The use of asynchronous multiple pan-tilt cameras makes it difficult to calculate 3D position of a moving object such as a ball in sports scene. This paper presents a method for calculating the 3D position using asynchronous pan-tilt cameras. The 3D positions are calculated from motion trajectory. Then, the 3D position of latest frame is calculated from previous 3D positions. The 3D position is recalculated using constraints from ray information. Since the 3D position is calculated at every shutter timing of each cameras, the 3D position can be obtained at number of camera × 30 points. We show that the proposed method achieves accurate 3D measurement using asynchronous pan-tilt cameras.
