[GRASS-dev] Re: [GRASS GIS] #807: r.watershed doesnt consider longer distance to diagonal neighbouring pixels

[GRASS GIS]

#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

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Ticket URL: <https://trac.osgeo.org/grass/ticket/807#comment:13>
GRASS GIS <http://grass.osgeo.org>