A measurement of the horizontal launch speed and launch angle of a person jumping or diving into a swimming pool can be obtained by filming the event with a video camera. The horizontal and vertical distance needs to be calibrated by filming an object of known length located in the same plane, while the time scale is determined by the frame rate, typically 25 or 30 frames/s. The object is to determine the launch speed and angle of the center of mass. If the jumper or diver maintains the same orientation through the air, the speed of the center of mass would be the same as that of any other part of the body, and there would be no need to locate the center of mass. However, a person jumping or diving usually moves his or her arms and legs into different positions during the flight phase, in which case an estimate of the location of the center mass needs to be made for each frame. Depending on the desired accuracy of the measurement, the location of the center of mass can be estimated by eye or calculated from the measured orientation of each body segment and an estimate of the fractional body mass of each segment.