Stationary Test 0-cm
The stationary test measured the ability of the
system to maintain static measurements when a moving marker passed in the vicinity of a
stationary marker. With most marker-based systems, this is a major problem which
necessitates human intervention to manually correct the problem. The point is, a
stationary marker should not move.
Slide 19. Measures from Static Marker. (Slide was photographed in the original
presentation)
This important test measures the influence of a
moving marker on a static marker, which remains immobile, or on another marker.
Theoretically, movement analysis should minimize noise created by movements which do not
actually exist. Slide 19, illustrates the moving markers relative to the stationary
marker.
| |
|
Rank |
Max |
Rank |
Markers |
Rank |
Total |
Rank |
Sub-Total |
| |
0 cm |
Score |
Error |
Score |
Crossed |
Score |
Error |
Score |
Score |
| Ariel |
0.140 |
5 |
0.245 |
5 |
No |
5 |
0.385 |
5 |
20 |
| Motion |
0.147 |
4 |
0.604 |
4 |
No |
5 |
0.751 |
4 |
17 |
| Peak *** |
0.282 |
2 |
1.183 |
2 |
Yes |
0 |
1.465 |
3 |
7 |
| Qualisys |
0.299 |
1 |
3.206 |
1 |
No |
5 |
3.505 |
1 |
8 |
| Vicon *** |
0.183 |
3 |
1.725 |
3 |
Yes |
0 |
1.908 |
2 |
8 |
2-cm-separation
Slide 20 illustrates the error for the 0-cm
separation. Motion Analysis performed the best and the APAS was second. Peak
and Vicon were unable to keep the markers on track so there was switching of the markers.
However, the investigator of this research chose not to include these errors in the
statistical analysis. If these measurements had been included in the statistics, the
error would be much larger !!!
Slide 20. RMS Error at 0-cm separation. (Slide was photographed
in the original presentation)
Table 4 illustrates the data for the 0-cm
separation. As can be seen, the APAS system performed the best with an average error
amounting to 1.4 mm in a 3000 mm volume. This result was the lowest of all other
companies. The maximum error amounted to 2.4 mm, again the lowest of all
companies. For both Peak and Vicon, only a subset of the data points were used since
the markers crossed and switched.
Table 4. 0-cm test results
***Markers crossed, only subset of data
which was properly indentified was use for analysis.
| |
|
Rank |
Max |
Rank |
Markers |
Rank |
Total |
Rank |
Sub-Total |
| |
2 cm |
Score |
Error |
Score |
Crossed |
Score |
Error |
Score |
Score |
| Ariel |
0.210 |
2 |
0.588 |
2 |
No |
5 |
0.798 |
2 |
11 |
| Motion |
0.153 |
3 |
0.571 |
3 |
No |
5 |
0.724 |
3 |
14 |
| Peak *** |
0.256 |
1 |
1.623 |
1 |
Yes |
0 |
1.879 |
1 |
3 |
| Qualisys |
0.054 |
4 |
0.210 |
5 |
No |
5 |
0.264 |
5 |
19 |
| Vicon *** |
0.083 |
5 |
0.458 |
4 |
Yes |
0 |
0.541 |
4 |
13 |
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[Next Page - Results] .
Slide 22 shows the incredible error the Peak
and Vicon produced in tracing markers. This means that when markers approach approximately
1 cm distance from each other, neither the Peak nor the Vicon system can detect the
difference between the markers. The APAS was able to do a perfect job. Markers were
never switched regardless of the distance between them. Even at a 0-cm
separation, which means no separation, the APAS system was able to detect the markers.
Slide 22. Marker Switching at 1-cm Separation.
(Slide was photographed in the original presentation)
As can be seen in Slide 21, the APAS system out
performed all of the other systems. As was seen previously with other conditions,
both Peak and Vicon demonstrated problems with a switching of the targets although the
largest error was observed in the Qualisys system.
Slide 21. Maximum Error at 0-cm Separation
In the 2 cm separation test, Qualisys had the
smallest total error. Vicon and Peak again had a problem with switching of the
points between the stationary and the moving targets. However, in spite of this
crossing problem, they were given a score. One should keep in mind that the error is
only 2 mm in 3M volume. This is approximately a .06 percent error. INCREDIBLE !!!
Table 5. 2-cm separation test results
