| 摘要 |
A method of determining in a game of tennis the point of contact of a service ball relative to a service line includes the steps of (a) monitoring a field of view along the service line and producing an electronic representation of an upper boundary of the ball as it passes through the field of view, (b) scanning the upper boundary of that representation progressively in the direction of the ball flight and determining at successive spaced positions along the path of the ball the angle of declination of the boundary, and (c) comparing successive values of that angle and noting the position of the ball at which that angle reduces relatively rapidly to a low or even a negative value. A preferred method determines and compares successive horizontal components of successive sections of the boundary which have successive equal value vertical components. Apparatus for performing the method is described.
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