Digitized contour lines

[martijn at scanner.frw.uva.nl]

On Wed, 1 Jun 1994, M.R. Lassche wrote:

> Trond masking does not work with r.surf.contour , but what you can do is make a mask and give it a value not equal to zero. Then patch this mask with your contour raster map. 
> r.surf.contour will now skip the masked area because all the cells in the masked area have a value
> 
> Hope this will work 
> Ronnie
> 
Although this will work, it is not a good idea, since the values in the 
mask will be used to interpolate new cell values. Thus, you will get 
incorrect height values in areas near the mask. A better solution would 
be to make the region as small as possible, run r.surf.contour without a 
mask, then cut the unwanted areas by r.patching a mask consisting of 0's 
(You can also do this by setting the mask, then run r.mapcalc 
old.dem=new.dem).

P. Martijn van Leusen

Institute of Prehistory, University of Amsterdam
martijn at scanner.frw.uva.nl