Goal-line technology in football: Questions and answers

This year’s Fifa Club World Cup in Japan is the first tournament to trial goal-line technology since it was approved by Fifa earlier this year.

Two systems have been given the green light by the sport’s governing body, Hawk-Eye and GoalRef, following the International Football Association Board’s (Ifab) decision after months of extensive tests.

Here are some of the key points about the technology which looks set to be introduced worldwide over the next 12 months.

How do the systems work?

Hawk-Eye
The Hawk-Eye system uses six to eight high-speed cameras set up at different angles at each goal to calculate the exact position of the ball. The data from the cameras is then transferred to video software. From this data, the system calculates the ball’s trajectory and position. The match officials are informed of whether or not it was a goal within one second.

GoalRef
The GoalRef system creates the radio equivalent of a “light curtain”. Low magnetic fields are produced around the goal, and as soon as the ball, which is fitted with wire coils, fully crosses the line, a minor change in the magnetic field is detected, thus allowing the exact position of the ball to
be established. If a goal has been scored, an alert is transmitted to the match officials via a radio signal within one second, with a message displayed on their watches and via vibration.

Are the systems ready?

The systems are ready, but still are subject to a final system test once installed.

Does the referee have to use the technology?

The referee can use the technology provided he is convinced of its functionality, for which appropriate tests shall be carried out before the match. However, the referee can disregard the information provided by his watch during a match, if certain the watch/system isn’t working properly.

How does the referee receive the information?

If the ball has fully crossed the line, the goal-line technology automatically sends the match officials a notification within one second. This message is displayed on the watches of the referee and his team.

Does a system have to be used for a whole season, or can it be utilised from whenever installed?

Fifa has left this entirely up to the competition organiser, meaning the technology could be introduced midway through a season.

GLT is the first step. Will further technology follow to assist in other areas of the game e.g. for offside?

Definitely not, according to Fifa. Goal or no goal is a clear and ultimate decision and it should be always made correctly. The key is that the systems alert the officials in less than second. The game does not have to stop. In north America, technology is used in ice-hockey, the NFL and baseball. In rugby, tennis and cricket in other parts of the world too. But some of these decisions take a long time, and slow down the whole spectacle.

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