Charge 2 consistently underestimates distances

[SunsetRunner]

I've had this issue since I bought my Charge 2 in May 2018, but have only just got around to proving it.  The Charge 2 always under-reports known distances.

I do Parkrun (a timed 5km run) every Saturday.  Today I wore my Charge 2 and my old Garmin Forerunner, and measured the run on Starva on the same phone supplying the GPS to the Charge 2.

Results:

Charge 2 distance: 4.84km

Garmin: 5.01km (same as it always used to report for this course)

Starva: 5.0km (so annoying that Starva reports to granularity of only 0.1km!)

These results are wholly consistent with a 5km walk I did, in a different location, on Thursday, with the Charge 2 reporting 4.81km and Starva 4.9km.

So the fault is obviously within the Fitbit Charge 2 (as Starva is getting the correct distance from the phone).

It makes the Fitbit Charge 2 more-or-less useless for absolute distance and rate purposes.  Has anyone any ideas what I can try, as I have probably left it too late to get a refund?

Thanks

N

[JohnnyRow]

Using connected-GPS to phone or not?

If not, distance is calculated as number of steps times stride length.  Your stride length is probably a bit off.  You can adjust that.

How do I measure and adjust sride length for my Fitrbit device?

Or, if you are sure the 5K course is exact, just try increasing your stride length by (5 / 4.84).

[SunsetRunner]

Charge2 doesn't have an internal GPS so if you're not connecting it to cellphone GPS then it uses your stride length x number of steps to figure distance. Based on that somewhat inaccurate accounting ...your stride length ...coming up .16km short doesn't seem too bad.

My fitbit will run consistently 2 tenths of mile short when I run 5 miles (4.98 mile fitbit reading)...but that's close enough for me. 

I suggest you either connect the cellphone GPS or tweak your stride a bit using your fitbit account website.

[SunsetRunner]

Thanks for your reply, and Johnny's too.

Sorry if I hadn't spelt it out but yes, this is using GPS supplied by my smartphone to give the distance.  I checked for the phone symbol before and after starting the run.  As stated in my post, Starva, running on the same cellphone, is giving the correct distance and my Charge 2, also connected to the cellphone, is underestimating.

That said, when I look at the run in the Fitbit app - which shows the course correctly - is there any way to see that the stats have been provided by the GPS and not calculated from the stride length?

Thanks

N

[SunsetRunner]

I raised this with Fitbit Support and was told that this is due to stride length - which I had assumed must be irrelevant when GPS is in use.

"No, the tracker will take your distance for sure. The phone is a tool to track your GPS, but at the moment when you sync your activity; the Fitbit app takes the information recorded by the phone and the information recorded by the tracker. Meaning that if you put your stride length, it will be more accurate."

This article seems to confirm that: https://help.fitbit.com/articles/en_US/Help_article/1135/?q=stride+length&l=en_US&fs=Search&pn=1

But this seems utterly ridiculous!  Why would the tracker ignore the wholly accurate distance provided by the GPS unit, and calculate an approximate one based upon an imprecise variable like stride length??

Any insight gratefully received.

[hvdutra]

I'm having the same issue but evaluating the data, I found something very strange....

Looking on the Fit bit app, my running stride is 0,932m (set in auto), my last run had 5005 paces, so by multiplying the numbers we reach 4664 meters. The Fitbit app is showing 3.76 km for my last run.

The Charge 2 was connected to the cellphone GPS...

[hvdutra]

One more information...  The registered track at the app map is correct, and correspond to 5km  (aprox)

[Gcgcg]

I had this problem but re setting my phone battery to full power corrected it.