> I suspect there's a better way by looking at more than one nearby > contour line and doing some interpolation....
I've got fairly good algorithm going now, but it requires a bit of modification of some sp package code. Currently spsample can return random or regular points on a line, but doesn't tell you which line the point came from. Hence there's no way to get the height of that line. But a bit of tweaking to the sampling code fixes that. My modification returns a spatial points data frame of points and line IDs. I'll not post that code here yet because Roger usually knows ways of doing my hacky things without hacking. I know that overlay() won't do it for you... Anyway, then I can get a set of (x,y,height) points on the contour lines, and then use any standard interpolation function (interp from akima for example) to get a grid. Looks pretty good, and also pretty quick. A 500x500 grid from a contour set with 212 contour lines is pretty instantaneous. Barry _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo