The professional tennis courts from all over the world literally emptied, leaving, only three protagonists in the singular (and five in the double): i players and the chair judge on his high chair. There technology he actually supplanted i Line judgesdeputies to call the ball “out”. Since 2025 ATP and WTA, the two associations that protect the rights of tennis players and organize most of the tournaments, have decided to do without them, giving full confidence to the “Electronic Line Calling Live“. In Slam the Australians Open embraced the technological turning point already in 2021followed a year later by the US Open, while this year it was up to Wimbledon to break a tradition that had lasted for 147 years. Roland Garros Parisian remains the only tournament in the main circuit that resists with the line judges.
The refereeing of a tennis match revolves mostly on calls “in” And “out“, That is, if the ball remains on the pitch (just touch the line) or not. Let’s find out together what science tells us on the margin of error of the human eye and technology.
What is the Hawk-Eye system and how the “Electronic Line Calling Live” works works
Elc Live It was experienced for the first time at Next Gen Atp Finals of 2017 in Milan and was designed by an English company, Hawk-Eye (literally “falco eye”), then purchased by the Japanese multinational Sony in 2001. Today many of the most popular sports use the Hawk-Eye system, a reason why the technology itself has commonly taken the name of “hawk eye”; A famous application is precisely the Goal-line Technology In football, which relies on a similar system to determine with millimeter precision if the ball has passed the goal line.
In tennis it serves to draw the trajectory of the ball in the most realistic way possible. To establish if it is inside or outside, the image captured by a camera is not used when the ball lands, but come “Triangular” (i.e. put together) the Information of 12 objectives. The latter, positioned in order to cover the whole fieldmanage to trace the movement of the ball a 340 frames per second and to transmit it to a computer, which based on these data immediately makes one 3D projection of the point where the ball is about to fall. After elaborating the images, the system says to high volume “Out!“When the ball is out, replacing, also” vocally “, to the line judges. In an interview with the CNBC the British company explained how L‘Equipment for a tennis court cost about 100 thousand dollars and that it usually takes three days to install it and calibrate it. It is done by pulling the balls several times on the lines, with a racket or a shooting-pallline car.
Margin of error in tennis: the numbers of the human eye and that of the “hawk”
We come to the edge of error and the comparison between the human eye and that of the “hawk”. An American study from 2008 estimated that i Line judges are missing 8.2% of decisions when the ball, which can travel at speeds above 200 km/hfalls in an area to a maximum of 10 centimeters from the line. The electronic systemon the other hand, was put on the market with a Margin of error between 2.2 and 3.6 millimetersequal to1%. The numbers therefore show a clear supremacy of the hawk eye in real time compared to the decisions of the line judge, also influenced by psychophysical variables such as stress or vision defects or, in general, by external distractions.
Red earth is a separate case
The Roland Garrosor the only slam on beaten earth, remains the only tournament of the major circuit that still adopts i human judgesbut the other events on red, such as the International of Romealbeit with delay compared to competitors on grass and cement, since 2025 they have chosen the technological way. This created many controversies among the players, primarily the German Sascha Zverev and n ° 1 of the world Aryna Sabalenkawho in recent months, armed with smartphones, have not thought twice and published the Errors of the hawk. Yes, because red earth is the only surface that Show the signs of all shots and, by regulation, Hawk-Eye’s judgment is unquestionable. Translated: even if the royal imprint shows the error of technology, the chair judge cannot change the decision.
One of the reasons why the red earth tournaments have delayed the use of technology is that the surface is more changingchanges according to atmospheric conditions (it can be humid or dry, swept by the wind or not) and to Passage of the players. This slightly increases the margin of error, and above all makes one necessary recalibration more frequent. In the tournaments on concrete, this is made only at the beginning of the event, while on earth it should be adjusted even between one game and another, in one operation that would require about half an hourdifficult practice in a dense programming of match.
Foxtenn, a fox challenges the eye of Falco
Over the past few years another player has been included in the market of arbitration technological support and movement: the Spanish company Foxtenn. The system was approved at the end of the 2016 Following a rigorous series of tests and criteria established by a committee made up of representatives of ITF, ATP, WTA and Grand Slam tournaments. Using about 40 cameras, scanner And laserFoxtenn captures the rebound of the ball on the field in real timeeliminating the need to simulations and boasting a error rate of 0 thanks to beyond 150,000 images per second. Several minor tournaments have adopted the Foxtenn system, especially on the red earth where the ball leaves, as mentioned, a physical sign, but among the disadvantages there are the high installation costs.
