During the 2010 World Cup in South Africa, English player Frank Lampard took a shot that bounced off the bottom of the crossbar. The ball ricocheted, landing just inside the goal line before rolling back onto the field. The referees, however, missed the play. They ruled that the ball never entered the goal. England went on to lose the round and was eliminated from the tournament.
That flubbed call has led FIFA, soccer's governing body, to reverse its long resistance to on-field technology and embrace computerized referees.
"It became evident the moment [that] ... happened in South Africa in 2010," FIFA president Sepp Blatter said at a press conference last year as the organization agreed to experiment with goal-line sensors. "I have to say, 'thank you, Lampard.' " After a successful showing at the Confederation Cup this summer, goal-line technology will watch over the World Cup next year in Brazil.
Soccer stood as one of the last major professional sports to thumb its nose at technology. For years, hardware has helped referees make better calls in tennis, basketball, hockey, baseball, cricket, and American football. As sensor systems improve – and as instant replay on television makes split-second mistakes obvious to the wider public – referees now increasingly defer to data-crunching computers.
At the 2014 World Cup, seven high-speed cameras will capture each goal from various angles around the stadium. The system, called GoalControl, can stitch together these 2-D videos into a 3-D model of the ball's position.
GoalControl works in near-real time. Less than a second after a player scores, special wristbands worn by the refs will vibrate and light up, alerting officials that the ball has entered the goal.
The system will cost $260,000 per stadium to install, according to The Associated Press, and $3,900 per match to operate.
The German company behind GoalControl says that with additional cameras its system could also identify rule violations, such as handballs and offsides. Mr. Blatter, however, has said publicly that he still opposes using machines to monitor other aspects of the game. It will ruin the flow of a match, he argues.
A competing service, Hawk-Eye, has kept careful watch over tennis, cricket, and soccer's English Premier League.
For several years, the camera-based system has judged whether balls land out of bounds at the US Open and Wimbledon tennis tournaments. While Hawk-Eye records the entire game, referees only consult it during challenged calls. The system overturns human umpires about 30 percent of the time, according to Hawk-Eye Innovations, which was recently purchased by Sony.
Computers can also mitigate human bias. In their book "Scorecasting," economist Tobias Moskowitz and sportswriter L. Jon Wertheim document referees' propensity for favoring home teams. In the National Football League, home teams enjoyed 8 percent more turnovers than their opponents, for example. But after the league introduced instant replay and the ability to challenge calls, that edge was cut in half.
That said, these computerized referees are not 100 percent accurate, either. GoalControl and Hawk-Eye claim to know the position of a soccer ball within about a fifth of an inch. In most cases, that margin of error can't be achieved with the human eye. But certain situations still require a referee's judgment.
For example, cricket players may not use their bodies to obstruct the wicket (for American readers: Imagine a rule against a baseball batter placing his leg in front of home plate instead of to the side of it). Hawk-Eye tries to determine if a player has unfairly stuck his leg out. But there's a "zone of uncertainty" where the system admits that it can't determine if a player's stance breaks the rules. In those situations, Hawk-Eye defers to human umpires.
Because of these uncertainties, referees at the World Cup may overrule the automated system. Officials can even order the stadium crew to turn off GoalControl if they question its accuracy.
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The original version of this article ran in the October 7 issue of the Christian Science Monitor magazine.