out of curiosity what is happening in the watch when sometimes the first record in FIT already has a distance not starting at zero?

Sometimes you have to look at the session wrapper vs the first record if there is already a distance on the first record.

It's only a few meters at most though when it happens.

Doesn't happen all the time though, I'd guesstimate maybe only 10-20% of the time

Is that from a "flying start" when running/cycling vs starting from standing still?

Or is it because maybe the watch has so many items to write to the file before the first record that sometimes it takes a second or two and some distance has been covered?

At first I thought it was maybe when "smart recording" is turned on but I also see it in some 1-second recording files.

  • The distance value in the record message is an accumulated value starting at zero. It is possible that some small amount of distance could be covered between the time the activity was started and the first record was written to the file. There is no hard and fast rule either way. Something else to keep in mind is for multi-sport files (either auto or manual) the distance accumulates across all sessions versus reseting at the start of each new session.