FAQs > Fun Stuff > Why does the race course measure too short according to my GPS?

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Often GPS watches / smartphones will measure the course shorter than it really is. This is because GPS takes measurements periodically, not continuously. When you make a tight turn, which is common in DINO race courses, the GPS will often shortcut through the turn. We have found that GPS usually measures 5% to 10% short on a typical DINO course. This also means the pace/speed shown on the screen is 5-10% slower than you are actually running or riding.

This graphic was made with a GPS watch on a high school running track. Four laps in the inside lane were recorded. Notice how the lines shortcut the curve. Also note the variation of position, even though each of the four laps were run in the same lane.

Making matters worse, heavy leaf cover reduces the accuracy of GPS and it will pick up even fewer data points. Thus, recording in the summer often yields less accuracy than in the winter (up to 20% short)

Last updated on February 9, 2017 by holzhaus