Free maps for your Garmin GPSr from Open Street Map

Since I purchased our Garmin GPSr I have always relied on the Garmin Great Britain TOPO maps to “show us the way”. This however, isn’t the only option for maps on our handheld GPSr’s. There is a free option – Open Street Map.

Map options

Garmins come with a worldwide basemap installed. It’s not very exciting though. Some sea, land, a few roads and rivers, etc. To start seeing contours, minor roads, footpaths and more detailed terrains then you need something else. There are a few options for UK cachers…

An example of the base map - No footpaths

There are the Garmin TOPO Great Britain maps. These show countours, roads, rivers, POI’s trig points, and some tracks and paths. They retail at ยฃ150. We’ve used these for about a year, and despite Garmin stating the data is provided by the Ordnance Survey not all footpaths are included, and in some cases there are footpaths included that we have walked over to only to be confronted by a gate that says “PRIVATE” on it. The maps are OK. I can’t say they are great.

The Garmin TOPO maps - Some footpaths, minor roads, forests, etc.

Next we have the option of GB Discoverer 1:50K maps. These are Ordnance Survey maps just like you get on the paper maps, or on the online OS website. The problem here is that you can’t zoom in very close as the maps blur, and they do include a lot less detail than the 1:25K maps which you can buy for certain parts of the country, but not all. You’re looking at a ยฃ200 retail for the Discoverer maps, however can be found cheaper on other outdoor sites, or if you purchase it bundled with the GPSr.

An example of 1:50k maps

So, what if you haven’t got any additional maps? Maybe you have two GPSr’s and only one has the maps, or maybe you are going abroad and would like something a bit more than what the base maps provide without having to purchase a Garmin Topo map for the whole of a country that you will only visit once or twice. Open Street Maps can give us a solution and it’s also possible to install this alongside your existing 1:50k/Garmin TOPO maps as long as you have enough free storage space on your device.

An Introduction to Open Street Maps

OSM is a collaborative project to provide a free, editable map of the whole world. It relies on people like us to add information to the maps using GPS tracks, aerial photos, or local knowledge. It’s not as simple as tracing over an OS map or Google maps as those are copyrighted and the idea is to keep these maps entirely free. You can think of it as being like Wikipedia for maps! As we all know, the information on Wikipedia shouldn’t be taken as gospel and the same applies to OSM. It’s not 100% accurate, however no map really is.

A massive advantage that I’ve seen with using OSM is that you can see many more places on your maps that not even Ordnance Survey 25k maps show. For example there are supermarkets, shops, toilets, parking places, pubs, restaurants, stiles, bridges, gates, and shops. You don’t however get to see all footpaths. You can only see what people have chosen to upload. In some parts it will lack things that OS and Google maps include, and in other parts it will include extras.

OSM maps of Saffron Walden. Notice how detailed the POI's are

Using OSM maps on your GPSr

Talky Toaster UK maps

These maps are compatible with a lot of Garmins, including GPSmap60 series, GPSmap62 series, Etrex Legend/Venture/Vista, Colorado, Dakota, Oregon, Edge and Nuvi. Full details on the precise models supported are available here.

Talky Toaster compiles the latest Open Street Map data for the UK every couple of weeks so that it is available on his website for download. The data is available elsewhere (which I’ll come on to later) however his maps will contain contour data as well. This is therefore the best place to go to get UK maps. If you scroll down the website the available maps are listed and you can select which ones you require. I usually select the top choice, “GB Map (with Contours) – Routable” you can of course download the whole British Isles maps if need be. Simply click the download link to the map that you require.

Screenshots of OSM maps on our Dakota 10

Once the file is downloaded you will have a .zip file on your computer. e.g. This isn’t the file that you need to place on to your GPSr, the file is contained in this zip file:

1. Plug in your GPSr and navigate to the Garmin folder.

2. Inside here you may find a file called GMAPSUPP.img depending on whether you have additional maps already installed. If you have this file already there then rename the OSM file inside the zip you downloaded to GMAPSUP2.img and copy it across. If you already have a GMAPSUP2.img file, then you can also call it GMAPSUP3.img. This allows you to switch between different maps on your device. If you don’t see any GMAPSUPP.img file on your GPSr, then rename the file in the .zip file to GMAPSUPP.img.

The view of the .img files on a Garmin with just 1 map (gmapsupp.img)

The view of a GPSr with 2 map files on (gmapsupp.img + gmapsup2.img)

3. Drag the file from the .zip file to the Garmin folder on your GPSr.

4. And you’re done. You now have Open Street Maps on your GPSr. Power on your GPSr and have a look to check it copied across ok. If you only have one map file (i.e. just gmapsupp.img) it should pick it up automatically, otherwise you can change the settings in the map menu by going to Setup -> Maps -> Map Information: Select Map -> Click on the desired map -> Choose Enable/Disable. You will only be able to see one map at a time so ensure that all are disabled apart from the one that you want to view.

Selecting which map to view on a Dakota 10

If you need additional help, Talky Toaster has a great FAQ section here.

International maps

As Talky Toaster only compiles maps for the British Isles then you’ll need to go elsewhere for international maps. Click here to visit the site.

At this page you’ll be presented with a world map. Simply zoom in to the country you require maps for and tick the ‘Choose a predefined country and/or enable manual tile selection’ box which means you can click the tiles you you require. After doing this enter your email address in the box on the left hand side and click ‘Build my map’.

Select the tiles on the map, then enter your email address and build the map

You’ll have to wait up to about half an hour for your map to generate. Once it is ready, you will receive an email. Click the link and you’ll be taken to a page where you can download it. You’ll get a list of options of files that you can download, however the if you want maps for your GPSr then you will need the ‘‘ file. Download this and then follow the instructions above again.

Download the file for your Garmin

Contributing to OSM

Anybody can contribute to OSM. Yes, even you! ๐Ÿ™‚ It’s easy peasy, and I’ve done it and will continue to do it now that I know how to…

The great thing about OSM and being a Geocacher

I’ve noticed that since we’ve been using OSM maps on our GPSr to find geocaches the vast majority of footpaths we have taken have been on the GPSr. You know why that is? Because other Geocachers use OSM maps and upload their tracks to the website once they have finished. When we did the Chiltern100 every single footpath was on the GPSr. Well established cache trails are likely to have their footpaths on OSM because other Geocachers will have put them there. Newer trails may not have footpaths added, however this is where you come in and if you walk a trail and notice that the paths aren’t on your GPSr then you can upload your track to the website and fill in the gaps.

Uploading a track (i.e. a new footpath)

1) Go for a walk with your GPSr. Before you set off, however it’s best to start with a blank canvas. If you’re using a Garmin, simply go to “Track Manager” and then Current Track -> Clear current track. (It’s no big problem if you forget to do this though as you will still be able to use the track)

2) Walk along the footpaths. Try to keep to those that you know are footpaths as if you start straying around farmer’s fields then you’ll be recording data for areas that don’t allow public access. If you do stray fro the path just make a mental note not to include these bits in your trace.

3) Once you’ve finished your walk save your current track. Perhaps give it a suitable name so that you know which one it is.

Saving your track on a Dakota 10

4) Copy the track file from your GPSr onto your computer. It will likely be in the Garmin\GPX folder and called something like “Track_18-APR-11 090751 PM.GPX” if you’ve left the default name.

5) The next step is to sign up on the Open Street Map website. You don’t need to have an account to view data, but once you want to upload data you need to register.

6) Log into your new account and click the ‘GPS Traces’ tab followed by ‘Upload GPS Trace‘. Click the ‘Browse‘ button to locate your trace, give it a good description e.g. “Footpath 377 in Saffron Walden, Essex”. You can then choose to make your trace public or private. If public, all users will able to see this in their traces lists. I just keep mine anonymous for now.

List of my GPS traces, waiting for one to upload (PENDING)

7) Your trace will take a few moments to get through the queue and accepted. It’s basically automatically checked to ensure it is a valid .GPX track file that can be used. You’ll get an email a few moments later to let you know your trace is approved.

8) Now, you just trace points over your GPS trace on the map. There are two methods of doing this… Through software that you download and install on your computer (JOSM) or via the web browser. I’ve tried both methods and have to say I find the web browser method a lot easier. The downloadable software isn’t as intuitive and I found myself hunting for what I needed. Therefore I’m going to focus on the web-based editor. To get straight to the area that your track covers, view “Your GPS Traces” and hit the ‘edit‘ button next door.

Click 'edit' next to your track to zoom to the map and add your footpath data

9) You’ll then be shown the area that your track is in and see the path that you walked as a cyan-coloured line.

The cyan line shows the map trace that I uploaded

10) Simply trace over your track line by clicking the mouse to create points. Once finished, double click the mouse to end the track. If you wrongly create a point, click the delete button in the top right hand corner. You also have ‘undo’ and ‘redo’ buttons along the top of the map.

Simply click on points over your track to draw a path

11) If you’re having difficulty getting your track to line up, click Background on the far left hand side of the screen and choose ‘bing‘ your background will then change to an aerial view which may be easier to line up the footpaths. In fact, if paths are obvious from aerial photos you can simply trace over this to add them.

12) Once you have created your track you need to assign it a type (footpath, bridleway, cyclepath, etc.) If your track contains multiple types of path then the best approach is to draw each section individually and double clicking at the end of each section to terminate before drawing the next. To assign a type to a path, click your path once and it will show as a yellow line, then on the left hand side of the screen click the arrow next to ‘unknown’ to bring up the path selection. Click the path that best matches what you walked along.

Select the type of path that best matches your track

13) Finally, click ‘Save‘. You may want to add notes on what your changes are to notify others. However, once you have done this then you’re finished and your changes have been submitted. For me, my changes seem to appear within a few hours.

Add a few notes about the changes that you made

Adding a place

Adding a place to OSM is very simple. Simply drag the icon from the left hand side of the screen onto the map and drop it where it belongs.

Drag the icon that best represents the place and drop it on the map

You can nudge the icon around after placing it to get it in just the right spot. After adding the place you can edit the attributes for it (e.g. Address) to provide extra information about it.

You can add additional details for the place on the left hand side

You can even add gates and stiles to the map

In Conclusion

I’ve put both of the Garmin TOPO maps and OSM maps on my GPSr and it looks like something I will stick with. There were a fair number of footpaths on the TOPO maps, but not every footpath. Fair enough, OSM maps don’t have every footpath either, but what they do have are supermarkets, restaurants, pubs, parking places, etc. the POI’s on the OSM maps are just brilliant. From the footpaths that are available on OSM and those that are not, it is obvious that many other Geocachers use the maps and upload their tracks to update the maps for others. I’ve found myself leaving the OSM maps enabled more than the TOPO maps, simply because they’re far more useful when out in unfamiliar places. For those who have the TOPO or 1:50k maps already then adding the OSM maps really won’t hurt as long as you have enough storage space on them.

It was a little bit daunting at first editing the maps on the OSM site. The thought of “I’m editing a map that anyone in the country might use, what if I mess something up?” was the first worry. However there’s the delete button, and the undo button, and if you do something that is a complete disaster, just close your web browser and it’s gone. It will only save when you ask it to, so just don’t save if you’re not confident with your changes.

I’d encourage anyone who decides to use the OSM maps on their GPSr to give back to the community by making a mental note of any footpaths that aren’t included on the maps and uploading their tracks when home and just drawing in the ones that are missing. It seriously only takes a few minutes and is well worth it when you consider how much some copyrighted maps can cost!

Do add a comment to this post if you have any queries, or just to let me know if this has come in useful!


19 Responses to “Free maps for your Garmin GPSr from Open Street Map”

  1. Neil (Goodluck247) Says:

    Thank you for taking the time to add all this information.
    We have only just got our Garmin GPS and have already managed to download maps using your instructions!

    Kerry and Neil

    • geocass Says:

      Brilliant! Glad it helped you both, I was hoping it would! ๐Ÿ™‚ Have you had chance to play with your new gadget yet to find some caches?

  2. John (eufone) Says:

    Another excellent, very comprehensive post. Thanks Cas. Don’t know where you find the time, but keep up the good work.


  3. Dave(BigBoy) Says:

    Thanks for the guide. I have been using OpenStreetMaps for over two years and have seen the detail increasing 10 fold. I have just used your guide to upload ‘hopeully’ the first of many.

  4. Elaine Ann Welch Says:

    What a brilliant blog/guide :o) Only found you today but with your clear and concise instructions I’ve managed to ‘build’ a map of Lanzarote, download it and put it on microSD cards for mine and my hubbies Garmin GPSr This will make such a difference to our imminent trip to The Canary Isles and I’m hoping I can do some footpath tracks to add to the OSM site (though I’m not sure about that!!)
    I then did the same for an OSM of British Isles but got the ready to use map fromTalkyToaster, nice and easy process :O) The only slight ‘hitch’ I had was that I discovered I could put more than one map on hubbies GPSr but mine ‘thinks’ only one map is there, even if there’s more than one!?! I’m assuming my older model can’t cope with more than one map so I’ve simply used 2 microSD cards for myself, with one map on each.
    Thankyou so very much for this helpful site…Just scrolling down archived blogs I’ve seen lots I want to check out, so will be coming back to look at more when we’re back from hols…
    THANKS :O)

    • Alvin Nixon Says:

      I’ve had a similar problem on my new Etrex 20 – it only sees one OSM map at a time. I like your idea of using miltiple SD cards. Very handy when travelling. But here’s another idea – I created a folder and loaded all my maps to that folder on a 16 GB SD card. With a USB cable and a computer I move the desired map into the Garmin folder as required. The problem is obvious – there may be no access to a computer when another map is required.

  5. Sam Says:

    Hi, I basically have Garmin GPS loaded with Canadian/US maps but I’m coming over to the UK and wondering how to get the UK street maps. Not sure if above procedure is just for someone who lives in the UK? Can you please guide me a little? Also, do i need to pay for the UK maps? Appreciate your help.


  6. TrekOntario Says:

    Excellent post. Have recently purchased up a Garmin eTrex 30 and will take a look at OSM.

  7. stuthehikeruk Says:

    Hi Cass,

    I took delivery of my Dakota 10 yesterday, and with the help of this great post I’ve been able to load my new toy a “real” looking map, rather than Garmins “joke map”. Thanks for a great post. I’m just waiting on a couple of custom map links for the USA & Canada.


  8. Dave Says:

    It’s nice to look at the os maps on my garmin, bit when I’m caching, and in a pickle, thinking I’m trespassing, or can’t find a path, I switch to the osm, and the footpaths are generally much clearer, and zoom able to much greater accuracy. From reading this, I now know how to contribute my paths back too, which I didn’t know so thanks cass.

  9. Rachel Barford Says:

    Thanks very much, Cass. Your clear and helpful blog guided me through uploading maps onto my Garmin – something I really thought I wouldn’t have the know-how to do. Now to get my head around uploading the footpaths to OSM…
    Thanks again, Rachel

  10. Gordon Wilson Says:

    Hi Cass. I retired earlier this year and as a retirement gift my colleagues got me a Garmin GPS Map62.I found your guide very useful indeed. I downloaded the GB OSM map from Talky Toaster, and used the information in your article to correct the file naming convention, and now have the map up and running for days out cycling and walking.

    Later this year I have trips planned to N Spain and Rome and in preparation have downloaded maps direct from the OSM sight. I think I’ve done this – and the unzipping correctly. ( a problem I had was making sure the files were called sup1 and not supp1 – vi, only one “P”) so now I can see that the Spanish map file on the Garmin. However, there doesn’t seem to be a way of actually opening this map to check whether its working ok. Is that because I’m not yet physically located withing the geographical area covered by the Spanish map? Are you aware of any way I can get around this.

    Best Wishes
    Gordon Wilson

    • geocass Says:

      Hi Gordon,

      I’ve never used the GPS that you’re using, however with other Garmins there’s a bit in the map settings where you are able to see what maps are being displayed. Start with that and make sure you can see it in the list (I think it’s Setup -> Maps -> Select map). Next, I’d probably load on a few Spanish geocaches to the device and then try to navigate to one. Then, zoom in as far as you can to where the geocache is and you should see details in the map which will confirm it’s loaded on ok. When I’ve gone abroad before I was able to just zoom in to the country I was visiting to check that the maps have displayed ok.

      Hope this helps,


  11. dave Says:

    Thanks for a really useful article.

    For those who can’t see more than one map try this:
    by default all visible maps must be in the Garmin folder. Maps can be on the unit mermory or an SD card. You can mix and match as long as the names are unique

    the first map on a Garmin is called gmapprom, the 2nd, gmapsupp, from then onwards gmapsup1, 2 etc etc.
    Some older units have a 2GB file limit, also some a 2 or 4GB card limit. Some older units only support 2 files, prom and supp.

    On my Montana I have a 16GB card with 6 mapsets, typically only 2 enabled at a time.

    Be aware that more/big maps take time to load when powering up the unit. This can be reduced using the enable/ disable mentioned above. Also I always use the fastest class 10 cards as they are faster read speed than the unit can read. (Sandisk Ultra have proven very reliable.) A side benefit means I can standardise on cards for my satnav, phone, tablet and camera (with an adapter) Unmarked cards are typically class 2 which is miserably slow and useless for cameras etc.


  12. Alvin Says:

    Thanks for the information. I have found all these things to be true when using my own GPS which is an eTrex 20.

  13. Free Garmin Geocaching Maps | Garmin Swim Says:

    […] Free maps for your Garmin GPSr from Open Street Map … โ€“ Jun 03, 2011ย ยท Free maps for your Garmin GPSr from Open Street Map June 3, 2011 โ€” geocass… […]

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