[OpenLayers-Users] Re projecting Google

[Thomas Wood]

> Message: 9
> Date: Wed, 9 Jan 2008 07:25:26 -0500
> From: Christopher Schmidt <crschmidt at metacarta.com>
> Subject: Re: [OpenLayers-Users] Re projecting Google
> To: Jon Britton <man_kills_everything at hotmail.com>
> Cc: users at openlayers.org
> Message-ID: <20080109122526.GA4446 at alta.metacarta.com>
> Content-Type: text/plain; charset=us-ascii
>
> On Wed, Jan 09, 2008 at 03:27:11AM -0800, Jon Britton wrote:
> >
> > Hi,
> > I've got data in EPSG:27700 (British National Grid) and want to overlay it
> > on Google data. However, I want to reproject the Google data into EPSG:27700
> > and not the other way around. Can this be done?
>
> Project the google *data*? Google ain't yours, man: You can't do
> anything fun with it (and definitely not reproject it!)
>
> > Alternatively, can OpenLayers convert from Google coordinates to EPSG:27700
> > coordinates? All I need is to be able to get the 27700 coordinates of the
> > current view.
>
> It is possible, using the trunk versio of OpenLayers, to convert from
> Google coordinates to lon/lat. It is possible, using proj4js or perhaps
> a custom transformation function, to convert from lon/lat to EPSG:27700.
> I know of at least one person who has done it -- I'll try and remember
> who and get him to post.
>
> Regards,
> --
> Christopher Schmidt
> MetaCarta

I have written a class that plugs into the existing reprojection code.

As you mention reprojecting coords here's a quick demo of usage:
ll = new OpenLayers.LonLat(-11554.3527964992,6686865.32722571);
ll.transform((new OpenLayers.Projection("EPSG:900913"), new
OpenLayers.Projection("EPSG:27700"));

This will convert Google coords (Google sphericalMercator) to OSGB.
The class supports OSGB to and from Google (ESPG:900913), and OSGB to
and from WGS84 lat/long (ESPG:4326).

Some of the math functions are poorly documented (it was a quick
convert from an already-existing conversion class)

Finally, the code is here:
http://ge.pythonmoo.co.uk/maps/OpenLayers.Projection.OrdnanceSurvey.js
Please don't hotlink it.

-- 
Regards,
Thomas Wood
(Edgemaster)