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Thread: Mixing Google and OS

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Permlink Replies: 4 - Pages: 1 - Last Post: 27-Oct-2008 22:20 by: chadwickBill
thistle

Posts: 6
Registered: 21/03/08
Mixing Google and OS
Posted: 22-Oct-2008 20:40
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Is it possible to use Google and Openspace on the same 'map'?

I tried adding Google as another base layer and although you can easily swap between the two, the coordinates don't tie up and overlays aren't where they should be. Is this because OS converts everything to an easting/northing rather than using lat/long?

I've seen the "Where is the path" page which uses the two side by side but I've not seen anything yet that swaps the background layer.

I guess it could be done by detecting when Google is selected, then converting all the eastings/northings to lat/long and redrawing all the lines!

rgphilpott

Posts: 146
Registered: 18/06/12
Re: Mixing Google and OS
Posted: 22-Oct-2008 21:29   in response to: thistle
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The OS is using OSGB36 rather than WGS84 (so even if it were using lon/lat and not national grid, everything would still be a couple of hundred metres out).

I've sort-of done it, at, for example:

http://www.centrallondonctc.org.uk/osmap.php?m=94

by having two completely separate versions of the page (ie using a "native" Google map rather than adding it as a new layer) and passing the current boundaries of the map (suitably converted) between the pages using temporary cookies.


Richard.

pwrobins

Posts: 48
Registered: 07/03/08
Re: Mixing Google and OS
Posted: 23-Oct-2008 14:45   in response to: thistle
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It's not just a question of coordinates. Google and OS/OpenSpace use different tile schemes (zoom-levels, etc), so you cannot simply overlay the tiles, as they won't match. In OpenLayers, it's the base layer which defines the projection, zoom-levels etc. You can have different base layers, but just clicking on the layer-change control doesn't 'reproject' your map. They all have to use the same definition, as Google's different layers do. I suppose you could add a listener and then 'reload' everything, but why bother? Much simpler just to have two maps :-)

nhopton

Posts: 9
Registered: 28/08/08
Re: Mixing Google and OS
Posted: 24-Oct-2008 20:06   in response to: pwrobins
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But there is a way of overlaying OpenSpace map tiles on Google Earth, see:

http://www.brock-family.org/gavin/google-earth/osmaps.html

I use this quite a lot, it can be slow at times and the tile limit is sometimes exceeded, but it's good. Just keep zooming-in in GE to change the scale of the mapping.

Regards,
Nick.

chadwickBill

Posts: 390
Registered: 07/02/08
Re: Mixing Google and OS
Posted: 27-Oct-2008 22:20   in response to: nhopton
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If you want to use OS maps and imagery with the same projection then have a look at the Multimap/Microsoft OpenAPI at http://www.multimap.com/openapi/

The OS have chosen not to provide their imagery via OpenSpace.

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