In running races, the winner is the athlete whose torso crosses the line first. Hands, knees and heads don’t count. How, then, does the device that records the winning times work? In particular, how does it know which part of the body has crossed the line first? And how does it distinguish between all the athletes, some of whom must be obscured from a beam across the finishing line by their rivals?
• The “beam” of the finishing line is really a camera that rapidly and repeatedly takes a picture of the plane of the finishing line. Over time, the slices of images of the finishing line are compiled into one picture and coordinated with the event clock to recreate a time-elapsed picture of the finishing line.
“A camera takes repeated photographs of the finishing line and compiles a single picture”
Advertisement
These pictures are how the times and places of the athletes are determined. They can be odd in appearance. For example, if an athlete’s foot lands on the finish line itself, multiple photo slices give it the appearance of a ski.
While the picture itself is auto-generated, the times and places are determined by a human judge. For each athlete the judge finds the position of the athlete’s chest. While this might not sound like a well-defined point, the athletes know how to contort their bodies at the last instant to make the chest cross the finish line at the earliest possible moment. Once the judge pinpoints the athlete’s chest the corresponding time of crossing the finishing line is determined from the picture.
To minimise athletes blocking each other, the camera is raised and gets a bird’s-eye view of the line.
I suspect there would be far more injuries from diving at the line if the hand rather than the chest were chosen to determine the winner.
June Andrews, San Francisco, California, US