Went for a run over the weekend - started my Garmin 220 watch ( which I have been very happy with) - but at the end of the run when I looked at my "average pace" - thought , "something majorly wrong here"
But I had to leave it until I got home and logged into the Garmin page. Everything looked OK there - nice straight GPS track - but Google maps showed me that the distance I ran was 1 klm longer than what Garmin was showing in the time of the run. When I scrolled across the timeline, the Garmin track trace got to around 0.5K from the start and then 2 seconds later it jumped ahead several street crossings and started counting from 0.5K onwards!! So it recorded the correct track on the map - but measured it at 1 klm shorter than it really is!!