A worked example: one ride, recorded twice
One ride, two devices: the bike computer saved a GPX with the route and power, the watch saved a FIT with heart rate and cadence. Neither file alone tells the whole story — the merged FIT does. The figures below are in-site example data, chosen so every number reconciles.
The two recordings
| File | Points | Time range | Streams it carries |
|---|---|---|---|
| Bike computer (GPX) | 6,500 | 07:00:00 – 08:48:20 | GPS, elevation, power |
| Watch (FIT) | 6,410 | 07:00:00 – 08:48:20 | GPS, heart rate, cadence, temperature |
Both devices recorded the same 38.42 km in 1:48:20. The watch missed 90 seconds of points along the way, and its GPS track is the noisier of the two — which is exactly why the stream choices below take position from the computer and physiology from the watch.
The stream choices
| Data stream | Source | Why |
|---|---|---|
| GPS position | Bike computer | Handlebar-mounted with a clearer view of the sky; the watch track drifts under trees |
| Elevation | Bike computer | Only the computer recorded it |
| Power | Bike computer | Only the computer was paired with the power meter |
| Heart rate | Watch | Only the watch recorded it |
| Cadence | Watch | Only the watch recorded it |
| Temperature | Watch | Only the watch recorded it |
Open the tool and load the built-in sample
The tool ships with a built-in sample in the same shape as this example, so you can make these choices yourself and download the merged file.
The reconciliation for the merged FIT
| Measure | Merged output | Check against the inputs |
|---|---|---|
| Points | 6,500 | Timeline of the bike computer file, the GPS source |
| Distance | 38.42 km | Matches the bike computer's total |
| Duration | 1:48:20 | 07:00:00 – 08:48:20, the range both files cover |
| GPS coverage | 100% (6,500 of 6,500 points) | From the bike computer |
| Elevation coverage | 100% (6,500 of 6,500 points) | From the bike computer |
| Power coverage | 84.2% (5,473 of 6,500 points) | The meter dropped out on the descents — same gaps as the source file |
| Heart rate coverage | 97.4% (6,328 of 6,500 points) | Every heart rate value the watch recorded, aligned to the merged timeline |
| Cadence coverage | 96.7% (6,285 of 6,500 points) | Every cadence value the watch recorded |
| Temperature coverage | 98.6% (6,410 of 6,500 points) | Every point the watch recorded carries a temperature value |
Nothing appears from nowhere and nothing vanishes silently: each stream's coverage in the output is exactly what its source file had to give. Exporting this merge as FIT requires a paid plan; the same merge exported as GPX or TCX is free.