[Mapserver-dev] Label rotation...

[Steve Lime]

Thanks for the quick replies, sounds like it should be left alone (but
documented). GD
does CCW rotation. No biggie for me, we'll just add a second column to
the data in
questions that stores a rotation value and another for a true bearing.


Ultimately Steve's idea about setting CW or CCW as a second argument to
the ANGLE
parameter is a good one, but nothing I want to tangle with at the
moment. I'll file a 
feature request in bugzilla.

Steve

>>> Daniel Morissette <dmorissette at dmsolutions.ca> 8/4/2004 9:35:51 AM
>>>
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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