to 
and 
4 5 
com COPAS 
Gm " 
CON 
The least squares solution gives, besides the orientation unknowns, the 
distortion coefficients Ky Ky and Ks The distortion A’ can now be computed 
with formula (73). However, usually the distortion curve is presented in such 
a way that À = O, for & suitably chosen d. Thus analogous to formula (71); the 
condition that 
"a = -(K 4 KP 4 RAT | 
K à = -(K@ + Kd * Kd) (80) 
must be satisfied. 
From (73) the right side of formula (80) equals -A! 
d 
Ab A : 
* $ 42 Al 46 
Ky = = a -(K, + Kd + Kd ) (81) 
and the final distortion curve is now 
x^ 3 5 7 
A= K à + Kj + Kd + Kd 
i (82) 
5 * 2 4 6 
or. ; À = d 5 + Kd 4 Kd T Kd 
The "focal length" associated with this distortion curve is again, in analogous 
to (71), i 
etos c(1 - K^) ; (83) 
Accuracy Considerations ; 
The mean error of an observation of unit weight denoted by m ig computed 
according to (58) | 
n s (ER yu 8 Cy 
where r is the number of observation equations 
u is the number of unknown geometrical parameters and 
K is the number of unknown distortion parameters carried in the solution, 
As described in Chapter IV E, the inverse of the normal equation matrix 
is the weight matrix of the unknown parameters of the solution and consequently 
the mean errors of the distortion parameters can be computed directly, 
25