[GRASS-dev] [GRASS GIS] #1688: ps.map: adding negative scale and offset to vpoints plotting -- patch provided

[GRASS GIS]

#1688: ps.map: adding negative scale and offset to vpoints plotting  -- patch
provided
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 Reporter:  alf             |       Owner:  hamish          
     Type:  enhancement     |      Status:  assigned        
 Priority:  normal          |   Milestone:  7.0.0           
Component:  Ps.map          |     Version:  svn-develbranch6
 Keywords:  ps.map vpoints  |    Platform:  All             
      Cpu:  Unspecified     |  
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Comment(by alf):

 Replying to [comment:2 hamish]:
 > I know what you mean, but "offset" is perhaps not the best use for the
 word, people are likely to think of spatial offset of the map feature from
 its original x,y position, not offset in the y=mx+b slope & offset sense.
 >
 > Can you provide an example of when this feature would be useful?
 (curious)

 Thanks for the comment, Hamish.  Imagine we would like to display points
 of acoustic measurements - with size proportional to the sound level
 referred to a certain threshold.  Some of the measurements will be
 positive and some will be negative.  To scale symbols accordingly we need
 to shift the measurements (or set the offset) so that we end up with all
 positive values.

 Although this can be easily done within the db with some scripting, I
 though this would be a nice feature in ps.map (together with the negative
 scale option) - as it is mainly a visualization technique.  Hope this make
 sense.

 Regarding the terminology - I agree, '''offset''' in GIS is most commonly
 referred to horizontal coordinate shift. Maybe something like
 '''scaleoffset''' can maybe be more adequate for ps.map?

 Alessandro

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Ticket URL: <http://trac.osgeo.org/grass/ticket/1688#comment:4>
GRASS GIS <http://grass.osgeo.org>