I started running on a new trail and have run three times. It is an out-and-back with clear markers. First two runs, the GPS on the watch measured 5.15 miles. When I ran on Saturday (maybe after a software update), it measured the same run as marked on the physical trail at 5.01 miles. A difference of a 10th, which seems way off given the physical landmarks I can check. I wondered if the new feature of reducing workout time with a slower heart rate is causing the watch not to measure my actual distance correctly? Or is the GPS a 10th of a mile off in error, which would be a lot these days.