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I went on a hike today with a friend. We both walked side-by-side the entire time. She turned her Google Fit app on "Hike", which GPS-tracked the entire hike. At the same time as she, I turned on my FitBit Charge 4 to do the same. At the end of the hike, we both concluded our hike workouts at the same time. Both Google Fit and FitBit gave the exact same time duration: 1 hour and 44 minutes. Both apps also showed the exact same map (we did a side-by-side comparison on blown up screenshots).

However, my FitBit app said the hike was 4.91 miles and her Google Fit app reported 3.89 miles. This is a mile off! I am baffled as to how this happened and not sure how to troubleshoot it. This is really bugging me because I want to know which of these 2 systems is faulty, because I do much longer workouts on e.g. my bike, and am concerned that the miles could be even more off then. Any advice or accounts would be useful.

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  • Which GPS mode are you using? Dynamic, built-in or phone?
    – NetServOps
    Jun 21 at 5:43
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    If you lose GPS or if GPS wasn't on, your Fitbit will calculate distance based on amount of steps times stride length. If you and your lady friend got up to some adult activity while on this hike, then its probable that your device picked up a lot of 'steps' while you were on top of her. How close am I?
    – NetServOps
    Jun 21 at 5:53
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    See DC rainmakers blog for comparisons. GPS drift and sensing can create real havoc with accurate distances.
    – JohnP
    Jun 21 at 13:58
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    Step one is to move a known distance and see how accurate either is, e.g., find a known route/trail and compare device vs. known distance. Then you can check if the device or app has a step distance setting or terrain variance (steps are generally shorter on harder terrain, meaning more steps, but same distance). Jun 21 at 21:59
  • This could help you measuring it : freemaptools.com/measure-distance.htm
    – Jimbot
    Jun 29 at 12:13
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Do some searching to find many similar issues. A comment recommended DC Rainmaker's blog but be sure to check the comments there on Fitbit GPS issues.

I have the same problem and here's some information that might help.

Even GPS equipped Fitbits seem to use the stride length and step count to calculate distance. People, including Fitbit support, will tell you that only happens when you lose GPS signal but that's not true. As you saw in your case the map can accurately show where you went and the distance can be way off. 10% off is common for me, I'm not talking about it showing me on the wrong side of the street or recording 5.07km instead of 5.09km.

On your dashboard on Fitbit's web page after you select an activity you can export the GPS track using the 'Export as TCX' button near the top right of the screen. Once you have the TCX file you can look at it in a web site (https://www.sunearthtools.com/tools/gps-view.php is one I found via search that seems ok). Alternatively, and probably easier, you can link your Fitbit account to Strava so that your activities automatically upload there. On Strava when you look at the activity you can click on the distance and select 'correct'. This will ignore the distance tags put in the track by Fitbit and recalculation the distance based on the location tags.

When someone challenged the accuracy of the Charge 4 on DC Rainmaker's blog he suggested the user create a test by combining running and cycling to see if the step count really was a factor. I did this and generated a GPS track that recorded no distance traveled during the portion of my 'run' where I cycled, because I wasn't generating any steps, even though the location tags showed I had moved a significant amount (100s of metres).

As far as I'm concerned I have objective proof that Fitbit uses steps instead of GPS to determine distance. This issue was raised a long time ago on their support page and there was no sign that they acknowledge it's a problem or plan to fix it.

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