The closed racket angle should be videoed so that the racket is seen edge on to the camera just before impact. To get by the 4 second pauses use the video slider and 'ms' time scale. Normally, to move one frame on Youtube use the '.' and ',' keys. This video pauses for 4 seconds on each frame with the brief text boxes. The video is made with some text boxes that only appear on one frame. I have posted this here and can answer questions. This method is very reliable and you would completely understand after using it for awhile.Īn easier was to estimate the serve speed is to use the average diameter of the ball to calibrate instead of the measuring tape or PVC pipe. In one frame time at at 30 fps - 0.033333 sec a 100 MPH ball would move 59'. or 0.03333 sec.Ĭonversion factor 100 MPH = 1760' per second. Or put black tape on a piece of PVC pipe.ģ) Know or calibrate the video camera's frame rate by viewing a clock.ĭistance - traveled in 1 or more frame timesįor a 30 fps camera, the time between frames is 1/30 second per frame. Camera on tripod.Ģ) Calibrate the distance out with a measuring tape or by videoing a yard/meter stick after the serve and before anything has moved.

The fundamental way to measure velocity is to measure distance traveled in a known time.ġ) Video squarely perpendicular to the ball's trajectory about 3 feet in front of impact.

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