Why Your GPS Watch Doesn't Match the Race Distance

Why GPS Doesn't Match Race Distance

You did it. You crossed the finish line of your much anticipated goal race you spent two months training for.

Then you look down at your GPS watch only to find out that the mileage doesn't match the distance you'd signed up to run. This can be an incredible source of frustration for runners, especially those gunning for a new personal best.

The course, according to your GPS, was either too long or too short, leaving you confused and not knowing what to believe. But which is right—the course or your GPS?

Before you send an angry email to the race director, here are some factors to consider about the course distance.

USATF Certified Courses

When doing research on which race to register for, you should check to see if the course is certified by USA Track and Field (USATF), especially if you have a specific time goal for that distance.

USATF has Road Course Certifiers who use a scientific method to certify that a race's course is actually the distance it claims to be. Race directors hire these Road Course Certifiers to measure the course and ensure that athletes are getting the distance they paid for.

This is especially important when it comes to world records, championship races and qualifying for other races. Once a course is certified, the certification stands for 10 years or until the course is changed.

While USATF does want the course to be as exact as possible, they'd rather a route be a foot too long than a foot too short. Because of this, they have a Short Course Prevention Factor of 0.1 percent built in. For example, a 10K course (6.21371 miles) is measured out to at least 6.21992 miles to ensure it doesn't come up short.

You can always check to see if a race course is certified by checking the USATF website. Occasionally races make mistakes by placing mile markers in the wrong spot on the course, but if the overall course is USATF certified, you can be sure that it's the correct distance.

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About the Author

Beth Shaw

Beth Shaw is a USA Track and Field Certified Coach and a US Masters Swimming Certified Coach who has completed numerous marathons, road races and an Ironman triathlon. Beth writes a fitness blog called Discombobulated Running and has contributed to Women's Running. She also coaches runners to reach their athletic goals. You can follow her on Twitter.

Beth Shaw is a USA Track and Field Certified Coach and a US Masters Swimming Certified Coach who has completed numerous marathons, road races and an Ironman triathlon. Beth writes a fitness blog called Discombobulated Running and has contributed to Women's Running. She also coaches runners to reach their athletic goals. You can follow her on Twitter.

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