Finally, it is obvious that: 
= + 
N; + 
The sign of N, is determined in the same fashion as M,. 
3 
The transformed coordinates of point P are then determined as: 
x! : (6) 
p 
y! : (7) 
p 
2! (8) 
p 
where D is the distance from P to the origin (A). In other 
words: 
  
2 
*, z^. (9 
Ds Vo, . Wk + 1% a) 
are the spatial coordinates of point A in the 
P 
A? Ya? 7A 
(X,Y,Z) coordinate system. 
where X 
3.4 Evaluation of the System 
  
To evaluate the overall accuracy of the sytem, three 
sets of 5 stereo models each were taken at three successive 
loadings in one of the tests. The first stereomodel taken for 
zero load was chosen as reference, and the spatial coordinates 
of the targeted points in all other models were transfromed 
to this reference coordinate system. 
The variation in the deduced planimetric (X,Y), and ele- 
vation (Z) object coordinates of the 81 points were used to 
estimate the standard errors in the determination of the 
spatial coordinates. The results are as follows: