Does the Health app measure walking distance by GPS or by estimating stride lenght and steps taken?

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Does the Health app measure walking distance by GPS or by estimating stride lenght and steps taken?

I need a specific answer to a specific question, please, about the Health app on my iPhone 6s running ios 9.whatever.

Does the Health app measure walking distance by GPS or only by estimating stride length and steps taken?

I've browsed message boards about this question, and the consensus seems to be that the phone does NOT ping GPS while I'm walking, to keep track that way of where I am and how far I've walked from point A to point B. Instead, it merely counts my steps and uses some sort of algorithm to estimate how many miles I've walked, if I've taken that many steps. Since I have never been asked by the phone to enter any physical data such as my height or my average stride length, it's hard for me to believe that any such estimate could be anywhere near accurate except by dumb luck.

So back to my question. Can anyone confirm for me accurately if the phone does or does not use real GPS information to determine how far I've walked, or is any distance walked that it reports in the health app merely an estimate or a SWAG based on its step counter?

Thanks.

Tom

iPhone 6s, iOS 9.2

Posted on Apr 13, 2016 4:23 PM

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James C Austin

Level 1

74 points

May 25, 2017 4:59 AM in response to gtomseeley

Tom, I cannot CONFIRM anything; I'm just another iPhone user. What I can say, based on my own experience and other reports, is that if Health uses GPS to measure distance walked/ran it does so in a complicated, inaccurate way. My wife and I have been walking together nearly every day, side-by-side, and her Health-measured distance are consistently 10-20% larger than mine. We both have iPhone 6s with current IOS. The two phones were bought at the same time. There's no evidence that GPS is faulty on either phone; Google Maps, for example, works perfectly. I've used Map My Walk and NikePlus and both do a decent job reporting distance.

Also consider that attempts to measure walking/running distance using only GPS would have to fail--how do you distinguish running from biking? From riding in a car? Even if GPS is used, that data has to be cross-correlated with accelerometer data, or some other kind of data. If I ride a bump road, does the iPhone think I'm walking? What if I walk with the phone in my pocket with very smooth strides? If I get up and bounce on the pedals of my bike, will it record that as running?

My point is that trying to distinguish different modes of motion is hard. On Nike+ or Map My Walk (or Run), you tell it when to start and stop. Presumably, if you got in your car and drove 5 miles, it would report that distance as the distance you've walked or run, because you started off telling it your run (or walk) was starting. The Health app can't do that, since it's going all the time. So it has to figure out when you're actually walking. You can't do that with just GPS.

In any case, it's unreliable.

Best,

Jim

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