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HomeSportsEXPLAINED: As Dean Elgar DRS Call In Cape Town Test Sparks Debate,...

EXPLAINED: As Dean Elgar DRS Call In Cape Town Test Sparks Debate, How Ball Tracking Works In LBW Decisions


Umpire Marais Erasmus was certain the ball was hitting the stumps. The reactions — relayed by the stump mics — of Team India skipper Virat Kohli, vice-captain KL Rahul and Ravichandran Ashwin, who bowled the delivery, suggested that, for them, there was no question of it going anywhere else. But the ball-tracking technology chose to differ, showing the ball actually flying over the stumps, leading to the denial of South Africa captain Dean Elgar’s wicket at a crucial juncture in the decisive third Test at Cape Town. So, how does the ball-tracking tech work and what discretion do umpires have vis-a-vis the Decision Review System (DRS).

What Is The Decision Review System?

The International Cricket Council (ICC), the sport’s apex world governing body, says that DRS is “a technology-based process for assisting the match officials with their decision-making”. It’s a facility that allows on-field umpires to consult the third umpire or TV umpire for help with arriving at any decision in the course of the game — known as ‘Umpire Review’ — while the provision for ‘Player Review’ permits players to appeal against a decision of the on-field umpires.

ICC says that in televised international matches, umpires can opt for DRS to check on “run outs, stumpings and fair catches”. As for players, they can call for a review of “any decision taken by the on-field umpires concerning whether or not a batsman is dismissed, with the exception of ‘Timed Out'”. For the batting side, only the batter who has been given out can request a review of the on-field umpire’s decision by the third umpire while for the fielding side, only the captain “may request a player review of a not out decision”.

The player review has to be sought by the designated player making a ‘T’ sign “with both forearms at head height”, taking care that no more than 15 seconds has elapsed between the ball becoming dead and the review request.

The rules stipulate that in each innings, each team can have a maximum of two player review requests that fail to overturn a said decision. If the review leads to the reversal of an on-field umpire’s decision, then “the player review shall be categorised as ‘Successful’ and shall not count towards the innings limit”, ICC says.

When it comes to LBW decisions, there is a category known as the “Umpire’s Call”, wherein the on-field umpire can use his discretion to rule on a dismissal “where the technology indicates a marginal decision in respect of either the point of first interception or whether the ball would have hit the stumps”. For decisions determined by way of the umpire’s call, the player review stands unchanged and does not count towards the innings limit.

What Is The DRS Process In LBW Decisions?

By their very nature, given the various factors involved, LBW decisions are among those most frequently appealed by players. The ICC, therefore, lays down an elaborate procedure for the review of LBW decisions.

To begin with, after an LBW decision is sent for review, the third umpire has to check whether “the delivery is fair, and second, whether or not the ball has touched the bat before being intercepted by any part of the striker’s person”.

If this initial review supports an LBW dismissal, the third umpire uses the ball-tracking technology to analyse “three pieces of information… relating to the path of the ball”. They are, the point of pitching; the position of the ball at the point of first interception, or impact; and, whether the ball would have hit the wicket.

It is the last aspect that has sparked the controversy in relation to Elgar’s dismissal after the ball-tracking technology showed Ashwin’s delivery overshoot the stumps even though the actual footage suggested that it was going on to hit the stumps. Discussing the review, former South Africa skipper Shaun Pollock said that the inputs provided by the Hawkeye ball-tacking technology has to be respected.

“Hawk-eye is something you rely on for decision making. It’s an independent body. They do their level best with everything they have got. They have got their own cameras. They got each little point that they plot. And that’s how they work out where it goes. That’s a lot more scientific than any of us. We rely on them to make the decision and that’s what they have done,” Pollock said.

But India legend Sunil Gavaskar said that what he ascertained from Ashwin’s delivery was that “because it hit Elgar on the knee roll, I thought at best it would if it was not hitting the top of middle stump then it would clip the top and that would mean umpires call and that was out”. Explaining his view, Gavaskar said that “On the knee roll (where the ball hit Elgar), for someone who is not that tall, nine times out of 10, even on South African pitches, the ball would hit the stumps”.

Team India players were visibly upset and mystified by the decision with comments picked up by on-field mics underlining their unhappiness. Ashwin slammed the broadcasters at the stadium, saying “you should find better ways to win Supersport”, while Kohli and Rahul, too, vented their displeasure. While th broadcasters are responsible for match production and camera feed, the ball-tracking Hawkeye technology itself is proprietary and used across countries and in different sports.

What Is The Hawkeye Technology?

Used for the first time in 2001 in an international match, Hawkeye was developed by Dr Paul Hawkins with the technology later leading to the setting up of a separate company, Hawk-Eye Innovations Ltd. It is a computer-based system that is now used in multiple sports to assess the trajectory of balls in flight.

According to this BBC piece, “Hawkeye uses technology originally used for brain surgery and missile tracking”. The system works by relying on six cameras placed at special positions around the ground to track the path of the ball. It picks up the trajectory of a delivery right from the moment it leaves the bowler’s arm to when the ball becomes dead.

The visual information it collects is translated into a 3D projection of how the ball would travel on an imaginary cricket pitch. “It’s so good it can track any types of bounce, spin, swing and seam. And it’s about 99.99 per cent accurate too,” BBC says.

However, as a report points out, “Hawkeye or any other ball tracking technology is still a work in progress [and] does not provide totally conclusive evidence”. It, therefore, should be regarded as more of an assistive tool “for making a better judgment” and, especially in touch-and-go cases, it is the on-field umpire’s decision that should receive greater weight. Which is what could have happened in Cape Town if Ashwin’s delivery was shown to be marginally clipping the bail. But given that it was passing clear, the ICC rules stipulate that the decision was to be not out.

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