Amidst the Gayle ‘storms’ and ‘whistle podus’, additional masala in an IPL match is provided by contentious LBW (leg before wicket) decisions. While in other formats of cricket there are options to review umpire decisions with the Umpire Decision Review System (UDRS), in the IPL, contentious LBW decisions remain confined to commentators’ speculation or discussion threads on social media websites.
Although the computerised ball trajectory tracking system, familiar to cricket fans as Hawk-Eye, has been around for a while, its full potential remains untapped in the IPL, for what would appear to be good cricketing reasons.
View from Hawk-Eye
The tracking system, or the set of simulations that project the likely trajectory of the ball after it leaves the bowler’s hand till it reaches the other end of the pitch, has become not just a tool of decision-making for umpires, but also for cricket coaches. It is also a source of heightened interest among cricket-crazy fans.
“Hawk-Eye replays add more detail and helps one understand certain nuances of the game, which otherwise would go unnoticed such as when Malinga delivers his yorkers at 140 kmph,” says Harsha Bhaskar, an ardent Mumbai Indians fan.
Two components
Named after the company that supplies the simulation solutions to the International Cricket Council (ICC), Hawk-Eye has appended itself in cricketing parlance.
Hawk-Eye, in fact, has two components. The first part is when it does a ‘retrospective reconstruction’, an actual reconstruction of the trajectory of the ball till it is either played, missed or hits the stumps.
The second, and perhaps more entertaining aspect of its role, pertains to the use of statistical probability; models that enable it to predict what could have happened after the ball’s impact with either the bat or any other part of the batsman’s armour.
Six cameras
Six cameras placed at different locations on the periphery of the playing area constantly track the ball, from the time a ball is delivered by a bowler until the end of that delivery. Advanced forms of popularly used pattern recognition algorithms process the images from multiple cameras, locate the movement of the ball in relation to the critical elements in the playing context — the stumps, the batsman’s pads, the location on the pitch and so on. A central computer program aggregates and consolidates these inputs from different Hawk-Eye cameras to rebuild the trajectory of the ball.
Factors, such as the height at which the ball was delivered, the point at which it pitches and the point of impact on the bat where the ball hits it, are assimilated to generate a high-fidelity reconstruction of the path taken by the ball.
In cases where the LBW decisions are to be reviewed, the ball’s trajectory is statistically computed and the possible path the ball would have taken in relation to the position of the stumps is calculated and visualised.
Based on the ‘reconstruction’, an extrapolation of the path is performed to predict its trajectory towards the stumps. This is the only portion that is simulated per se.
Technology vs. umpires
With the use of technology such as high-resolution cameras, many contentious decisions have been avoided in cases of run-outs and stumpings.
Technology such as Hawk Eye has, to a great extent, improved the quality of decisions, but can it replace umpires or make their decades of expertise redundant?
Not infallible
Hawk-Eye is not infallible. Even the official claim is that the simulations are accurate 99 per cent of the time, whereas many researchers think this is an exaggerated claim.
Many factors such as the nature and surface of the pitch, weather characteristics, specific characteristics of the bowler (such as Malinga, or the giant West Indian fast bowler Joel Garner) and even the condition of the ball are not accounted for in the simulation of deliveries. If not the best, Hawk-Eye is the closest aid umpires can have in a cricket match. So, it appears prudent to use it as an appendage to the accumulated wisdom of human umpires, rather than as a quick fix.
Hawk-Eye verdict
Viewers now expect Hawk-Eye’s verdict on lbw ‘shouts’. Fans no longer consider all sixes equal; one is better than the other because it has travelled farther. So they want to know how far the ball actually travelled.
Similarly, they want to know who bowled the fastest ball in a match. All this and more can be done by Hawk-Eye.
Nuanced analysis
Hawk-Eye’s other great impact has been in the way it enables a more nuanced and detailed analysis of a game, even as it is being played.
Its Wagon Wheel, for instance, shows the trajectory of every shot played by a batsman in an innings. Its Pitch Map shows the constellation of spots where a bowler had pitched, and Beehives depict the batsman’s encounter with the ball, how he handled each delivery, and what happened as a result.
Although purists wring their hands in despair at the growing commercialisation of the game, even they cannot deny that they now know much more about the game than ever before.
