Stride length determinations

[JoeGV]

In the App, under advanced settings, one can put the "set automatically" option on.  So here're my questions.

If it's set to on, does it override stride length for walking at some other length too?  Can one see what that adjusted run stride is anywhere?

I ask, since I walk fairly fast for my walks.. like 4mph.  And I notice that my route is calculated to be shorter than what my other aps had shown.  Also, my speed is like 3.9mph vs my 'normal" 4.0-4.1.  

I guess related to this is a question about having the GPS option on/off.  I may start a different topic on that, but I'll bring it in here anyway.  So, is the GPS used to determine ones speed while walking?  Is distance determined by the GPS or just by step number and stride length.  Sorry if confusing.

In summary.. how does GPS and auto stride length impact recorded distances?

Thanks

[Julia_G]

Hi, @JoeGV , auto stride length setting simply calculates your stride length based on the average person of your height.  Without GPS turned on, the Fitbit calculates distance based on stride length times number of steps.

If you find that your distances seem to be short, it may be that your stride length is different from the average person, and therefore you may find you get a more accurate calculation by entering a custom stride.  You can find information about how to do this here.  

Obviously Fitbit does not reveal the details of the algorithms that it uses to calculate its stats.  My understanding is that if GPS is turned on, the distance and speed are calculated using GPS and not stride length, although you may find that some users question this.

[JoeGV]

I'm not looking for the formula and I understand how to manually adjust stride length.

But, if the button is set to use GPS, does that new length change the walking length too?  What happens if one WAS set with GPS, but then later one has the GPS set to off on the HR?  Or what happens when one sets the button to set automatically to off AFTER it was one for a few days?

It's not clear as to what really happens.  I don't need to know HOW, just WHAT happens with these options.  Frankly I would think that having it set automatically would be the most accurate, but I didn't notice ANY change in my route lengths or speeds unless I adjusted my walking stride length manually.

I'm thinking that the GPS set to on on the fibit, just gets the route to be saved on the map.  The route distance covered is determined by stride length... NOT by the distance of the route covered.  With my Phone ap (Samsung Health) it used GPS to track speed and distance without using stride length.  This methods appear more accurate when using a GPS option.

[Julia_G]

@JoeGV , whenever auto stride is set to ON it will use a standard stride length for calculations.  If you turn it OFF, it will use your custom stride length.

It will not make any retrospective changes to distances of walks previously taken, even if you later turn it on or off.

If you use GPS then my understanding is that stride length settings are irrelevant, as the Fitbit program will use GPS to determine distance and speed.  Some users, however, have disputed this, but I am fairly certain that Fitbit has not addressed this issue to confirm either way.  

Using GPS for a walk (or walks) will not cause your auto stride length to be updated or corrected.  You will need to adjust this manually yourself if you believe the auto stride to be incorrect.

Does this clarify?

[JoeGV]

Julia,

Thanks.  Your response makes sense.  However, like your post indicated.... I wonder if that's what we all get.  It is what it is though.

Thanks, as I wan't clear how the GPS and stride length interacted.

[LZeeW · Accepted solution]

@JoeGV   I think @Julia_G misunderstood your first sentence.  I want to clarify a few things.

• When you set up your account, Fitbit sets default stride lengths based on height, gender, etc.
• Users who have different walking/running styles might want to measure their stride lengths for features where the distance is being calculated using a steps x stride length (non GPS activities or GPS turned off).
• The Set Automatically ONLY refers to the running stride length when using the Run option using GPS.  You cannot auto-adjust your walking stride length.
• If you walk using SmartTrack (autorecognition) the distance is a steps x stride length.  You do not get a specific distance in the Exercise Summary, but the distance is added to your daily total.
• If you walk using the exercise app with GPS on, your distance is the GPS distance and the number of steps is what the tracker recorded.
• If you walk using the exercise app with GPS off, you get a steps x stride length distance.  Some reasons to walk with GPS of would be known bad satellite connectivity or tunnels along the route.

If you always use GPS during your walk, there is no reason to manually measure and set your walking stride length.  If you don't use GPS and you set your walking stride length manually, you might get into some distance issues and here is why.  Generally as we walk faster, our stride length tends to shorten.  A length that is set manually is good at the speed measured.

If your 4 mph stride length is a lot different from your "just walking" stride length, then you might want to try tracking these Walks as GPS connected Runs with Set Automatically ON -- but only if you don't run.  That would mess with you running stride length.

Does this help?

[JoeGV]

LzeeW

That's how I suspected that it acted.  I was wondering if the algorithm overtook both stride lengths.  Also, did the GPS only get used for a map trace.  Your description makes pretty good sense... and thanks.

I still subscribe that Fitbit's distance (through the GPS) is flawed.  I say this since I've tracked my route with 2 different apps (though they may use the same program) and get a faster and longer route (google maps and Samsung's app.)  It's not a big deal, but I was surprised with the differences.- about 3% difference.  I did notice a different pace when I used the self set stride length too.

One point that I think you cleared up is the order of how distances are computed and speed computations.  I didn't know that when one is setting run stride automatically, if that would adjust the walking stride.  You indicated probably not.. and that makes sense.  

Thanks again!

[4gary]

I've used and compared my fitbit gps and my samsung health gps at the same time when going for walks, and both are always EXACTLY the same (maybe a few steps off, like less than  10) in every respect. Therefore I know for sure that Fitbit uses gps during a walk.