A simple demonstration of judging a tennis line call.
Inside the court is on the left of the line, outside the court is on the right of the line. When you click 'Next Point' a ball appears briefly (after a variable delay) and bounces near the line. If the ball bounces (changes direction) to the left of the line, or if any part of the ball touches the line at the instant it bounces, the call is 'in'. Otherwise the call is 'out'. Click IN or OUT to record your decision. You can use the buttons on the right to retrieve your score.
The relative sizes of the ball and the line are to scale, and the bounce position values reported are correctly scaled in millimetres. The 'speed' of the ball is much slower than required for a realistic simulation (it is not possible to make it move fast enough on a computer screen!).
To simulate the more difficult task faced by players as opposed to line judges, click the buttons to make the objects small (simulating a greater viewing distance), and to make the line move (simulating a moving player).
This is not intended as a realistic simulation, of course, but as a loose approximation to the kind of visual task faced by tennis line judges and players. Please contact me by email to let me know what you think of it, or with suggestions for improvements.