My idea is to develop a system that show if the ball hits on or out of the tennis court.

This could be achieved with an array of three sensors which detect the sound of the ball hitting the ground. One is located on the right side of the end of the court, other on the left side of the opposite end, and the last in the middle of the net.

We could measure the time the sound takes to reach each sensor, and with simple 2D mathematics we are able to say the precise location of the ball.
-- alexandre, Jan 10 2009

welcome! For the home viewer nothing will replace the slow motion replay.
-- WcW, Jan 10 2009


Even that slo-mo replay shows the ball smooshing as it hits the ground so it's still unclear... what we need is a non-smooshing tennis ball :)
-- phundug, Jan 10 2009


Thanks for the feedback. Yes, I agree with WcW. And Yes, Hawk-eye do the job, but it requires "at least four high speed video cameras located at different locations and angles around the area of play"

But when I suggested this idea I was thinking in something cheap, that could be used by amateur weekend players... :-)
-- alexandre, Jan 10 2009


Building something that would be cheap enough for casual play is interesting -- but I'm skeptical, especially in an ambient noise environment, that you could be accurate enough where it matters (i.e. where the ball is not obviously out), and still use cheap sensors.

What might work, I think, are line-of-sight lasers -- of the type used in garage doors to prevent the door from closing on the pooch.

Positioned at the four corners of the court at the appropriate distance from the line (let's say half the diameter of the ball to the side and above the ground), they will get interrupted if and only if the ball hits very close but not on the line or inside.
-- theircompetitor, Jan 10 2009


Couldn't one just rework one of those radioshack golf ball thingumalocationators with laser sight action?
-- Spacecoyote, Jan 11 2009


Or one portable laser.
-- Spacecoyote, Jan 12 2009


I'd suggest a non-laser photosensor; such sensors detect whether anything is between the transmitter and receiver, and can be essentially as sensitive as those using lasers, but they are much easier to set up and align.
-- supercat, Jan 12 2009



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