Is there any explanation for my observed lack of accuracy (off by maybe 20%) when walking indoors (i.e., without GPS)? I have set an accurate custom stride length in the Connect app and I know my walking pace +/- a minute a mile. But in numerous outings, I can walk at about an 18 minute/mile pace while the 645 ends up clocking me at 22 min/mile, making a measured 4-mile walk record as only about 3.2 miles on the 645.
Since distance can be easily computed from time, step length, and step count, I can only conclude that the steps are not being accurately counted by a good bit. Is this a known issue? I made particularly sure the last time to keep my hands free so my arms were swinging normally -- isn't that how it counts steps?
