In a quarter-final game at the U.S. Open tennis championship in August, a line judge made a bad call against Serena Williams. The match ended in a Jennifer Capriati victory and embarrassed officials apologized, but Ms. Williams was still the loser — and so was professional tennis.

International Tennis Federation officials deflected press criticism by revealing that they were assessing a system designed to stop such errors. Just two weeks earlier, the ITF had been looking at a Canadian-made computerized refereeing system called Auto-Ref.

This week, that high-tech referee is undergoing a second and final stage of testing. Its maker, Auto-Ref Inc. of Waterloo, Ont., is setting it up at the Bell Challenge in Quebec City, where a panel of five officials from the tennis world will scrutinize it under real-time conditions.

The system, developed for $600,000, involves eight cameras pointed at the court from high above the action. Each camera is connected to a computer, and all eight are attached in turn to a central server. Peter Szirmak, president of Auto-Ref, says the company’s sophisticated software was designed to run on off-the-shelf hardware.

With the help of computer programmers from the University of Waterloo, Mr. Szirmak developed a system that “elegantly mimics human judges.” Auto-Ref films the ball, travelling as fast as 240 km/h, and calculates its trajectory and point of contact with the court. It then creates an animated 3D image showing the path of the ball and where it bounced, which is sent to the chair umpire’s monitor and TV studios broadcasting the game.

The system, Mr. Szirmak says, is accurate to within four millimetres. If any cameras conk out or a tournament cannot afford to rent the full package, it still works: A four-camera setup is accurate to within 10 to 12 millimetres.

More here.