[OpenLayers-Dev] Map Rotation

Christopher Schmidt crschmidt at metacarta.com
Thu Dec 17 17:41:40 EST 2009

On Thu, Dec 17, 2009 at 02:39:41PM -0800, Alexei Peters wrote:
> Hi Everyone,
> I currently work for a small GIS consulting firm and one of the projects we're currently working on has a potential requirement for rotating the map (so north doesn't point up, but rather to the right for example).
> Has anyone any idea of how to do this, or has done this?  My company would be even willing to fund this effort if need be.
> I'd love to hear anyone's thoughts on this.

 1. In Javascript/Images/DOM (ignoring Canvas for the moment), there is 
    no way to make an image exist on an angle.
 2. Canvas has some support for this, I believe, but is limited in where
    you can use it.

Generally speaking, what you would do to solve this problem would be to
pre-rotate your map (in a tool like photoshop, or something equally non
OpenLayers related), and then work with at that point. Some people on
the list have had some experience with that way of using OpenLayers; a 
key aspect of this would be to write a translation from your map coordinates
(which will likely be in pixels after the rotation) to geogrpahic coordinates,
but that's not too hard, in general.

Best Regards,
Christopher Schmidt

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