How do they get the info on where the tennis ball lands???

Question

do any of you guys know how or know a site where they find out how the tennis ball lands? i am doing a computer project on this so please be very opinionated.

Answer 1

When the ball changes trajectory from downward to upward. That's the point where it hits the ground.

Answer 2

http://www.hawkeyeinnovations.co.uk/

there you go:D