the hawk-eye and the cricket

Hawk-eye is the name of a computer system which traces a ball's trajectory, with a claimed accuracy of 5 mm, and sends it to a virtual-reality machine.
Method

Hawk-Eye uses six or more computer-linked television cameras situated around the cricket field of play. The computer reads in the video in real time, and tracks the path of the cricket ball on each camera. These six separate views are then combined together to produce an accurate 3D representation of the path of the ball.
History

The Hawkeye system was launched in 2001. It was first used in television coverage of sporting events such as Test cricket, and has now reached the stage of being used by officials in tennis to assist in adjudicating close line calls.
Uses

The system was first used during a Test match between Pakistan and England at Lord's Cricket Ground, on 21 April 2001, in the TV coverage by Channel 4. Since then it has been an indispensable tool for cricket commentators around the world. It is used primarily by the majority of television networks to track the trajectory of balls in flight, mostly for analyzing leg before wicket decisions. In this case, Hawk-Eye is able to project the likely path of the ball forward, through the batsman's legs, to see if it would have hit the wicket. Currently this information is not used by the umpires to adjudicate on LBW decisions - it is only available to television viewers, although in the future it may be adopted by the third umpire. Currently the central umpire only get to see it once - and they have to make their minds up instantly.

The ball by ball tracking by the Hawk-Eye system allows the broadcasters to showcase many other features of the game, such as comparing the bowlers' speeds, spin, swing, line and length.
Criticisms

Although Hawkeye is very accurate in measuring the actual path of a ball, when it comes to predicting the future path of the ball, such as in LBW decisions, it is not as clear. If the ball is heading to the pitch, there's no way Hawk-eye can tell if a delivery is going to skid a bit more than normal or hit a crack, bit of grass, or worn patch of the pitch. The predicted path of the ball is based on the average and expected pathway.