[Mapserver-dev] Label rotation...

[Daniel Morissette]

Paul Ramsey wrote:
> Yes, I always considered the label behavior correct, because here in BC 
> our toponymy comes with CCW label angles, so applying them directly gave 
> me the "correct" looking results. If you invert the behavior then I have 
> to negate all my input values before drawing :)
> 

I've always seen angles specified CCW everywhere (that's not specific to 
GIS or compass, that's the way it is everywhere in trigonometry, 
engineering, physics, etc) so I think we should go with that. I never 
checked what MapServer used, but I always assumed it was CCW. If GD uses 
CW then it is the exception.


> Unfortunately there is no standard here, people will definately have 
> angles of both sorts. (And different start points for measurement too... 
> start at north, or start at the positive X axis?)
> 

If you are just rotating an object, as long as you know what the anchor 
point for the rotation is, you don't need an absolute reference for the 
angle: rotating a symbol 45 degrees CCW is the same whether your start 
at the North or the positive X axis.

Daniel
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  Daniel Morissette               dmorissette at dmsolutions.ca
  DM Solutions Group              http://www.dmsolutions.ca/
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