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A. The photogrammetric bundle and its orientation 
By connecting any identifiable detail on the photographie plate with 
a point situated outside of the plane of the photograph, it is possible 
to construct a bundle of rays. (Fig. 1) The point, thus common to all 
rays, is the so called center of projection, denoted by O. It is hardly 
possible, and for our purposes certainly unnecessary, to interpret this 
point physically. The position of this point relative to the photographic 
plate is fixed if, for example, an arbitrarily oriented rectangular plate 
coordinate system (x and y) is introduced in which the base of the perpen- 
dicular to the plane of the plate through O, denoted by P (principal 
denoted by c, is & scale factor and must not be physically interpreted. 
The sole purpose of this phase of the photogrammetric evaluation technique 
   
  
   
   
   
is to provide means suited for an unambiguous construction of a bundle of 
rays. This 1s accomplished by measuring x, y plate coordinates of identifi. 
able detail on the photograph in the same plate coordinate system, in 
which the point P is being described by its parameters Xs and Yo“ The 
parameters c, % and Y5 are commonly referred to as the elements of interio 
orientation. 
After such a bundle is obtained, the problem is to orient it unanbiguou 
in space, (1) by assigning to the point O, & specific spatial position ex- 
pressed, for example, by three linear parameters, X Y, and Zu With respect 
to an arbitrarily established Cartesian spatial coordinate system; (2) by 
defining with respect to the axes of this coordinate system, the direction 
of the vector as formed by the extension of the line PO into Space by two 
rotational components, (e.g., @ and w rotations), and (3) establishing the 
spatial position of the plate coordinate system by a third rotation (swing 
angle |) around the vector described, and positioned according to (2). 
The parameters X? Y» A OQ, w, kare commonly referred to as the 
elements of exterior orientation. 
Both groups, the elements of interior and the elements of exterior 
orientation, shall from now on be considered jointly if reference is made 
simply to the elements of orientation. The notation Q is used if all