UK Topographic Mapping for a Garmin GPS

One of my very early posts that still gets regular traffic is this post on the problems of getting good topographic data for the UK for a Garmin GPS. Back then whilst you could get hold of a topographic mapping for the United States, in the UK it was very difficult.

Subsequently Garmin released their Garmin TOPO Great Britain product which whilst it was an improvement still isn’t great, and is eye-wateringly expensive – the whole of the UK retails for £150. There are several problems with it, firstly if you come from having used a regular Ordnance Survey map there is a distinct lack of detail, and also in a number of places due to copyright issues paths are missing. Garmin themselves alude to this on their website when they say “includes many tracks and paths”.

Following on from that, and with the more powerful processors and colour screens in more modern GPS units Garmin have now added their GB Discoverer product. This contains the 1:50,000 Ordnance Survey mapping for the whole of the UK, but again it’s expensive – retail is £200 – although it is included in a number of special packs with various GPS units so you can save quite a bit by buying the maps at the same time as upgrading your GPS unit. The 1:25,000 mapping is available for download in 600sq-km chunks at £20 each – so you’re looking at over £8000 for the whole of the UK. The OS mappings are also not without their issues, chief among them is that they are raster based maps rather than vector based. Essentially the maps are high quality scans of the paper maps so zooming is limited as the maps are pretty well useless if you zoom in too far for a particular map, or if you zoom out too much.

The following screenshots taken from my Garmin GPSMap 62S show some of the issues.

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The first two pictures are of the junction of Nine Mile Ride and Lower Wokingham Road between Finchampstead and Crowthorne. You can see the difference in detail between the 1:50,000 and 1:25,000 mapping at the 500m scale, however look what happens when I zoom in to 50m. On the 1:50,000 you can see the jagged edges caused by zooming in too much, the 1:25,000 is better detail wise, but there are still zooming issues apparent.

Now take a look at these two shots, again from my Garmin GPSMap 62S.

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There isn’t quite as much detail in places, certainly not compared to the 1:25,000, but there isn’t the zooming issue. If I also say that this map is absolutely free to install onto your Garmin GPS, it starts to get more interesting.

The map is using data from the Open Street Map project, started in 2004 by Steve Coast as a result of frustation at the vast amount of data Ordnance Survey in the UK kept locked away. You can take a look at the full map at OpenStreetMap.org. Whilst the coverage varies, in general after a decade of work the coverage is now pretty good across the whole of the UK. It takes a bit of work to get it to a usable form for a Garmin GPS, but again that is freely available from the site of talkytoaster, a UK Geocacher.

There are other advantages. I’ve had the Garmin GB Discoverer in my GPS for a number of years now, bought when I upgraded my GPS. Whilst the road maps in my regular Garmin Satnav are upgraded quarterly, the Ordnance Survey mapping has never been updated. Whilst mountains don’t move, new housing estates are built, roads change route and new roads are built, so steadily the sizeable investment people have made in maps goes out of date.

It’s different with the Open Street Map project. The UK mapping from talkytoaster is updated every two weeks, again for free. Another example:

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All of the shots are of junction 11 of the M4. You’ll see that the 1:50,000 and the 1:25,000 aside from the resolution differences show the same layout of the roundabout. As anybody who lives around Reading will tell you over the past few years there have been significant changes in the layout of this junction, changes which aren’t reflected in either of the OS mappings. However the layout from the Open Street Map data is different, as you can see from the third shot, and in the fourth I’ve overlaid the OS 1:25,000 with the Open Street Map data to show the difference.

So in summary your options for a UK Topographic Mapping for a Garmin are to go with the official options – £150 for a not great vector based topographic mapping or £200 or over £8000 for detailed raster based mapping that doesn’t get updated, or a free vector based mapping that is updated every two weeks… If you need the detail then that might sway you towards the OS mapping, but for the older GPS units that don’t support raster based maps it’s not really too hard a decision really…

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