Walk 2: Steps Counted
I suppose it's not surprising that two different pedometers would yield closer results over flatter terrain, but I think it's pretty impressive that they are so close. Both devices also show a pace of about 1755 steps per mile, which as I mentioned earlier, is consistent with the typical number of steps I cover per mile while walking casually.
Walk 2: Floors Counted
Coincidentally, Walk 2 also featured exactly 2 real flights of stairs, which the iPhone 6 counted precisely. Once again, the iPhone 6 counted only true floors, while the Fitbit's floor count is more indicative of walking up hills in general.
I have to say, I'm a bit surprised that the Fitbit counted so many more floors given my perception of the elevation changes that I encountered, but I think this just further underscores the Fitbit's sensitivity to elevation changes while your feet are moving.
Counting real floors
Since my two walks show just how differently the Fitbit and iPhone 6 count floors over varied walking surfaces, I thought it would be interesting to see how they performed in a more controlled, "industrial" setting. So I decided to walk up to the sixth floor of a parking deck in downtown.
According to at least one source, the standard height of a parking deck story is 10 feet. The parking deck I chose, to me, looks like most any parking deck, but it's worth noting the first flight was slightly shorter (maybe 25% shorter) than the others because the first level of the deck is actually a little below street level.
At the 6th floor, the Fitbit was dead-on at 6 floors, while the iPhone 6 recorded only 5. It's quite possible that the shorter first floor caused the iPhone 6 to fall just a little short, but that's impossible to know. Unfortunately this parking deck only had 6 floors, so I couldn't go a little higher to test that theory.
It would be interesting, if tiring, to test this in a really tall high-rise to see just how much, if any, the two devices diverge in such a continuous, controlled setting. If you do this, let me know how it goes.
But as I noted earlier, both the Fitbit and iPhone 6 consistently measure floors climbed in my home with equal and exact precision.
Effect of non-walking motion
First World humans have many ways of moving up, down, and sideways that don't require moving feet. Obviously, just being able to detect small changes in barometric pressure isn't enough to detect steps. Otherwise, we could really game step counts by taking elevators and escalators.
Both the Fitbit and iPhone 6 performed equally well (zero activity) in an elevator in my testing. In other words, both devices are really smart about the motion pattern that defines a human step going up stairs.
Driving in a car, however, is a tougher test than an elevator because of all the little bumps and undulations in a typical car ride. I was curious what effect, if any, driving had on the Fitbit and iPhone 6.
I tested this by looking at my Fitbit and iPhone 6's step counts before and after driving across town. It was a roughly 15-minute drive that covered everything from residential roads to a 6-lane interstate.
The Fitbit correctly recorded zero steps, but the iPhone 6 logged 18. This surprised me a lot.
First, I was impressed that the Fitbit was good enough to know all the little ups and downs were not the result of taking steps.
Second, it's funny that the iPhone 6 got beat considering it has the potential to gather so much more contextual information. Compared to the Fitbit, the iPhone 6 is a super computer. My iPhone 6 is totally aware of my current speed, which it could use as a check on the step count. For example, if my body is moving at 65 miles per hour across the earth's surface along a coordinate path that matches a known interstate route, I'm probably not walking.
As with any arbitrary measurement system, it's more meaningful to look at trends than fret over individual data points. Fitbit and iPhone 6 are both terrific at measuring steps, and both inform you about your movement over time. If you walk from A to B, both will credit you steps for that, even if it's a slightly different number of steps.
When it comes to measuring floors, the Fitbit is clearly more sensitive to elevation changes than the iPhone 6. However, the iPhone 6 is a networked, location-aware computer. If elevation really matters, it's probably better to use something like MapMyWalk to more accurately measure vertical distances anyway. A "floor" is just an arbitrary unit of height after all. It really only makes sense for people who mostly walk indoors.
Rather than get hung up on data accuracy, I think it makes sense to focus on the main goal: move more. I'm absolutely fascinated with the fact that small computers can constantly measure my motion and give me incentive to move more by constantly informing me about my movement patterns. I fully expect the Apple Watch and its future descendants to take this to an entirely new level.
I'm no anthropologist, but I believe the version of the human body we inherited evolved to move around a lot—certainly way more than we move in modern environments. If the first generation of computers made us sit down, hopefully the next generation will put us back on our feet.
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3/28/2015 Update: Elliptical Test
I decided to see how the Fitbit and iPhone 6 differed on a NordicTrac elliptical. I was on the elliptical for 20 minutes straight, covering a (supposed) distance and elevation of 1.7 miles and 895 feet, respectively. There were a variety of resistances and inclines.