Tracked mileage is only 75%, energy impact is WAY over

[LauraVA]

I did a quick read-thru of other GPS topics but did not see this exact case.

If I start tracking manually on the Charge 5, it generally records only 3/4 of the actual distance. I feel sure it's the Charge 5 which is in error because my Garmin, my phone GPS in another app, and the trail maps all agree on length and it's only the tracked exercise which is short. 

If I then manually enter an exercise with the exact start time and duration but with the correct mileage, Fitbit will calculate it completely differently. Despite the identical heart rate data for the identical period, it will initially report different active minutes and different low/high heart rates, and wildly different calorie counts. The shorter, slower route always has a higher energy impact than the longer, faster one!

A few hours after the workout, the active minutes usually are adjusted to be at least close, if not identical, and that's good enough. Heart rate data is also close enough for my purposes. But calorie counts remain crazy off, and I do need that information too for my doctor. Today's route was 4 miles exactly, and Fitbit recorded it live as 3.09 miles and 531 calories. My manual log with the same time and for the same duration, but with a 4 mile length, shows 303 calories burned. That's a 40% difference while the workout duration is within seconds.

4 miles3.23 miles

This makes the Charge useless for mid-workout data such as pace and distance, and also for logging.

GPS is set to dynamic or phone, I've tried both, and the phone consistently approximates my Garmin and trail maps in other apps I test simultaneously (All Trails, Zombies, Run! etc.). I don't know why Fitbit records such a different number. And I cannot explain the divergent calorie estimates.

Why does a longer distance reduce the number of zone minutes?

Here adding distance reduced zone minutes?

Suggestions?

[JohnnyRow]

I really tried but I cannot follow your scenario. 

"After a few hours, the active minutes usually are adjusted"  Do you mean a few hours into the workout, or do you mean a few hours after you are done, the data is changing?

If you are comparing 2 sets of data, please make it clearer exactly what you are comparing.

And if you are comparing data from a manually logged workout, be aware that a manually logged workout ignores any data that was actually recorded; i.e. actual heart rate data is ignored; it is assumed that it was a completely steady effort.   Fitbit assumes the reason you are manually logging a workout after-the-fact is because you were not wearing the tracker during the workout.

[LauraVA]

>> Do you mean a few hours into the workout, or do you mean a few hours after you are done, the data is changing? <<

A few hours after I have completed the workout, the figures are often different than at first. I edited my post to better state this, I hope.

>>  if you are comparing data from a manually logged workout, be aware that a manually logged workout ignores any data that was actually recorded; i.e. actual heart rate data is ignored; <<

Then why do the manually logged workouts report heart rates and active zone minutes? You can see the HR graph in the two workouts above, one recorded on the Charge 5 and the other logged manually for the same time period, and they match, as they should.

My question boils down to this: Why is the GPS mileage so low on my Charge 5, and why do the energy estimates vary so widely and which should I use?

[LauraVA · Accepted solution]

Update: I have logged lots of runs with significant distance errors, no matter what settings I change. However, the latest firmware update appears to have fixed this issue. Now running 57.20001.171.50 and distances are within a few hundredths of what I know is correct (mile markers). So good update on this one.