When Your Garmin and Race Distance Don’t See Eye-To-Eye: The Truth About USATF Certified Courses

We often get questions about course length and why your Garmin, the Ride with GPS map, or your route measures longer than the distance of our certified USATF courses. Since many of our courses over the years have become USA Track & Field certified and it can be confusing, we will break it down for you:

1. First off, most of our courses are certified and accurately measured by a course certifier with USA Track and Field, the governing body for road running in this country. That means they are measured using a standard bicycle fitted with a calibrated mechanical ‘Jones Counter’ on the front wheel. This method ensures that the course is measured by the shortest-possible route available to runners on race day. Courses are NOT measured by GPS, a garmin device, a watch, a tape measure, surveying equipment, car or by walking with a measuring wheel.

2. Courses are measured from start to finish multiple times and typically on multiple days. Each course final measurement must be within a certain distance of each other or additional rides must be completed until it is spot on perfect according to the USATF certification rules. A detailed map and worksheet are submitted to USATF after the course certification to be reviewed, analyzed and approved.

3. Courses are measured by the shortest-possible route available to runners on race day. This means that the measuring bicycle is ridden within one foot of the curb and turns are “straightened out” as much as possible. This means we are certifying the course as if you are running the tangents (not the curves) on the race course. This method is used to ensure that no one runs shorter than the stated distance. With other runners on the course, this shortest route can be difficult to run exactly as measured.

4. But wait, why does this mean GPS readings on the course are almost always slightly longer than the distance measured with this mechanical counter? Well, there are several reasons for this. All certified courses include a 1/10th of 1 percent “short course prevention factor.” This is a small extra cushion to make sure no one runs less than the stated distance. For example, a certified 10 km (10,000 meters) road race is actually measured as 10,010 meters.

5. Additionally, consumer GPS devices are not 100% accurate and are typically 1-to-2% off. GPS accuracy is affected by elevation, the number of turns, mountains, tree coverage, tall buildings, bridges, overpasses, and the quality and quantity of satellite reception. In other words, there are a lot of variables that can affect the accuracy of your device. While the GPS watch is a useful and informative training device, runners have come to understand and accept that the information it provides about distance, paces, average pace, elevation, etc., though very close, is not completely accurate.

6. It’s important to note that mile markers, though accurately measured, are not certified. Only the TOTAL race distance measured is certified. This is why mile markers may fluctuate their position from year to year on a course and not be in exact locations.

So, when it comes down to it, trust the ‘time’ function on your watch but know that the distance feature will almost always give a reading that is “too long” when used on a certified course. It’s just the nature of the beast!

If you want more information about how courses are measured, visit the “Course Certification” section of the USA Track and Field Website. And of course, if you have any additional questions, don’t hesitate to reach out out to us directly at iDaph Support: support@idaph.net.