[GRASS-dev] [GRASS GIS] #2531: v.parallel/v.segment: strange output

GRASS GIS trac at osgeo.org
Fri Jan 9 03:32:27 PST 2015

#2531: v.parallel/v.segment: strange output
 Reporter:  hellik                 |       Owner:  grass-dev@…              
     Type:  defect                 |      Status:  new                      
 Priority:  critical               |   Milestone:  7.0.0                    
Component:  Vector                 |     Version:  svn-trunk                
 Keywords:  v.parallel, v.segment  |    Platform:  MSWindows Vista          
      Cpu:  Unspecified            |  

Comment(by mlennert):

 In Vect_line_parallel2 in
 lib/vector/Vlib/buffer2.c], a call to clean_parallel is commented out.
 clean_parallel exists in buffer.c, not in buffer2.c. Maybe this might be a
 path to a solution.

 What seems to be the issue (AFAIU) is that the length of the parallel line
 segments is longer than that of the original line segments, as if the
 lines as projected outward. This seems to be what leads to the loops.
 Don't know why such a projection is done... I'll attach a screenshot to
 show what I mean.

 Have you checked out the -b flag ? And possibly tried to generalize the
 line before creating using v.parallel. Both might actually give you what
 you are looking for ?

Ticket URL: <http://trac.osgeo.org/grass/ticket/2531#comment:11>
GRASS GIS <http://grass.osgeo.org>

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