Walking miles underestimated

[ROBTEMPLIN]

I have a Garmin bike computer (with GPS) that I can use to compare accuracy of Luxe Fitbit.    When biking, both show similar distances (but the Garmin with a chest strap is far more access far as heart rate is concerned).   However, when walking the Luxe consistently undercounts miles walked compared to Garmin GPS.   The Luxe uses my phone GPS, and after a walk both my Garmin and Luxe will display the same route on the app used for both (in other words they both seem to show the exact same route taken on the maps).    Why would the Luxe consistently show substantially less miles walked than the very accurate Garmin unit (on a regular basis)?

[ByTheC42]

I am so frustrated with this very thing.   I can walk 10,000 steps and it records it as 1 mile.  No lie and no exaggeration.  This is just one of many flaws to the luxe.  I'm about ready to return it.  This is my fourth Fitbit and I've never had a problem like this before.  

[SunsetRunner]

@ROBTEMPLIN Believe it or not, every Fitbit (including the top of the line Sense) use GPS only to trace the path in the map while distance is calculated via stride multiplied by steps. As steps measured by Fitbit while walking/running are fairly accurate the culprit falls into the stride that evidently is not properly set.

It appears Fitbit somehow use the GPS to sometimes., somehow, somewhere tweak the stride but it is evident that the stride can vary drastically during the time, even within the same session. 

This doesn't happen when cycling as steps are not considered and GPS is instead properly used.

Why is Fitbit doing like this? It's a mistery that no Fitbit representative cared to explain despite the complains by the community in these many years.

[ROBTEMPLIN]

Thanks, great answer (even if it's not a great approach to accuracy that Fitbit promotes!).