iPhone Health app distances walked are always inaccurate

Not terribly helpful, SravanKrA. :-(

1) Yes, I am keeping the phone with me while I am walking (duh!), and I am walking over measured courses, whose distances are known and documented, i.e. 1/4 mile running tracks, urban streets whose distances have been measured with both an automobile and Apple's own Maps app (both of which match each other). But my iPhone Health app consistently records a 4-mile loop as 3.1 miles... a 2-mile loop as 1.4 miles... and a 1.5 mile out-and-back as 1.1 miles.

2) No, there is no manual step counting. Strictly relying on the Health app and the iPhone's internal systems (should be gyro, GPS, etc.).

3) The "app or instrument" that is consistently wrong is the iPhone 13 Health app. The others (fixed measured distances over flat terrain) consistently match each other to within a few hundredths of a mile.

After speaking with three different Apple tech support representatives, we appear to have finally resolved the problem.

Unfortunately, Apple's iPhone instructions tell you to simply "carry iPhone with you to count your steps..."

https://support.apple.com/guide/iphone/track-health-wellness-iphone-iph62fd9714f/ios

This is incomplete. Other more detailed instructions elsewhere instruct you to carry your phone close your waist, so it records your movements more accurately. However, in the past, Apple has also warned that iPhones should be carried "at least 5mm away from your body" to ensure (radiation) exposure levels remain at or below the as-tested levels.

Thus, according to Apple, iPhones should *not* be carried in a pants pocket (although many people do) because of potential long-term exposure hazards. That's one reason why many people carry their iPhones in a purse or fanny pack (as I have for years), or even a belt case or backpack.

But one of Apple's Health app tech support experts yesterday said doing this will cause significant inaccuracies in walking / running distance measurements on the iPhone. He said in order for these measurements to be accurate, the iPhone must be carried in one's pants pocket, so that the accelerometers can better detect the movements of your legs. The iPhone's GPS signals alone are not sufficient to deliver distance accuracy. They must also have accurate leg movement and step counts via the accelerometer input.

He also said that the iPhone will recalibrate itself within two or three 20-minute walks once you've repositioned it in a pocket. I found this to work. I took a half-hour walk last night with the phone in my pocket, followed by another that was close to five miles this morning, and the iPhone was recording my distances far more accurately than before.

This is unfortunate mixed messaging from Apple, but at least the inaccurate distance measurement problem has been resolved.

I suspect it would be wisest to continue to carry an iPhone a minimum distance away from your body (such as in a purse or fanny pack) for everyday use, but to switch it to a pocket temporarily when more accurate recording of your walking / running distances are desired. 🙁