66
test the absolute position data errors are calculated by using the line which best fits the data points as found with linear regression analysis. The errors found with lateral (along the X axis) translation are somewhat affected by headpiece orientation and are as much as twice those found with diagonal (along the -450 line) and anteroposterior (along the Y axis) translation. The results also indicate that perhaps more than half of the magnitude of these errors can be attributed to the DAS fixed position resolution limitations previously presented.
Table 2
DAS Accuracy with a Stationary Subject
Parameter Y Axis X Axis Rotation
(mm) (mm) (deg)
Test 1 Rapid succession 32 trials
Intertrial mean of intratrial S.Ds. 0.25 0.32 0.07 Intertrial S.D. of intratrial means 0.27 0.43 0.08
Test 2 Subject moved and returned 32 trials
Intertrial mean of intratrial S.Ds. 0.24 0.33 0.07 Intertrial S.D. of intratrial means 0.31 0.45 0.08
Test 3 System turned off and on 25 trails
Intertrial mean of intratrial S.Ds. 0.29 0.33 0.08 Intertrial S.D. of intratrial means 0.54 0.50 0.12
Test 4 Extensive source operation 15 trials
Intertrial mean of intratrial S.Ds. 0.25 0.30 0.07 Intertrial S.D. of intratrial means 0.22 0.40 0.07
..