An illustration of the Hawk Eye system in tennis

How the Hawk Eye System Works in Tennis


For tennis fans, Hawk-Eye needs no introduction. The sophisticated piece of technology has been an integral part of tennis decision-making since 2006. Those close calls that were previously left to the eagle-eyed umpires are now much less contentious, with players given the option to let Hawk-Eye have the final say.

What does Hawk-Eye do?

Hawk-Eye is able to identify whether a ball is classed as in or out of play. It tracks the ball’s path to show exactly where the ball bounces so that the umpire’s decision can be confirmed or overturned. Tennis is not the only sport that uses Hawk-Eye technology; it is used in cricket (bowling/LBW) and also football (for goal-line technology). When so much is at stake in games and umpires/referees struggling to make accurate calls on shots that are particularly fast, or if vision is blocked by a player standing in their eye-line, Hawk-Eye is able to offer a second, more scientific opinion.

When can Hawk-Eye be used?

In tennis, the game would be continually delayed if players were allowed to use Hawk-Eye for all decisions, so they are limited to three unsuccessful challenges of the umpire’s decision. So if the player’s challenge is successful, they can continue to make more challenges until three incorrect challenges are made. Hawk-Eye has become a huge part of tennis now, with TV showing the ball trajectory even when a challenge isn’t made. It can also add to the intensity and excitement of the game, as often in big matches the crowd will do drumroll sounds and then a cheer on decisions that help their favourite player. Hawk-Eye has made some huge tennis decisions that have ultimately decided the results of high profile matches.

How the technology works

The system is based on the principle of ‘triangulation’, which finds a location of a point by using measurement of the angles of two other fixed points. It comprises of a tracking system (camera and speed gun) and the video replay system that relays it back to the umpire or television viewers. At big tournaments, you will usually have a big screen that also shows the video replay to the spectators.

Cameras are placed high above the tennis court to enable them to track the path of the ball and it is said to be able to show the bounce to a precision of 3.6mm, or an accuracy rate of 99.99%.

The usage of Hawk-Eye

Many players have publicly criticised the use of Hawk-Eye and doubted its accuracy in the early days, although it has improved significantly over the years. Initially, the ball area was shown on the replays as a circular shape but it was pointed out that the ball changes shape on impact, meaning that a more oval shape is a truer reflection of the shape of the ball.

The use of Hawk-Eye is mainly in the bigger tournaments and matches, due to how expensive it is to have installed. It is also used by coaches to break down a player’s strokes for analysis, in a greater level of detail than you would get with just video alone. Hawk-Eye offers a SMART Tennis coaching system that is used by professionals.

There are even Hawk-Eye tennis simulators that allow tennis fans to see how it feels to play in a big tournament and to use their skills to accurately show where the ball would land on the court. It is a bit like the Wii tennis game that came out some years ago but of much better standard in terms of showing the correct ball outcomes and the overall graphics.

According to the Hawk-Eye Innovations website, it is now used in over 80 tennis tournaments around the world. The system has come a long way since it was first used for TV coverage of the Davis Cup in 2002. From being a part of the TV viewing experience to making the most significant decisions at grand slam matches, Hawk-Eye is now an integral part of the game of tennis.

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