A mechanical golfer with a 120 mph swing speed hits balls with a titanium driver, and a launch monitor measures each ball’s speed, launch angle, and spin. This is the first ingredient to measuring ball distance. The USGA system then uses an array of sensors that accurately measure the flight of a golf ball during a short, indoor trajectory from a ball launcher. From this flight data, a computer calculates the lift and drag forces that are generated by the speed, spin, and dimple pattern of the ball. Balls are tested at high speeds, like a ball is hit off the tee, at lower speeds, like a ball during flight, down to the speeds a ball might encounter at the top of a drive. The computer puts all of this aerodynamic and launch information together to create an accurate simulation of the golf ball trajectory. This test is repeatable to within 3 yards (better than 99 percent), more repeatable than outdoor testing could ever be. The distance limit is 317 yards.