Why There Is No Hawkeye on Clay

While Hawk-Eye technology has become synonymous with accuracy in line-calling across most televised tennis tournaments, its notable absence on clay courts, particularly in prominent tournaments like the French Open, presents a complex scenario.

This article explores the reasons behind this and the evolving landscape of electronic line-calling technology in tennis.

What is Hawk-Eye and How It Works

Hawk-Eye technology in tennis is a sophisticated electronic system used to visually track the ball’s trajectory and accurately determine its landing spot, particularly for close-line calls. Here’s how it works:

1. Cameras and Data Collection. Multiple high-speed cameras, usually around 10 to 12, are installed around the court. These cameras continuously capture the movement of the tennis ball from different angles.

2. Image Processing. The images captured by these cameras are processed in real-time by a computer system. The system uses multiple camera angles to triangulate the exact position of the tennis ball in three-dimensional space.

3. Ball Trajectory and Landing Spot. The system calculates the ball’s trajectory, including its flight path and bounce. Analysing the data can precisely determine where the ball landed in relation to the court lines.

4. Review and Challenge System. Players can challenge a line call if they believe it is incorrect. When a challenge is made, Hawk-Eye generates a graphical representation of the ball’s path and where it landed, displayed on screens for the players, umpires, and spectators.

5. Accuracy and Speed. Hawk-Eye is renowned for its accuracy, claimed to be within 2.2 millimetres. The system processes the data and provides the result within seconds, minimising disruption to the game.

6. Decision Finality. The decision given by Hawk-Eye is considered final and is used to overturn or confirm the on-court call made by the line judges or umpire. 

Understanding Hawk-Eye Technology and Its Limitations on Clay

Hawk-Eye’s absence on clay courts is twofold.

The first is that the technology faces specific challenges when used on clay courts, primarily due to the nature of the clay surface itself.

Here are the main reasons why Hawk-Eye struggles on clay courts that are made from crushed brick:

1. Challenges with Clay: The shifting nature of the clay surface is a significant challenge. Clay surfaces are more susceptible to change during play than hard and grass courts. This continuous change requires constant recalibration of the system to maintain accuracy. Hawk-Eye’s technology includes measuring the undulations of the court’s surface, and on clay, these undulations change more frequently and significantly due to the nature of the surface.
2. Recalibration Frequency: On hard courts, recalibration is typically done once at the start of the tournament, as these surfaces do not change much. On grass courts, like at Wimbledon, recalibration is done more frequently due to the wear and tear of the grass, which alters the court’s conditions as the tournament progresses. However, clay courts present the most challenging scenario, as the surface can change significantly from match to match, necessitating a potential recalibration after each match.
3. Practicality and Time Constraints: Maintaining and recalibrating the Hawk-Eye system on clay courts (this takes about 30 minutes after each match) poses practical challenges, especially during a busy Grand Slam tournament. This delay could disrupt the tournament schedule, making using Hawk-Eye for official line-calling purposes on clay courts less feasible.
4. Cost and Practicality: Implementing Hawk-Eye on clay courts may be deemed less cost-effective or necessary due to the natural ability of the surface to show ball marks. The cost of installing and maintaining the system (circa $40,000 per court) might not justify its use, mainly when players and officials generally accept the traditional method (inspecting the mark).

Side note: Contrary to popular belief, the brick dust particles swirling around in the wind on a blustery day do not present a problem to Hawk-Eye.

The second reason Hawk-Eye is not used is tradition; many tournament directors agree it’s not required.

1. Historical Trust and Familiarity: The practice of using clay marks to determine line calls has been in place for well over a century. It’s a time-tested method that players, umpires, and spectators are familiar with and trust. This tradition forms a significant part of the game’s history, especially on clay courts.
2. Visible Physical Evidence: Clay courts have the unique advantage of leaving visible, dusty red marks where the ball lands. These marks provide clear physical evidence that can be used to judge whether a ball was in or out. This immediate visual feedback is something players, and umpires can directly inspect and use for decision-making.
3. Player Involvement in Line-Calling: Players on clay courts can be more involved in line-calling decisions. They can inspect and discuss the mark with the umpire, giving them a sense of control and participation in decision-making.
4. Reducing Discrepancies: There can be discrepancies between the traditional clay mark system and electronic review systems like Hawk-Eye. Players and officials may trust the physical evidence of the mark over an electronic system that might not always align with what’s visible on the court. This is particularly relevant given Hawk-Eye’s calibration and accuracy issues on clay surfaces.
5. Simplicity and Efficiency: Using clay marks is a simple and efficient way to make line calls. It doesn’t require complex technology or frequent recalibration, and decisions can be made quickly without significant disruptions to the match.

The Issue with Broadcasters Using Hawk-Eye on Clay

If you have watched any of the clay events on TV, you’ll have undoubtedly seen a Hawk-Eye replay replayed after a close-line call. Yet, while you saw it, it wasn’t available to the players or the umpire.

While not used for line calling, hawkeye is installed at most televised tournaments. For example, the Hawk-Eye system installed at Roland Garros, accessed only by broadcasters, is identical to those used on other surfaces for officiating purposes.

This distinction presents a problem, as despite the consensus among tournaments that Hawk-Eye is not suitable for official line-calling on clay courts, broadcasters continue to use Hawk-Eye replays during matches.

This is intended to add an element of technological insight for viewers, but this practice has unintended negative consequences.

1. Conflicting Visuals: Broadcasters show Hawk-Eye replays, which can sometimes contradict the decisions made by umpires on the court. Since Hawk-Eye on clay isn’t calibrated for the precise conditions of each match, these replays may not be accurate.
2. Eroding Trust in Officials: Using Hawk-Eye in broadcasts, especially when it disagrees with an umpire’s call, can undermine viewer trust in the officials. Viewers at home, seeing the Hawk-Eye replay, might assume it’s as accurate on clay as on other surfaces, leading them to question the umpire’s competence or integrity.
3. Impact on Umpires: Umpires, who are already under significant pressure to make correct calls, find themselves unfairly criticised. This criticism is exacerbated by social media platforms like Twitter, where decisions are scrutinised and often vilified based on the Hawk-Eye replays shown in broadcasts.
4. Misleading Representation: While Hawk-Eye provides an advanced technological approach to line calls, its use on clay court broadcasts creates a misleading representation of its accuracy and reliability on this particular surface.

Given the limitations of Hawk-Eye on clay courts, a more responsible approach to broadcasting would be to refrain from showing Hawk-Eye replays in situations where the technology is not officially sanctioned for line-calling. This would help maintain the integrity of the umpires’ decisions and avoid confusion among viewers.

I’m not a fan of broadcasters using it because every time a conflicting replay is shown, the debate about Hawk-Eye on clay raises its head on social media. 

Players on the receiving end of a bad call are often tagged in replays and photo stills of Hawk-Eye clips that they then see as 100% proof they were correct.

Hawk-Eye Alternatives: The Advent of Foxtenn Technology

FoxTenn, a Spanish start-up, recently entered the fray with a bold promise of eliminating doubts in line-calling, especially on clay.

The system was approved in late 2016 following a rigorous series of tests and criteria set by a committee comprising ITF, ATP, WTA and Grand Slam tournament representatives to review decisions made by on-court officials.

Utilising around 40 cameras along with scanners and lasers, FoxTenn captures the ball’s impact on the court in real time, bypassing the need for simulations and claiming a zero-error rate. This claim is backed by a study approved by leading tennis federations like the ATP, ITF, and WTA.

Approximately thirty men’s and women’s tournaments have adopted FoxTenn to date. The technology has been used for a couple of years at the Marseille Open, where it initially had some issues due to the speed of the ball, but this has since been corrected.

It was also used in Madrid at the Masters 1000 event, where tournament director Tiriac was a big proponent of line-calling technology.

Foxtenn works in the following way:

1. Real Bounce Technology: FoxTenn uses “Real Bounce Technology,” which involves high-speed cameras and laser technology to track the ball’s movement and exact point of contact with the court. This method is more suitable for clay courts, where the ball leaves a physical mark.
2. High-Speed Cameras and Lasers: The system employs over 40 high-speed cameras and laser technology to capture the ball’s movement at thousands of frames per second. This allows for a highly accurate representation of the ball’s trajectory and bounce.
3. Accuracy in Tracking Ball Marks: Unlike Hawk-Eye, which estimates the ball’s position and path, FoxTenn provides a more literal and precise representation of where the ball has landed. This is crucial on clay courts, where the physical mark of the ball is vital in making line calls.
4. Complementing Traditional Clay Marks: FoxTenn complements the traditional method of inspecting clay marks by providing a technological confirmation of the ball’s landing spot. This hybrid approach enhances line-calling accuracy on clay courts while respecting the traditional practice.
5. Gaining Acceptance in Professional Tournaments: FoxTenn has been gaining acceptance in professional tennis, especially on clay courts. Its ability to provide accurate real-time data without frequent recalibration makes it a suitable alternative for tournaments played on this surface.

How Foxtenn Compares to Other Line Calling Systems

Below is Foxtenn’s copy designed to show “how we compare”, so it’s not to be treated as an unbiased comparison of technology.

Based on the above, Hawk-Eye appears redundant, but I think Foxtenn’s marketing is rather sensational in its claims. They seem to want to rubbish alternatives while massively hyping up their product. 

Their website is also riddled with grammatical and spelling errors. This is probably due to translation from the firm’s native Spanish, but it’s a bit amateur.

We’ve seen it’s not infallible when in use, and there has been some confusion between players, umpires and the Foxtenn replays shown.

At the 2023 Madrid Open, Foxtenn was in use as the official line calling system, where it called a ball out in a disputed point between Davidovich Fokina and Rune. Tennis TV had access to Hawk-Eye, which called the same ball in. Which was correct?

Players have also criticised the product with Taylor Fritz. In a now-deleted tweet, he said when a tournament uses FOXTENN, he will challenge anything close because he thinks it might call it in.

On the flip side of that, while no system is perfect, Hawk-Eye has enjoyed a monopoly over line calling technology since 2006, so the addition of Foxtenn as competition makes things more exciting and potentially forces Hawk-Eye to innovate, which can only be a good thing.

Player Perspectives on Technology in Tennis: Clay Court Controversies

Integrating technology like Foxtenn and Hawk-Eye in tennis, especially on clay courts, has sparked diverse opinions among top players.

Naomi Osaka appreciates the focus shift technology brings: “I don’t mind it at all because the technology helps me focus on the match rather than feeling the need to argue calls as often.”

Stefanos Tsitsipas advocates fairness and technological advancement: “I think it’s time for Hawk-Eye on clay… We must keep growing and adding new things to the sport that will help make it better and more fair.”

Dominic Thiem acknowledges the practical challenges, favouring Hawk-Eye for clarity: “I would support 100% Hawk-Eye on clay… sometimes you just cannot see the mark. It’s too difficult, especially after the set break.”

Conversely, Taylor Fritz and Reilly Opelka express scepticism about the accuracy and effectiveness of Foxtenn: “When a tournament uses FoxTenn, I’ll challenge anything close cause it might just say it’s in,” says Fritz. At the same time, Opelka remarks, “I think the FoxTenn challenge system works about 20% of the time.”

Adding to the criticism, Maria Sakkari raised concerns about its accuracy: “We saw in Madrid that the Hawk-Eye (Foxtenn) they had there was not accurate at all. I spoke with other players. They said the same. If it’s accurate, then yes (use it on clay). If it’s not accurate, then there’s no point.”

It’s interesting to note that players seem to be confused regarding the specific technologies in use, which is evident in statements from players like Maria Sakkari, Holger Rune, Roger Federer, and Gael Monfils:

For example, Maria Sakkari mentioned Hawk-Eye when referring to Foxtenn’s inaccuracies.

Holger Rune also mistakenly referred to the system as Hawk-Eye when he meant Foxtenn.

When he was playing, Roger Federer expressed uncertainty about whether he had used Foxtenn, indicating a lack of clear distinction between the two technologies in players’ minds.

Gael Monfils acknowledged being accustomed to Hawk-Eye but noted that FoxTenn might have an advantage in showing where the actual ball landed.

This confusion underscores a broader issue in the sport: the need for more transparent communication and understanding of the technological tools implemented in tennis, especially regarding their distinct functionalities and accuracy.

Clay Tournaments That Have Used FoxTenn

FoxTenn has been used at several clay challenger events and the following ATP and WTA tournaments:

When Will Electronic Line Calling Become Commonplace on Clay?

The ATP anticipates that by 2025, technology will replace line judges in officiating tennis matches full-time.

While this projection indicates the increasing trust in and dependence on technology and tournaments like Barcelona, Madrid, Estoril, and Bastad have embraced Foxtenn, other events are reluctant to move away from the traditional role of line judges.

Tournaments like Monte Carlo, Rome and perhaps most importantly, the French Open have rejected the idea several times during tournament press conferences.

As it stands, none of them are planning to change unless they are forced to.

I know Madrid has been using Foxtenn for a long time. We are going to watch this and study this for the future. ATP might even impose this on us in the future, but for the time being, we are waiting and we are very satisfied with our human linesmen. David Massey, Monte Carlo Tournment Director.

The French Open is also standing firm against technology entirely replacing line judges, expressing a preference for traditional line-calling methods over electronic systems, emphasising the importance of human roles in tennis officiating.

According to the tournament director, this choice is not solely about the accuracy machines can provide but also about the impact on people’s jobs and the tradition of the sport.

The bottom line, before doing anything new, is that it’s people’s jobs that we’re talking about. It’s not just ‘machine versus a man’s eye.’ We have a very good way of teaching from a young age, a chair umpire and linesman. In our country, we have some of the best umpires, and one of the reasons is that this is so consistent; we have multiple tournaments in France throughout the season, they are very active, and they go from being a linesman to eventually a chair umpire and [some] to a referee Of course, the machines are very accurate, although, on clay, its only drawback is you could potentially have a mark … touching the line, everyone would see the actual picture of the mark on the screen, and [the computer] would [say] out. Every single player in the world, when there’s a [disputed] call, will go to the mark and look Would you like to have a court with no chair umpire, no linesmen, just electronic line-calling? Is that something we really want in the future? I think we’d miss something. Guy Forget, French Open Tournament Director.

Final Thoughts

The ongoing discussion about electronic line-calling in tennis, especially on clay courts, raises some critical questions about the future of the sport.

The French Open’s decision to stick with line judges over technology isn’t just about accuracy; it’s about valuing tradition and the human aspect of the game.

As technology like FoxTenn starts to appear in more clay tournaments, we’re left to wonder what tennis will look like in the coming years. Will technology take over completely, or is there still a unique value in human judgment that machines can’t replicate?

What’s your take on this shift towards technology in tennis? Are you all for electronic line calling on clay? Let me know in the comments.