Eric Grinaker asks:
I am creating a sea-floor elevation model with s.surf.tps, the source
data is from digitized bathymetry points labeled with there respective
depths. The resulting raster layer has "above zero" elevations that
appear to be related to sharp drops in depth. The small amount of
documenation I have suggests increasing the tension, however, an increase
great enough to level the "overshoots" results in my depth locations
appearing as a "sink hole" on the ocean floor. Any suggestions would
be greatly appreciated:)
Go back to a lower tension and make sure you define some non-zero
smoothing (my guess 0.1) it reduces the overshoots significantly and
still preserves the topography. If you still get some"above zero"
values change them to zero using r.mapcalc (it will create a sharp edge
what may be appropriate.)
Are there any net sources for s.surf.tps
documentation?
just the manual page and articles in GRASSClippings (Surfaces and modeling)
(not available on net, but I can put it on moon).
However, I will be presenting a short tutorial on s.surf.tps at the upcoming
conference on Integration of GIS and Environmental modeling.
I can put my notes which will be distributed there on moon, if there is
enough interest.
We plan to prepare a tutorial, however, this is an alpha program and
is still undergoing important changes and enhancements so we will write
it when it gets more stable.
Helena
helena@zorro.cecer.army.mil