Hawk-Eye captures images from each of the cameras, which are then processed in a powerful computer system to locate the ball, and then control software combines the information and tracks the trajectory of the ball in the goal area. If and when the whole of the ball has proved to have crossed the goal-line, a signal is instantly (within a second) sent to the referee. The specially adapted wristwatch with display and vibrating function was developed in conjunction French group Adeunis.
The GoalRef system, based on original research by Danish scientists and further developed by engineers at the Fraunhofer Institute for Integrated Circuits in Erlangen, Germany, is a radio-based sensing solution that generates a low-frequency magnetic field around the goal area. The ball has ultra-thin coils embedded in it. As it approaches the goal area, it is detected by changes in the magnetic field. These changes allow the ball to be precisely tracked. If the whole of it has passed the goal line, an encrypted signal is immediately transmitted to games officials, again picked up by (different) specially modified wristwatches.
Another German system, the result of collaboration between Cairos Technology and Adidas, relies on thin cables installed below the turf in the goal area that generate a weak magnetic field. Tiny sensors embedded in the ball measure the strength of the fields as the ball comes nearer the goal line. The transmitter in the ball then sends the encrypted data to receiver antennas, which determine whether the entire ball had crossed the line. Again, it takes less than a second to send the signal to the match officials.
These were whittled down to two -- Hawk-Eye and GoalRef, following thorough testing and evaluation by the International Football Association Board and FIFA. Late in the bidding process, the authorities licensed a fourth option, dubbed GoalControl-4D, from a two-year old German company, GoalControl GmbH, that, to the dismay of many, won out against the more established options, notably Hawk-Eye, which was considered to be the firm favorite.
The two systems are remarkably similar. GoalControl-4D also deploys 14 high speed cameras strategically located around the stadium roof or galleys and directed at the goals. They are connected to a powerful image processing computer system that tracks the movement of all objects on the pitch and filters out the players, referee, and any other objects save the ball. The system knows its three-dimensional x-, y-, and z- position to within a few millimeters in the coordinate system of the pitch. Again, when the ball passes the goal, the system instantly sends an encrypted signal to the officials' specially modified wristwatches.
Asked whether he was surprised to have won the contract for the World Cup, Dirk Broichhausen, managing director of GoalControl GmbH says he was not, “because we had already been awarded in April 2013 the contract to trial the system at the 2013 Confed Cup,” the precursor tournament played last year in Brazil.
Dirk Broichhausen, managing director of GoalControl GmbH
“This proved the system’s effectiveness and total reliability. We think the complete package of system solution and performance, the attractive price and service ratio, the project management plan, and the fact that technology made in Germany stands for reliability, quality, enduring value, and innovation in engineering and system solutions contributed to FIFA’s decision,” Broichhausen tells EE Times.
The GoalControl-4D is expected to cost $260,000 per stadium to install, and $3,000 per match to operate. Interestingly, and perhaps controversially, he added, “an important fact to point out is that our transmission code of the sender is extremely secure and has a frequently changing encrypted code. Contrary to our British competitor, we are not using the Wi-Fi/LAN frequency band of 2.4GHz. This frequency bears many disadvantages and security risks regarding the system. Just think how many access points and smartphones are in the stadiums during the matches which are all sending on the 2.4GHz frequency.”
Numerous attempts to clarify from Hawk-Eye Innovations precisely what frequencies its system works on have to date proved unsuccessful. Thomas Pellkofer, project leader for GoalRef at the Fraunhofer IIS, tells EE Times:
Yes, we were disappointed not to have won. We believe our approach to GLT and our technology is the most reliable and cost-effective currently on offer. But there are numerous opportunities for our system in the future; Russia in 2018 for the World Cup and before then, lots of football associations, in Asia and Europe are expected to install GLT, and have shown interest in GoalRef.
Editor's note: A further installment in this series will look much more closely at the different technologies proposed for Goal Line Technology
-- John Walko is a technology writer based in London (who failed in all attempts to secure tickets for England's matches in Brazil).