[GRASS-user] r.shade.relief: Results Not As Expected

[Markus Neteler]

On Tue, Jan 5, 2010 at 2:32 AM, Rich Shepard <rshepard at appl-ecosys.com> wrote:
> On Tue, 5 Jan 2010, Glynn Clements wrote:
>
>> Run r.slope.aspect on the interpolated map, and check for grid-like
>> artifacts.
>
> Glynn,
>
>  Did this. Yes, there is a grid-like appearance to the resulting map.

this sounds like a resolution mismatch. If you want to significantly change
the resolution of a raster DEM, use
- r.resamp.interp - Resamples raster map layers to a finer grid using
interpolation.
- r.resamp.stats - Resamples raster map layers to a coarser grid using
aggregation.

>> How good is the underlying data? If it's noisy, it may need to be
>> filtered before interpolating.
>
>  How do I check for noisy data? I have all the basic information about the
> source data and derived maps.

Using r.shaded.relief gives a good visual impression. Or create a polar diagram
of the aspect map:

r.slope.aspect mydem aspect=myaspect
d.polar myaspect

>> Also: which version of GRASS are you using?
>
>  6.5svn.

Markus