[GRASS-dev] [GRASS GIS] #2516: r.stream.distance elevation above streams produces unexpected null values

[GRASS GIS]

#2516: r.stream.distance elevation above streams produces unexpected null values
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 Reporter:  madi                        |       Owner:  grass-dev@…              
     Type:  defect                      |      Status:  new                      
 Priority:  normal                      |   Milestone:  7.1.0                    
Component:  Raster                      |     Version:  svn-trunk                
 Keywords:  r.stream,r.stream.distance  |    Platform:  Unspecified              
      Cpu:  Unspecified                 |  
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Comment(by hellik):

 Replying to [comment:2 madi]:
 > Replying to [comment:1 hellik]:
 > > Replying to [ticket:2516 madi]:
 > >
 > > >
 > > > elev2stream map has several null values.
 > >
 > > where are the null values?
 > >
 > > I know only the null values at the border of the DEM (red in the
 screenshot) where no stream information is available.
 >
 > Hi, in my case null values are scattered all over the map, see attached
 screenshot (the large spots however are water). I realised that the
 command line i actually gave is slightly different from the one i posted
 earlier (if matters) and is:
 >
 > r.stream.distance --verbose stream_rast=stream1500 direction=drainage
 elevation=dem method=downstream distance=dist2stream_2
 difference=elev2stream_2 memory=2000
 >
 > Thanks
 > madi

 some tests with a DEM subset:

 {{{
 - maybe differences in the r.stream.*-modules between all-in-memory and
 swapped memory mode; in my tests I can't see any difference

 - I've done a r.geomorphon run on the DEM; it seems the DEM is very
 heterogenous. may be these null values are DEM artefacts?

 - I've done a r.neighbor size=3 and size=5 on the DEM; there seems to be a
 less number of null values. maybe this indicates DEM artefacts?

 - I've done a r.stream.distance run with r.stream.extract-outputs (streams
 and flowdir) instead; there are some differences regarding null values
 between using r.watershed or r.stream.extract-output as r.stream.distance
 input
 }}}

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Ticket URL: <https://trac.osgeo.org/grass/ticket/2516#comment:3>
GRASS GIS <http://grass.osgeo.org>