Connected GPS bike ride distance is inaccurate

[VikSteps]

Hi all

I'm having a problem with my Blaze and bike rides, it's reporting under the actual distance by quite some margin.

This morning I rode into work and used my Blaze, a Garmin watch and running the Endomondo app on my phone, these were the distance results:

Garmin: 19.4 km

Endomondo: 19.2 km

FitBit: 15.5km !! (using same phone as connected GPS source)

The map of the route looks good so I don't understand why it's so off even with GPS smoothing. There is one section where I enter a tunnel and lose GPS for about 1km but I don't see a GPS spike in the map.

This contrasts with when I use Connected GPS with a Run, it's a bit over distance but never out by a huge amount, usually 100 metres over a 10km distance.

Does anybody have any tips on getting this a lot more accurate?

Also a Strava question, if I use Strava - will FitBit sync back HR data within the same time period? 

thanks!

[SilviaFitbit]

Welcome to the Community @VikSteps! I appreciate the details that you've provided. Since, you're using different trackers and your phone to track the distance, it will show different stats. Also, whenever the GPS signal is lost, it will show on the map as a blank space. You can check this article How accurate is GPS? to know the things that may affect the GPS data. 

Regarding your Strava question, you can learn more about what's going to sync between those apps by checking this Strava third-party post.

Hope this helps. Let me know how it goes. 

[Colinm39]

@VikStepsTo establish where your issue maybe I would not use the Blaze as Connected Mode to start with. I would use the Exercise, Tracking and select Run on your phone.

If it's the Android phone just pause and Finish at the end because you could lose your maps (being researched by Fitbit Support). Just in case take a screen shot. I'm not sure about the iPhone with this issue. You only need at least one minute to do the testing rather than miles of testing.

I have found the Android Phone GPS as accurate as MapMyRun GPS  and Google Earth to plot the routes. The Surge is as accurate as the Phone GPS..

I also test my Phone in the car the same way and that convinces me the GPS is accurate on MY phone..

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@VikSteps wrote:

Hi all

I'm having a problem with my Blaze and bike rides, it's reporting under the actual distance by quite some margin.

This morning I rode into work and used my Blaze, a Garmin watch and running the Endomondo app on my phone, these were the distance results:

Garmin: 19.4 km

Endomondo: 19.2 km

FitBit: 15.5km !! (using same phone as connected GPS source)

The map of the route looks good so I don't understand why it's so off even with GPS smoothing. There is one section where I enter a tunnel and lose GPS for about 1km but I don't see a GPS spike in the map.

This contrasts with when I use Connected GPS with a Run, it's a bit over distance but never out by a huge amount, usually 100 metres over a 10km distance.

Does anybody have any tips on getting this a lot more accurate?

Also a Strava question, if I use Strava - will FitBit sync back HR data within the same time period? 

thanks!

---

After I'm happy the phone isn't at fault I then test the Blaze..

[Rich_Laue]

@VikSteps as for what i find that works.

If my phone doesnt have enough free memory, to many other programs running, or my phone is running slow,  the GPS is off.

As for stravela yes gor your heartrate, provided that you used GPS to track your event, and synced the tracker before hitting the end button on the event tecirding. This is explaned in the pinned post on the third party forum.

https://community.fitbit.com/t5/Third-Party-Integrations/Third-Party-Apps-Informational-Post/m-p/144...

[VikSteps]

@Colinm39 I believe my phone GPS is pretty accurate as using the Endomondo app accessing the same GPS gave the same result as my Garmin, I am using an iPhone 6 Plus and it's GPS is pretty good.

I like your idea of tracking it as a run to see if it is different, I'll try that out when I ride again tomorrow.

[VikSteps]

@Rich_Laue I don't think I had many other apps running in the background but I will experiment and see if it makes a difference.

[VikSteps]

@SilviaFitbit Thanks for the 3rd party post, very useful! My map doesn't have any blank spaces and it looks pretty good visually, it's just the distance is off by some large amount.

[VikSteps]

I have done a bit more research on this so I thought I'd share my findings. The problem with GPS distance appears to have been ongoing for some time according to other posts and this led me to believe that the problem is most likely to be the calculation itself.

To test this theory was simple and I followed these steps.

1) Export the activity as a TCX file from FitBit

2) Open the file to see the distance calculation (open in notepad++ or similar) and it is 15536.69 metres

3) Find some tool to recalculate this distance using all the data points in the file. I used http://tcxtools.com/tcx/distance/ 

4) Look at distance in new tcx file and it is 18839.3431 metres

The calculation used by FitBit is incorrect.

Now to figure out where it is wrong will be up to FitBit, the formula used by everybody appears to be the Haversine formula and some clever tricks to remove outliers (those GPS points that are way off).

[josephmcd]

100% it's a problem with the algorithm.  Even on short rides I've seen the same behaviour.  Logging with Strava directly in app and using the "Exercise" option from my Blaze (and waiting for full bars before starting) I often get very contradictory information regarding not only the distance, but the start/stop times, max speed, average speed, etc.

It appears that Fitbit applies a lot of data smoothing to the GPS data to make the charts look better and this seriously impacts the accuracy of the data.  This despite the fact that, as you observed, the GPS data in the tcx file itself is accurate.

I would greatly prefer more accurate information to smoother speed/HR stats.  Please fix this!

[kolibri70]

Hello! I,had also noticed wrong distance at Bike exercise. Tested different Fitbit app settings. Today had make test with Fitbit app settings, where i forced distance ( Fitbit app - Tracker settings - choose Distance as Main Goal ). At this point i,ve get more correct distance statistic result.

Equipment i use: Fitbit Blaze, Mobile Phone Microsoft Lumia 950xl, Fitbit App

[Dries]

I am having the same issue , did a bike ride today used the blaze to select the exercise "Bike" .

Put on the app on my phone, then connected it to my phones gps and started to ride. (phone is a Lumia 550 native windows 10 ) the app stayed active during my ride.

Came home and did a comparison of the distance , the fitbit app gave a bike ride of 4.15km google maps is giving a distance of 7.7 km. I checked the map the fitbit app gives and it was spot on.

I have seen the same diferences when doing my runs , my blaze tells me the run is 2.9km long and my wifes charge2 gives a distance of 4.2 km ( here google maps gives a distance of 4.15 km)

Is there a way to get these reading correct or is it just something that i will have to accept ?

[MayLeaBee]

Same issue yesterday.  Started bike ride on blaze.  Have it synced also to Strava.  I know my ride was about 14 miles.  Looked at fit bit as nd it said 9.5 miles?  Strava correctly said 14. Same issue during running. So the raw data being sent from fit bit to Strava is correct but calculated wrong by fit bit. This is not good.  I like fit bit but will have to just use the blaze as a daily fitness driver and watch and pull out my old moto 360 sport for GPS tracking.  This is very dissapointing.  Fitbit needs to investigate this and fix it since I know the raw data is correct.

[VikSteps]

This is just more evidence that the calculation is wrong! Sadly for those of us who want relatively accurate data, we can't rely on it. I could not recommend the Blaze for tracking GPS activities.

[Colinm39]

@VikStepsIn your earlier posts you mention under reporting, in the Southern Hemisphere some of us have tested and proved there is over reporting on distance. In an East/West direction we have proven there is about a 12"/30cm gain per second while walking and a pace gain of about 2km/hr. North/South is OK.

This was compared to MobileRun app, MapMyRun and Surge. 

[AlejandraFitbit]

Hello all, I hope you are doing fine!

If you are having inconveniences with your GPS information, I recommend taking a look and follow the instructions provided in the My Blaze GPS is not working. Also, keep in mind that in order to have more accurate information your phones need to be compatible mobile devices.

I hope this helps, see you around. 

[MayLeaBee]

I usually don't reply to posts in a negative way but the post above must be autogenerated because it just restates useless help info and does not address what any of us are trying to tell fitbit.  The raw data is correct when loaded into Strava but incorrect within the fitbit app.  That is the issue.   Not compatibility.  And I see more of this for the Blaze and not the Charge 2.  Why?  I do t know I am not a fitbit engineer.  All I know is now I ha e to use my old GPS watch when I want to do GPS based exercise.

[AlejandraFitbit]

Thanks for the information @MayLeaBee. I just would like to know if you have compare your GPS information with another app? If you haven't, I recommend this and also check that if this information is being registered correctly in the Fitbit app. Also, if you can provide some screenshots of what you are seeing would be great.

Hope to hear from you soon. 

[MayLeaBee]

Yes.  That is what I stated in previous post.  I have fitbit linked to Strava so fitbit is sending data to Strava.  Strava shows the actual distance correctly with the raw data it receives as I have done this ride before and know it should be around 14 miles.  Strava is also more correct as far as elevation gain.  This behavior appears if starting exercise from the blaze and if road cycling at higher speeds.  This issue does not seem to be as bad with slower pace mountain biking started on the phone and calling it a run since biking is not an option in the app itself on ios.  Therefore the raw data is correct but something is happening in how fitbit looks and interprets this data.

[Dries]

did the test 2 times now , and this time i did not start the run excercise from my blaze but directly on my phone in the fitbit app,.

These 2 times it registerd the distance correctly so there is something different happening to calculate the distance of your run when using the blaze to start the excercise.

[MayLeaBee]

Yes.  That is what I am seeing.  Correct if started on phone.  Incorrect sometimes (don't know how often would have to go back and look) if started on Blaze.  The point of having the Blaze is to control your GPS runs or cycling on the Blaze, not continue to use the phone.  Don't want to have to pull out the phone during a ride