This has to be one of the best mashups I’ve seen for a while. Gavin Brock has created a KML file that links google earth to the OS map site, basically allowing you to overlay the Ordnance Survey Maps onto your current google earth view.

Google Earth is great, and I’ve already worked out nice methods using GPSBabel+ on the mac to create routes on GoogleEarth and export them to my Garmin 60CSX handheld GPS.

During the summer when we were walking around the thames path, I traced out the route on GoogleEarth, exported it to a KML/XML file, and used GPSBabel to convert it to a format the Garmin could understand.

Recently we’ve been walking the The Test Way, A 44 mile long-distance walking route takes you from a dramatic start, high on the chalk downs at Inkpen, following much of the course of the River Test to Eling where its tidal waters flow into Southampton Water at Romsey.

Because I dont have The Test Way on OS maps, or in a form I can directly use on the Garmin, I was wondering how I could trace out the route from the description of the walks on an OS map and get the route into the GPS to follow.

A quick hunt and Gavins KML seems to be the answer. The KML itself is very easy to install, basically pull it down from his website and load it into Google Earth. Turn it on or off depending on if you need the OS view, and it will automatically update the view when GoogleEarth is idle and not zooming.

It’s obviously not a substitute for the real OS maps you’d take on a walk, but it’s a good option for helping to plan up a route for a walk, given that things like public footpaths, pubs (pubs are very important on walks!!). It does however also remind me that I probably should post up a tutorial on how to get the route off GoogleEarth and onto the Garmin, as it took me a few go’s to get it right.

I also probably should do the reverse and put the Test Way route up as KML’s or similar for other people to use if they want to do the walk (this may involve walking the first leg again to get the GPS track). Still, back on the subject of the actual OS Map/Google Earth KML integration. The really nice thing about how this works is that the OS maps show the most relevant map type for the level your currently at.

The 60 mile up view shows the miniscale view of the OS maps, as you progressively zoom into google earth, the KML network link refreshes and displays the most suitable scale of the OS map. right down the the higher views that show topography, foot paths, right of ways and the like. This higher detail view is just perfect for mapping out the paths and routes for walk.

This is a great addon for Google Earth, and I’ve had hours of geeky inspired fun zooming round the UK looking at all the OS map levels, turning them on and off and comparing them to the underlying Google Earth views.. So far it looks solid, stable, and quick..

9 Responses to “Google Earth and Ordnance Survey (OS) Maps”
  1. Justin says:

    This is actually illegal under the Ordnance Survey copyright licensing terms. There is a view charge involved. Google are currently paying Ordnance Survey for the view charges for the road networks that appear in Google Earth. Maybe Google could start paying for the 1:50,000 mapping!

    If you want even more detail and to do this legally then you can do this through some OS Partner sites that actually have their own servers serving at all scales (even down to individual buldings at 1:500 scale) using faster technology including WMS which can also be overlaid in Google Earth. You just have to pay for it ;)

  2. Gavin says:

    Looking through the OS terms of service and there does not seem to be any issues about personal, non-commercial linking to their data, which is all that is happening in this KML. The data from OS is not being copied, just linked in a KML file.

    If that was ‘illegal’ then so would be posting the following URL here:

  3. Paul says:

    re. Ordnance Survey in Google Earth

    Wrong chart datum being used. GE uses WGS84, OS uses OSGB36. Needs converting.

  4. Gavin says:

    Paul: Yes – I can believe this is wrong. I’ll post back here when I get it fixed! Thanks!

  5. Gavin says:

    Happy New Year everyone!

    Version 2 is now up!! The URL is the same so there is no need to re-download.

    Fixed the the lat/long offsets and also put in proper convergence handling for the ‘north’ alignment.

    Should look a little better now.

  6. Allan Jones says:

    Legal,Illegal, who cares? This is the most useful piece of work I have seen in ages. I’m using it & it’s saving me time.

  7. Paul Livingston says:

    I have recently been using Google Earth to look at UK places and have noticed the Ordnance Survey view/overlay, which seems to appear whenever I look at UK places, whether I want it or not. While this is sometimes nice, I would like to be able to remove/disable it at times to see the traditional Google ‘earth from the air’ view. Do you (or might anyone you know whose email you can pass on to me) have any suggestions as to how to remove/disable the OS view/overlay? Please could you kindly email me any help.

  8. Gavin says:


    Have a look at the Google Earth side bar (go to “View” menu -> “Sidebar” if it’s not visible).

    In the “Places” section of the sidebar, you should see a “Gavin’s Unofficial Overlay of the Ordnance Survey Maps” item. This has a check box next to it. Try unchecking it, and the overlay should be disabled.

    Another trick, if you have the overlay item selected in the sidebar, then you can use the “slider widget” at the bottom of the “Places” section to control the transparency of the overlay.

    .. Gavin

  9. Jack says:

    I have found “Gavin’s Unofficial Overlay of the Ordnance Survey Maps”, which is all cool.
    however, when zooming in far enough, to try and get the 1:25000 maps, all i can see is rivers.
    any help…

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