The waypoints are not distributed regularly, but the track points are.<p>Here is why performance mattered in my case.<p>I needed to predict future positions of the cyclist (see <a href="https:&#x2F;&#x2F;www.ibm.com&#x2F;developerworks&#x2F;community&#x2F;blogs&#x2F;jfp&#x2F;entry&#x2F;Predicting_Cyclist_Trajectory?lang=en" rel="nofollow">https:&#x2F;&#x2F;www.ibm.com&#x2F;developerworks&#x2F;community&#x2F;blogs&#x2F;jfp&#x2F;entry...</a>).  The computation relied mostly on weather forecasts provided for each track points.<p>I then needed to know where to start my computation, i.e. find the track point closest to the current location of the cyclist.