I recently bough a Garmin eTrex 30x in preparation of a bigger adventure happening next year :-)

I choose the eTrex 30x because it was an affordable, outdoor-proof, quite robust and long-lasting GPS device for trekking. I need a device that has some hours runtime to be able to follow and record tracks.
And I wanted a device with a significant amount of storage, where I can put OSM (OpenStreetMap) maps on.

The procedure to put OSM maps on your Garmin is documented sufficiently insufficient, but fortunately there are enough shattered pieces available, so that you can put the steps together. I try to write here down, what I have done to bring multiple recent OpenStreetMap-maps to your device.

This post is based mostly on the OSM Wiki page for Garmin.

Put multiple OSM maps on your Garmin eTrex 30x

First you need a new SD-Card, where the maps will be located. I prefer to write directly to the SD-Card, but you can go as well through the USB-Mass Storage configured Garmin. Your call.

A fat32 formatted SD-Card works pretty well for me. I have not tested any other filesystem and since most of the pre-build OSM Maps are blow 4 GB, this should be fine. Yes, it’s an outdated, crappy filesystem, but it does the job.

Download the prebuild-Garmin image files (you find links here. You may have to look a bit around, but in the end you will find what you need.

Store the extracted gmapsupp.img files in the folder Garmin" on the SD-Card. You may need to create this folder.

To store multiple cards on the SD-Card just rename them, but keep the .img ending. Keeping the ending is an assumption by myself, I have not tried it out, but would not recommend removing it in order to prevent confusions.