What happens in tennis when a ball hits the 'service line' but you are unsure if it also touched the 'central service line' to call it in?

For example in the drawing the player serving must throw the ball to the left service box, it is clear that the ball is not long because it touched the service line but how to tell if it is left enough?

It might be touching the center line but you don't know for sure because those two lines merge. Even with hawk eye you won't see the limit of the center line because it merges with the service line and both are white.

Any example of a hawk eye challenge like that?

enter image description here

  • 2
    What level of play are you interested in, and what role do you have in this scenario? Obviously at high level tournaments, there are separate line judges for each line so this problem becomes trivial.
    – Philip Kendall
    Commented Sep 6, 2022 at 7:28
  • 1
    Further, HawkEye knows exactly where the separate lines are, even if a human can't see the difference.
    – Nij
    Commented Sep 6, 2022 at 7:49
  • How is it trivial?. When they challenge it all depends on differentiating the green from the white but in this case it's the white from the white.
    – Cacti-Math
    Commented Sep 6, 2022 at 14:14
  • When they challenge, there is no colour at all involved, just mathematical expressions and numerical results, either the number is small enough or it is not.
    – Nij
    Commented Sep 6, 2022 at 23:34

1 Answer 1


In general, if players are calling their own lines, it's considered courteous to award your opponent the point if there is uncertainty of whether a ball is in or not, regardless of where that ball was played (groundstroke, serve, etc).

You can think of the service box T as an intersection of two planes: one for the service line and one for the center service line. Depending on the direction of the serve, different edges of the planes are used to definitely determine whether a ball is in or out.

In this example below, if serving from left-right (deuce side), a ball will be in if it touches any part of the red plane, as well as any part of the yellow plane in the deuce court.

Service box diagram

  • While this may be true, it doesn't answer the question.
    – Chenmunka
    Commented Oct 20, 2022 at 18:44
  • @Chenmunka Can you elaborate? The question is pretty clearly stated in the first paragraph. "What happens in tennis when a ball hits the 'service line' but you are unsure if it also touched the 'central service line' to call it in?" In that case sportsmanship dictates that you give your opponent the point.
    – slugis
    Commented Oct 21, 2022 at 14:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.