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Sport technology enables improved decisions

Sport and electronics have been bedfellows for decades – ever since the first live sports broadcasts by radio and TV. And electronics is used now in many other ways throughout sport – in training and medical applications, analysis, data recording and so on.
But for some sports, electronics and computing have become even more critical in the last decade – by playing a key role in controlling the games as they are played, making match changing decisions on what has happened.

It is the result of several areas of electronics coming together – powerful wireless data transmitters and receivers, wireless charging and ever greater chip integration for handling huge amounts of data, allied with computer processing capabilities that can assess and judge complex 3d graphics in extremely short times. All this is vital for use in live sport.

A notable success has been Hawk-Eye, now widely used in cricket, tennis, snooker and other sports. Developed at Roke Manor Research in 2001, Hawk-Eye can track the trajectory of a ball and almost immediately show its most likely path.

Hawk-Eye has transformed the sports it which it is used, especially cricket and tennis, and whatever some of its human judges think, it is more accurate than any person. It uses the principles of triangulation, taking visual images and timing data provided by at least six high speed video cameras around the area of play. A data store contains a predefined model of the playing area and includes data on the rules of the game.

As each frame is sent to the system from the cameras, Hawk-Eye identifies the pixels corresponding to the ball and calculates for each frame the ball's 3d location by comparing its position using a minimum of two separate cameras simultaneously. A series of frames creates a record of the path the ball has taken. Hence, for tennis, it can report exactly where a ball has landed, with an average error of 3.6mm, according to tests performed by the International Tennis Federation.

Hawk-Eye also predicts the future flight path of the ball and where it will interact with any playing area features already programmed into the database – like the wickets in cricket. Cricket was the first sport to use Hawk-Eye, more than a decade ago. Tennis took it up for Grand Slams in 2007.

It also creates a graphic image of the ball path and playing area, so information can be shown to commentators, tv audiences and coaching staff virtually in real time. The tracking system is combined with a backend database and archiving for analysing trends and statistics about players, games and so on.

Ironically, sports that were seen as old fashioned – like cricket and tennis – have pioneered the use of technology, whereas the world's leading and richest sport – soccer – has been almost passionately anti technology. At least, that was the case until the last World Cup, when an infamous event occurred in the match between England and Germany. Just before half time, England's Frank Lampard's shot hit the crossbar and bounced down. TV replays showed immediately, and beyond any doubt, that it had crossed the line by a clear margin, but the goal was not given, potentially influencing the whole match. Similar goal line mistakes have occurred quite regularly.

Just using video replays would have a major impact on soccer. A recent study by journalist Tim Long suggests that, in last season's Premier League matches, errors took place nearly 30% of the time that video replays could help prevent – like penalties given or not, and incorrect offside rulings.

Finally, soccer's governing body FIFA has given in and various technologies for monitoring the goal line are being tested, with the aim of implementing one by 2012. Several companies are participating in trials, including Hawk-Eye, Munich based Cairos, Austrian company Abatec and UK firm Goalminder.

They think it's all over
With trials completed at FIFA's Zurich headquarters earlier in 2011, Goalminder has been invited by FIFA to complete further trials. Goalminder's technology delivers actual images from high speed cameras built into the fabric of the goal posts and cross bar.
"We show the actual event, at the point where the ball goal line incident happened," the company says. "Nothing predicted, no guesswork, just indisputable pictures. All in high quality, 2000frame/s video."

Another developer of goal line technology is Germany's Fraunhofer Institute, which has developed a soccer ball that uses high speed transmitters to create a triangulation method. This is important for accuracy, according to Erik Jung, of Fraunhofer's Medical Microsystems Department in Berlin.

"Some people think it is a straightforward RFID scenario, where the goal serves as the RFID portal; if the ball passes over the goal line, its position is known. Unfortunately, that would give you little more information than the ball was in the vicinity – accuracy would be about 3m."

Clearly, this is no good. Triangulation, however, can offer an accuracy of centimetres. Four receivers are fitted to the goal frame and the football contains inside it an rf transmitter, which constantly emits a signal. However, fitting the electronics inside the ball is a major challenge.

"One technique," said Jung, "is to mount the electronics on tiny carbon fibre reinforced strings, which can hold the system inside the middle of the ball, so that it is not affected even when the ball undergoes the major distortions that happen when it is kicked."

Technology for all
For various reasons, like cost, Hawk-Eye has been very much for professional events, but a sister company, Hawk-Eye Sensors, is aiming to offer line judging technology to potentially every tennis player. This will use a 'tribo-electric' wire based sensor system placed just below the surface of the court, which can make line calls accurate to several hundredths of an inch. This could be used on courts at clubs, schools and even personal home courts.

Tribo-electric energy is the static charge resulting when two objects rub against each other. In Hawk-Eye's case, the insulation on the wire rubs against the insulation on the inner side of the laminate which is sealed onto the wire. The pattern emitted when a tennis ball hits the sensors is very clear and discernible – a foot hitting or scraping across a tennis line results in a very different pattern.

Hawk-Eye Sensors includes a hub which consolidates the sensor wires, an amplifier/filter which cleans the signals and an a/d converter that connects to software running on a standard notebook. This can show the status of the most recent close shot as well as the time since it occurred, and other data.

In cricket, Hawk-Eye now has a partner – Hot Spot. As its name suggests, it works by detecting the heat generated by the friction caused when a cricket ball (or potentially other objects) makes contact with something. In cricket, the basic question is: did the ball make contact with the bat or glove, in which case the player is out, or did it hit something else like the pad or arm, or even just the ground, in which case they are not?

Typically, two cameras on opposite sides of the ground and above the field of play, record every delivery at a rate of around 100frame/s. Using a subtraction technique, a series of black and white negative frames is generated and fed to a computer, which locates the ball's point of contact precisely.

In some matches, it is used by the umpires to make decisions; in others, just for the TV commentary. In this summer's England Test series, India refused to accept Hot Spot as an aide for the umpires – and mistakes were made as a result.

Hot Spot uses extremely high end infrared cameras offering the greatest possible resolution, similar to ones used in jet fighters, warships and tanks.

"We tried lower end detectors, but they simply did not give us what we need," says Walter Brennan, founder and managing director of BBG Sports, the Australian developer of Hot Spot.

The cameras come from various sources, beginning with ones made in France, then Australia using Israeli detectors and, most recently, from electronics defence contractor Selex Galileo.

"I have been talking with them for a couple of years on how to adapt what they have to what we need. The main problem for Hot Spot when there is a very fine edge is that when the bat swings through quickly you get a blurred picture, making the spot difficult to detect."

A related cricket technology is the Snickometer – or Snicko – which is a sound based detection system exploiting the fact that a microphone is installed in one of the stumps, making it possible to listen to and view the shape of the recorded soundwave. If the ball has touched the bat, it typically produces a short sharp sound in synchrony with the image. Other sounds, like the ball hitting the pads or the ground, have a more spread out shape on the waveform.

So far, Snicko has only been used by tv because it is too slow to generate the images of the sound wave. However, Brennan has worked closely for some time with Allan Plaskett, the inventor of Snicko, and is hoping to combine the two technologies, producing something called Hotsnick.

"Snicko is very good at what it does – if there is a sound out there, it generally finds it," Brennan says. "The problem is it doesn't always tell you exactly where that sound comes from."

Combined with Hot Spot, it should be able to. Brennan is hoping to provide Hotsnick for the 2012 season in England.

"One of the reasons I went down the infrared route was that I felt people would believe infrared more than what I call a cartoon," Brennan says. "There is still a lot of conjecture about how accurate Hawk-Eye is – admittedly there has been about our system as well. But people typically accept that when objects collide, friction is caused, and with infrared technology you can see it."

Future advances are possible. Brennan says Selex Galileo, for example, has a much higher resolution infrared camera than is currently being used, closer to HD.

"That is definitely a possibility, something we will look at," he says. "The bottom line is that technology gives you information that is extremely difficult for a human being to discern. In difficult cases, humans probably get decisions right less than 50% of the time, Hot Spot is in the high 90s."

Disastrous goal line mistakes and bad cricket decisions should soon be a thing of the past and, whether they like it or not, human judges are slowly being ousted in favour of their electronic counterparts.

The result? We may never hear a McEnroe like rant again. Are you serious?

Author
David Boothroyd

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