[GRASS-user] Artefacts when interpolating DTM from Contour Lines with v.surf.rst

[Markus Neteler]

Andreas,

here some older post from Helena (I have taken out non-relevant 
comments, and it is now v.surf.rst):

On Thu, Jan 10, 2002 at 11:01:13AM -0500, Helena Mitasova wrote:
> 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).
...
> 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).
...
> Helena 

You also find this addressed in the new GRASS book (3rd edition).

Markus
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