95.8-degrees test Results
The 95.8 degrees test measured the angle
between the markers on the rotating plate. The known angle between the plate markers
was 95.8 degrees. These results are presented in Table 3.
This measurement is probably the most
sensitive to errors since 3 markers are involved. Any movement in any of the
individual marker will significantly affect the angle. In addition, these 3 markers
were obscured from any camera at least 50 percent of the time. This means that the
power of the DLT was measured to see how systems can cope with this effect.
The APAS system utilized a powerful DLT
algorithm with a PPT algorithm, which represent linear and non-linear Direct Linear
Transformation. Therefore, the APAS system was the top performer for this
test. Note as well, that the RMS and the maximum errors recorded were the lowest for
the APAS system.
Slide 15. Angle measurement from Top Plate Markers.
Table 3. 95.8 Degrees
test from the top plate markers.
illustrates the average measured angle between the plate markers. The Motion
Analysis system measured the average the closest. The APAS recorded the second
closest score. However, when measuring the maximum error in estimating the angle,
the APAS scored the highest with an RMS error of 1.2 degrees. Although the Motion
Analysis system had the best average with 95.1 degrees, the maximum error amounted to more
than 7 degrees. The APAS system's calculated average with 95.1 degrees had as it's
maximum error only 2.9 degrees. When combining the average error with the RMS
error, the APAS system scored the best with 4.1 degrees total error with the next
equipment being Vicon with 6 degrees.
The largest error recorded
was the Qualisys with 23.7 degrees and Peak with a 16.4 degree error. If
consideration is given to the switching point problem previously mentioned, this error
would increase by an order of magnitude and raise questions among researchers as to the
appropriateness of these equipment choices for serious research.
Slide 16. Average Measured Angle between Plate Markers.
The APAS system
performed remarkably well on this test. This test happened to be very crucial since
it had to detect 3 markers on a rotating plate. This situation would never occur in normal
human movement but the APAS system was amazingly accurate in determine the angle.
Other companies produced as much as 23 degree errors. This measure was particularly
useful in demonstrating the superiority of the APAS system over the other systems.
Of particular interest, was the poor performances by the Peak, Qualisys, and Vicon
Slide 17. RMS Error from Plate Angle Measures.
Slide 18. Maximum Error from Plate Angle Measures.
system performed fantastically well when compared to all other companies. When
the dollar value of the APAS system is included in the evaluations criteria, clearly the
APAS is in a class by itself. (This remarkable APAS system, including hardware and
software, is available for only $10,000).