[GRASSLIST:1829] Re: Creating a DEM

[Roger Bivand]

On Fri, 11 May 2001, michele.rocc at libero.it wrote:

> Hi,
> 
> I'm trying to create a DEM from a "scannerized" map, because of the 
> large amount of feature I thought to extract in some way the contour 
> lines using r.thin and r.line, then I heard that maybe there is som 
> problems in doing that (something like r.surf.contour doesn't work fine 
> yet..).

The present weakness with r.surf.contour is only that it does not generate
floating point output, just CELL. However, in my experience it works well,
and we have used it to produce output with much less "dominance" of
contour valued terraces than interpolating treating contours as sites. If
you look at the "leics" example files, you will find that that is how the
"topo" layer was constructed. It does run quite slowly for very large
regions, and you may need to watch local troughs and summits, but I
wouldn't drop r.surf.contour unless you have a better alternative for use
with contour data.

Roger

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: Roger.Bivand at nhh.no
and: Department of Geography and Regional Development, University of
Gdansk, al. Mar. J. Pilsudskiego 46, PL-81 378 Gdynia, Poland.