3D impact analysis in tennis

Two dimensional video impact analysis has been routinely used to assess racket/ball interactions in tennis. For impacts off the longitudinal axis of a racket, impacts of oblique incidence, or spinning balls, 2D analysis is limited in terms of accuracy when tracking the position of the ball and racket, and in the information that can be gained from these particular impacts. This paper outlines a method of 3D impact analysis which can track ball velocity and trajectories within a 3D space, and a series of experiments performed using this method. It was found that the trajectories and velocities of both incoming and outgoing balls had scatter that amounted to ±5° and ±1ms-1. The source of scatter was due to limitations of the air cannon and racket support used in testing, and from errors in digitisation. Off-set impacts have much more scatter which cannot be accounted for by experimental error. It was concluded that this method of 3D impact is an ideal method to investigate such discrepancies.