[GRASS-dev] Re: [GRASS GIS] #398: r.watershed with MFD

[GRASS GIS]

#398: r.watershed with MFD
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  Reporter:  mmetz        |       Owner:  grass-dev at lists.osgeo.org
      Type:  enhancement  |      Status:  reopened                 
  Priority:  minor        |   Milestone:  7.0.0                    
 Component:  Raster       |     Version:  svn-trunk                
Resolution:               |    Keywords:                           
  Platform:  Unspecified  |         Cpu:  Unspecified              
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Comment (by mmetz):

 I have submitted a new version of r.watershed to trunk with various
 changes

 MFD is fully supported: drainage directions, stream segments, basins,
 half-basins, RUSLE LS and S factors are all in accordance with MFD flow
 accumulation.

 The module is slightly faster and uses a bit less memory. See updated
 documentation to estimate memory requirements for the ram (all in memory)
 mode (max 31 MB of RAM for 1 million cells).

 It is no longer necessary to create a MASK for cells with unknown
 elevation (NULL values). All cells with unknown elevation (masked or NULL
 values) are skipped. Zero and negative values are valid elevation values.

 The color rules generated by the module for flow accumulation have worked
 for all tests so far and allow visual inspection without manually
 assigning a color table. I'm using standard deviation and log transform,
 based on Hamish's (I think) suggestions. Visual output is obsolete but
 left for comparison.

 The output drainage direction is slightly changed in case an input map
 with real depressions was supplied. Previously, real depressions had a
 drainage direction of -1, but -1 was and is a valid drainage direction
 indicating a drainage of 45 degree CCW from East towards a cell with
 unknown elevation. Therefore real depressions have now a drainage
 direction of 0. As before, if a cell drains due East the drainage
 direction is 360 degrees, 0 (zero) as drainage direction was unused.

 RUSLE LS and S factor output maps are now of type DCELL without
 multiplication by 100. Both factors have always been processed as type
 double, previously the output maps for the two factors were written out by
 typecasting from (DCELL * 100) to CELL.

 Please read the updated documentation before using the new module.

 Best regards,

 Markus M

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Ticket URL: <http://trac.osgeo.org/grass/ticket/398#comment:7>
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