Richard, So this gives you yet a 3rd method. While interpolating a smooth DEM from contour lines is a difficult problem (similar or worse problems reported with ArcGIS), all 3 of these methods will do a much better job than using v.extrude.
You can also use a 2 step process. Use any of these 3 methods and take a look at the results. To improve them you can use a neighborhood smoothing routine, as Maciek mentions below. Or you can generate a set of random points across your somewhat 'steppy' surface and do a new interpolation on the basis of the random points to smooth things out. There are even more routines to interpolate a surface from points. The bottom line is that there are a variety of ways to solve this problem in GRASS, giving you a lot of options to achieve the results you need. Michael On 7/31/07 4:14 PM, "Maciej Sieczka" <[EMAIL PROTECTED]> wrote: > Michael Barton wrote: >> Thanks for the clarification. This is good to know. Any other options >> besides r.surf.contour? > > I prefer r.surf.nnbathy, as I find natural neighbor or plain > triangulation most robust for interpolating contour lines. However, > these methods have their own problems - the output surface is not > smooth (only partly - in case on nat. neigh.), kidney shape contours > might be interpolated as plateus. But at least the result is > predictable. If I want it smoother, I filter the DEM afterwards. > > But that's just me. > > Maciek __________________________________________ Michael Barton, Professor of Anthropology Director of Graduate Studies School of Human Evolution & Social Change Center for Social Dynamics and Complexity Arizona State University phone: 480-965-6213 fax: 480-965-7671 www: http://www.public.asu.edu/~cmbarton _______________________________________________ grassuser mailing list [email protected] http://grass.itc.it/mailman/listinfo/grassuser
