There's even a dedicated page on the GRASS-wiki: http://grass.osgeo.org/wiki/Contour_lines_to_DEM
HTH, Pierre 2011/7/13 Dylan Beaudette <dylan.beaude...@gmail.com>: > I would second Roger's comments. I have found r.surf.contour does well > in complex terrain, especially at interfaces with water (i.e. alpine > lakes). There are several related threads on the GRASS mailing list. > > Dylan > > On Fri, Jul 8, 2011 at 8:09 AM, Roger Bivand <roger.biv...@nhh.no> wrote: >> On Fri, 8 Jul 2011, Barry Rowlingson wrote: >> >>> On Fri, Jul 8, 2011 at 2:26 PM, Robert Hijmans <r.hijm...@gmail.com> >>> wrote: >>> >>> >>> >>>> # now there are many ways to interpolate. See, e.g., the 'gstat' and >>>> 'automap' packages. See raster::interpolate for an example with splines. >>>> # using gstat and inverse distrance weighted interpolation: >>>> >>>> library(gstat) >>>> g <- gstat(id="level", formula = level~1, data=p, nmax=7, set=list(idp = >>>> .5)) >>>> x1 <- interpolate(r, g) >>> >>> Statistical interpolation techniques may be right for this, but >>> thinking about it last night made me realise that contours are more >>> than just linear estimates of height at location. There's the >>> implication that between any two contour lines of height H1 and H2 >>> there are no locations with height outside the bounds of (H1,H2). >>> Otherwise there would be a contour line there. >>> >>> And this may not be so uncommon in elevation models. Consider a steep >>> sided valley with a wide flood plain. You have close contours on >>> either side with a big gap between. Would a "statistical" >>> interpolation run down the valley side and plummet on down, then back >>> up the other side, turning the flood plain into a deep rounded valley >>> bottom? Sure it all depends on the parameters of the smoothing, but a >>> method that knew it was dealing with contours would constrain the >>> surface such that points between contour lines were always between the >>> contour line values. >>> >>> I think at least one of the algorithms in GRASS-GIS does this by >>> "drawing" the contour lines on the raster and then doing a 'flood >>> fill' operation between them. >>> >>> I'll have to dig out some GIS books... >> >> r.surf.contour in GRASS does what is required: >> >> http://grass.osgeo.org/grass64/manuals/html64_user/r.surf.contour.html >> >> gives its description; the input is a raster of the contours where the >> non-missing cells take the contour elevation values. I have found that >> spline interpolation can create artefacts, and geostatistical interpolation >> (or IDW for obvious reasons) does not like many neighbouring data points >> along a contour line. >> >> Roger >> >>> >>> Barry >>> >>> _______________________________________________ >>> R-sig-Geo mailing list >>> R-sig-Geo@r-project.org >>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >>> >> >> -- >> Roger Bivand >> Department of Economics, NHH Norwegian School of Economics, >> Helleveien 30, N-5045 Bergen, Norway. >> voice: +47 55 95 93 55; fax +47 55 95 95 43 >> e-mail: roger.biv...@nhh.no >> >> _______________________________________________ >> R-sig-Geo mailing list >> R-sig-Geo@r-project.org >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >> > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > -- Scientist Landcare Research, New Zealand _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo