Newbie stride length/gps question

[wicked_sticky]

I'm sure this has been asked and before, but I can't find it. 

I upgraded from an inspire HR to a Versa 2. The inspire was very close to accurate, the versa is consistently over by 10-13%. Im not asking how to fix it, I've got 2 questions about how FB work.

1)Does fitbit calculate automatic stride length by my sex/height/weight or is it being constantly adjusted with GPS data? 

2)Inspire HR had the option to switch connected GPS on/off. Versa 2, can only do that in individual tracked exercises. Does this mean connected GPS is always off or on? (when not doing tracked exercises)?  ie the train station is 0.2miles away... that 4min walk does not show up as an activity, so were those 400 steps calculated by GPS or arm movement?

Versa 2 is massive, Im probably moving my arms differently and throwing off the step count. I'm wondering it will self adjust/

[SunsetRunner]

Hi @wicked_sticky , a 4 min walk is indeed not registered by the Versa 2 as the minimum period is 10 min. Regarding the inaccuracy in steps, indeed the Versa 2 calculates your step amount by your physics. If it does not adjust within a few days, that are needed to adjust to your activities, then you press the account icon in the dashboard of your Fitbit app, scroll down to advanced setting, press it and then scroll down to stride lenght and adjust it accordingly. Regards kuzibri

[LZeeW · Accepted solution]

@wicked_sticky   With respect to stride length, Fitbit uses known average stride lengths based on gender and height.  Perhaps the only reasons to manually measure your stride length is if you have atypical proportions (all legs or all torso) or if you have a restricted gait.  Something like that.

Fitbit will do a GPS adjusted run stride length, but there is a specific setting in the app.  Tap on your profile picture > Advanced Settings > Stride Length > toggle it to ON.  This only adjusts running stride length, not walking stride length.  This is an app setting.  You could have done this with your Inspire HR.

While you have the ability to have the GPS on or off for each GPS connected exercise, GPS is only on and active when you are using it and the little phone icon says connected.  When the GPS is not connected any distance is a steps x stride length, just like your Inspire HR.

It is interesting that your experience is that the Versa 2 overcounts.  I have used the Versa 2 and the Inspire HR.  As a long time Fitbit users, I have also used a Charge 2 and a One.  My experience is that the Inspire HR overcounts steps.  But, that's one observation.

[wicked_sticky]

LZeeW, all good info. 

After reading your answer, I re-thought my question's premise. There are tons of articles saying to make you step count more accurate adjust you're Stride length. But Fitbit uses that 3-axis sensor to count steps. Stride length would never have a bearing on step count, its just there to estimate of how many miles I walked when the GPS is not on.  

Am I right in now thinking the sensor will detect the same motion as a step Weather I tell it Im 5'0" or 6'8" have a 20" stride length or 35" stride length?

[LZeeW]

@wicked_sticky   Yes, your final statement is correct.  The accelerometer detects the motion and counts the steps.  The number of steps x the stored stride length calculates the distance.  Most of the threads you are referring to are distance questions and come from users who say things like, "I know I walked a mile because the trail is marked.  My Fitbit doesn't agree."  (GPS not being used).  Stuff like that.

I want to add some addition information.  Users might wonder why they would want to track an exercise with the GPS off.  One of my favorite routes goes through a tunnel.  GPS is useless.

[wicked_sticky]

yup, my new hypothesis, some coincidental thing is causing the versas over-counting. Like: 
I'm checking the versa more, or swinging my arms more because I'm not used to wearing something so heavy, or when I tested the inspire I was 30lbs heavier and my fat arms might have swung less, or the versa has better sensors thus more sensitive to detecting motion (the inspire was more likely to miss a step if Im holding my arm steady enough to read the display, I have to put effort into how I walk to get the versa to not count a step.

That's just a pointless final thought, count doesn't really matter, as long as its counting the same way consistently.  

[JoakimK]

Hi, I was tour skating (ice skating) and my Fitbit device used my iPhone's GPS to correctly map the track (geographically) on the lake. However, the distance calculated by the device was 3.0 km whereas the actual distance was 6.8 km (which was measured by me manually afterwards). Since there is no "tour skating" activity defined in the device I had to choose "running" to get some kind of log of my activity in the first place. I suspect that the device then used my stride length to calculate the distance rather than the GPS data.

1) Is there a way to ensure that GPS data are used instead of stride length in future distance calculations?

2) Is there a way to re-calibrate an already logged track by applying the recorded GPS data (and discarding the track length calculation based on stride length)?