GPS inaccurate

[AmandaOrlando]

I'm so disappointed!! I've been suspecting that Blaze GPS is overestimating my mileage the last couple of weeks, but here is proof! Ran the Disney marathon on Sunday and my watch said 27.83 miles. 0.3-0.5 off, I can understand, but 1.63 miles off is not acceptable. Can anyone help? I love my Blaze but may need to go back to Garmin 😞

[icewarnerd]

I think this is because the Blaze doesn't have its own GPS, it's using your phone's. When I'm running long distances, I use both my Blaze and my Forerunner with a heart rate strap. I secure the Blaze in a pocket without the wristband. This way, I get the benefit of a watch with its own GPS plus I still get all of my FitBit steps.

The Blaze is a great product and I'm absolutely sold on using it all the time, especially with the social component, but without its own onboard GPS, it's not going to be as accurate for long distances. FitBit does have the Surge with its own GPS, but I haven't tried comparing the accuracy of the Surge to competitors' products.

[AmandaOrlando]

Thanks for the response! You might be right... I don't want to wear 2 watches, but maybe this is the only way to go. Kind of a bummer. Thanks again 🙂

[MikeF]

I don't personally see that what device a GPS receiver is fitted in will have any impact on the accuracy of the plot. At worst you'll get a bit of latency from the Bluetooth link but nothing significant at human running speeds.

Off the top of my head, I don't know what GPS accuracy Fitbit (or your phone) provides but we're talking about a 6% error here which is significant but maybe not monstrous. I also don't know at what rate Fitbit sample the GPS signal but given a quoted 2m accuracy for the civil SPS service, at worst it only takes 250 2m errors to give you an extra distance travelled of 1 km (2m out to each error point and 2m back to actual track).

This is an extreme and unrealistic example but given the distance of your run is calculated from lots of little route legs added together it isn't going to be as accurate as simply comparing start and end points and calculating the distance between them.

None of this is an attempt to excuse anything but I find people quickly fall into the trap of assuming that the use of GPS automatically means everything is magically accurate which is a long way from being true.

[AmandaOrlando]

Thanks for your response! This is a fair point. However, I find this % error to be too high to consider the measurement valid. Something is not right. I realize GPS will be off a bit, particularly in a race with a lot of curves, but this is just too much. 

[Tbads]

My blaze is more than 20% out in distance and pace as compared to both strava and the Nike run app. All linked to my iPhone7. Really upset with the fob off by customer service who, after a string of generic suggestions have  admitted that this is a known problem. So, Garmin or apple watch? 

. 

[AmandaOrlando]

Sorrry to hear that you have this issue too! Unfortunately my issue never got resolved and even got worse, so I no longer use the GPS on my Blaze. I bought a cheap Garmin and wear 2 watches when I run. Once my Fitbit wears out (it still works for steps), I will probably go with Apple! 

[Colinm39]

@AmandaOrlando@TbadsHi... When you say off, is that over or under reporting.

Most of those reporting with logical mapping on the Connected GPS are reporting over stating distance... Some are reporting dropped Bluetooth and others wiggly tracking in different topics..

[AmandaOrlando]

Hi Colin- it overstates. It varies on how much it is off, but sometimes > 20%. Last time I tested it on a known 2 mile run and it said 2.38. That's when I knew I was done with it 😕

[Tbads]

Hi guys
Yes, mine overstates. A recent 8km fun run measured 10.67km by Fitbit. My Garmin wearing friend remarked on the accuracy of the fun run distance! Hmmm. I'm now wanting to step up my distances from regular 10km runs to do a half later in the year so distance and pacing is becoming much more important to me.
Interesting to hear what response I'll get from the customer service team...if anything.


Sent from my iPad

[Colinm39]

@AmandaOrlando Thanks for that. In the Southern Hemisphere a few of us have established there is a mathematical error in an East/West (E/W) direction. North/South (N/S) is OK.

The error is an increase in distance of approximately 12" or 30cm/second.  We know it is there, because when I walk in the E/W direction my Blaze has my walking pace at 2 min/km faster than my Surge. OK on the N/S route.

Over the weeks we have been posting this inaccuracy Fitbit have not remarked.  In the Charge 2 forum at this link you can see some of the analysis. Because of my findings I have to assume the Connected GPS in the Blaze and the Charge 2 are the same.

My Surge, MapMyRun and MobileTrack map as expected.