Here's my semi detailed comparison of the Garmin 620 (admittedly a running watch), and the Strava android app for tracking a cross country ski workout (technique: classic) at Mt Bachelor Nordic center near Bend, OR. The temperature was in the mid-upper 20s and I was using a combination of some start grip tape (under foot) with a mix of Swix blue extra, and toko red in the kick zone. The phone was in my front jacket pocket, and the watch was on my wrist (under my sleeve).
|Avg moving speed (KPH)||12.6||12.6|
|Max speed (KPH)||50.2||54.0|
|Elevation gain (meters)||613||664|
The basic statistics appear to be very similar. The distance is off by about only about 1/2 percent. The average speed matches pretty much spot on. The moving time is also very close. My phone measured my top speed at 54.0, almost 4 kph more than my watch. Based on the map in Figure 1, the precision of the position on the moto x was a little noisy during downhill sections, but quickly became very good after slowing down.
|Fig 1: Strava Android app recording of downhill section on blue jay loop.|
The paths really come together for the workout recorded on the phone, as they should, since I was always skiing on the same trail. Now compared to the Garmin GPS (fig 2) the data from the phone is looking pretty good. The Garmin watch seems to have a steady offset, rather than adjusting after changes in speed. By looking closely at the maps, I'm impressed how close the final numbers were for both devices.
|Fig 1: The Garmin 620 on same downhill section, skied many times on same workout.|