(a) (®) 21°) 
21) 7 70) * M5) (5) " 712) * §5am(2) 
If we again call attention to the fact that the values of X, Y and 2 
which appear in the above written relations are the same, it becomes evi 
dent that a suffioient number of equations of the type (2.2) can solve the 
problem of relative orientation. 
There are 12 unknowns relative to beam (2) (not taking into oonsidera 
tion whether all or less than all are oomputable). The ooordinates X, Y, Z 
of the points of intersection are also unknowns, with the exception of 2, 
concerning which we gave an earlier explanation. In all, therefore, the un 
knowns ares 
12 + 3n - 1 
where n indicates the number of pairs of homologous radii. Since each pair 
of homologous radii gives rise to 4 equations, i.e., to 4n in all, it is ne 
cessary to write at least 44 equations (for 11 pairs of homologous radii) in 
12 + 11 x 3 = 1 = 44 unknowns. Of course, by using the method of least squa 
res for the solution of the problem, it is possible to formulate more than 
11 quadruplets of equations. Each quartet, moreover, introduces 3 new unknoms 
(the coordinates of the point of intersection) and still another equation. 
The only serious difficulty of such a method of computation rests in 
the fact that during the act of computation, having to give the appropriate 
values of the unknowns for the iterative process, it is necessary to define 
the approximate values of the coordinates of the points of intersection of 
the homologous radii in a congruent manner. 
This difficulty can be overcome only if preliminary computation is used, 
which furnishes the approximate values of the coordinates. A computation of 
this type, however, is only a method of resolving the problem of the relative 
orientation, in which the unknowns relative to the coordinates of the points 
of intersection are eliminated. : 
We therefore must conclude that the method of computation based on e 
quations 4) cannot be considered as that of the relative orientation of two 
beams of directions, but the method of compensation of the results obtained 
gives an effective computation of relative orientation. 
We therefore must define a method of computation of relative orientation 
which does not take into consideration the determination of the coordinates 
of the points of intersection of the homologous beams, simultaneously with 
the computation of the other 12 unknowns. 
4.2 - BQUATIONS OF PARALLAX AND SCALING 
Let us again examine the four equations 4). From the first and third 
we obtain 
  
and 
From 
( 6) 
tion 
nates 
which 
tions