Abstract: A computerized system determines the trajectory of an object based upon video images captured by cameras at two fixed viewpoints. Two video cameras are arranged so that each will contain the anticipated trajectory of an object within its field of view. The video cameras are synchronized and have shutter speeds slow enough to yield an image of the object containing a blur due to the object's motion. An audio or an optical trigger, derived either from the event causing object motion or from the object itself, causes at least two images to be captured in digital frame buffers in a computer. Software in the computer accesses each of the digital frame buffers and subtracts the background image to isolate the blurred object. A two-dimensional projection of the object's trajectory is derived for each frame buffer image. The two dimensional trajectories are combined to determine a three dimensional trajectory.