[GRASSLIST:3384] Re: seeking advice on improving results with s.surf.rst

[Markus Neteler]

On Mon, Mar 25, 2002 at 05:44:13PM -0800, Eric G. Miller wrote:
> On Mon, Mar 25, 2002 at 12:02:35PM -0500, Neil Ripley wrote:
> > Hello all,
> > 
> > I am attempting to interpolate a continuous surface using s.surf.rst. My 
> > source data is a rasterized contour map which I have converted into a GRASS 
> > site file using the r.to.sites command.
> > 
> > The problem I have is that the segment edges are very apparent in the 
> > results I am getting from s.surf.rst. I am not getting a smoothly 
> > continuous surface as I expect I should. Instead I have clear and distinct 
> > breaks that coincide with the segmentation boundaries.
> > 
> > I have tried running the operation with different segmax values, different 
> > tension values, and different smoothness settings in an effort to reduce or 
> > eliminate the discontinuities but with little success.
> > 
> > Has anyone got any advice they would be willing to share on how to go about 
> > producing surfaces from contours using s.surf.rst?
> 
> Maybe look at some of the other modules that do the same thing:
> r.surf.contour, r.surf.idw[2].  Seems r.surf.contour was written for
> your particular data source (rasterized contour lines).

Please note that r.surf.contour is limited to integer DEMs, it won't
produce floating point output (quite a limitation).

s.surf.rst is quite good, according to Helena Mitasova the contour
lines are oversampled when using the default values. When modifying
them you will get an excellent result. Eventually Helena will write
a comment (she is not on this list) and/or we extend the man page.
The default parameters are defined for interpolation from distributed
points, not from contour lines.

Best,

 Markus Neteler