World Cup: Ref’s Watch Vibrates When a Goal Is Scored

Sports technology pioneer Hawk-Eye Innovations has vigorously denied suggestions that its Goal Line Technology (GLT) for football is not sufficiently robust and could pose security risks when sending decisions to match officials about whether a goal should be allowed.

In the first part of this series we looked at some of the sporting, economic, and political reasons the FIFA World Cup that kicks off June 12 in Brazil will be the first where technology should ensure that goals are not falsely awarded or ruled out. We reported that Dirk Broichhausen, managing director of Goal Control GmbH — the German company that, to the surprise of many, won the hotly contested contract to supply GLT to all the stadia being used — questioned whether its British archrival's transmission protocol may have flaws as it deploys the freely available 2.4 GHz frequency.

Broichhausen was responding to questions from EE Times about the potential of interference in his company's GoalControl-4D system as the signal is transmitted to match officials' specially adapted wristwatches. The message tells the referee whether all of the ball has crossed the goal-line.

The ref's watch vibrates when a goal is scored.

The ref's watch vibrates when a goal is scored.

“Although I cannot specify the frequency (it is our IP), our units are secure and free from interference — something which would not be the case if we were using the 2.4 GHz 'free' spectrum. It seems that whatever information Goal Control have on our system is incorrect,” Laurence Upshon, technical Lead for GLT at Hawk-Eye Innovations, told EE Times.

So even though the traditional footballing foes are not scheduled to meet each other (at least in the early stages) in the four-week long tournament, rivalry is certainly alive and kicking in other arenas.

GateControl vs. Hawk-Eye
In fact, the way the two systems work are remarkably similar, though neither company would reveal much about exactly how they were developed. And both can trace the initial ideas back to research projects — Hawk-Eye to work done by Dr Paul Hawkins, a specialist in artificial intelligence at the UK's Roke Manor Research center, then owned by Siemens but originally a core research establishment within Plessey for radio and military communications.

Hawkins, who gave his name to the system, led a spinoff of the technology that in 2011 was acquired by Sony.

The core technology was developed in the late 1990s for use in tennis and international cricket, and the company now sees the US as a major potential market in, for instance, Major League Baseball and NASCAR.

Meanwhile, the roots of GoalControl-4D go back to a spinoff of research at the Institute of Plastics Processing at the University of Aachen in Germany. Not much is known about GoalControl GmbH the company. It is based in Wurselen, near Aachen, and is closely linked with Pixargus, which develops and sells systems using cameras and software to handle quality control on production lines manufacturing precision components for the automotive and medical sectors.

According to Broichhausen, the system was developed in just four years, and was licensed for use by FIFA “almost immediately.” The short time-scale was possible because the crucial image processing and analysis expertise within the companies was already being applied to machine vision systems sold by Pixargus, and the system needed for GLT adaptation was all done in-house. “Outstanding features of the GoalControl-4D system are high accuracy, the real-time processing and high frequency of the pictures as well as the absolute reliability and repeatability,” he told EE Times.

FIFA decided to use Goal Line Technology for the first time in the World Cup, to be held in Brazil next month.

FIFA decided to use Goal Line Technology for the first time in the World Cup,
to be held in Brazil next month.

These attributes, and others, are all shared by Hawk-Eye. Both are passive technologies and can be used without the need to adapt or interfere with the ball, goal posts, or playing surface. They are agnostic as regards ball manufacturer.

“The technology is a proven success in the English Premier League following its inaugural year,” notes Hawk-Eye's Upshon.

Both work with seven high-speed cameras per goal, the most common location being on the stadium roof, but there are flexibilities in exact location. They work at 500 frames per second. If one assumes the ball is traveling at 60 mph, then the systems can detect, well within the stipulated one second, if a ball has crossed all of the goal-line, even for a fraction of a second.

The images are transmitted to a bank of computers via fiber.

Next page: Encrypted signals

Powerful image processing algorithms identify the ball and its position within each camera's viewpoint and calculate via triangulation its position in the goal mouth to within millimetres. The original FIFA specification regarding accuracy was +/- 3 cm, but this has now been halved to +/- 1.5 cm, and both GoalControl and Hawk-Eye confirmed their systems better the revised tolerance level.

The system can work with any pattern, and both companies maintain that the result will be precise even in adverse weather conditions, different lighting positions, mud on the ball, or if there is a maelstrom of players in the goalmouth.

All camera images of every event are stored and can be replayed at any time.

Encrypted signals
Where there is a difference between the two is how the encrypted signals are transmitted to the officials' specially adapted wristwatches, which are supplied by different companies. At least it is believed the frequencies used are different; neither company would reveal details, citing this as confidential information for security reasons.

In Hawk-Eye's case, the company worked with Adeunis RF, a specialist in supplying RF products for a variety of sports. The watches are guaranteed to be “secure, robust, and interference free,” stressed Upshon.

Broichhausen simply said GoalControl, too, worked with another company. However, EE Times can exclusively reveal that the watch being used at the World Cup was specially adapted by researchers at the Fraunhofer Institute for Integrated Circuits near Erlangen, Germany (see below).

So, following the decisions by FIFA and the English Premier League, have we reached a Betamax vs. VHS moment in goal-line technology? Not necessarily.

As already noted, GoalControl 4-D was chosen from a shortlist of four FIFA licensed and independently tested technologies, whittled down from 12 contenders, some of which were based on rather quirky ideas such as putting stickers on the ball or using laser beams on the goal line. The two others in the running were GoalRef and Cairos, both of which use low-frequency magnetic fields in the goal frame to track what is being described as an “intelligent ball.”

GoalRef got very close to being selected by FIFA, and its proponents still believe it is the most cost-effective and elegant GLT on offer. Originally a Danish invention, it was further developed by researchers at the Fraunhofer IIS.

Thomas Pellkofer, operations manager for GoalRef at the research group, told EE Times, “Our system is cheaper, more flexible, and more reliable than camera-based options — it is a closed ecosystem, and there is no need for an operator looking and monitoring screens.”

Accurate, real-time tracking of the ball is made possible by a combination of just a few high-precision antennae attached to the goal frame and three coils embedded in the ball, one in each dimension, located between the bladder and the ball synthetics. The coils do not require a power source, and thorough testing has proven that the characteristics and behavior of the ball are completely unaltered, an important consideration for the players.

“Basically, GoalRef works like a bistatic, low-frequency RFID system with 'RFID reader' antennae surrounding the goal that excite the 'RFID transponder' inside the ball,” says Pellkofer. The changes in the magnetic field allow precision location.

The Cairos system, also developed in Germany, is a collaboration between Cairos Technologies and sports goods conglomerate Adidas and involves embedding thin cables in the turf of the penalty area behind the goal line. The electric current running through the cables generates the necessary magnetic field. A chip sensor within the ball detects the magnetic field as soon as in range and transmits encrypted data to receivers strategically located behind the goal, which is then instantly sent to a computer. Here the exact location is interpreted, and, as with the GoalRef system, if the entire ball has crossed the line, a signal is sent to match officials.

Fraunhofer's Pellkofer says that, in addition to GoalRef, the group has also developed another potential line of business, the officials' watch, dubbed Watchlink. Since this is FIFA approved, it could be used with all GLT systems. “And certainly, it will be used in conjunction with the GoalControl-4D system in Brazil.”

The Watchlink is basically a specially adapted Texas Instruments watch that uses the chip maker's CC430F6137 chipset. “The extremely secure and robust wristwatch uses our patented software and protocol, can work with just one transmitter for the whole stadium, and is remarkably power efficient,” says Pellkofer. He added the frequency ranges of the links are 865 to 870 MHz and 915 to 930 MHz, and that the modified devices are assembled by a specialist company in Germany whose identity he would not reveal.

Now that football has embraced technology for goal-line decisions — and barring any controversial outcomes or computer errors in Brazil during the summer — the obvious question will be asked whether it could, or more probably if it should , encroach on other parts of the pitch. Many national and international footballing authorities will continue to resist, using the example of other sports such as the rugby union, international cricket, NFL games in the US, and even in tennis, where the flow of play is increasingly disrupted as more and more incidents are subject to video replay.

But the supplier companies and technology developers have other ideas. For instance, a two-year trial is already under way in the Dutch top division in collaboration with Hawk-Eye Innovations.

“The main aim of a video referee is to address issues where television replays almost immediately show a clear and contradictory result to that of the referee,” said Upshon. “These are the contentious calls that really influence a match, whether it be an offside call, simulation [by a player to gain an advantage, generally a penalty] or an off-the-ball foul that the officials have missed.

“In many scenarios that we have looked at in Holland, the decision has been made by the video referee within seconds.”

Whatever the outcome, referees will continue to rule the roost. Even with GLT, the final decision is theirs, and if the watch vibrates and alerts the official that a goal has been scored, the referee can (and must) still overrule if he has spotted a prior, separate infringement. Nor will the most sophisticated camera or computer ever be able to rule on intent in handball incidents or ugly tackles.

So spectators and TV watchers will still have plenty to argue over, even decades after the event.

This article was originally published on EBN's sister publication EE Times .

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