#1688: ps.map: adding negative scale and offset to vpoints plotting -- patch
provided
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Reporter: alf | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: normal | Milestone:
Component: Ps.map | Version: svn-develbranch6
Keywords: ps.map vpoints | Platform: All
Cpu: Unspecified |
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Hello,
herein you find a patch that will enable negative scaling and introduces
offset for vpoints representation in ps.map.
This will be useful if you are dealing with representation of vpoints
symbols scaled by negative attribute values.
This patch introduces also the '''offset''' parameter in vpoints so it
will be possible to shift the scaling values (useful when the values are
both positive and negative).
In this patch documentation has be updated consequently.
please try the patch, revise improve and/or apply to GRASS!
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)
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?