Comment by nradov

Some users may be confused about Garmin functionality. If you select the Track Run activity profile on a standard 400m track then it will generate a perfectly smooth and consistent route every time. This is only possible because it knows the exact shape of a standard track and can adjust the location data points to fit.

All fitness trackers (and mobile devices in general) do some level of smoothing on location data before recording it to an activity. There is no "raw data" to get back. The developers try to select smoothing algorithms that produce a good result in most cases but there will always be occasional discrepancies. This is usually due to poor signal quality including multipath reflections when the device doesn't have a clear line of sight to the sky due to structures or trees.

Garmin devices don't only use "GPS". They support multiple GNSS constellations including Glonass and Galileo, and depending on the selected mode may use all of those simultaneously to improve location accuracy.