that a direction is available which is not affected by accumulated errors, 
At least equally importantis the fact that because of the infinity position 
of celestial targets, the solution is able to discriminate between rotational 
and translational parameters. If only terrestrial control points are used 
these parameters are closely correlated. (Compare [5] ). 
Generally speaking, we can say that each recorded sun image gives rise to 
two observational equations in terms of the three rotational parameters (a, w, 
K) of the corresponding station. Obviously, it is necessary that the 
measured sun image plate coordinates, recorded with a special sun camera, be 
normalized in such a way that they are compatible with the metric character- 
istics of the aerial camera taking the corresponding ground photography. 
Mathematically speaking, it is necessary to normalize the corresponding 
comparator measurements, by transforming the x,y,c system of the sun camera, 
with three rotations and three translations, so that it conforms with the x,y, 
c system of the aerial camera. The corresponding rotational and translational 
parameters are obtained from preceding camera calibrations, for example by 
taking star photography. 
D. Teking into Consideration Additional Geometric Conditions 
Tn order to complete a generally acceptable analytical solution it is now 
necessary to study the problem of incorporating certain geometric conditions 
such as may exist for one or all of the unknown parameters, including both the 
coordinates of the model and the orientation elements. 
In the above outlined solution, a system of normal equations exists, at 
least temporarily, in terms of both the elements of orientation and the 
coordinates of the model. The incorporation of any additional conditions 
existing for any one or all of these unknown parameters, can be performed by 
a computational technique which was presented by Helmert in [4] dealing in 
Chapter IV, paragraph 24 on page 196ff with the problem of indirect measure- 
ments, the unknown parameters of which have to satisfy certain conditional T 
equations. | 
22