elements involved, does of course not result to be safe and completely 
free from any error possibility. 
To reduce the various causes of error during this transportation 
of photographs and values, the manufacturer has provided Stereo- 
simplex III with a suitable control device realizing the best transfer, 
from the lefthand to the righthand camera, of the three parameters 
w, cp and x. (2). 
This device (see fig. 1) called ‘ areopiane ’ owing to its form, con 
sists essentially of a tubular support and a cross arm. The first is 
suited as a support on the main y guiding track of the plate-holder; 
the latter has some adjusting screws at both ends and is suited for 
lateral support on the secondary y-track of the said plate-holder. 
The tubular support holds a counterweight and two levels set 
cross-wise and provided with adjustment screws. On the inside, instead, 
it holds a small type of binoculars provided with a Gauss eyepiece, a 
lamp for grid illumination and a right prism deviating by 90°, the 
sheaf projected by the grid. 
Fig. 1 - Device of w, <p, 
x 
- value control in aerial triangulation.