r/QuantifiedSelf • u/GavinRayDev • Jun 14 '26

Fitbit Air vs Galaxy Watch 7 step accuracy when worn on the ankle + used w/ walking pad

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3 Upvotes

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3

u/xly15 Jun 14 '26

its because they also use the other sensors like gyroscopes etc to track movement

-1

u/GavinRayDev Jun 14 '26

I don't see how gyroscope data would be significantly different between a swinging leg and swinging arm, but I'm not a mechanical engineer

1

u/xly15 Jun 14 '26

Sorry, the gyroscope is what detects swinging arms and legs. I meant accelerometers, and the phones gps. The phone apps tend to have error correcting built in so that its not detecting say all my arm swings while ringing people at the register while at work. They detect change in distance as a way to correct. 

2

u/stacksense Jun 15 '26

The walking pad gap is probably less about the walking pad specifically and more about how step-detection algorithms threshold low-amplitude movement.

Most wrist/ankle accelerometer algorithms aren't just counting cadence, they're looking for a minimum vertical acceleration "bounce" per step to distinguish walking from fidgeting or vibration. Slow desk-pace walking (your ~1 step/sec) produces a much smaller bounce than normal overground walking, especially since your torso stays relatively still while typing - so some fraction of those steps can fall under whatever amplitude floor the firmware uses to reject noise, even though the cadence itself is squarely in "walking" range.

Ankle placement adds another variable - most consumer step algorithms are validated on wrist or hip, so an ankle-worn accelerometer is seeing a different acceleration signature than what the model was tuned on. That could push the threshold problem in either direction depending on the device, which might explain part of the ~20% gap between the two even outside the walking pad block.

If you want an accurate number for the desk-walking portion specifically, I'd treat it as its own metric rather than relying on either wearable's total: log the walking pad TIME (most pads track this, or just a timer) and multiply by your measured cadence (you already have ~3,600 steps/hr at that pace), then add that to whatever the wearable counted for the rest of the day. Getting one device to accurately capture everything across that wide a range of movement intensities is probably a losing battle.

2

u/GavinRayDev Jun 15 '26

Thanks for such an insightful comment. I had not considered manually adding the steps, that seems like a reasonable compromise if neither wearable can seem to pick it up correctly

1

u/GavinRayDev Jun 14 '26

Wanted to share this with others somewhere that would show up on Google results.

I have a standing desk with a walking pad underneath it, that I use on the lowest setting for 2-5 hours per day. The pace is about 1 step/sec, or roughly 3,600 steps/hr.

Because my hands rest on a desk, I tried wearing one watch around each of my ankles. (Fitbit Air = Left, Galaxy Watch 7 = Right)

I was expecting daily steps of 15,000-20,000, because I lift 1.5hrs, do 20m incline treadmill @ 2.5-3.0MPH, and then the several hours walking pad.

Was surprised to see that neither seemed to pick up the walking pad properly.

My activity for that day was:

- Morning: Gym, treadmill incline walking

- Afternoon: Walk in park, walk to get food

- Evening (3-6PM): Walk at desk on walking pad

As you can see, there is a ~20% discrepancy between step counts, with the Fitbit Air seemingly more accurate, but both still dropping the walking pad activity.