Open Street Maps

Since I’m delayed going on my adventure due to the COVID-19 global pandemic I thought I’d use the time constructively to cover some of the things I’ve been doing during my preparation that I haven’t blogged about yet.

Whilst investigating GPS solutions for the trip it soon became obvious that Garmin don’t really cover the entire world when it comes to maps for their GPS devices, especially the Garmin Zumo 350LM that I have and use regularly on my bikes.

So I started to investigate the Open Source alternatives for mapping and soon discovered that Open Street Maps can be compiled into the correct format for the Garmin series of devices.

Having worked in IT all my professional life I’m am somewhat of a techie and have a good understanding of Open Source Software and how to apply it to everyday needs.

Open Street Map is an Open Source project that has been going for a number of years now. Originally started by Steve Coast in the UK in 2004, it was inspired by the success of Wikipedia and the predominance of proprietary map data in the UK and elsewhere.

Open Street Map User Interface

The Open Street Map website provides a fairly simple user interface to select and generate maps based on squares. For most travellers the easiest way to get the mapping information is to select the country from the drop down lists, enter your email address and then click the “Build my Map” button.

This will generate two emails, one to confirm that the request has been received and how long it is going to take to generate your map and then a second email detailing the link where the ZIP file containing the image files can be downloaded from.

This is the easy bit!

Once you’ve downloaded the ZIP file containing the .img image files you need to use a tool to convert them to Garmin GPS compatible format.

Since I’m an Apple MacBook and Ubuntu Linux user I will show how to generate the Garmin compatible files using Linux tools.

If you’re using a variety of the Windows Operating System please have a look here for the details on how to do this. It does appear to be much more complicated!

Using a Linux Terminal window unzip the ZIP file and list the contents as shown below.

Output from Linux Terminal

Once the files are unzipped you need to generate the gmapsupp.img file that Garmin GPS devices require to interpret the map data. This is easily generated using the mkgmap tool on the command line. Default installs of Linux don’t have this tool installed and so you will need to install it using the following command:

sudo apt-get install mkgmap

Once installed you are ready to proceed by issuing the following command:

mkgmap –gmapsupp ./*.img

mkgmap output during map generation

As you can see above, once the programme has run you will have the necessary gmapsupp.img file ready to go into the Garmin folder on your device SD card. Note that the folder must have an uppercase G for it to be recognised by the device.

Garmin Zumo 350LM screen showing Open Street Map Entry

Once the Open Street Map is on the SD card it will appear on the device under the “myMaps” menu item as shown above. The maps are always called OSM Street Map and not by the country name. It’s also worth nothing that you can only have one gmapsupp.img file at a time in the Garmin folder on the SD card as you cannot have two files with the same name.

If like me you are going on a trip and need to have many countries stored then the best thing to do is create a folder structure and keep each country gmapsupp.img file in a separate folder, then all you will need to do is copy the appropriate file into the Garmin folder for each country as you move around.

If don’t have the facility to generate these files yourself please contact me on social media and I’ll happily generate the files for you.