Backroadmapbooks uses Garmin License technology to unlock and display the maps on your unit. The license files are used to unlock the maps on your device and can also be used to unlock the maps you have installed in Garmin Basecamp.
The .gma file is used to authenticate the maps on a GPSr when loaded from a microSD card.
Garmin Basecamp requires you import this file to authenticate the installed maps before they will display a fully detailed map.
The .unl file is the unlock key file and consists of your 25 digit key.
License files are located in the Garmin folder on the microSD card and are unique to each card.
Copying data from the original microSD card to another card will display an error message:“Cannot unlock maps.”
The “Cannot unlock maps” error is displayed when the license file does not match the card it was generated for.