ation 
rvation 
3 one 
nN since 
re of 
  
   
a triplet is of the order (18 + 3n), where 18 is the fixed number of 
exterior orientation parameters for three photographs, and n is the 
number of points in the total model area. 
N N 
18,18 
Ns 2 4 
Nt N 
> 3n,3n 
The computation of v as given by equation 3 for this size matrix is 
rather prohibitive for present on-line systems. Therefore, let us 
propose an alternate scheme in which v, the measure of efficiency, is 
computed with only that portion ef the normal equation matrix which is 
associated with the exterior orientation parameters (N). For this 
case equation 3 may be modified as follows: 
  
_ det (N:) 
Va = - — : 5 
det (N.) 
where, 
i: is the N portion of the normal equation matrix after an additional 
observation is selected and added to the solution. 
N; is the N portion of the normal equation matrix before the 
additional observation is included. 
To justify equation 5 and the departure from theoretical considerations