Monday, 22 August 2011

Hawk-Eye

Hawk-Eye is a complex computer system used in cricket, tennis and other sports to visually track the trajectory of the ball and display a record of its most statistically likely path as a moving image. In cricket and tennis, it is now part of the adjudication process. It was developed by engineers at Roke Manor Research Limited of Romsey, Hampshire in the UK, in 2001. A UK patent was submitted but withdrawn by Dr Paul Hawkins and David Sherry. Later, the technology was spun off into a separate company, Hawk-Eye Innovations Ltd., as a joint venture with television production company Sunset + Vine, which was bought outright by Sony in March 2011.

All Hawk-Eye systems are based on the principles of triangulation using the visual images and timing data provided by at least four high-speed video cameras located at different locations and angles around the area of play. The system rapidly processes the video feeds by a high-speed video camera and ball tracker. A data store contains a predefined model of the playing area and includes data on the rules of the game.
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. It also "predicts" the future flight path of the ball and where it will interact with any of the playing area features already programmed into the database. The system can also interpret these interactions to decide infringements of the rules of the game.

The system generates a graphic image of the ball path and playing area, which means that information can be provided to judges, television viewers or coaching staff in near real time.

The pure tracking system is combined with a backend database and archiving capabilities so that it is possible to extract and analyse trends and statistics about individual players, games, ball-to-ball comparisons, etc.

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