r.slope.aspect

[colin mcclean]

4?07?35?pm%bnr?ca}?{199505151357?JAA02846%snow?ant?albany?edu}@bnr.ca>
organization: University of Newcastle upon Tyne
newsgroups: info.grass.user
originator: daemon at ux1.cso.uiuc.edu


wg1938 at csc.albany.edu (GREEN WILLIAM G) wrote:
>
 
> > Bill Green writes:
> > > 
> > > Second problem of the day:  when I use the r.slope.aspect command the res
ults
> > > appear very linear.  I am not the only one to experience this problem as 
> > > someone who has worked with the data before generated the same linearized
 
> > > output.  Is this a function of the elevation map? If not how do I correct
 for
> > > this problem?  Thanks again.
> > > 

By linear, do you mean that your gradient map gives a step like image?
If this is the problem, I'm afraid it is a data quality problem in your
original DEM. The elevations are probably heavily biased towards the
contour intervals from which the DEM may have been interpolated. Therefore,
close to contour lines you will have low gradients, followed by a step of 
high gradient before the next contour has become dominant in the interpolation.
Without working on this problem for a long time I don't think I have a
solution for you. Sorry!

Cheers, Colin McClean

Centre for Land Use and Water Resources Research
University of Newcastle-Upon-Tyne
Newcastle-Upon-Tyne, UK.