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Figure 9 Isometric plot of vectors and 95% confidence 
ellipsoids between epochs 10 and 11 
6. ANALYSIS OF RESULTS 
Computed AX, AY and AZ values and their associated 3D 
confidence regions were directly downloaded into the 
Integraph Microstation CAD system using in-house 
developed software. Figures 9 and 10 are isometric plots 
of 10x exaggerated target differences between: epoch 10 
and 11 and; 10 and just before failure of the rotor blade 
during epoch 17. In figure 9, corresponding to the 
difference between 100% and 150% design load, no 
significant movement is seen on the rotor blade. The only 
significant movements are on the survey control points to 
the bottom right of the figure. Whilst these points have not 
physically moved, they have moved with respect to the 
mathematical datum defined by the congruency testing 
procedure. Figure 10, a comparison between epochs 10 
and 17, shows significant change in shape of the rotor 
blade. Again the survey control points have moved with 
respect to the congruency datum, this time in the opposite 
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Figure 10 Isometric plot of vectors and 95% confidence 
ellipsoids between epochs 10 and 17. 
direction since the jig angle and therefore the angle of the 
blade was changed many times between these two 
epochs. This change in angle is confirmed by movements 
of the target points on the jig to the bottom left of the 
figure. In both cases the larger ellipsoids on targets at the 
blade’s change in section, towards the right of the view, 
are caused by fewer photogrammetric observations to 
these targets. 
Figure 11, an elevation, details the movements before a 
failure occured outside of the targeted area towards the 
rotor blade tip. In this figure the upwards movements due 
to compression in the lower portion of this section of the 
rotor blade root can be clearly seen. 
Finally the extraction of a profile from the data set is 
shown in figure 12. Here change is shown simply in 
exagerated vector form, but it is a simple matter to fit a 
new section to the data and measure for example change 
in section length. 
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Figure 11 Elevation showing vectors and 95% confidence ellipsoids between epochs 10 and 17 
497 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996