to the necessity of a good aerophotogrammetric cartography at 
medium or small scale some components were eliminated, for 
the first those permetting terrestrial plotting. 
Other peculiarities contributed to improve the general structure 
and kinematics. In particular the components by and of the 
base were eliminated and the bridge was provided with micrometric 
screws which permitted the general <J> rotation of the model while 
the rotation Q relied upon the single rotations to' and to'' (primary). 
A successive progress has been recently realized with the Stereo- 
simplex II/c that we will describe further on. 
Q THE STEREOSIMPLEX II/c. 
The necessity of the employment of maps at medium and small 
scale of vast regions, little known or completely inexplored, demands 
an extensive amount of work. 
A high degree of precision is necessary for the successfull realization 
of this work. These two reasons together with many other of signi 
ficant nature, have required the study of an instrument that does 
not need photographic plates of a reduced size. On the other hand 
the fact could not be ignored that in this field of cartography the 
use of cameras of supergrandangular lenses (120° field) can become