Slashdot Mirror
Casting Doubt On the Hawkeye Ball-Calling System
Human judgment by referees is increasingly being supplemented (and sometimes overridden) by computerized observation systems. nuke-alwin writes "It is obvious that any model is only as accurate as the data in it, and technologies such as Hawkeye can never remove all doubt about the position of a ball. Wimbledon appears to accept the Hawkeye prediction as absolute, but researchers at Cardiff University will soon publish a paper disputing the accuracy of the system."
Assuming you could build a radio transmitter tough enough to handle it...
With tennis balls, I imagine there would be problems with balance and the response of the ball. Especially with such a small ball, mounting a rugidtized radio transmitter (a ball probably has to go through 20gs or something) would probably mess with the balance and how the ball deforms. Not to mention, unless you can mount the system directly in the center of the ball, then you still have a margin of error the diameter of the ball. I imagine that would be fairly significant amount of error in tennis (perhaps on the same level as this Hawkeye system?) when calling the lines.
Further to that, if the transmitter can't survive in a soccer ball (where a well-struck shot probably moves around 120-130 kph) then there's no way it will handle travelling over 200 kph after a serve, followed by a (at least) 100 kph forehand return (a net >-300 kph in a fraction of a second!).
Also, a radio transmitter cannot account for the distortion of a ball upon impact, which will depend on velocity, angle of rotation, angle of impact, surface being played on, etc etc etc...
Triangulation of radio signals is not accurate enough to give sub-centimeter accuracy and the added mass to the tennis ball would probably cause the players to have some objection to adding a radio transmitter into the ball.
The claim that the Hawkeye system gives an average of about four millimetres of error seems somewhat reasonable, given that we're getting accuracy greater better than two centimetres on detecting objects with a single camera with optics as large as the last segment of a typical pinky. (FWIW, here's a short demo of what we're working on for our autonomous underwater vehicle)
However, the suggestion to display the error range for a particular shot and leaving the final decision to a human from TFA is quite reasonable and is how it should be. Blindingly trusting technology or discarding it altogether is unreasonable.
Jean-Francois Im's blog
I still don't understand why there isn't more research on developing a surface for the out-of-bounds area that temporarily registers the exact impression of any impact on it.
I envision something that looks like a big LCD touch screen (but more durable). Every time something made contact with the active surface, a record of the ball's "footprint" could be recorded (and even temporarily displayed wherever it touched the surface). That would allow for highly precise measurement of the ball's landing position, and it wouldn't need to incorporate any new materials into the ball itself. The active surface would only need to be in the out of bounds area, and even then, it would only need to be half a foot wide in order to cover the important zone where the ball's landing position is questionable.
For a system like Hawkeye to be useful, it doesn't need to be perfect. It just needs to consistently be more accurate and impartial than a referee can be.
Nor is it required for the system to be fully automatic and autonomic. Referees can sit in front of their monitors, observe the cameras from all angles, with any time slowdown, and ultimately come to a better decision than a single person could make while the ball buzzes past them at Warp 9.
But from the social aspect, one has to decide on what is the referee's role, and what kind of influence, if any, do we want to delegate to a computer. And that depends on the type of sport.
For non-interactive sports such as sprinting, an automatic system works very efficiently, and most people readily accept it as better than a human time tracker.
But for many GAME sports (soccer and boxing come to mind) many people consider that a referee is PART of the game rather than just an observer. As long as a referee is comparatively competent, and acts in good faith, he has the authority to judge events in the game, and while mistakes are unavoidable, they are considered part of the game as well.
I'm not sure why this position is popular in these kinds of sports. Maybe it's the whole "humans should be judged by humans and not machines" aspect. Or maybe it's because having a Review Comission in front of CCTV monitors be judging every little move just feels too 1984-rish for spectators and players alike. Or maybe its something else. But this is a rather popular feeling.
Depending on the features and benchmarks of the electronic system, it may or may not be more accurate than a human observer. In the long term, a joint human-computer analysis system would be certainly more accurate than a human referee alone, especially in team or high-speed sports. But one has to ultimately question, whether, by gaining mathematical precision, we lost some human touch of sport that makes it enjoyable to play and watch. Fun can't be generated with a mathematical formula. And sometimes sitting on the couch and thinking "OMG that referee is such a dumbass" is part of the fun as well.