A Performance Analysis System for the Sport of Bowling

3.6.2 Accuracy
The question of accuracy has not yet been addressed. Just how accurately do the graphs
displayed in the "Analysis" screen of the MASTER program depict the actual response of
the ball? What accuracy can be claimed for the SMARTDOT system and, more
importantly, how can this accuracy be verified?
The SMARTDOT system is intended to serve the following functions: quantify the
consistency of a bowler's release; provide objective feedback with which to measure their
performance and improvement; and capture and measure the response of a bowling ball
over the course of a game or match, as well as capture its response to varying lane
conditions.
Therefore, it is more important that the system give consistent and repeatable results,
rather than absolutely accurate results. Ideally, if the bowler rolls the ball the same way
on two different shots, and the ball responds identically to that stimulus, then the results
that the MASTER reports should be the same. If the bowler releases one ball with a
velocity 10% higher than another ball, the MASTER should report a 10% difference in the
two release velocities.
There are several options available for accurately verifying SMARTDOT's performance:
• Take SMARTDOT to a CATS-instrumented facility and correlate the MASTER's
analysis results against the CATS findings [12] and/or contact Brunswick and
possibly obtain time on their "Throbot" machine, which can apply known
amounts of velocity, spin, and loft to the ball, and then correlate the MASTER's
findings against the release parameters of "Throbot" [9].
• Instrument a lane and perform external verification and validation. By fitting a
lane with a fast and accurate position/velocity sensing system, the actual response
of the ball from foul line to head pin could be captured. Since the linear velocity
and distance results are derived from the angular velocity data, if those results can
be externally quantified, it will be possible to determine the accuracy of the
assumptions and the calculations underlying the entire SMARTDOT system.
• Add a solid-state accelerometer/tilt-sensor to the module and correlate the actual
results of the accelerometer with the inferred angular velocity results from the
light sensor. This is a realistic possibility, using the ADXL202E accelerometer
from Analog Devices [15], although it requires a fair amount of additional
development effort on the sensor module.
To this point, the only practical (meaning cost-effective) assessment method has been to
use video analysis. With markers applied at known distances on the lane, and additional
markers applied to the ball each 30° of rotation, multiple shots have been simultaneously
captured with SMARTDOT and on videotape. Through this practice, the current MASTER
analysis techniques appear to be accurate to within 1/2 mph and 90° of rotation.
However, standard video is limited to 30 frames per second, yielding a resolution of 33
msecs per frame, which is insufficient for verifying accurate measurement to 0.1
revolution and 0.1 mph. It is also not possible, using this technique, to verify the angular
velocity measurements resulting from the filtered waveform, nor the actual locations of
each revolution. It will eventually be necessary to utilize one or more of the previously
mentioned techniques to reliably validate SMARTDOT.
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