lO 
On studying the results presented in Table 1, it can be gener- 
ally concluded that the use of the quadrustational close range 
system has not only improved the accuracy of measurement but 
also removed the elements of uncertainty in the results. 
It is apparent that the accuracy is fairly consistent for the 
individual stereopairs for the normal case and less consistent 
for the general case. The results of the quadrustational system 
reveal that 36$, 34.5% and 54.8% improvement has been achieved 
in the x,y and z directions respectively in normal case, and 
further slight improvement when using the general case. There 
is no noticeable difference between the results obtained from 
optimisation using rays from that using planes. 
On comparing the results in Table 2 with those in Table 1, it 
can be stated that there is no noticeable difference as to 
whether the base of the pyramid is square or rectangular in the 
case of the quadrustational system. 
Table 3 shows the results when all the camera axes were con- 
verged towards the centre. It indicates that an increase in 
the convergence results in a decrease in the accuracy. 
CONCLUSIONS 
The results of the experimental studies presented in the last 
section support the view that the quadrustational system gener- 
ally offers a higher degree of accuracy and reduces the elements 
of uncertainty as compared with the conventional two-station 
System. This was due to the fact that: 
a) the number of degrees of freedom are increased 
b) any gross error can be easily detected. 
Based on the theoretical and experimental studies, it can be 
concluded that: 
1l. The accuracy is more homogeneous in all coordinate axes 
when using the quadrustational system as compared with 
the two-station system. 
2. The system produces higher accuracy in the z-dimension 
which is of the paramount importance to most engineering 
measurement problems. 
Incorporation of optimisation principles into the system, to 
determine the optimal point, has the following advantages: 
1. The optimal point represents an acceptable point for the 
location of intersection of the four rays involved in the 
quadrustational system. 
2. .The system is reduced to a 3 x 3 matrix, while eight 
equations are formulated for a simultaneous vector 
intersection. 
3. Most of the available minicomputers can execute the simul- 
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