Helena, All,
I have run v.surf.rst on a dataset which consists of sparse elevation contour lines and single elevation points (for hill tops) and several spots of very dense elevation points, indicating elevation faults.
On
http://www.biol.uni.wroc.pl/sieczka/udostepnione/vsurfrst.png (160 KB)
and it's 10x exagaration http://www.biol.uni.wroc.pl/sieczka/udostepnione/vsurfrst_exag.png (237 KB)
you can see that there is a strange artifact in the interpolated DEM. I mean these series of pits between the isoline on the right and the elevation points indicating faults to it's left. How come? The elevation of the isoline is slightly (decimeters) more than the elevation of the highest points in the fault, so I expected a smooth elevation gradient from the isoline towards the fault - but there is a ditch instead!
DEM resolution 1m, distance between the isoline and fault about 10-30 meters.
Such sudden ditches occur everywhere where faults contact the continous surface. No matter how far is the closest isoline. Why is v.surf.rst introducing such an error?
Maciek