How to fix GPS drift or a jumpy track
The map shows you running through the middle of a building, or a ride that zigzags along a straight road, or a single point that leaps 200 metres sideways and comes back. The rest of the activity is fine. You can fix the bad stretch in the FIT file itself and upload the clean version, without touching the parts that recorded well.
Where drift comes from
- Tall buildings. Signals bounce off glass and concrete before they reach the watch, so the position wanders. City centres are the classic case.
- Tree cover and narrow valleys. Fewer satellites in view means a looser fix and a wobbly line.
- Starting before the GPS had a fix. The first minute or two jumps around until the device settles, sometimes with a straight line from wherever it last knew you were.
- Tunnels and covered paths. The device loses the signal and either draws a straight line across or guesses badly when it comes back.
Fixing it in the file
- Open the file in FIT File Editor. The route is on the map, with the timeline underneath.
- Press Adjust GPS under the map. Every recorded point shows as a small handle.
- Pick the fix that matches the problem:
- A wobbly or zigzag stretch: drag across that part of the timeline to select it, then press Smooth. The track in the selection is averaged into a steadier line. With nothing selected, Smooth applies to the whole track.
- One point way off the route: drag its handle back onto the road or path. The points next to it ease along so the line stays natural.
- A point that shouldn't be there at all: Option-click it on a Mac, or right-click it, to delete it. The route joins the points on either side.
- Every change can be undone. The map redraws as you go, so you can see the result before you commit to it.
- Press Export and upload the new file.
What about the distance
Moving points changes the route on the map, not the distance the device recorded. If the drift added distance you didn't do, press Edit details at the top and set the right Total distance: every distance in the activity scales to match, and speed and pace follow. If the drift came from a car ride or a stretch you didn't do under your own power, cut it out instead (see forgot to stop your Garmin).
Uploading the corrected file
Delete the original activity on Strava or Garmin Connect first, then upload the edited one. If you upload first you'll get a duplicate activity error.