1. INTRODUCTION In the past few decades, skepticism about umpiring follies hasn¶t abated. In the world of sports, where stakes are increasing by every passing minute and an erroneous line-call can mean change of fortunes, there is an increasing reliance on technology to ensure that all arbitrations are unbiased. The HAWKEYE is one of the most commonly used technologies in the game of cricket today. It has been put to a variety of uses, such as providing a way to collect interesting statistics, generate very suggestive visual representations of the game play and even helping viewers to better understand the umpiring decisions, especially in the case of LBWs. While the system provides for things which we see every day on television, there is very impressive technology going into it, which many of us are oblivious to. In this paper, we attempt to explain how the technology works, in detail. The game of cricket has attained great commercial importance and popularity over the past few years. As a result, there has been felt a need to make the game more interesting for the spectators and also to try and make it as fair as possible. The component of human error in making judgments of crucial decisions often turns out to be decisive. It is not uncommon to see matches turning from being interesting to being one sided due to a couple of bad umpiring decisions. There is thus a need to bring in technology to try and minimize the chances of human error in such decision making. Teams across the world are becoming more and more professional with the way they play the game. Teams now have official strategists and technical support staff which help players to study their past games and improve. Devising strategies against opponent teams or specific players is also very common in modern day cricket. All this has become possible due to the advent of technology. Technological developments have been harnessed to collect various data very precisely and use it for various purposes. The HAWKEYE is one such technology which is considered to be really top notch in cricket. The basic idea is to monitor the trajectory of the cricket ball during the entire duration of play. This data is then processed to produce life like visualizations showing the paths which the ball took. Such data has been used for various purposes, popular uses including the LBW decision making software and colorful wagon wheels showing various statistics. This paper attempts to explain the intricate details of the technology which goes behind the HAWKEYE. We first start off with a general overview of the system and an outline of the challenges that we might face, then move on to the details of the technology and end with various applications where one sees this technology being put to use. Not only in the game of cricket, has Hawkeye found its importance in the game of tennis. It all started in Serena Williams' quarterfinal loss to Jennifer Capriati at the 2004 US Open, many crucial calls were contested by Williams, and TV replays demonstrated that some were indeed erroneous. Though the calls themselves were not reversed, the chair umpire Mariana Alves was removed from consideration for further matches at that year's U.S. Open. These errors prompted 1 talks about line calling assistance especially as the Auto-Ref system was being tested by the U.S. Open at that time and was shown to be very accurate. 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 during 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 Stella Artois at Queens, 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. In March 2006, at the Nasdaq-100 Open, 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 on Rod Laver Arena was allowed 2 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 2 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 3 incorrect challenges per set instead. Any leftover challenges didn't carry over to the next set. Once, in one of Amélie Mauresmo's matches, she challenged a ball that was called in, Hawk-Eye showed the ball was out by less than a millimeter but the verdict was called in. As a result, the point was replayed and Mauresmo didn't lose an incorrect challenge. Hawk-Eye has also been proposed for use in Association football but has yet to win general approval from the major governing bodies of the sport. The Football Association, English football's governing body, has declared the system as "ready for inspection by FIFA", after tests suggested that the results of a goal-line incident could be relayed to the match referee within half a second (IFAB, the governing body for the Laws of the game, insists on goals being signalled immediately i.e. within five seconds). 2 FIFA secretary general Jerome Valcke admits Hawk-Eye goal-line technology will be considered if the system's developers guarantee a 100% success rate. Football's governing body has previously been reluctant to use video technology to settle on-pitch disputes. Testing of the Hawk-Eye's suitability in football is expected to continue and there could be a trial run in the Premier League, according to Dr. Paul Hawkins, who invented the system. "We will speak to FIFA over the next week or so to get the detail, but it looks positive I think," Hawkins said. At the World Snooker Championship 2007, the BBC used Hawk-Eye for the first time in its television coverage to show player views, particularly in the incidents of potential snookers. 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 uses the system sporadically, for instance in the 2009 Masters at Wembley the Hawk-Eye was at most used once or twice per frame. In contrast to tennis, the Hawk-Eye is never used in snooker to assist referees' decisions. 3 2. LITERATURE SURVEY Cricket is a ball game played within a predetermined area. A system comprising of video cameras mounted at specific angles can be used to take pictures. These pictures are then used to locate the position of the ball. The images are then put together and superimposed on a predetermined model to form a complete visualization of the trajectory of the ball. The model includes, in this case, the pitch, the field, the batsmen and fielders etc. For this to be possible, we need to sample images at a very high rate and thus need efficient algorithms which can process data in real time. Such technologies are widely used today in various sports such as Tennis, Billiards which also fall in the category of ball games played within a restricted area. Our discussion will mostly contain applications which specific to the game of cricket, however in some cases, we will mention how similar techniques are applied in other games. There are various issues which crop up when one tries to design and implement such a system. In the game of cricket, the general issues are: y The distance at which the cameras see the pitch and the ball are dependent on the dimensions of each ground and can vary greatly. y Just the individual images don¶t help too much; for the system to be of practical use, one must ensure that it can track the 3D trajectory of the ball with high precision. In order to get this accuracy, the field of view of each camera should be restricted to a small region ± this means one needs more cameras to get the coverage of the entire field. y Fielders and spectators might obstruct the camera¶s view of the ball and the ball might get µlost¶ in its flight in one or more of the cameras.