- gmapprom.img - primary mapset, factory installed USA or Europe or other country.
- gmapprom1.img - secondary mapset, example: North American / European units
- gmapsupp.img - supplemental mapset, located on the Nuvi drive
- gmapsupp.img - supplemental mapset, located on the SD card
- gmapoem.img - OEM mapset, user accessible, cannot be unselected from the unit via Tools/Settings/Map/Map Info
*Note, when using the following default system maps as user maps, you'll naturally lose their default map attributes.
- gmapbmap.img - default basemap, configurable as a supplemental map; NOT selectable and does NOT show up under installed maps (Tools/Settings/Map/Map Info) but may be visible under Tools/Settings/System/About/Basemap
- gmaptz.img - Timezone map, configurable as a supplemental map
- gmap3d.img - 3D Buildings map, configurable as a supplemental map
- gmap3d1.img - secondary 3D Buildings map, configurable as a supplemental map
Now, if you're wondering which files to delete from your Nuvi drive or SD card to clear up some space, this should provide some insight.
You can easily remove/replace the primary, secondary or supplemental mapset, however you should keep the timezone map. Basemap can be deleted, however it's only around 50 MB in size.
With an SD card in the Nuvi you can fit around 4 custom maps, with the following naming conventions: gmapprom.img, gmapsupp.img. You can even use gmapbmap.img, but note that it will not be selectable from the settings.
Maps on the SD card are located in the folder Garmin.
Maps on the Nuvi drive are located in the .System folder (with a dot) or in the Map folder.
If you can't see the .System folder, you might need to change the USB mode on the Nuvi from MTP to mass storage.
You can get free maps for Garmin from OpenStreetMaps:
or from Open MTB maps (Mountanbike and Hiking):