By Author – Rishabh Sontakke
Hawk-Eye is a computer system used in numerous sports such as cricket, tennis, Gaelic football, badminton, hurling, Rugby Union, association football, and volleyball, to visually track the trajectory of the ball and display a profile of its statistically most likely path as a moving image.
The Sony-owned Hawk-Eye system was developed in the United Kingdom by Paul Hawkins. The system was originally implemented in 2001 for television purposes in cricket. The system works via six (sometimes seven) high-performance cameras, normally positioned on the underside of the stadium roof, which track the ball from different angles. The video from the six cameras is then triangulated and combined to create a three-dimensional representation of the ball’s trajectory. Hawk-Eye is not infallible, but is accurate to within 3.6 millimeters and generally trusted as an impartial second opinion in sports.
It has been accepted by governing bodies in tennis, cricket, and association football as a means of adjudication. Hawk-Eye is used for the Challenge System since 2006 in tennis and Umpire Decision Review System in cricket since 2009. The system was rolled out for the 2013-14 Premier League season as a means of goal-line technology. In December 2014 the clubs of the first division of Bundesliga decided to adopt this system for the 2015-16 season.
How does it work?
The whole setup involves six high-speed vision processing cameras along with two broadcast cameras. When a delivery is bowled, the position of the ball recorded in each camera is combined to form a virtual 3D positioning of the ball after its being delivered. The whole process of the delivery is broken into two parts, delivery to bounce and bounce to impact. Multiple frames of the ball position are measured and through this, you can calculate the direction, speed, swing, and dip of that specific delivery.
Deployment in sports
The technology was first used by Channel 4 during a Test match between England and Pakistan on Lord’s Cricket Ground, on 21 May 2001. It is used primarily by the majority of television networks to track the trajectory of balls in flight. In the winter season of 2008/2009, the ICC trialed a referral system where Hawk-Eye was used for referring decisions to the third umpire if a team disagreed with an LBW decision. The third umpire was able to look at what the ball actually did up to the point when it hit the batsman, but could not look at the predicted flight of the ball after it hit the batsman.
Its major use in cricket broadcasting is in analyzing leg before wicket decisions, where the likely path of the ball can be projected forward, through the batsmans legs, to see if it would have hit the stumps. Consultation with the third umpire, for conventional slow motion or Hawk-Eye, on the leg before wicket decisions, is currently sanctioned in international cricket even though doubts remain about its accuracy.
The Hawk-Eye referral for an LBW decision is based on three criteria:
? Where the ball pitched.
? The location of impact with the leg of the batsman.
? The projected path of the ball past the batsman.
In all three cases, marginal calls result in the on-field call being maintained.
Due to its real-time coverage of bowling speed, the systems are also used to show delivery patterns of a bowler’s behavior such as line and length, or swing/turn information. At the end of an over, all six deliveries are often shown simultaneously to show a bowler’s variations, such as slower deliveries, bouncers, and leg-cutters. A complete record of a bowler can also be shown over the course of a match.
Batsmen also benefit from the analysis of Hawk-Eye, as a record can be brought up of the deliveries from which a batsman scored. These are often shown as a 2-D silhouetted figure of batsmen and color-coded dots of the balls faced by the batsman. Information such as the exact spot where the ball pitches or speed of the ball from the bowler’s hand (to gauge batsman reaction time) can also help in post-match analysis.
In late 2005 Hawk-Eye was tested by the International Tennis Federation (ITF) in New York City and was passed for professional use. Hawk-Eye reported that the New York tests involved 80 shots being measured by the ITF’s high-speed camera, a device similar to MacCAM. During an early test of the system at an exhibition tennis tournament in Australia (seen on local TV), there was an instance when the tennis ball was shown as “Out”, but the accompanying word was “In”. This was explained to be an error in the way the tennis ball was shown on the graphical display as a circle, rather than as an ellipse. This was immediately corrected.
Hawk-Eye has been used in television coverage of several major tennis tournaments, including Wimbledon, the Queen’s Club Championships, the Australian Open, the Davis Cup and the Tennis Masters Cup. The US Open Tennis Championship announced they would make official use of the technology for the 2006 US Open where each player receives two challenges per set. It is also used as part of a larger tennis simulation implemented by IBM called PointTracker.
The 2006 Hopman Cup in Perth, Western Australia, was the first elite-level tennis tournament where players were allowed to challenge point-ending line calls, which were then reviewed by the referees using Hawk-Eye technology. It used 10 cameras feeding information about ball position to the computers. Jamea Jackson was the first player to challenge a call using the system.
In March 2006, at the Nasdaq-100 Open in Miami, Hawk-Eye was used officially for the first time at a tennis tour event. Later that year, the US Open became the first grand-slam event to use the system during play, allowing players to challenge line calls.
The 2007 Australian Open was the first grand-slam tournament of 2007 to implement Hawk-Eye in challenges to line calls, where each tennis player in Rod Laver Arena was allowed two incorrect challenges per set and one additional challenge should a tiebreaker be played. In the event of an advantage final set, challenges were reset to two for each player every 12 games, i.e. 6 all, 12 all. Controversies followed the event as at times Hawk-Eye produced erroneous output. In 2008, tennis players were allowed three incorrect challenges per set instead. Any leftover challenges did not carry over to the next set. Once, Amlie Mauresmo challenged a ball that was called in, and Hawk-Eye showed the ball was out by less than a millimeter, but the call was allowed to stand. As a result, the point was replayed and Mauresmo did not lose an incorrect challenge.
The Hawk-Eye technology used in the 2007 Dubai Tennis Championships had some minor controversies. Defending champion Rafael Nadal accused the system of incorrectly declaring an out ball to be in following his exit. The umpire had called a ball out; when Mikhail Youzhny challenged the decision, Hawk-Eye said it was in by 3 mm. Youzhny said after that he himself thought the mark may have been wide but then offered that this kind of technology error could easily have been made by linesmen and umpires. Nadal could only shrug, saying that had this system been on clay, the mark would have clearly shown Hawk-Eye to be wrong. the area of the mark left by the ball on hard court is a portion of the total area that the ball was in contact with the court (a certain amount of pressure is required to create the mark)
The 2007 Wimbledon Championships also implemented the Hawk-Eye system as an officiating aid on Centre Court and Court 1, and each tennis player was allowed three incorrect challenges per set. If the set produced a tiebreaker, each player was given an additional challenge. Additionally, in the event of a final set (third set in women’s or mixed matches, fifth set in men’s matches), where there is no tiebreak, each player’s number of challenges was reset to three if the game score reached 6?6, and again at 12?12. Teymuraz Gabashvili, in his first-round match against Roger Federer, made the first ever Hawk-Eye challenge on Centre Court. Additionally, during the finals of Federer against Rafael Nadal, Nadal challenged a shot which was called out. Hawk-Eye showed the ball as in, just clipping the line. The reversal agitated Federer enough for him to request (unsuccessfully) that the umpire turns off the Hawk-Eye technology for the remainder of the match.
In the 2009 Australian Open fourth round match between Roger Federer and Tom Berdych, Berdych challenged an out call. The Hawk-Eye system was not available when he challenged, likely due to a particularly pronounced shadow on the court. As a result, the original call stood.
In the 2009 Indian Wells Masters quarterfinals match between Iva Ljubii and Andy Murray, Murray challenged an out call. The Hawk-Eye system indicated that the ball landed in the center of the line despite instant replay images showing that the ball was clearly out. It was later revealed that the Hawk-Eye system had mistakenly picked up the second bounce, which was on the line, instead of the first bounce of the ball. Immediately after the match, Murray apologized to Ljubicic for the call and acknowledged that the point was out.
The Hawk-Eye system was developed as a replay system, originally for TV broadcast coverage. As such, it initially could not call-ins and outs live.
The Hawk-Eye Innovations website states that the system performs with an average error of 3.6 mm. The standard diameter of a tennis ball is 67 mm, equating to a 5% error relative to ball diameter. This is roughly equivalent to the fluff on the ball.
Currently, only clay court tournaments, notably the French Open is the only Grand Slam, are found to be generally free of Hawk-Eye technology due to marks left on the clay where the ball bounced to evidence a disputed line call. Chair umpires are then required to get out of their seat and examine the mark on the court with the player by his side to discuss the chair umpire’s decision.
Unification of Rules
Until March 2008, the International Tennis Federation (ITF), Association of Tennis Professionals (ATP), Women’s Tennis Association (WTA), Grand Slam Committee, and several individual tournaments had conflicting rules on how Hawk-Eye was to be utilized. A key example of this was the number of challenges a player was permitted per set, which varied among events. Some tournaments allowed players a greater margin for error, with players allowed an unlimited number of challenges over the course of a match. In other tournaments, players received two or three per set. On 19 March 2008, the aforementioned organizing bodies announced a uniform system of rules: three unsuccessful challenges per set, with an additional challenge if the set reaches a tiebreak. In an advantage set (a set with no tiebreak) players are allowed three unsuccessful challenges every 12 games. The next scheduled event on the men and women’s tour, the 2008 Sony Ericsson Open, was the first event to implement these new, standardized rules.
- Association football
Hawk-Eye is one of the goal-line technology (GLT) systems authorized by FIFA. Hawk-Eye tracks the ball and informs the referee if a ball fully crosses the goal line into the goal. The purpose of the system is to eliminate errors in assessing if a goal was scored. The Hawk-Eye system was one of the systems trialed by the sport’s governors prior to the 2012 change to the Laws of the Game that made GLT a permanent part of the game, and it has been used in various competitions since then. GLT is not compulsory and, owing to the cost of Hawk-Eye and its competitors, systems are only deployed in a few high-level competitions.
As of July 2017, licensed Hawk-Eye systems are installed at 96 stadiums. By the number of installations, Hawk-Eye is the most popular GLT system.Hawk-Eye is the system used in the Premier League, Bundesliga among other leagues.
At the 2007 World Snooker Championship, the BBC used Hawk-Eye for the first time in its television coverage to show player views, particularly of potential snooker. It has also been used to demonstrate intended shots by players when the actual shot has gone awry. It is now used by the BBC at every World Championship, as well as some other major tournaments. The BBC used to use the system sporadically, for instance in the 2009 Masters at Wembley the Hawk-Eye was at most used once or twice per frame. Its usage has decreased significantly and is now only used within the World Championships and very rarely in any other tournament on the snooker tour. In contrast to tennis, Hawk-Eye is never used in snooker to assist referees’ decisions and primarily used to assist viewers in showing what the player is facing.
- Gaelic games
In Ireland, Hawk-Eye was introduced for all Championship matches at Croke Park in Dublin in 2013. This followed consideration by the Gaelic Athletic Association (GAA) for its use in Gaelic football and hurling. A trial took place in Croke Park on 2 April 2011. The doubleheader featured football between Dublin and Down and hurling between Dublin and Kilkenny. Over the previous two seasons, there had been many calls for the technology to be adopted, especially from Kildare fans, who saw two high-profile decisions go against their team in important games. The GAA said it would review the issue after the 2013 Sam Maguire Cup was presented.
Hawk-Eye’s use was intended to eliminate contentious scores. It was first used in the Championship on Saturday 1 June 2013 for the Kildare versus Offaly game, part of a doubleheader with the second game of Dublin versus Westmeath. It was used to confirm that Offaly substitute Peter Cunningham’s attempted point had gone wide 10 minutes into the second half.
Use of Hawk-Eye was suspended during the 2013 All-Ireland hurling semi-finals on 18 August due to a human error during an Under-18 hurling game between Limerick and Galway. During the minor game, Hawk-Eye ruled a point for Limerick as a miss although the graphic showed the ball passing inside the posts, causing confusion around the stadium – the referee ultimately waved the valid point wide provoking anger from fans, viewers and TV analysts covering the game live. The system was subsequently stood down for the senior game which followed, owing to “an inconsistency in the generation of a graphic”. Limerick, who was narrowly defeated after extra-time, announced they would be appealing over Hawk-Eye’s costly failure. Hawk-Eye apologized for this incident and admitted that it was a result of human error. There have been no further incidents during the GAA. The incident drew attention from the UK, where Hawk-Eye had made its debut in English football’s Premier League the day before.
Hawk-Eye was introduced to a second venue, Semple Stadium, Thurles, in 2016. There is no TV screen at Semple: instead, an electronic screen displays a green T if a score has been made, and a red Nl if the shot is wide.
It was used at a third venue, Pirc U Chaoimh, Cork, in July 2017, for the All-Ireland hurling quarter-finals between Clare versus Tipperary and Wexford versus Waterford.
- Australian football
On 4 July 2013, the Australian Football League announced that they would be testing Hawk-Eye technology to be used in the Score Review process. Hawk-Eye was used for all matches played at the MCG during Round 15 of the 2013 AFL Season. The AFL also announced that Hawk-Eye was only being tested, and would not be used in any Score Reviews during the round.
BWF introduced Hawk-Eye technology in 2014 after testing other instant review technologies for line call decision in BWF major events. Hawk-Eye’s tracking cameras are also used to provide shuttlecock speed and other insight in badminton matches. Hawk-Eye has formally introduced in 2014 India Super Series tournament.