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Average power discrepancy between Garmin Connect and Strava

5999514
over 1 year ago

I use a 4iiii precision 3 power meter with my 1040 Edge and the average power shown in Garmin Connect is consistently higher than the figure presented in Strava (for my last ride, GC: 180 and Strava 171).

After doing some research online I have tried playing around with specific settings (going from auto-pause to pausing manually, including zeros etc.), but nothing seems to help. 

Before buying my Edge, I used the FR955 watch together with the same power meter and had better results (the difference, if any, would never be more than 3-4w). Friends of mine use similar equipment (830 Edge together with 4iiii PMs) and do not experience any discrepancies at all. So I am expecting that one way or another there is something wrong with my specific devices. Perhaps I am experiencing dropouts?

Does anybody have a clue what might be causing this?  

  • 0 over 1 year ago

    Your head unit may be set to exclude zero power values showing a higher average power than strava.  Stava will include zero power values regardless of how your head unit is set.

  • 0 over 1 year ago in reply to ac-cycling

    Thank you, but that’s not the case. As noted, I have been playing around with these settings - both definitely include the zeros. 

  • 0 over 1 year ago in reply to 5999514

    You would need to post one of the FIT activity files. 

  • 0 over 1 year ago in reply to aweatherall

    Please see the FIT file: https://www.transfernow.net/dl/20230925CE3KRd7K

    This is my latest ride, which resulted in 180 avg power on the head unit and 171 avg power in Strava. 

  • 0 over 1 year ago in reply to 5999514

    So the difference is due to the fact that the Edge and Strava are computing the value off of different values in the FIT file.

    The discrepancy between the values if due to communication issues from the power meter to the Edge and how those lost signals are managed.

    The power meter sends torque/cadence from which the Edge can compute power. Each message also contains an accumulated value.

    If you look in the FIT file you will find an accumulated_power value and a power value. If there were no data loss then the sum of the individual power records would equal the reported accumulated power.

    In this case there is around a 5% difference.

    The accumulated power is 1564778 kJ

    The sum of the individual power records is 1486061 kJ

    The activity duration is 8,688 seconds.

    This gives averages of 180 and 171.

    if you look at the plot below you can see how these two values diverge. 

  • 0 over 1 year ago in reply to aweatherall

    Much appreciated, aweatherall. Do you have a view on what is causing the communication issues? If I recall correctly there were (Bluetooth) connectivity issues between 4iiii power meters and the Edge 1040 upon launch of the latter.

  • 0 over 1 year ago in reply to aweatherall

    Is it kW not kJ ? (I know accumulated kW is a nonsense unit of course, I guess it’s just used to produce an average?)