Garmin FIT Course (Flexible and Interoperable Data Transfer)
Open BetaFIT is Garmin's binary fitness protocol that powers Forerunner watches, Edge bike computers, Fenix multisport devices, plus Wahoo, Polar and Bryton gear. On osm2cdr we write FIT in the Course profile: your OSM line route becomes a sequence of trackpoints (latitude, longitude, time) wrapped in a header, definition/data messages and a CRC-16 checksum. Coordinates are encoded in semicircles, Garmin's integer units. To be honest: this is an export of the route geometry, not a recorded workout — there is no heart rate, cadence, power or elevation in the file, because those come from sensors during the ride, not from the map. Very long routes are downsampled to 10,000 points.
Key Features
About FIT Format
FIT is the binary ANT and Garmin protocol that sports devices use to store and transfer data. It is more compact than text formats and is understood far beyond Garmin: FIT is read by Wahoo, Bryton and Polar, as well as by the Garmin Connect, Strava and TrainingPeaks services.
The protocol has several profiles, and two of them are easy to confuse. Activity is a workout that has already happened, with sensor readings. Course is a route the device is supposed to guide you along. Only the second can be made from a map, so a Course is what we write.
The file contains route vertices with coordinates and timestamps, packed by FIT's rules: a header, definition and data messages, and a checksum. Coordinates are stored in Garmin semicircles — as integers rather than fractional degrees. Long routes are evenly thinned down to 10,000 points, with the first and last always kept.
There is no heart rate, cadence, power or barometric altitude in the file, and there cannot be: those values are captured by sensors while you move, not by a map.
What Program Opens FIT Files
The following programs and applications can open, edit, and work with Garmin FIT Course (Flexible and Interoperable Data Transfer) (.fit) files exported from OSM2CDR:
Format specifications
- Proprietary format
- 2D only
- Lossless (no quality loss)
- No attributes
- Output: 1 file
- A Garmin FIT Course file: route vertices as trackpoints (lat/lon/time) in semicircles with CRC-16; route geometry only (no HR/cadence/power), downsampled to 10,000 points.
Who Uses FIT Maps
How to Export FIT
How to Open After Export
- Garmin Edge, Forerunner, Fenix — connect the device over USB and copy the .fit into the Garmin/Courses folder (on some models, NewFiles); after unplugging, the route appears in the courses section.
- Garmin Connect Mobile — "Training → Courses → Import", then send it to the watch or bike computer over Bluetooth, without a cable.
- Strava — upload it as a route into "My Routes"; from there the track goes to the device if synchronization is set up.
- Wahoo ELEMNT, Bryton, Polar — import through the vendor app or copy into the routes folder on the device: these units read FIT Course.
- GPSBabel — gpsbabel -i garmin_fit -f route.fit -o gpx -F route.gpx turns the course into GPX if you need a format you can read with your own eyes.
Popular maps in FIT
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