release - I would need testers to run it with
various types of data to see whether the fix does not have uninteded
consequences (I will forward the fix in the next email)It is not too difficult to fix the visible segments problem - the errors
is very small so it is more cosmetics (but a very unpleasant one) - so
those segments just need to be smoothed out withing the program - we used
to have it with older segmentation that we used for the MG93 paper).If anybody with good programming skills would be interested in making
improvements and new developments for multivariate interpolation for GRASS
part of their research (even PhD) I will be very happy to work with
him/her. I have a long list of improvements that need impmenetation,
testing enhancement etc.Helena