Fitbit Charge 5 off HR Distance

[DTL7]

Yesterday did Nordic Walking. I wear a Polar chest band linked to my PolarVantage M.   I noticed the distances were not the same.  Just did a treadmill test to further investigate

Total distance

Treadmill: 2.1 miles

Polar Vantage M: 2.0 miles

Fitbit Charge 55: 1.77 miles

Snapshot HR

Polar Vantage M: 108

Fitbit Charge 5: 124

Polar Vantage M: 135

Fitbit Charge 5: 147

These numbers are not even close. Yes I wore the Fitbit correctly.

Is there any reason to believe this can be fixed? 

I am a long time Fitbit user: Flex, One, AltaHR, Charge 4. So this is really disappointing. Wrist based distance has always been less accurate than clip ons like the One. HR has always been an issue when the HR goes up.   The Charge 4 distance matched the Polar watch. You would think they would have this fixed or at least better.  This seems to be a step back. Bummer.

Moderator Edit: Clarified subject

[N8teGee]

Hi @DTL7.

Unfortunately it seems to be how Fitbit's GPS algorithm works. Even with a good GPS signal, distance is still predominantly based on steps using the accelerometer - stride length x number of steps. I believe the GPS is then used to adjust the stride length periodically. Unless you are almost robotic and can run/walk at a consistent pace, I don't believe this implementation to be very accurate.

There are threads on the other device boards discussing this very issue, although upto now it's been difficult to get any sort of official response.

You can do a simple test yourself if you are curious. Get into your car and start a walk/run (with GPS), then drive a mile or so. You will notice your route has been plotted on the map, but distance will be close to zero. 

[DTL7]

Thanks!  I did not have this much trouble with the other Fitbits. They much much closer to true steps /  distance.  The One of course was the best.  The Polar Vantage M is dead on so you would think Fitbit could also do this. 

I do use my phone for GPS because of the issue with using the Charge 5 GPS and heart rate. This is a bummer because I thought Charge 5 infernal GPS great no phone to carry. But then again as I mentioned Heart Rate is no so good when activity gets strenuous. I do not think any of the Fitbits that I had did well in HR. To be fair the Vantage M wrist based HR is not good either but better than Fitbit.  I use the chest strap anyway.

Seems the Charge 5 is not well thought out. Some better clock faces would be nice.

EDIT: actually thanks again. I will set my stride length manually.