You can see the effect on this heatmap: http://labs.strava.com/heatmap/#15/116.40337/39.96947/gray/both http://labs.strava.com/heatmap/#15/116.40337/39.96947/gr

You can see the effect on this heatmap: http://labs.strava.com/heatmap/#15/116.40337/39.96947/gray/both http://labs.strava.com/heatmap/#15/116.40337/39.96947/gray/b... There is a "ghost" trail a few meters to the east of the real trail.