The USTA's Arthur Ashe and Louis Armstrong stadium courts [Ashe shown here] are ringed with 10 high-speed cameras that individually capture the position of the ball at 50 frames per second during each shot. Each camera's computer then calculates the exact center of the ball in each frame and feeds that two-dimensional information to a mainframe in a control room situated high above the court. In a split second, that information is converted into a three-dimensional view of the trajectory of the ball and exactly where it landed. If a player challenges a call, the trajectory and landing point are simultaneously transmitted to the umpire´s chair, the high-definition screens at either end of the stadium, and the television feed. So far, during the first week of play at the U.S. Open, players have been successful in just one third of the 102 challenges.