Fifa Quality Programme for Goal-Line Technology
Goal-line technology is a technical means of instantly determining whether the whole of the ball has crossed the goal line.
The International Football Association Board requires that goal-line technology (GLT) does not interfere with the game. As a consequence the requirements were set up to determine that only the match officials are to receive a signal to indicate whether or not the entire ball has crossed the line.
The information is transmitted within one second which ensures an immediate response from the referee. Due to this design there are no stoppages or other forms of interference in the game. The match officials are the only ones to receive the signal on their watches. Unless there is a conscious choice by the competition organiser to show a replay, the information is only available to the referee and helps in challenging situations.
What technologies are there?
Several approved systems work with cameras that detect the ball and use software to evaluate the footage from all the cameras. In this way, the system can determine whether the whole of the ball has crossed the goal line. Currently licensed systems work with seven cameras per goal installed as high up as possible within the stadium structure.
Several systems operate with magnetic fields. For these systems, cables are placed underground and around the goal, and the ball has elements of the technology inside. The interaction between the receptors in the ball and the magnetic fields created through the underground cables allow the software to calculate the exact position of the ball and determine when a goal has been scored.
Two incidents involving England and Germany in 1966 and 2010 tend to dominate discussions and the perception of the typical goal-line incident. In recent years, there have been many more such situations. The following videos show a variety of goal-line incidents from the past couple of years.