A second possible source for the spread in the CL data is the procedure by which we obtain
the ball’s coordinates during the time camera 1 films. As figure 4 shows, we use a circle’s
centre to locate the ball’s centre of mass in each frame. The procedure for extracting the lift
coefficient is sensitive to the centre-of-mass coordinates obtained by camera 1. By ‘sensitive’,
we mean that the value of CL could easily change by a factor of 2 if one is not careful to align
our in-house software circle’s centre with the centre of the ball.