—John Vaughn, Newnan
A: The computerized line-calling system is called Hawk-Eye, which also is the name of the British company that developed the technology. Hawk-Eye uses 10 cameras per court to record the flight of the ball at tennis tournaments. The system uses that input to map the ball's trajectory and reconstruct its path, projecting where the ball most likely would have landed. Players receive three challenges each set, and if used, Hawk-Eye determines whether the ball was in or out, sometimes overruling umpires and line judges. The system, which is approved by the International Tennis Federation, is used at the Australian Open (hard court), Wimbledon (grass court) and the U.S. Open (hard court), among other tournaments, but not at the French Open, which has a clay surface that shows ball marks. Creator Paul Hawkins said in 2008 that the system was 99.9 percent accurate.