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High technology meets world sport. Fungus gives you the lowdown on Hawk-eye. |
Kumble bowls the top-spinner. The batsman is beaten all ends up. Kumble turns to the umpire and screams. The umpire is unmoved. "Too far forward" his expression seems to say. But you know, as does the despairing Kumble, that the ball was headed straight for the middle stump. Is not that the point of the LBW decision: Disregard for which part of the pitch the batsman was touring at the time?
Or imagine Federer looking for the elusive win against Nadal on clay. He hits the perfect pass down the line only to have the linesman call it long. You know it was perfect. You could swear you saw a puff of chalk dust. The linesman is wrong as was the umpire earlier. If only you could show them.
Enter Hawk-eye - the latest avatar of high-tech gadgetry designed to make every game an immersive experience for the armchair umpire. Borrowing heavily from techniques used in Brain Surgery and Missile Tracking Hawk-eye has become the de-facto tool used for criticising cricket umpires. But to leave it at that would be to do it a great disservice. Invented by Dr. Paul Hawkins, a former Buckinghamshire player and a Ph.D. in Artificial Intelligence, Hawk-eye has revolutionised the way live cricket coverage is broadcast. Here’s what goes into bringing the armchair umpire the ball’s trajectory once it leaves the bowler’s hand.
The Hardware
Six fixed monochrome cameras, with a 120Hz frame rate, are placed around the playing field at specific points - long off, long on and square for each end of the pitch. These synchronised cameras track the ball’s entire trajectory - at intervals of every 1/100ths of a second - from the moment it leaves the bowler’s hand until it stops or passes the bat. The camera square of the batsman is used only to cover the flight of the ball only over the last third of the pitch.
The Software
The six cameras are divided into two sets of three cameras, one set at each end of the pitch, each set being captured by a frame grabbing and imaging software. The resulting images are processed into a 3D image by the Hawk-Eye system which then calculates where the ball pitched, the extent of its lateral movement in the air and off the pitch, its velocity and bounce, and - if applicable - exactly where it made contact with the batsman’s pad.
Brain Surgery?
Image analysis is what brain surgery lends to Hawk-eye. Tumours are hard to operate on. Imaging techniques help get a 3D picture of the brain and the tumour by combining data from multiple MRI scans. Hawk-eye, similarly, combines the hundreds of stills obtained from each of the 6 cameras to get a fix on the trajectory of the ball. A cricket ground with 16 people on the field and the multitude of agitated fans in the stands is not an environment best suited to spotting a cricket ball.
And Missile Tracking?
The flight of the ball is broken down into a series of parametric equations, suitably modified to incorporate the effects of the pitch, wind speed and the swing of the ball. Given the final set of equations it is possible to predict, theoretically, the flight of the ball, ad infinitum. Missile tracking is where this system was first extensively used. These are the parametric equations that make it possible for the Hawk-eye system to extrapolate path of ball travel even after the ball has crashed in to bat or pad.
The Uses
Hawk-eye does all the image gathering, analysis and prediction in a couple of seconds and is ready with consolidated results that include a video of the ball’s motion and spotting. Spotting give us that scatter diagram that allows analysis of where the bowler is pitching his deliveries and where each delivery hits the batsman’s pads or where it would have hit the stumps, if that is where it was headed.
Player performance can be analysed on the basis of bowler faced or even the weather played in. And this is just cricket. Hawk-eye, as the underlying technology matures, is being increasingly embraced in other sports as well. It is responsible for tracking line-calls in tennis where it serves as a linesman. It is finding support among football players and officials where it promises to resolve all controversy regarding whether the ball crossed the line or not. It is being used in conjunction with Virtual Reality systems to help batsmen replay balls to help improve their stroke-play and help tennis enthusiasts play against their favourite players with the help of VR goggles and force-feedback bats and rackets. Plans are underway to adapt the system to games like pool, basketball and virtually any other game where video analysis can be supplemented to help the players or viewers.
The Controversy
"Theoretically" and "predict" are the two words in a previous paragraph causing the controversy about the use of Hawk-eye. Hawk-eye is a "predictive" system. This means that, on the basis of data collected, it predicts the behaviour of the ball that point forth. There is a lot of opposition to letting technology usurp human intervention as far as predictive decisions are concerned. The question is not whether an equation can correctly predict the flight of the ball or not. The question is whether the system ends up with the correct set of equations at all.
Many elements of the ball’s flight like swing, effect of the pitch and buffeting due to wind are random and very difficult, if at all possible, to factor in. The developers admit the system is not perfect. Sometimes cameras fail. In bright light the system has to be manually guided to distinguish between the ball and its shadow. There are no reports on the tested efficacy of the system but two things are generally accepted. One, that it hovers around the 99.9% mark and two, that the system is being constantly improved with better imaging and better predictive techniques.
Bane or Boon?
Humans tire, are biased and are frequently incorrect for a number of other reasons. This causes uncertainty. The objective behind technological developments like Hawk-eye is to minimize this uncertainty to merely the players and not those who oversee them.
The question remains whether a particular technology is any more accurate than the human it replaces. For instance, how does Hawk-eye factor in an over-pitched "doosra" from Muralitharan? It is not certain that even Murali himself knows how the ball is going to behave. What luck could a machine system have? Or take the effect of a sudden gust of wind. Surely something as random as that could not be factored in.
There is a lot to be said for Hawk-eye, however. With its instantaneous processing of data the results are available in a couple of seconds. And, as time goes by, the system is bound to get better. But I’m sure we will still find something to attribute our teams loss to. All hope is not lost.
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