Table tennis is often referred to as the game of spin and speed. However, these are not the only parameters characterising the game In this research we concentrated on measuring the ball speed and height in the moment when the ball passes the net. These two parameters can reveal several information about the players (skill, playing type) as well as the game type (competition, training). We developed a measuring protocol for the automatic offline measurements in laboratory conditions. The protocol includes aligning the high speed camera with the net, calibrating it using the chess board pattern, and then recording the game at the rate of 1000 fps. The video processing software tracks the ball from frame to frame and records its trajectory until it leaves the camera view field. In each image the distance from the net top to the ball centre is calculated and the one most closely aligned with the net is recorded. Using the camera calibration data, the tracked ball trajectory path and the delay between images in video sequence, the ball speed is determined. We recorded 40 sets played by players of different skills, one top European, two top national, one middle-ranked and one low-ranked national player, resulting in 3 TB of video data. We find out strong correlation between the player skills and both measured parameters. There was almost no difference in average ball height (within 1%) and slight difference in speed (within 6%) when the top European player and top national players played among each other. There was an increase in average ball height (7.17%) and decrease in speed (9.53%) when the top national player played the middle-ranked national player in comparison to top national players played between each other. When the middle-ranked player played the low-ranked player the increase in height was 29.89% and the decrease in speed was 20.37% in comparison to when he played the top national player.
© Copyright 2019 Science and Racket Sports VI. Veröffentlicht von Mahidol University, Badminton World Federation, International Table Tennis Federation. Alle Rechte vorbehalten.