Path: bloom-picayune.mit.edu!snorkelwacker.mit.edu!americast.com!americast.com\!americast-post Newsgroups: americast.mech From: americast-post@AmeriCast.Com Organization: American Cybercasting Approved: americast-post@AmeriCast.com Subject: The U.S. Tennis Association (USTA) is testing a new technology Date: Wed, 4 Nov 92 10:28:41 EST Message-ID: The U.S. Tennis Association (USTA) is testing a new technology aimed at improving the accuracy of line calls during matches. In turn, it hopes the move will tame the often-audacious players who challenge the calls of umpires and line judges. The national tennis governing body tested the automated line-calling system at the recently concluded U.S. Open in New York. The system is called Tennis Electronic Lines (TEL). At a cost of between $80,000 and $100,000, the TEL system, manufactured by TEL Pty Ltd. (Camden Park, Australia), is an alternative to the currently used laser-based Cyclops machines which, in conjunction with rulings of umpires and line judges, determines whether a ball is hit in or out of play. The TEL system works on all court lines, including service lines, baselines, and separate sets of sidelines used in doubles and singles matches. The Cyclops, which detects balls traveling up to 129 miles per hour, is used only for serves. TEL is an electromagnetic tracking machine that provides information on the velocity, trajectory angle, and elevation of the ball and data on the position of the ball in relation to the edges of court lines. The system has four primary components-several antenna arrays buried beneath the court lines, a tennis ball with embedded metal particles, an instrument box with 13 computers, and a handheld computer that displays the system decisions and is operated by a chair umpire. The tennis ball, made by Wilson Sporting Goods Co. (Fountain Inn, S.C.), has a hollow rubber core that is covered with felt and embedded with particles of a proprietary ferrous metal. An electronic signal is produced when the ball moves to within range of the antennas, 4 inches above and 12 inches on either side of a line. The metal particles in the ball disturb the magnetic field generated by the antennas and produce a signal. The electronic signals on ball position travel from the antennas to the computers. When a ball falls within the range of the antennas, information is transmitted within one millisecond. In a fully installed system, TEL would dispatch its line call to a handheld computer operated by the chair umpire, and the system would synthesize ÒoutÓ calls. ÒThis system responds to the ball slightly better than the Cyclops does, because it can be tuned into the extreme edge of the line,Ó said Jay Schneider, head umpire at the U.S. Open. ÒAlthough test data are still considered proprietary, what we can say is that the system seems to be working.Ó The tests, however, were just that. The system was used only to provide data for further evaluation; umpires, line judges, and the Cyclops machines made all of the official calls at the Open. After reviewing the data, the USTA will decide whether to use the TEL system at the 1993 Open championships. No date has been scheduled for the systemÕs official introduction. Telltale Footprints A major advantage of the TEL system is its accuracy. It is not easily triggered by mistake. The laser-based Cyclops system sometimes makes unprovoked noises at inappropriate times during a match. The undesired blips not only distract the players but also reduce confidence in the machineÕs ability to work properly. When a player is serving the ball, the Cyclops machine responds to anything in the path of its laser beams-a ball, a blade of grass, or a grasshopper. It also exhibits problems with overheating when the court expands on hot days, Schneider said. ÒWhat the TEL system does, which others donÕt, is look at the footprint of the ball as it hits the court,Ó said Richard Garvais, a factory manager at WilsonÕs Tennis Balls division. Knowing the full print of the ball is important, because it can be the difference between a point going to one player or the other. If any part of the ball touches a line, it is considered still in play. ÒWe have a saying in tennis that if the ball is 99 percent out and 1 percent in, itÕs really 100 percent in,Ó Schneider said. A hard shot with a low angle of attack, for example, would register a different print from a ball that hits the court softly at a right angle to the surface. Usually, the hard skimming shot would leave an oval print, the vertical lob a smaller round mark. The shot would be ruled in or out, depending on the size and shape of the print. A key factor in the ability of TEL to monitor the complete print shape is the placement of metal particles in the rubber core. ÒThis would be easy to do if you donÕt care how the ball plays,Ó Garvais said. But the new ball, like the traditional one, must meet specific size, weight, bounce, and hardness criteria set by the USTA. In developing the ball, Wilson used high-speed photography and a powdered court to obtain response data. It took the company about a year to devise a method of making a ball with metal particles. ÒThe key was to identify the size of grains and figure out how to put them into the rubber matrix to get a uniform reading all around the ball,Ó Garvais said. ÒOne doesnÕt know which part of that hollow rubber sphere is going to hit the court.Ó In August, before the U.S. Open, the new ball was tested at the Indianapolis Hard-Court Championships. Players at both tournaments were unable to tell whether they were hitting standard or newly designed balls, Garvais said. m Copyright 1992, Mechanical Engineering. For more information, send-email to American Cybercasting Corporation (usa@AmeriCast.COM)