[GRASS-user] v.surf.rast - surface tuning

M S mseibel at gmail.com
Mon May 14 08:49:18 EDT 2007

Greetings All -

I have been using different parameters for tension and smoothing to best
approximate the contours provided to me.

Using a tension of 50 and a smoothing of 5, I as able to produce a pretty
close approximation to the input data on two foot intervals.  To validate
the interpolation occuring between the 2 foot contours, I created 1 foot
contours to visualize what was occuring between the 2 foot contours. The
input data contours were more conceptual than practical at this stage, so it
is given that the input surface is not for exact interpretation.

The following webpage (http://mseibel.googlepages.com/v.surf.rast-tuning)
shows the input and output results.  1) original 2 foot contours 2)
interpolated 1 foot contours 3) input and interpolated data overlaid.

This particular area is conceptualizing a stream valley.  What parameters
might I tune in order to get the resulting interpolated contours between the
input data to have a similar shape as the contours that follow the 2 foot
input contours?

Meaning that the output 1 foot contours, which are on 2 foot intervals
approximate the data fairly well, with a "bell shape" for the stream valley,
but the intermediate 1 foot contours between the 2 foot contour data is
rounded out too much, and doesnt preserve the same "bell shape" as
approximated on the output 2 foot contours.  Basically I would like to
replicate the shape of the 2 foot interpolated contours through the surface
to the next 2 foot contour to keep the stream valley as smooth as possible.

What parameters should I be tuning to get the desired results mentioned

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