How do challenges work in tennis?

Tennis Challenges

Sports are becoming increasingly digitalized, drastically reducing the margin of error. Tennis is no exception, as it has been one of the pioneering disciplines in video refereeing. A great example of this is with the introduction of Hawkeye, which has revolutionized the sport since its implementation. In this article, we will discover the history and implementation of the player's challenge and the Hawkeye system.

🎯Hawkeye
🔍Which surfaces?
🎾The rules
✨FoxTenn

The origin of the Hawkeye and how it works

The Hawkeye system was first used in 2006, although its creation and development had been in the works for several years before this release. As we've all experienced, having your tennis prediction fall short because of a refereeing mistake can be incredibly frustrating. This was commonplace in tennis until the early 2000s. A memorable match at the 2004 US Open between Serena Williams and Jennifer Cipriati, which was full of controversy, ended with the American losing the match after the head umpire made several wrong calls. Television replays left clear evidence of the accumulation of human errors and marked the starting point for the need for a more accurate review system. With technology having advanced to a certain level, it was time for a digital revolution in the world of tennis.

Strictly speaking, you should know that Hawkeye is an advanced technology that uses a software system and cameras to determine the impact site of the ball on the court, which was taken and adapted to tennis from a previous implementation in cricket and snooker in the United Kingdom.

In its most conventional form, this system works with a set of 10 cameras installed around the tennis court, which capture the trajectory and speed of the ball. Through this capability, a computer indicates the precise location of the ball's bounce and generates an accurate image in real time to be viewed by judges and spectators.

Does Hawkeye have a margin of error? Yes, but it is around 2 to 3 millimeters, which does not affect the accuracy of the decisions and confirms its value as a tool to correct refereeing errors.

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What surfaces is Hawkeye used on and what are the regulations for use?

Beyond the advantages mentioned above, it is important to know that Hawkeye is not used on all tennis surfaces. For example, Hawkeye isn't used on clay courts since the ball bounces are visible on the surface and the referees review the plays in the traditional method. For this reason, you won't find Hawkeye decisions in tournaments like the French Open. On the contrary, this system is used on hard or grass courts.

Unlike sports such as football or basketball, where the review of video referees can take up to a few minutes, in tennis a correct decision can be made within a few seconds after a player requests the Challenge. How does it work?

The rules for using the Challenge or Hawkeye

The rules for using the Hawk-Eye or Challenge have been established by the ITF (International Tennis Federation). This technology must be used by participants in the following manner:

Electronic review may only be requested after a decisive blow or if play is stopped during a rally. If a return is allowed, the player must stop play immediately.
The chair umpire must use electronic review if there is any doubt about the decision but may refuse it if he or she considers the request to be unreasonable or late.
In doubles, the appeal must stop play and the chair umpire reviews the proceedings. If a mistake was made or the appeal was made late, the opposing team may win the point.
The original decision will prevail if electronic review cannot resolve the dispute for any reason.
The chair umpire's final decision based on the electronic review is not appealable. If a manual review is needed, the referee will decide which impact is reviewed.

What is the FoxTenn system?

Hawkeye had and still has a wide following, but in 2017 a powerful alternative called FoxTenn appeared, which was implemented in 2024 in more than 50 recognized tournaments. It is a system invented by the Spaniard Javier Simón, which has already been accepted by the ITF, ATP, and WTA, in addition to the Grand Slam tournaments.

One of the main innovations of the FoxTenn system is that it has more than 40 ultra-high-speed cameras, which is 300 percent more than those used by Hawkeye. As if that were not enough, these cameras have a laser system that facilitates the capture of every movement, and they are located at ground level to make them less vulnerable to inclement weather that could affect their operation (weather factors or public movements, for example). In short, the cameras capture 3,000 images per second and are synchronized with these high-end lasers, which prevents any possibility of error.

Another difference with respect to Hawkeye is that the FoxTenn system for the Challenge works with a mathematical estimate based on the cross-referencing of images taken by 10 aerial cameras with a previous measurement of the court. Here there is no margin of error of a few millimeters like we know with Hawkeye.

To finish illustrating the precision of the FoxTenn system, it is worth mentioning that this system supports the capture of 150 thousand photos of the same ball bounce, while the human eye can only detect 30 images per second.

Why tennis was at the forefront of video review

As mentioned, tennis has been a pioneer in technology applied to refereeing. Its implementation in the mid-2000s, while in other sports the inclusion of video refereeing systems was hardly considered, is proof of this. Without going any further, it was due to the success shown by tennis that other disciplines such as soccer, baseball or football (among others) were inspired to develop their own tools. Another of the great reasons is the positive belief in this system by players and spectators, unlike what happened in other activities, which gives it a framework of greater transparency.