ps.map: adding negative scale and offset to vpoints plotting -- patch provided

[alf]

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! Best,

Alessandro Frigeri

[alf]

ps.map patch that introduces negative scaling and offset parameter to vpoints group

[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)

Hamish

[alf]

Replying to 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

[martinl]

Milestone renamed

[neteler]

Ticket retargeted after milestone closed

[martinl]

What is the state of this issue?

[martinl]

All enhancement tickets should be assigned to 7.6 milestone.

[martinl]

Ticket retargeted after milestone closed

[martinl]

Ticket retargeted after milestone closed