Garmin IMG

IMG is the format of the vector maps Garmin installs on its devices: eTrex, Oregon, GPSMAP, Edge bike computers, automotive Drive units. It is not a picture but a map with a road graph, so the device will plan a route on it, find an address and warn you about turns — with no internet.

The export is for when the stock map is not enough: in your region the manufacturer only provides rivers and highways, and you need hiking trails, recent development or a district that simply is not in the catalog. OpenStreetMap is updated by the community daily, and a map built from it is often more detailed than the factory one.

On export the selected layers are converted into OSM data and compiled by the mkgmap program — the standard Garmin map building tool the whole community uses. The output is a single gmapsupp.img file with routing, a search index and points of interest; labels are written in UTF-8.

If the server-side build is unavailable for some reason, the export will honestly report an error rather than hand you a file the device will not accept.