Hi.

> > Using contour lines as input, I have found the r.surf.nnbathy module to
> > perform very well.
>
> Previously, contour lines created by land surveying provided more
> detail than available DEMs. Nowadays (since SRTM of 2001), DEMs
> provide more detail than contour lines and contour lines are usually
> derived from a DEM. Therefore creating a DEM from contour lines which
> if in doubt have been created using a DEM is no longer recommended,
> rather use any DEM instead.
>
>
I certainly agree that contour lines are poor quality input data, however,
for situations involving conceptual reclamation, contours are used to build
the post-development DEM.  This still allows for (albeit generalized)
conceptual modeling of the drainage areas for reclaimed streams and
drainage areas, and allows for pre/post development analysis of drainage
areas (as it is understood the contours are conceptual, not as-built).
Nice to know that GRASS has modules that can cope with contour data, and
still produce adequate and reliable results.


Mark
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