Strava Android vs Garmin 620 (XC Skiing) comparison

So I use Strava, and I also use Garmin.  I sometimes use my phone (Motorola Moto X on verizon) to record workouts in strava.  I've been wondering, how good is the phone at tracking position / speed during a workout, vs my expensive Garmin watch?  The phones have got alot better at position, especially the iPhone 5S which can monitor motion / movements while using even less battery.  Technology has improved alot in the last 5 years with phones.

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).

	Garmin	Moto X
Moving time	2:32:25	2:30:05
Distance (KM)	31.56	31.7
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.

I will continue to use my watch (and my phone) to track workouts.  I pretty much use my Garmin watch exclusively for tracking running workouts, since it's really built for running, and has running specific features like cadence, ground contact time and vertical oscillation.  With the hardware on more phones implementing features to accommodate fitness tracking, it seems like Garmin may have their work cut out for them.  However, I still do not like to carry my phone while running, but with the announced Samsung Galaxy S5 having ANT+ capability, hopefully more phone manufacturers will follow suit, since phones do seem to have a pretty good handle on the position tracking.

Garmin 620 VO^2max

I was sort of an early adopter to the new Garmin 620 smart watch.  Well, it's smart in that it has a heart rate strap with an accelerometer in it, so it is able to measure your cadence, vertical oscillation (how high you 'bounce') and also ground contact time.  It also measures your average stride lenght for the run based on all the parameters.  So far I really like it. It's super easy to use, automatically uploads to Garmin connect and Strava (with copymysports). I honestly don't know if it's worth the price, but I don't regret buying it, yet anyway.

One of the cool things it does is measure (or estimate) your VO^2max.  Below you can see the trend since I got the watch in late November.  I hadn't been running a ton before then so you can clearly see a trend of increased fitness.

Essentially it measures your heart rate and pace, and uses a formula to calculate your estimated VO2max. You can see the formula in action on the two points I highlighted.  Point (1) I visited Mesa, Arizona and ran in Mesa (1,243ft ele) one day and the next day in high elevation Flagstaff, AZ (6,910ft ele).  It makes sense that I would have a higher pace / lower heart rate in Mesa than in Flag, especially considering my buddy and I summited Elden lookout (~9200ft) on the run in Flagstaff.  Also, on point (2), I was traveling to central California where it is around 375ft elevation. Now I'm back in Central Oregon so I'm sort of back to my current baseline of 57.

Hopefully I'll update this again later in the year, after a few more key workouts and races.