Thanks for that information. Sounds reasonable, but like you said, never know for sure with Apple's secrecy on a lot of its functions.

I do not care about steps; only distsnce. I was wondering if after doing a long-stride outdoor walk, when I come inside, and just putter around the house, the GPS may not be able to pick up all that small movement, so wondered if my actual step is then sensed, and the distance is extrapolated from that. Half mile to a mile just around my house seems grossly over-estimated. Or perhaps, the GPS itself cannot accurately detect distance on small back and forth movements.

I did a 6-mile walk yesterday, that I have previously traced on an actual Garmin GPS, and it was spot on with the I-phone.

Another factor may be that cell coverage is spotty (never get more than 2 bars) so perhaps parts of my walks are not recoreded at all.

Just saying that if you plan to use your I-phone for distance on actualy backpacks, be careful!