Precision Measurement at Track & Field Competitions

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Track and field competitions, like the construction and survey industries, rely on precision measurement. For all throws except javelin, such as the discus and hammer, the angle of the sector in which all thrown implements must fall is 34.92 degrees (±0.1 degree). The lines defining the sector must be 5 cm wide. The sector must lie in the same plane as the throwing circle or runway with a vertical variance of no more than 1:1000. The interior of the throwing circle must be level and 2 cm (± 6mm) lower than the upper edge of the rim of the circle. These specs are as tight as those for super-elevated highway ramps.

The implements themselves also have tight specs. Measured 6 mm from the edge, the discus must be at least 12 mm thick and not more than 13 mm. (The exception is the 0.75 kg discus thrown by women age 75 and up, with min/max values of 10 and 13 mm.) The variation in thickness of the javelin immediately in front and behind the grip must not exceed 0.25 mm and a cross-section of the javelin at any point must be circular within 2 percent.

Yet in this world of precision, athletic performance is still measured with tapes. George Leaf is out to change that.

A Man on a Mission to Measure
One of George Leaf’s beliefs is that "The essence of fairness is accurate measurement." This man understands accurate measurement. In his 47-year career he saw tolerances as tight as a few centimeters over several kilometers when setting up antenna arrays for the U.S. Navy. Among the measurement tools where he has fluency are total stations. He uses a Sokkia SET650X at track and field competitions to measures distances. Now retired, he and his Sokkia instrument are showing up at a lot more events.

To measure horizontal distances at track and field events, a field official sets the tip of an upright rod holding the end of a tape measure near the point of impact. The tape is connected to the rod by a loop and leader. The rod is turned or tilted to adjust the leader until the zero mark on the tape is properly aligned with the point of impact. Two other officials pull the tape back to a specific point and then read the measurement from the edge of the circle used for most throws or the foul line for jumps. Fiberglass tapes can be used, but tapes used for measuring records must be steel and must be certified.

Even with a certified steel tape, procedural errors can affect accuracy. Some of these errors are easy to spot, such as twists or slack in the tape measure. Parallax can be tougher to see. It’s not much of an issue at the reading end of the tape since the tape is lying on grade. But the end attached to the stick is slightly elevated and it’s up to the official to determine when the zero mark is properly positioned. But with certified tapes and proper procedures, the system works quite well. So if it ain’t broke, why is George Leaf so committed to fixing it?

The Promise and Perils of Electronics
While the existing system provides adequate accuracy, a total station is even more accurate and more consistently accurate. "Everybody deserves a fair measurement," said Leaf, "and that means a consistent measure."

But the big advantage of electronic measuring with an instrument like the SET650X is time savings. "Using a total station, time between throws is 40 to 50 seconds," said Leaf, "about half what it takes with a tape measure." With faster processing, events move more quickly and run smoother. Event organizers like that because smooth is good at a venue where things can and often do go wrong. Athletes like it because there’s less idle time between their competition performances.

Leaf said that when lasers were used at the 1996 Olympics in Atlanta they were checked against a steel tape at the beginning and end of each flight. (A "flight" is a group of like competitors in one event, such as men age 35 to 40 throwing the hammer. Flight sizes are limited; 12 to 16 athletes are typical maximum numbers per flight.) The USA Track & Field rulebook addresses the use of electronic measuring devices in Rule 137 and requires that such devices be verified accurate before and after each event (Rule 137.4). The rulebook also outlines the procedure for verifying records using electronic measuring in Rule 264.3.

So whether measurements are gathered via tape or laser, steps must be taken to ensure accuracy. But Leaf points out that there is a fundamental difference between using a steel tape and a laser. "You have to understand a technology to use it correctly, and tape is easy to understand. If you mess up using a tape, it’s obvious. The tape is twisted or not properly aligned with the throw. An error with electronic measuring can be less obvious, depending on the scale of the error."

A total station uses the law of cosines to find the missing line measurement (MLM). The unit is set up a known distance from the start point, such as the center of a throwing circle. A shot is taken to the rod held by the field official at the point of impact. The missing line is calculated and that value minus the radius of the circle equals the length of the throw. Slight variations in the procedure allow measurement of other events, such as jumps and javelin throws, that don’t start from a circle. Operators aren’t likely to be able to perform this MLM function in their heads for comparison to the readout they get from their total stations, so discovering errors in real time can’t take place.

Then there are those who simply cannot master the use of a total station. Although the instruments are relatively easy to set up and use, "there are people who won’t be able to learn to do it," said Leaf. "It’s not within their skill set."

Semi-Custom Total Station
North American Survey Supply (NASS) in Philadelphia has helped Leaf configure his instruments for the unique needs of track and field. "George is always looking ahead," said Bob Marron, general manager at NASS, "always seeking ways to improve the accuracy of measurements he takes at sporting events. We enjoy finding technological solutions for special projects and George’s situation had strong interest for us."

Both hardware and software were adapted. NASS modified reflectors by adding bifilar lines and configuring Euro-style prism pole extensions to specs provided by Leaf. Sokkia worked with Leaf to optimize communication between the SET650X and his laptop computer.

It was NASS who originally suggested the SET650X to Leaf. "The versatility of the Sokkia total station provided him with an affordable prime measurement instrument," Marron said.

There is at least one electronic measuring device built specifically for use at track and field events, but Leaf prefers total stations in general and his Sokkia in particular. "Total stations are built for commercial duty. They’re designed to be used in demanding environments, to be hauled around in pickup trucks." While total stations are not made to withstand deliberate abuse, they are robust. And they can be calibrated by any number of survey sales and service companies throughout the country. The cost of a total station is comparable to that of the track-and-field-specific device.

Leaf has added a Sokkia SHC236 data collector to his setup. The unit will automatically compensate when calculating distance, such as subtracting the radius of the circle from which a hammer must be thrown. The SHC236 will store an entire event’s-worth of data, includi
ng slope and elevation numbers. This is especially important when records are set as the numbers will confirm that the field is within the 1:1000 limit of negative slope.

Meeting the Need
Leaf said if you add up all the colleges, high schools, and other organizations with track and field teams, the need for measurement officials is virtually unlimited. Assuming the shift to electronic measuring continues, where will we find enough officials who can use the technology? Leaf predicts a mix from two sources. First will be surveyors and others who use total stations in their daily lives who are drawn to serve at athletic events. The second will be officials and volunteers at such events who decide to learn how to use a total station.

And where will we find all these total stations once we populate the ranks of officials? The obvious answer is to buy new or refurbished units from survey equipment dealers. But Leaf suggests officials ask contractors and surveyors for help. "As more and more people in construction and surveying update and upgrade their instruments, their older equipment becomes available. Often these older total stations can be bought for very reasonable prices. The owner may even give the unit at no cost to get fair market value credit at tax time, depending on the status of the organization to which the equipment is given."

"Free" is a good price point for officials seeking equipment. Many volunteer their time and services. Even those that get paid aren’t living large on the compensation they receive. Leaf said top rates are around $300 per day, plus expenses, for major events. It takes a lot of major events to hit break-even if equipment is bought at full price. The real beneficiaries are the contractors who recover some cost or maybe get a break on taxes while supporting their communities’ athletic teams.

With his duties complete, George Leaf packed up his Sokkia SET650X for the drive back to Kentucky. He moves with some pain and fair amount of effort. A near-fatal motorcycle crash years ago left Leaf with a hitch in his gait. The old injury slows him down, but it won’t stop him. He’s going to popularize precision measurement at track and field events by setting up his Sokkia as often as he can at as many events as he can. He’s also scheduled to teach the advanced course in electronic measurement at a USATF clinic in Birmingham, Alabama in a few months. George Leaf is on a mission.

Richard Ries specializes in technology stories with human interest appeal. He works from his office in Madison, IN.

A 1.802Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE