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experimental design developed by these authors, we may proceed to 
a discussion of the problem of selection of pass points for an 
automated comparator system. 
IT.1 Criterion for Pass Point Selection fjr On-Line Systems 
In a conventional analytical triangulation, using a least 
squares adjustment, the parameters of the adjustment are the elements 
of exterior orientation and the object space coordinates. The 
aposteriori variances for each of the parameters are proportional 
to the diagonal elements of the inverted normal equation matrix. 
If X represents the vector of estimated parameters from a least squares 
adjustment, and for convenience they are assumed to be normally 
distributed with a mean value vector of X, and N is the normal 
equation matrix then, 
(x.-3) ANO XM voie 
is the equation of a hyperellipsoid centered at X. The volume of this 
hyperellipsoid is proportional to the determinant of the inverted 
(5). 
normal equation matrix 
Consequently, if M is the inverse of the normal equations matrix, 
the volume of any hyperellipsoid may be given by, 
4m 
Vn: 3 {det (M) 77