Use OpenStreetMap on your Garmin GPS
OpenStreetMap (OSM) is a collaborative mapping wiki that anyone can make edits to, just as long as you register with the service. This means that maps can be frequently updated. Edits to OSM only take up to 2 hours to be available to everyone, whereas Garmin maps are updated on a yearly basis. Not to mention the Garmin maps are a paid upgrade. OSM is completely free!
The OSM data is not in a format that can be used by the Garmin device so we will be using pre-packaged OSM maps from http://openmapchest.com. These pre-packaged maps are updated on a weekly basis but since OSM is open, you are free to create your own map packages. If you’d like to create your own, more info can be found on the OSM wiki.
Here’s how to put OSM on your Garmin:
1. Format your SD card using FAT or FAT32
2. Create a folder on your SD card called Garmin
3. Download the gmapsupp.img file for your country from http://openmapchest.com/
4. Place the gmapsupp.img file in the Garmin directory
5. Insert the SD card into your Garmin device
6. Turn on your GPS
Your GPS should automatically load the new map. If not, you will need to go to Tools/Settings/Map/Map Info & select the OSM map. It’s also probably a good idea to disable the default map if areas overlap.