How a Marathon is Measured

Olympic race distance calibration is a fine-tuned science

(RxWiki News) The Olympic marathon distance is difficult to accurately measure at over 26 miles. A team of scientists worked together to come up with near perfect calibration.

Marathon runners in this summer’s Olympic games can rest assured that the race distance is as precise as can be. The calibrator was tested in a climate controlled environment down to 15 hundredths of a degree.

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Researchers and technicians, led by Chris Blackburn, a physical science technician from the National Institutes of Standards and Technology (NIST), were asked to calibrate the tape that will officially measure the marathon distance at the 2012 Olympic Games.

The Olympic marathon is 26 miles and 385 yards long. The International Association of Athletic Federations (IAAF) didn’t award world records for the marathon event until 2004 due to the difficulty of accurately measuring the length of the course.

In the 1970s, the Jones Counter was created. It counts the revolutions of a bicycle wheel and can be compared to a measuring tape for calibration. Then the revolutions can be counted to determine any length.

The NIST ran into one problem. For the marathon distance, they needed a 100-meter tape, which is longer than the testing space at the NIST.

Blackburn said, “The uncertainties associated with our laser interferometer system are very small. And, by applying the proper tension in the tape to pull it straight and keeping the temperature at 20 degrees Celsius, plus or minus 15 hundredths of a degree, we achieve uncertainties of 0.00018 meters, which meets or exceeds our customers’ requirements in most cases.”

Originally the IAAF contacted David Katz of Finish Line Road Race Technicians, Inc., and his colleague, Hugh Jones, to help with the measurements. Katz enlisted the NIST for their calibration expertise.

Katz said, “I was thrilled with the result. This level of agreement, with a difference of about two centimeters per mile, is pretty remarkable.”

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Review Date: 
July 6, 2012