Finally, I managed to go to an outdoor track to test both Fenix 5X+ and Stryd, to understand a bit if I should blindly trust Stryd just because people say that it is the most accurate distance measurement tool.
I did trust Stryd for a long time, more than a year and usually, when running in official events, my measured distance was below the expected distance … for example two half marathons with less than 21km (20.6km and 20.8km). It’s not crazy, but I imagined that my Stryd is a bit conservative when measuring distance. When I allowed Garmin to “compensate” by calibrating with GPS measurement, you get another value …it seems that the calibration factor eventually settles for 102.9-103.1, but that’s not right as well knowing that Fenix 5X+ is not that accurate GPS wise.
So .. now I went to the track, first lane, setup Stryd calibration factor to 100.0 and “Auto Calibrate=disable” and waited several minutes for the GPS lock-on. I used only GPS (no Glonass or Galileo) and 1 second measurement. The result?
6.29km for 16 laps – it should have been 6.4km (16x400m), but what can you do? At least, the “loss” was consistent from the first lap and I did more then 2-3 laps just to make sure that we are not looking at some punctual issue.
The GPS track looks decent on the left side and less on the right, for no reasons – there is a building on the right side, but it’s not that close and not that tall to create that much of an issue (at least in my mind).
So, the conclusion is that I might use for the next period a calibration factor of 101.7 and auto-calibration off for my Fenix 5X+ (or any other device which allows manual calibration).
For me, Stryd works just fine with the proper setup because it delivers consistent results independent of the GPS conditions (tall buildings, forest or plain sky) – I kind of knew that it measures less, but at least it was doing that consistently. The second advantage is the pace, which is reliable and doesn’t depend on the GPS quality. Add running power to that and you’ll understand why I’m using Stryd (…yes, I’m a data geek as well and that explains it better).
So, trust your Stryd because it’s consistent, but measure yourself to make sure that you have the best calibration as well.
PS: Polar, I’m looking at you when I say that we need calibration – I can’t replace one source of information with one less reliable (like the Vantage V GPS).