Philip,
Thanks for the suggestion, but the problem isn't large flat areas. It appears
that when there is a steep slope, every other "line" of pixels is showing a
slope of 0. In the area that I'm working (West Point, NY) the relief is pretty
dramatic so I know this can't be correct. I will try your suggestion of using
s.surf.tps anyway and let you know if it works.
Bill Green
Bill Green writes:
>
> Second problem of the day: when I use the r.slope.aspect command the results
> 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.
>
Yes, it is probably due to your DEM, especially if the elevation
differences on your map are not extremely high. r.slope.aspect does
a 3x3 neighbourhood filter known as Horn's method in order to determine
slope, and will therefore tend to come up with large flat area and
contour-like steep slopes in places where your pixel-value changes.
One possible solution is to re-interpolate your DEM (I don't know if
it comes from contourlines or elevation points) in cms or inches, in
order to avoid large 'flat areas'. If you use s.surf.tps for this,
slope and aspect will be calculated at the same time, and probably
more accurately.Hope this helps!
Philip Verhagen
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