http://en.wikipedia.org/wiki/Hawk-Eye#Tennis Several poor calls occurred at the 2004 US Open. In Serena Williams' quarterfinal loss to Jennifer Capriati, many crucial calls were contested by Williams, and TV replays demonstrated that some were indeed erroneous. Though the calls themselves were not reversed, the chair umpire Mariana Alves was dismissed from the tournament. These errors prompted talks about line calling assistance especially as the Auto-Ref system was being tested by the U.S. Open at that time and was shown to be very accurate. 鷹眼出現的引爆點是 2004年小威被誤判連發 而且被電視的清楚的重播卻無法平反. The Hawk-Eye Innovations website states that the system has an average error of 3.6mm (it does not indicate what the maximum error is). The standard size of a tennis ball is reportedly 65 to 68 mm. This means that there is a 5% error relative to the diameter of the ball. This could throw into doubt the accuracy of such calls as the one mentioned in the Nadal-Federer 2007 Wimbledon final. For the sake of comparison, approximately 5% of the diameter is the fluff on the ball. 鷹眼的「平均誤差」是 3.6mm, 與網球的直徑比起來 這5%的誤差是球毛的差距 上面那個wiki連結還有講好幾段歷史, 有興趣的可以進去看看 --

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