How accurate is your GPS?
On most of my (our) bikes, I use both an analogue cycle computer (that relies on wheel revolutions to record the ride) and a GPS (usually a Garmin).
However, I have recently acquired another bike (but more of that in a future post) on which I use only the Garmin and a tracking app on my phone. I decided that fixing an analogue system was too ‘yesterday’. So today, and not for the first time, I used only my Garmin and Strava on my phone to track my route, and interestingly, they came up with very different statistics. Different enough, in fact, to hold in question the accuracy of GPS technology. But there could be a simple explanation…….bear with me.
Here is the Garmin map:
It records me covering 70.90km, at an average speed of 24.3kph, with an elevation gain of 310 metres, and a maximum speed of 51.5kph. For a flattish ride out to the fens, the elevation gain is quite startling………..but it is barometric, and not necessarily accurate.
This is the Strava map:
Strava, on the other hand, records me covering 69.90km, at an average speed of 24.9kph, elevation gain of 381 metres, and a maximum speed of 45.5kph.
So Strava had me cycling 1000 metres less than the Garmin, had me climbing 71 metres more, at an average speed of 0.6kph faster, but with a maximum speed of 6kph less.
I can’t explain most of these anomalies, but I can add that the auto-pause functions of both devices would have made some difference. The Garmin had me cycling for 2:55:20, and the Strava for only 2:47:38. That critical difference of some 8 minutes would have affected the average speed, and might have affected the divergence in distance, especially if one device took a few more seconds to kick back into activity when moving off from stationary.
Funnily, when I did use an analogue system, I always relied more on the wheel revolutions for giving me a more accurate record of my ride. Maybe I’ve not been so wide of the mark after all……….