Hawk-Eye was the brainchild of British inventor Dr. Paul Hawkins, who graduated from Durham University with a PhD in Artificial Intelligence in 1999 and once described himself as a ‘pretty reasonable cricketer’. Indeed, Hawk-Eye was originally intended as a cricket application and, in 2001, was first used by television broadcasters to analyse leg before wicket (lbw) decisions.
Neverthless, the principle of employing a network of computer-controlled cameras to ‘triangulate’ the position of a ball in three-dimensional space and calculate its probable trajectory, or path, is equally applicable to tennis. Nowadays, Hawk-Eye is used in tennis tournaments worldwide, not just as a broadcast enhancement aid, but as an officiating tool, on which chair umpires and line judges rely.
Hawk-Eye, as a line-calling system, made its debut in an Association of Tennis Professionals (ATP) and Women’s Tennis Association (WTA) Tour event at the Miami Open at the Crandon Park Tennis Center in Key Biscayne, Florida in 2006. Later that year, Hawk-Eye was put into operation at the US Open at the USTA Billie Jean King National Tennis Center in New York City. According to ‘Tennis Week’, ‘Hawk-Eye eliminated interminable arguments and verbal assaults on umpires and linesmen that became such a nightmare and a form of gamesmanship years ago.’
Hawk-Eye™ is an officiating tool, intended to assist human line judges by providing an impartial second opinion on close line calls. Hawk-Eye uses a series of computer-controlled cameras, up to ten in total, placed around the court to gather information on the speed and trajectory of the ball. Using triangulation or, in other words, by determining the location of a point by forming triangles to that point from other, known points and measuring the angles of the triangles, Hawk-Eye constructs an animation of the most likely path, statistically, of the ball.
If a player challenges a line call, the animation can displayed on a screen, which can be seen by everyone involved, including spectators, to remove any doubt about whether a ball has bounced in or out. Hawk-Eye uses an algorithm, or a series of computer instructions, to estimate where a ball should have landed but, while it is not infallible, it is accurate to within a few millimetres and approved by the ITF, which employs the technology in 80 tournaments worldwide.
Hawk-Eye technology was first employed in a tournament sanctioned by the International Tennis Federation (ITF) at the Hopman Cup in Perth, Western Australia and in a Association of Tennis Professionals (ATP) and Women’s Tennis Association (WTA) Tour event at the Miami Open, formerly the NASDAQ-100 Open, at Key Biscayne, Florida in 2006. The U.S. Open, later in 2006, was the first ‘Grand Slam’ event to use Hawk-Eye technology.
The Wimbledon Championships were first staged at the AllEngland Lawn Tennis and Croquet Club in Wimbledon, southwest London, in 1877. The inaugural Championships featured just one event, the Gentlemen’s Singles, which was contested by twenty-one amateur players, each of whom paid an entrance fee of £1 1s 0d, or a ‘guinea’. The tournament started on July 9, 1877 and the final was played ten days later after being postponed from the Monday to the Thursday because of rain. In a one-sided final, Spencer Gore, a 27-year-old rackets player, beat William Marshall, a 28-year-old real tennis player, in straight sets. Gore received a silver cup, donated by ‘The Field’ magazine, and 12 guineas in prize money.
The first Ladies’ Singles competition was not staged until 1884, by which time the All England Lawn Tennis and Croquet Club had dropped ‘Croquet’ from its name to become, simply, the All England Lawn Tennis Club. The inaugural female champion was 19-year-old Maud Watson, who defeated her elder sister, Lillian, by two sets to one in the final. Miss Watson received a silver flower basket and 20 guineas in prize money.
Modern tennis balls consist of an inner rubber core, filled with pressurised air, and a outer cover, made of wool or nylon, which is bound to the core by means of a heated press. According to the International Tennis Federation (ITF), when a tennis ball is dropped, vertically, onto a smooth, granite block from a height of 100”, or 8’4”, it should rebound to a height between 53” and 58”.
However, after a period of serious play – typically about three hours – the cover of a tennis ball may become fluffed up, so that the ball does not fly through the air as fast as a new one, and the ball may lose internal pressure, so that it does not bounce as high. Obviously, both these factors can adversely affect the control and accuracy of a tennis player, so tennis balls are routinely changed after every seven and nine games, alternately, throughout the course of a tennis match. The first ball change takes place after just seven games to allow for the warm-up. High humidity increases the moisture content of a tennis ball, and hence its mass, and high temperature can cause the ball to bounce higher, so ‘new’ balls are stored in a courtside refrigerator, maintained at a constant 68°F, or 20°C, to keep them in optimal condition.