Line Referees or Hawk-Eye? – Tennis Column #56

Every crisis push people to look for innovations. The corona outbreak is not an exemption. Tennis is a good example. To reduce people on and around the court, the tournaments start to use the hawkeye system instead of line referees. Southern & Western Open, US Open, and Bett1 tournament in Cologne did not need line referees on their courts anymore. (S&W and US Open used line referees on the top courts out of seventeen.) Therefore, I expect a heated debate around the question “Line referees or Hawkeye” between many tennis tournament organizers and players. Here is my take on this interesting subject.

How Hawk-Eye Works?

Hawk-Eye was invented by a British computer expert Paul Hawkins in 2001. It was developed for use in cricket matches.

However, the technology was adopted by tennis very soon. Today, the hawk-eye and its variations are also used in football (goal-line technology) and in many other sports.

By the way, it is still unclear to me if the name Hawk-Eye is related to the name of the inventor or the bird.

Hawk-eye technology uses cameras (six or more) around the court and a computer that reads all videos and tracks the ball trajectory. It prepares a 3D presentation of the ball path in almost real-time (with a delay of a few seconds).

Is Hawk-Eye one hundred percent right?

The hawk-eye is not an error resistant. It has a margin of error of approximately 3.6 millimeters.

The tennis ball has an average of 67 mm, which gives us a deviation of circa 5%.

Hawk-Eye use in tennis

Line referees or hawkeye

The hawk-eye technology is used on all surface courts, except for clay. At the clay, the mark the ball left on the clay is sufficient enough for check and control by the umpire referee.

On the grass and hard courts, the hawk-eye was used as a tool for the challenge of line referees calls. Players have three opportunities per set to challenge the wrong call.

This year, tournaments adopted the Hawk-Eye Live system to replace the line referees. Hawk-Eye Live usually use more cameras to follow also foot faults.

The system has prerecorded voices for calling “out” and “foot fault” loudly.

PROs and CONs of Hawk-Eye over Line Referees

This is solely my opinion from watching tens of tennis matches with and without line referees.


Hawk-Eye Live made the tennis game quicker. The flow of the game is much smoother without interruptions for challenges.

Three challenges for each player per set could cause six pauses in the important moments of the match. That is too many per my opinion.

Hawk-Eye system reduced any arguing of players to zero. Nobody has a reason to argue with a computer voice calling the ball out.

The biggest difference was seen at Roland Garros this year. There were so many discussions about where the ball’s mark is exactly and if the ball hit the line or not.

We did not see any of that in New York or Cologne.


The downside of the system used worldwide in all tournaments is the many job redundancies we will see.

To be a line referee is not a full-time job. Still, many people will lose the chance to earn something extra during a week of the professional tennis tournament in their city or country.

And that makes me feel bad in these hard times.

My conclusion

Yes, I know that Hawk-Eye can call some shots wrong. However, I believe that its margin of error is lower than the man’s eye error margin.

I would prefer to use Hawk-Eye on all ATP and WTA professional tournaments next year. I would include also clay ones.

The innovations can not be stopped and it is good for tennis to be a leader in that field.

What is your opinion?

Let us know in the comments section or vote in our poll below:

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Tennis Pro Guru

Simon is the leading editor of from 2015. He is an avid tennis player from age of 5, however, he never reached the pro level. Still, he likes playing tennis on different courts, with different rackets, and against different opponents. In his free time, you can find him watching all possible tennis matches he can find on the web or tv. Challenger or Grand Slam? It does not matter, just tennis matters.

He currently plays with:
Racket: Wilson Shift 99 V1
Strings: Babolat RPM Blast
Grip: Head Xtreme Soft
Shoes: Asics Gel Dedicate 7 (for hard outdoor and indoor courts) & Asics Gel-Game 5 Clay (for clay courts),
Balls: Dunlop Fort All Courts and Head Championship
Bag: Axiom Backpack

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