approach, and, perhaps more important, the relative inexpen- 
siveness of such cameras, efforts have been made in recent years 
to use stereometric systems in fields of high accuracy require- 
ments. Of the several fine projects reported on in the litera- 
ture, only two will be briefly discussed here to indicate the 
obtainable accuracy. 
Konecny (1965), for example, used a WILD C-12 stereo- 
metric camera to measure deflections and horizontal displace- 
ments of discrete points on a beam under testing conditions. The 
camera was set in a horizontal position at a distance of 7 meters 
from the beam. A ZEISS-JENA 1818 Stereocomparator was used in 
data reduction. The following accuracies were reported by 
Konecny: (refer to Fig. 12 for coordinate system) m = + 0.23mm, 
m + 0.38mm, and m, 7 t l.7mm. The vertical deflection AY 
should be determinable with an accuracy of m, V2 or + 0.5hmm. 
According to Konecny, 'this accuracy is sufficient for the 
determination of ultimate strength design parameters, which 
cannot be obtained reliably from strain gauges.'' 
Wasil and Merchant (1964) reported on the use of à WILD 
C-12 stereometric camera to determine the deflections of a 
laterally loaded plate under test conditions. The camera 
was set in a horizontal position over its tripod at a distance 
of 3 meters from the plate which was in a vertical position. A 
B & L Balpex 525 was used for data reduction. A comparison of 
results indicated the accuracy of the measurements was within 
+ 0.02 inch (+0.51 mm). As Wasil and Merchant indicated, this 
type of accuracy is adequate for structural measurements where 
deflections as such are required, but it is far from sufficient 
for purposes of stress analysis. 
The work done along these lines at the University of 
lllinois is outlined in some detail in Section 3.