6 
from the intrinsical parameters of the external orientation; more precisely the coordinates 
change with the staggering 1, while the abscissi depend from the dihedral 2y opening 
and from the magnitudes of the single base components d, and d, on the dihedral faces. 
For a dihedral opening close to 90° (y = 45°) and for d, d,, the dimensions of the 
abscissi of the nuclear points remain in a degree of photographic magnitude: (u, =u, = f). 
By enlargening the opening of the dihedral the abscissa increase, up to becoming of 
an infinite size for 2 y — 180°. The ordinates v,, v, practically always maintain themselves 
in a degree of photographic size, also for considerable staggering. 
The distances d, d, are instead always in the order of topographic size, these being 
the components of the length of the take base along the faces of the dihedral. 
  
© / 
& 
& / 
= 
S 
/ 
e / 
N A 
\ A S 
N 
N 
\ A » 
s 3 
„x e 
- v 
uS -— "T. v 
Fig. 3. Spheric relations between conventional take parameters &,, €, 20 
and intrinsic parameters 2 y gi, g». 
c) Projective identification of the homologs. 
Let us now consider the take dihedral and the two frames of the perspective lying on 
their faces. The take centers will find themselves upon the verticals to the faces in the 
principal points P and P' of said frames, at distance f (principal distance, the same for both 
cameras). (Fig. 4). 
The joining line of the take centers is the nuclear axis of the stereophotogrammetric 
pair: it is the axis of the bundle of the nuclear planes, and it intersects the dihedral faces 
in the nuclear points N, and N,.