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Goal Line Technology

Written By Koka Albert on Saturday, May 26, 2012 | 11:20 PM


Goal-line technology will be used in England vs Belgium friendly

In association football, goal-line technology is a proposed technology currently in testing stages, which determines when the ball has completely crossed goal line, assisting the referee in calling a goal or not. In the wake of recent controversial calls made in the Premier League and the 2010 World Cup, FIFA (previously against the technology) is testing potential candidates for goal-line technology. Nine systems were initially tested, but only two remain.
The question of the inclusion of goal-line technology began to be raised in 2005 after a game between Manchester United F.C. and Tottenham Hotspur F.C., in which Tottenham midfielder Pedro Mendes hit a shot 45 yards from goal. United goalkeeper Roy Carroll caught the ball and then dropped it at least a yard over the line before hitting it back out, but neither the referee nor the linesman saw the ball cross the line. In response to this, FIFA decided to test a system by Adidas in which a football with an embedded microchip would send a signal to the referee if it crossed a sensor going through the goal. According to FIFA president Sepp Blatter: "We did different tests at the Under-17 World Cup in Peru but the evidence wasn't clear so we will carry out trials in junior competitions in 2007". However, those trials did not materialise and by 2008, Blatter had rejected the system outright, describing the technology as 'only 95% accurate'.

Another incident occurred in August 2009 in a league match between Crystal Palace and Bristol City. Striker Freddie Sears knocked the ball over the line from close range, but the ball bounced off the stanchion below the net and then came back out. The goal was not given and Palace manager Neil Warnock was furious. In March 2010, the International Football Association Board, which determines the laws of the game, voted 6-2 to permanently ditch the technology, with the Scotland and England football associations casting the dissenting votes. In a recent poll of 48 captains in the UEFA Europa League, 90% of respondents said that they wanted goal-line technology introduced. Following several refereeing errors at the 2010 FIFA World Cup – including the disallowed goal in Germany's 4–1 victory over England, when Frank Lampard hit a shot from outside of the penalty box that bounced off the crossbar and over the line; the ball came back out and the goal was disallowed because the assistant referee did not call for a goal – Blatter announced that FIFA would reopen the goal-line technology discussion.
Another instance of a controversial call was Chelsea’s 2–1 victory over Tottenham in 2011. Frank Lampard hit a shot just before halftime that slipped through the legs of the goalie, and almost crossed the line before being tipped back into play, however the assistant called for a goal and Chelsea tied the game. Chelsea were credited with another goal that did not cross the line against the same opponents in the 2012 FA Cup semi-finals, leading again to calls for goal-line technology.
Yet another incident occurred in the final of the 2012 FA Cup in the match between Chelsea and Liverpool, when Liverpool's striker Andy Carroll headed the ball toward goal at close range in the dying minutes when a goal would have equalised the score. No replay showed that the ball had entirely crossed the goal line, vindicating the decision of the assistant referee not to signal a goal.

The Hawk-Eye system was first developed by Dr. Paul Hawkins in 1999. The Hawk-Eye system has since been improved by engineers at Roke Manor Research Limited and is an existing technology currently used in cricket, tennis and snooker. It is based on the principle of triangulation using the visual images and timing data provided by high-speed video cameras at different locations around the area of play. The system uses six, spread out, high speed cameras to triangulate and track the ball in flight. The software calculates the ball’s location for each frame by identifying the pixels that correspond to the ball through at least two cameras.

The margin of error for the system is 3.6 millimetres. The software can track the ball and predict the flight path, even if several cameras are being blocked and as long as 25 percent of it is visible. The high speed cameras allow the ball to be tracked even if they only cross the line for a fraction of a second. The ball would have to travel an unattainable 500 kilometres per hour to avoid detection. The system also records the ball's flight path and stores it in a database that is used to create a graphic image of the flight path and the field, so the images can be shown to commentators, coaches and audiences. The data from the system can also be used to determine statistics for players and analyse trends. The proposal involves placing six cameras in the stands at each end of the playing area at a total cost of £250,000. The system is not real-time, so play has to stop for the referee or another match official to review the disputed play. Critics of the system claim the system will slow down the game and that the statistical margin of error is too large. Both Roger Federer  and Rafael Nadal have criticised the accuracy of the system in tennis (though Roger Federer now supports the use of the system in football).

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