A first phase of testing of different goal-line technology systems gets underway next month, with the potential for the technology to be used in football – provided a series of stringent requirements are met.

Following the decision by the International Football Association Board (IFAB) in March to grant a further year for the testing of goal-line technology, nine European companies have registered to take part in the tests, which are set to be held behind closed doors in stadiums chosen by the technology providers in consultation with FIFA.

The first test phase, due to be carried out in November and December by a team of independent researchers from the Swiss materials science and technology research institute EMPA, will comprise three main elements aimed at evaluating whether the technologies can accurately detect that the whole of the ball has crossed the line between the posts and under the crossbar.

One of the main elements consists of shots being fired into the empty net from all over the pitch. “With this test, it’s clear even to the naked eye whether the ball is behind the line or not,” explains EMPA’s project leader, Martin Camenzind. “Crucially, however, the system should not indicate a goal in the case of shots past the posts or into the side netting.”

Correctly identifying shots into a completely empty net is one thing, but what about the more common situation when goalkeepers or defenders are standing in the way? To examine the accuracy of the various systems when it comes to shots that hit the goalkeeper or rebound off defenders standing near the goal line, another part of the test will see the researchers set up an impact wall, similar in size and shape to a goalkeeper, in different positions either on or at varying distances behind the line. A ball-shooting machine is then used to fire shots against the impact wall.

Need for consistency
“Although professional footballers like David Beckham might have a wonderful shooting technique, it is easier for the ball-shooting machine to replicate the same shots time after time than it is for a player,” says Camenzind, pointing to the fact that the testing conditions must be consistent for all nine technology providers.

The other main element of the test is known as the “sled test”. For this, the ball is positioned on two parallel rods, which are in turn mounted on a wooden base straddling the goal line, before being rolled slowly across the goal line by hand until the system indicates a goal. Using this machine allows the team to obtain more precise readings than if the ball were simply rolled directly along the ground.

Of course, the test institute itself has to be able to determine with absolute certainty whether or not the ball has crossed the line during the tests. “Parts of our tests are set up in such a way that the ball is only behind the line for a fraction of a second and it’s impossible to see with the naked eye whether the ball has crossed the line or not,” explains Camenzind. With this in mind, the testing institute deploys a high-speed video system which records 2,000 images per second.

Second phase
To pass the first phase of testing, the technologies must display 100% of the shots into an empty net correctly and achieve a success rate of at least 90% in the impact-wall and sled tests. The results from this first phase – during which the technology provider must also prove that its system can automatically indicate a goal to the referee’s watch within one second – will then be used to establish a shortlist of companies that will proceed to the second testing phase commencing in March next year.

As well as evaluating the system’s ability to handle an increased number of shots, speeds and elevations, this second phase will take in other situations which might crop up during a match, such as the presence of a second ball outside the line or people moving and standing close to the posts. Assuming the technology is able to detect a goal reliably under these second-phase conditions, the reliability of the overall system will then be assessed.

Camenzind points out that the technology must function without any problems on both natural grass and artificial turf, and importantly, considering the number of evening games played, explains that the tests will be carried out both during daylight hours and at night under floodlights – all on the same day.

“We’re in for some long shifts,” admits Camenzind. “But it’s fascinating for us to be involved in a project of this kind. Our work requires us to evaluate a wide range of materials and systems, only normally we’re based in the lab and the materials come to us!”

Following the second phase of testing, FIFA will present the results of the tests to the IFAB, which is the only body able to make amendments to football’s Laws of the Game and therefore decide on the possible implementation of goal-line technology.

The board is due to hold a special meeting on the subject in July 2012, following the completion of the UEFA European Championship. At the same meeting, the board will also decide on the future of the Additional Assistant Referees experiment, which was in part also conceived to reduce the chances of error in goal-line decisions.

What is needed
The International Football Association Board has laid down four basic requirements that goal-line technology systems have to fulfil:

1. The technology applies solely to the goal line and only to determine whether a goal has been scored or not.
2. The system must be accurate.
3. The indication of whether a goal has been scored must be immediate and automatically confirmed within one second.
4. The indication of whether a goal has been scored will only be communicated to the match officials (via the referee’s watch, by vibration and visual signal).