Tennis Hawk Eye – What is it and how does it work?

Hawk-Eye is a complex computer system designed to visually track the trajectory of the ball and display a record of its most statistically likely path as a moving image. Its usage is famous mainly due to its implementation in Tennis matches. This system implemented by the company ‘Hawk-Eye Innovations Ltd’ is also used in Cricket and will be used in Soccer in the next clubs’ World Cup in Japan, as recently announced by FIFA.

The Hawk-Eye system is based on triangulation principles that make use of visual images and timing data provided by 10 high-speed video cameras placed at strategically locations and angles around the Tennis Court. The system has embedded a predefined model of the court and includes data on Tennis rules which allows rapidly processing the video feeds through the means of a high-speed camera and a ball tracker system.

In each frame sent from each camera, the system identifies the group of pixels which corresponds to the image of the ball. It then calculates for each frame the 3D position of the ball by comparing its position on at least two of the physically separate cameras at the same instant in time. A succession of frames builds up a record of the path along which the ball has travelled.

The system then generates a graphic image of the ball path and the court, allowing information to be provided to the umpire, line judges, players and television spectators.

The Hawk-Eye system was tested in 2005 by the International tennis Federation in New York City and was approved for professional use since then, including in several major tennis tournaments, such as Wimbledon, the US Open, the Australian Open, the Davis Cup and the Tennis Masters Cup that will held its 2012 edition shortly next November. In clay surfaces tournaments, such as Roland Garros, this technology is not used since officials of the French Open refuse to implement it. Nonetheless, the ball leaves a mark on this type of court traceable to the umpire allowing him to alter a decision if that may prove to be the case.

The 2007 Australian Open was the grand-slam tournament where Hawk-Eye in challenges to line calls was first implemented.

Until March 2008, the several tennis associations and in different tournaments had conflicting rules on how Hawk-Eye was to be utilized, namely in what respects to the number of challenges a player was allowed per set.

Some tournaments allowed players a greater margin for error, with players allowed an unlimited numbers of challenges over the course of a match, while in other tournaments players received two or three per set.

From March 19, 2008 forward a unified rule of three unsuccessful challenges per set, with an additional challenge if the set reaches a tiebreak, is in force.

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