[GRASS-dev] Re: [GRASS GIS] #807: r.watershed doesnt consider
longer distance to diagonal neighbouring pixels
GRASS GIS
trac at osgeo.org
Sat Feb 20 10:30:39 EST 2010
#807: r.watershed doesnt consider longer distance to diagonal neighbouring pixels
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Reporter: aread | Owner: grass-dev at lists.osgeo.org
Type: defect | Status: new
Priority: major | Milestone: 6.4.0
Component: Raster | Version: 6.4.0 RCs
Resolution: | Keywords: r.watershed
Platform: All | Cpu: All
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Comment (by helena):
Replying to [comment:12 hamish]:
> Replying to [comment:11 helena]:
> > However, when running r.watershed with elev_lid792_1m in the nc_spm_08
> > data set I get this as the result for mfd (which looks great):
> > http://skagit.meas.ncsu.edu/~helena/grasswork/accum_mfd.png
> > [[BR]]
> >
> > but this is where the negative values are:
> > http://skagit.meas.ncsu.edu/~helena/grasswork/accum_mfd_neg.png
> > [[BR]]
> > why does it switch from positive to negative in the middle
> > of the slope even for the flow accumulation that apparently originates
> > on the top of the hill well inside the area?
>
> I suspect that it hasn't switched to negative, just that the color map
is stale and needs to be recalculated. (the slopes steeper than the last
time r.colors was run go beyond the current color rules and so get mapped
to the default color (white))
>
> try re-running r.colors on it & d.redraw. and d.what.rast (or gui equiv)
to query actual values.
Sorry that my image was misunderstood - the image with white spaces is the
exact same data as the image with full color except displayed as d.rast
myaccum val=-250000-0 (or something like that) and then just to make sure
I also extracted the negative values using r.mapcalc myaccum<0. And I did
use d.what.rast to check the actual values - I was trying to find out
whether they switch to negative along particular elevation contour, but
they don't. So if you query downslope you get for example 25, 33, 56,
-78,-90, ...
>
>
> > Just a note that the man page has description and option twice,
> > this should be an easy fix.
>
> check the .tmp.html file in the module build dir. There's a chance that
it didn't get cleaned and every time you rebuild another copy of the auto-
generated help text gets appended. (I haven't seen that in a while, but
maybe it's back)
this is for the on-line man page
http://grass.osgeo.org/grass65/manuals/html65_user/r.watershed.html
as you have noticed it does not really repeat itself rather the OPTIONS
section should have been a subsection of DESCRIPTION, maybe just removing
the OPTION title and replacing it with sentence "Detailed explanation of
flags and parameters:" would minimize the confusion.
>
> the actual second OPTIONs section in it gives a paragraph explaining
each option, which is too much for the command line quick help but useful
to have. shrug.
>
just randomly checking r.surf.contour has section "Parameters" twice.
There is probably more of it (nobody is apparently reading the manual
pages anyway).
Helena
>
> regards,
> Hamish
--
Ticket URL: <https://trac.osgeo.org/grass/ticket/807#comment:13>
GRASS GIS <http://grass.osgeo.org>
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