[GRASS-dev] Re: [GRASS GIS] #1654: v.extract: allow direct transformation of centroids to points

[GRASS GIS]

#1654: v.extract: allow direct transformation of centroids to points
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  Reporter:  mlennert     |       Owner:  grass-dev@…              
      Type:  enhancement  |      Status:  closed                   
  Priority:  normal       |   Milestone:  7.0.0                    
 Component:  Default      |     Version:  unspecified              
Resolution:  wontfix      |    Keywords:                           
  Platform:  Unspecified  |         Cpu:  Unspecified              
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Changes (by mlennert):

  * status:  new => closed
  * resolution:  => wontfix


Comment:

 Replying to [comment:3 hamish]:
 > sorry if that came out harsh, I was in a hurry and meant to be brief,
 but not curt.

 No offense taken at all. KISS is a principle that can also be applied to
 trac tickets  :-).

 I see your point, and am inclined to agree with it. At the same time, I
 have the feeling that when extracting centroids out of polygons being able
 to treat them as points from there on would be the expected behaviour
 without having to go through v.type. But I guess a wrapper script would be
 ok.


 > option 3 is the most acceptable to me, but even then I'd open access to
 it with a lot of caution. Remember that the absolute position of a
 centroid is just somewhere within the area, it is not guaranteed to be in
 the middle, so users must be very careful treating them as points with
 absolute x,y,z meaning. e.g. "C", "O", "L" shaped areas; areas created by
 v.buffer or v.overlay may have centroids may have their centroids right
 near an outside edge; etc.

 I'm aware of the issues with GRASS centroids, but for many applications
 this kind of precision is not necessary.

 > I'm not sure how you are using it,

 Here the use case was a colleague trying to use v.what.rast, with polygons
 as starting vector features. Centroid precision was enough for his needs.
 But other use cases exist.

 In GRASS one can often treat centroids as points, but that's not the case
 for all of them, so in this particular use case, I'll rather file a ticket
 for v.what.rast to allow use of centroids.

 Closing this for now.

 Moritz

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Ticket URL: <https://trac.osgeo.org/grass/ticket/1654#comment:4>
GRASS GIS <http://grass.osgeo.org>