I did a quick ride to test the GPS. As to the distance, I must say is fairly accurate.
According to Endomondo, I did 3.89km
. Also, the path doesn't seem so bad as yours. Considering the road is always curving, I think the straight line between two points on curve is acceptable. Look quite straight on the longer stretch.
After checking my stats on Endomondo site, I opened up Google Earth, and drew by hand the exact path I took (Included in the screenshot below). I tried to reproduce my path as I was going around manholes, joggers, cats, taking a turn into car park to wave hello to a friend.. etc....
According to Earth, the distance is 3.88km
, that's off by 1m.
I would seriously expect more inaccuracy, and I would be very happy if it was rounded up to 20 meters. Even 50 meters would be fine.
I always had very good results with Endomondo. In the period of about two years , it only messed my activities twice. Once it made me run at 70km/h and triple app my millage
Once cut me short 3km. That's very little error given I use it almost every day.
By the way, my WIFI was off, I only use DATA. Perhaps is not just phone but the GPS signal or satellites itself ?