[GRASS-user] r.shaded.relief visual banding

[Markus Metz]

Looking into a different direction: how come you noticed ~30m bands
while SRTM is 3 arc sec (~90m at the equator)? Have you reprojected
and resampled the DEM? I use this banding in the output of
r.shaded.relief to check if the reprojection/resampling settings are
ok.

OTOH, SRTM v4 elevation sometimes deviates substantially, far more
than by the original SRTM vertical error, from SRTM v2.1, and the SRTM
v4 grid geometry is weird, v4 tiles won't fit into the same
computational region because of subcell shifting, shifted by 0 to 1.5
arc sec and everything in between against each other.

my 0.2c

Markus M



On Wed, Nov 17, 2010 at 5:14 PM, Patrick Dolan <pdolan39 at gmail.com> wrote:
> Hello all,
> Are there known issues with "banding" in the output of the r.shaded.relief
> command? When I say banding, I mean the generation of regularly occurring,
> narrow vertical and horizontal lines. I've just created a large shaded
> relief map of the northern Pacific coasts of the USA and Canada from the
> STRM 90m v.4 Arc/Ascii files. At ~380 m intervals, ~30 m bands have been
> generated that crisscross the output. I'd like to know if this is a
> consequence of the STRM 90 data set (notably 3DEM appears to have no similar
> trouble with the same data), or an artifact of the shaded relief command in
> GRASS. I can attach an image if this would help the diagnosis.
>
> Much appreciated,
> Patrick Dolan
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