[GRASS-dev] [GRASS GIS] #2100: r.proj bounding box too small by half a cell size (-g or -p):

[GRASS GIS]

#2100: r.proj bounding box too small by half a cell size (-g or -p):
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 Reporter:  awickert     |       Owner:  grass-dev@…              
     Type:  defect       |      Status:  new                      
 Priority:  normal       |   Milestone:  7.0.0                    
Component:  Default      |     Version:  unspecified              
 Keywords:  r.proj       |    Platform:  Linux                    
      Cpu:  Unspecified  |  
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Comment(by glynn):

 Replying to [comment:2 awickert]:

 > Therefore, I have attached a working diff that removes the parts that
 take the bounding box a half-cell away from the cell margins... mostly. I
 have not adjusted the for loops at all,

 The change moves the sample points from the cells' centres to the
 midpoints of their edges. This generates the region's boundary but with
 chamfered corners.

 > Also, I found that the output of the projection would shrink to 2 cell
 widths (though still spanning the whole N-S range) if I completely removed
 the western offset, so I just made that fairly small for the time being;
 this may be a reason that the cell centers were used.

 That's the hallmark of the 360-degree wraparound. Much of GRASS
 unconditionally treats 180W and 180E as the same thing, so a 360-degree
 range becomes a zero-degree range. The issue isn't in r.proj per se but
 the core libgis functions which manage regions.

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Ticket URL: <https://trac.osgeo.org/grass/ticket/2100#comment:3>
GRASS GIS <http://grass.osgeo.org>