[OpenLayers-Users] Two displayProjections on a map

[Richard Greenwood]

On Thu, Jan 10, 2013 at 7:48 AM, Jan Hartmann <j.l.h.hartmann at uva.nl> wrote:

> **
> Yes, this is the difficult solution. It works, but I was thinking in
> another direction. As Bart pointed out, it is possible to put multiple
> Mouseposition controls with different DisplayProjections on a page by means
> css classes. This means that I can influence the position of these controls
> and their projected coordinate values without any other formating. However,
> I would also like to be able to change to format of a lon-lat value to
> degrees-minutes-seconds. Is there a way to get at the numeric value of a
> MousePosition control and alter it?
>
> There are other possibilities for this. Older maps often have national
> central meridians, like Paris, Amsterdam, Djakarta. To see the lon-values
> on those map in Greenwich values, all lon values need to be added with a
> constant. It would be nice if that could be done automatically via the
> MousePointer control.
>


My feeling is that the centeral meridian should be handled by the
coordinate transformation. In my applications I display the map in its
native local coordinate system. I show these in the the first (left)
coordinate display. I then transform that to lat/long (both decimal and
DMS) and display that in the middle, and then transform lat/long to UTM
which is displayed to the right.

So three proj-style coordinate system definitions have to exist: local,
lat/long, UTM. The local one would handle differences in central meridian.

Best regards,
Rich

-- 
Richard Greenwood
richard.greenwood at gmail.com
www.greenwoodmap.com
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