Moreover, it is possible, as done already, to reduce distance between 
the two cameras by approximately one half of the standard distance 
used. 
Quite evidently, photographs are placed at 90° rotation with respect 
to the conventional position. As a consequence, whereas the first 
carriage materializes altitude variations (Z), the second one mate 
rializes Y and the third one X. 
Component By of the base (see fig. 1) is set by making either or 
both cameras slide on the guides borne by the bridge by means of 
micrometric screws. Component Bz may be set for one or both 
cameras in the same way, shifting the cameras in the direction 
parallel to the guides of the first carriage. 
We must stress that these motions are facilitated by the fact that 
they occur on horizontal planes. 
Coordinates X Y of plotted points are measured through finely 
graduated discs; to these rotation is imparted by the same screws 
that action the relative carriages. Recording is done at remarkable 
magnification from a lighted screen, to less than 0,01 mm. 
Displacements of carriage « Z » (first carriage) for measurement of 
altitudes, are read from three graduated drums whose rotations are 
controlled by screw « Z », through its transmission parts where 
ratios may be changed in such a way as to suit them to the scale selec 
ted for the optical model. 
Values may be expressed either in metres, decimetres and centime 
tres or in feet and decimal fractions of same. 
Rotations (co, cp, k) of cameras. Setting of the focal distance 
(see fig. 2 and 4). 
Rotations to be imparted to the cameras in order to reset elements 
of outer orientation are the following: one rotation around a (pri 
mary) vertical axis for w, and one rotation around horizontal (sec 
ondary) axis for 9, both controlled by worm screws fitted with 
knobs graduated to the one hundredth of one degree (centesimal), 
stating also fraction values. 
Rotation k is obtained through the same type of device.