[GRASS-dev] [GRASS GIS] #2526: extend r.slope.aspect to compute the values at the edges

[GRASS GIS]

#2526: extend r.slope.aspect to compute the values at the edges
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 Reporter:  hellik       |       Owner:  grass-dev@…              
     Type:  enhancement  |      Status:  new                      
 Priority:  normal       |   Milestone:  7.1.0                    
Component:  Raster       |     Version:  svn-trunk                
 Keywords:  slope        |    Platform:  All                      
      Cpu:  All          |  
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 taken from the ML

 http://lists.osgeo.org/pipermail/grass-dev/2015-January/072779.html

 {{{
 Another way would be to modify r.slope.aspect to compute the values at the
 edges - a second order polynomial min.square approximation
 is used to estimate the derivatives in r.slope.aspect (you get the well
 known differencing function when you do the math) and it can be used also
 to compute the values at the edge cells, but I had no luck convincing
 others that it is the right thing to do.

 I believe that any reasonable estimate is better than the current
 shrinking region (in r.flow we just propagate the same values to the
 edges), but that does not seem to be the consensus.

 Also, implementation  for the edges is not straightforward because of how
 GRASS works with rows, but a smart developer could certainly do it.
 }}}

 it would be nice that r.slope.aspect compute the values at the edges, at
 least as an option. I agree that any reasonable estimate is better than
 the current shrinking region.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/2526>
GRASS GIS <http://grass.osgeo.org>