Feature

A threat or an advantage?

Hawk-Eye isn't just a great tool for television coverage; it could also end up being a very handy tool for the umpire

S Rajesh
S Rajesh
14-Jun-2006


The Hawk-Eye technology has already enhanced television coverage. How long before the umpires start using it as an aid? © Hawk-Eye
It's a key moment in the Ashes 2009 contest. Andrew Flintoff comes steaming in, delivers a scorcher which nips back into Ricky Ponting, raps him on the pads on the back foot, seemingly in front of the stumps. All of England go up in a full-throated appeal. Aleem Dar, the umpire who has to make the verdict, takes out a gadget from his pocket which tells him accurately the path the ball would have taken had it not struck the pad, and rules Ponting not out. The reason: the ball would have missed the top of the stumps by 1.6 centimetres.
The scenario seems far-fetched - at least for the moment - but the advent of the Hawk-Eye technology has opened up various possibilities. For the viewer at home, it has meant a whole new dimension to watching cricket on television. Every time a bowler reckons an lbw verdict should go his way, along comes the Hawk-Eye graphics on the screen, tracing the path of the ball and conclusively telling the viewer if the ball was heading towards the stumps or not. The visuals have become commonplace for the regular cricket watcher, but the technology and its workings haven't been written about much. Let's see what Hawk-Eye is all about.
The technology
Six cameras, usually placed at long-on, long-off, third man, fine leg, and two square of the wicket, operate at 120 frames per second (the regular television cameras operate at 25). Three of those cameras are used to capture the path of the ball from each end, and the pictures from each of those cameras are fed into a central computer. Taking into account the sideways movement and the bounce of the ball, the computer then extrapolates this information to predict the path of the delivery. Because processing of the data happens as soon as it is fed in, the output is available almost instantaneously. Together with the pitch mat - the strip drawn through the middle of the pitch from one set of stumps to the other - Hawk-Eye accurately indicates where the ball hit the batsman (in line with the stumps or not) and whether or not the ball would have gone on to hit the stumps.
In the words of Paul Hawkins, the brains behind the technology: "Hawk-Eye does not try to predict the path of the ball after the bounce. Instead, the Hawk-Eye cameras track the ball both before and after the bounce, so the correct trajectory of the ball leaving the wicket is determined. Hawk-Eye simply observes and then calculates the actual trajectory of the ball. Whether the cause of this trajectory was due to atmospheric conditions, the wicket, or the ball hitting the seam is irrelevant from a Hawk-Eye perspective. Hawk-Eye just tracks what happened - it does not try to predict nor to answer why it happened."
Accuracy
According to Hawkins, in most cases Hawk-Eye's output is accurate to within five millimetres in predicting the path of the ball. The accuracy levels are highest when the ball has travelled a fair distance after pitching, but even when the point of contact is very close to the pitch of the ball, the accuracy levels are still within 20mm.
At the moment, concerns over using Hawk-Eye as an aid for umpires in lbw decisions centre on the number of marginal cases which would go in favour of the bowlers. While that's a reasonable worry, Hawkins insists that there can be a benefit of doubt built within the system, so that close decisions - when the ball is grazing the outside of the stumps, or striking the pad marginally in line - go in favour of the batsmen, just as the spirit of the law indicates it should.
In fact, Hawkins suggests that batsmen get the wrong end of the decision fairly regularly as well, something that will be eliminated if the technology is used. A lot of the umpiring errors with lbws currently happen due to misjudgement of the height of the ball, with batsmen being given out when the ball was actually going over the top of the stumps. Umpires suffer from the parallax since their eyes aren't level with the top of the stumps, an error which is eliminated by Hawk-Eye.


The pitch map, according to Hawk-Eye © Hawk-Eye
The technology might expose the errors made by the umpires, but that, says Hawkins, is hardly the objective. "By no means is it the intention of Hawk-Eye to undermine the role of the umpire. In a very high percentage of cases the Hawk-Eye replay confirms the umpires' decision to have been correct. Hawk-Eye has helped to highlight just how difficult their job is."
And quite apart from being able to accurately judge lbws, Hawk-Eye is a handy tool for much more: its ability to track line, length, movement and speed means that it's a great aid in television coverage and for analyses. For example, a pitch map of where a bowler landed his deliveries is an indication of his accuracy, and could also offer clues on which type of deliveries went for runs or troubled the batsmen.
That the technology is here to stay is a given. The ICC hasn't yet been convinced that it should be an aid to umpires, but the tennis world has been more forthcoming: the International Tennis Federation has already used it in a couple of tournaments this year - including the Nasdaq-100 in Miami, the largest tournament on the men's tour outside the four Grand Slams - and was satisfied enough to indicate that it would be used at the US Open later this year.
It was also used in a Senior Masters event at Royal Albert Hall in London late last year, where it got ringing endorsement from a player who, in his pomp, wasn't famous for his affection towards umpires.
"I hate to say this, but the linesman did a great job today," he said, before going on to add, "It's just so good for tennis because it takes away the potential for antagonism. There are no subjective calls, the ball is either in or out, and that allows the humorous side of my personality to emerge, which I prefer, rather than my dark side." Hmm. Perhaps Hawk-Eye might help reveal the funny side of Glenn McGrath as well.
And in case you still haven't guessed the tennis player in question, he answers to the name John Patrick McEnroe.

S Rajesh is stats editor of Cricinfo