You may have noticed that the elevation profile wasn’t showing up properly. The path used to calculate the elevation profile was only the last segment of the route. This was a hold over from the last big update where the route length limit was erased. Now the elevation profile is calculated over the course of the entire route.

In itself this update doesn’t really merit a post. I’m making the post because I wanted to point out the limitations of the elevation service. The elevation is calculated from 500 points equally spaced along your route. If the the points are very close and the profile will be very accurate. If the the points will be spread out and the route will be inaccurate.

According to signal detection theory you must sample twice as fast as the signal you are trying to measure. In other words, if you want to find the height of the peak of a hill you will need to take elevations that are separated by only half the width of the peak. So if the peak of the hill is only 50 feet across you will need to take elevation measurements every 25 feet. Given that there are at max 500 elevations taken from a route, that route will be only 2.367 miles long. This example may be a bit extreme but it illustrates how the elevations can be inaccurate.

Keep this in mind when bragging to friends. You can always say the hills were even taller because the app missed the true peak of the hill.