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.