I've got the 42mm SS Apple watch and want to use it for tracking my outdoor runs (i.e. distance, calories, etc...). Since I do not plan to carry my phone with me, I'm trying to calibrate first by carrying my phone with me on a few runs....per this article on the topic from Apple: https://support.apple.com/en-us/HT204516 Here is the issue I'm having: I went to a regulation 440 yard track today to run 2 1/2 miles to calibrate the watch. I carried my 6 Plus with me on the run. The problem is that my my watch measured 2.71 miles when I only ran 2.5 miles. Now, my wife also has an Apple watch and we ran together today (both of us carried our phones) Her watch registered the 2.5 mile run as 2.54 (very close), but mine was way off! I tried this once before on a different track, but ran 3 miles (carrying my phone) and the watch registered 3.25. This is only about 92% accuracy rate carrying my phone (i.e. with GPS). I've got both location services and motion calibration & distance turned on (on my phone), both of my test runs were well over 20 minutes and the tracks where I've done my test runs are both in wide open areas (clear access to the sky...so GPS connection should not be an issue). Just curious if anyone else has had this issue? One question I have: When I carry my phone, I don't have any particular app open (i.e. apple watch app, activity app, etc...) and the phone is in sleep mode (i.e. display goes off). Does GPS work when the phone is in sleep mode? Could this be the problem?