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Marine Corps Marathon

A Race Made To Measure

Published February 23, 1998, in The Post-Standard.

By Dr Kamal Jabbour, Contributing Writer

On the morning of the 1997 Marine Corps Marathon, Bob Thurston rode the course ahead of the runners looking for problems. Thurston is the regional USATF certifier for the District of Columbia, responsible for certifying that the course is at least 26 miles 385 yards. He found a few mistakes: cones out of place in the north Pentagon parking lot, timing clocks at the wrong place near Mile 8 and the halfway mark, and mile 14 about 20 yards off.

Then, disaster struck. The course marshals shortcut an entire block near mile 15. Thurston was too late to fix it. By stopping to fix the earlier problems, some 15 runners were already ahead of him. It was too late to divert the flow of runners back on the right course. Quickly, he measured the damaged. The course was 75 meters short.

In recent years, USATF has setup an elaborate process for course measurement and certification, to insure that runners' efforts do not go to waste on a short course. First, a race director designs a course, using a map and a wheel to approximate its distance. Second, an approved measurer measures the course, adjusts its length, and draws a detailed map of its layout. Third, a regional certifier approves the layout, and assigns a course certification number.

The official length of a course is the shortest distance that a runner can follow from the start to the finish. This includes cutting the tangent on the turns and running a straight line on the straight-aways. The need to measure close to the curb eliminates the car from consideration. Conversely, the wobbliness of a surveying wheel over long distances eliminates its use. Thus, the bicycle became the tool of choice for measuring courses. It can ride close to the curb and travel straight between two points.

Dr. Alan Jones, a former engineer at IBM in Endicott, NY, transformed course measurement from an art into a science by developing the Jones counter. Essentially a precise mechanical odometer, the Jones counter attaches to the front tire of a bicycle and increments a count every 3 or 4 inches.

Before measuring a course, a measurer lays out a calibration course using a steel tape. The tape must be strung with a specified tension, and a temperature correction may be necessary. Then, the measurer rides the bicycle over the calibration course several times, notes the number of counts, and computes a conversion factor from counts into distance. The measurer also notes the pressure of the tires and the ambient temperature.

With a calibrated bicycle, the measurer rides the course at least once in each direction. Adjustments to the course are usually necessary. Eventually, after numerous measurements over several days, the measurer sets the start and finish lines, and the mile and kilometer marks. An extra meter is added for every kilometer, providing a 1/1000 short course protection factor. The measurer drives nails into the pavement to mark key points, and accurately measures their location relative to permanent fixtures.

Since course measurement takes several hours, the pressure and temperature of the tires change due to friction and weather, affecting the conversion factor. Therefore, the measurer must re-calibrate his bicycle over the calibration course, at the end of each measurement, and compute a new conversion factor from counts to distance.

Fortunately for those of us who ran the 1997 Marine Corps Marathon, Bob Thurston could think as fast as he could ride. He had less than 15 minutes to find a place to stretch the course by the right amount (mile 24 in the South Pentagon Parking Lot), get there before the lead runners (that's 10 miles on the bike in the rain), measure the required correction, move the cones, and incidentally, relocate a water station with 15,000 cups.

On the morning after, careful re-measurement on a dry pavement showed that the new course was about 7.4 meters shorter than the certified course. Since the original course was 1/1000 or 42.2 meters longer than a marathon, the new course was certified as a valid marathon course.

Kamal Jabbour runs and writes on the hills of Pompey, New York. His RUNNING Column appears in The Post-Standard on Mondays. He maintains The Syracuse Running Page and receives email at

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