You can see the effect on this heatmap: <a href="http:&#x2F;&#x2F;labs.strava.com&#x2F;heatmap&#x2F;#15&#x2F;116.40337&#x2F;39.96947&#x2F;gray&#x2F;both" rel="nofollow">http:&#x2F;&#x2F;labs.strava.com&#x2F;heatmap&#x2F;#15&#x2F;116.40337&#x2F;39.96947&#x2F;gray&#x2F;b...</a><p>There is a &quot;ghost&quot; trail a few meters to the east of the real trail.