[GRASS-user] TIN in GRASS

[Maciek Sieczka]

On Mon, 26 Jun 2006 14:47:55 +1200
Hamish <hamish_nospam at yahoo.com> wrote:

> Simone Bonzano wrote:
> 
> > I continue to be a rookie in GRASS, I know.
> > Today I'm interested in elaborate TIN from contour vector file in
> > GRASS, how I could?
> 
> 
> Do you really need a TIN or are you generally interested in a smooth
> surface from contour data? If the latter, GRASS has strong support for
> raster (gridded) data which usually creates a nicer result. See
> v.surf.rst, v.surf.idw, r.surf.contour, ...

Also try r.surf.nnbathy from the Grass WIKI add-ons page. For me,
natural neighbor interpolation really performs best in interpolating
surface from such clustered, irregular input as contour lines ususally
are. At least try all methods and look for artifacts on areas of big
gaps and sudden gradients in the input, then compare all method's
performance - nn should be OK.

Note: it will listen to your input exactly, so if you don't want flat
peaks, add elavation points at tops. If you want a hollow, add a spot
of lower elevation at the hollow bottom. Good thing about this problem
is that you can have flat areas where you really want them :). Pretty
much like r.surf.contour, but it doens't have all it's other problems
and limitations.

> If you do need a tin, see the v.3dtin script in the wiki add-ons page.

Maciek

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