Fig. 1. The take dihedral and the intrinsic parameters of the take arrangements. 
meters 1) of reciprocal orientation of the generical ground take arrangement with photo- 
theodolites (if the swings of the take frames are thought nil, as is normal after the 
levelling). 
—b —length of the horizontal projection of the distance between the principal points 
of the take frame (reduced base); 
—h — difference of height of the principal points; 
,£, — elevation angles on the horizontal plane of the axes of the photographic cameras; 
a,, a, — azimuth of take vertical planes in respect to the base vertical plane, by means of 
spherotrigonometrical relations that qualitatively appear in Figs. 2 and 3. In 
particular Fig. 3 shows, on the representative sphere, the relations between the 
current angular parameters ¢,, €, 2a (= a, — a,), with the intrinsical angular 
parameters considered in the take dihedral: »y, g,, g». Fig. 2 shows the trigono- 
metrical relations between the current spatial parameters b, h, the intrinsical 
spatial parameters d,, do, 1, considered in the take dihedral and the before men- 
tioned parameters of spatial angular orientation, a,, a,, whose difference is 2a. 
€ 
These relations will be obtained in a quantitative form in a subsequent study, it could 
be interesting to observe meanwhile that the swings g,, g, as well as the opening of the 
dihedral 2y do not depend from each one of the single values of a, and a», but from 
their sum 2a, as well as from the single values of s, and e,, (see Fig. 3). 
The two representations in the figure do not take into consideration the curvature 
1) In order to simplify the translation formulae, we will consider as current topographic 
parameter of the take, the distance between the two principal points of the take, namely, 
the reduced base, instead of the normal base (distance between the take centers).