I think both this explanation and the one in the article are correct, but ignore the fact that GPS distance measurements typically are made by summing the distances between many correlated noisy position measurements.<p>[GPS devices must use frequent position measurements because approximating a continuous real path by line segments will underestimate the length of curved paths]<p>Because of that, the largest contribution to the summed error of the distance between points A and B does not occur when the position of B is erroneously measured at a position B&#x27; that is farthest from A. Reason is that, likely, the next measurement will happen when the GPS device is at a position C such that B is roughly halfway between A and C. That means B&#x27; lies in the direction of C, and the distance between C&#x27; and B&#x27; will be smaller than that between C and B, correcting for the measurement error between B and A.<p>Because of that I think it is more insightful to describe the measured path as randomly zigzagging around the actual path. For any reasonably smooth real path such a zig-zag path will be longer than the real path. Even if the real path zigzags around a lot, it is very, very unlikely that the measurement errors happen to undo the zigzagging.<p>[paper at <a href="http:&#x2F;&#x2F;www.tandfonline.com&#x2F;doi&#x2F;full&#x2F;10.1080&#x2F;13658816.2015.1086924" rel="nofollow">http:&#x2F;&#x2F;www.tandfonline.com&#x2F;doi&#x2F;full&#x2F;10.1080&#x2F;13658816.2015.10...</a>, by the way]