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Hawk-Eye Line-Calling System

Hawk-eye is a technology used in tennis for determining if the ball is in or out. This line-calling system uses multiple camera angles to trace the tennis ball's trajectory. Hawk-Eye uses six or more computer-linked television cameras situated around the court. The computer processes the video in real-time, and tracks the path of the tennis ball on each camera. These six separate views are then combined to produce an accurate 3D representation of the path of the ball.

hawk eye systemIs the ball in or out?

Hawk Eye History

The Hawkeye system was invented by a young British computer expert Paul Hawkins, and 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.

The Nasdaq-100 Open in Miami was the first tour event to officially use the technology. The 2006 US Open was the first Grand Slam event to feature the system, followed by the 2007 Australian Open.

In 2020, in response to the need to reduced the number of people on the court, the U.S. Open tennis tournament replaced human line judges on 15 of 17 match courts with Hawk-Eye Live, an advanced system that makes automated line calls in real time. This Hawk-Eye Live system features 18 cameras, six of which are used by a review official to monitor foot faults. The system uses recorded voices to make its calls, which shout "out," "fault" or "foot fault." The courts using Hawk-Eye Live at the U.S. Open will have only a chair umpire to call the score after the system makes the call, and they will take over only if the system malfunctions.


The current rules under which Hawk-Eye is used:


Players have said that they instinctively know when a ball is in or out, though based on their use of the review system the evidence so far has not been conclusive. One analysis of the player challenges that have been made found that they were correct only about 46% of the time.

Officials of the French Open have so far refused to take up the technology, saying that the unique characteristics of the clay court do not warrant it. As the ball makes a mark on the clay surface, it is possible for the chair umpire to get out and have a look at the mark to determine if the ball was in or out, thus avoiding the need for hawke-eye.

Anyone who has watched a match on TV where they have used this system may have noticed that the ball seems to be elongated when projected on the court surface. This may be explained by imagining the ball hitting the ground with a lot of topspin, that it actually spins forward when in contact with the ground and is deformed so much as to flatten on the ground. The mark doesn't have to have the exact surface area of the cross-section of the ball to accurately represent the impact point of the ball.

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