[GRASS-dev] [GRASS GIS] #1248: r.thin may be broken

[GRASS GIS]

#1248: r.thin may be broken
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 Reporter:  cmbarton     |       Owner:  grass-dev@…              
     Type:  defect       |      Status:  new                      
 Priority:  normal       |   Milestone:  7.0.0                    
Component:  Raster       |     Version:  svn-trunk                
 Keywords:  r.thin       |    Platform:  Unspecified              
      Cpu:  Unspecified  |  
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 I recently tried to use r.thin in GRASS 7 (compiled from trunk a few days
 ago) and it seems to be behaving oddly. So I tested it against the
 Spearfish demo set. I ran r.watershed to generate a stream network
 (delete_streams) and then tried to thin it. The network generated by
 r.watershed is already down to a single cell in most places; only a few
 need thinning. But the r.thin output seems odd. It says it is deleting
 thousands of cells each iteration, with the number of cells deleted
 dropping by 8 each iteration. After 200 iterations, r.thin says that
 thinning is not completed. Looking at results, only a small fraction of
 the stream network was actually generated by r.thin. Here is an example of
 r.thin output:

 r.thin input=delete_streams at PERMANENT output=delete_streams_thinned
 File delete_streams at PERMANENT -- 466 rows X 633 columns
 Bounding box:  l = 2, r = 634, t = 2, b = 467
 Pass number 1
 Deleted 2194  pixels
 Pass number 2
 Deleted 2186  pixels
 Pass number 3
 Deleted 2178  pixels
 Pass number 4
 Deleted 2170  pixels
 Pass number 5
 ...
 Deleted 618  pixels
 Pass number 199
 Deleted 610  pixels
 Pass number 200
 Deleted 602  pixels
 Thinning not completed, consider to increase 'iterations' parameter.
 Output file 466 rows X 633 columns
 Window 466 rows X 633 columns

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Ticket URL: <http://trac.osgeo.org/grass/ticket/1248>
GRASS GIS <http://grass.osgeo.org>