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With this paper I shall try to briefly describe the calibration 
operations and the necessary conditions of rectification which the AP/C 
Analytical Plotter must comply with. 
I shall also try to describe at the same time the construction 
criteria followed in designing and which were used to make the optical 
mechanical parts of this instrument as simple as possible with regard 
to both their stability and precision. I shall also give the procedure 
to be followed in the tuning of the instrument and finally I shall 
describe the tests carried out on the prototype model in order to arrive 
at the simplest and surest way to calibrate and rectify it. These tests 
were carried out to determine above all the intrinsic precision of the 
individual mechanical parts making up the instrument. 
Before undertaking the systematic description of these operations, 
it is necessary to recall that this instrument is made up of a cast 
basement on which the main frame, which includes the two co-ordinato- 
meters, is placed. 
On this frame all the properly pinned supports of the plate-holders 
guide tubes, of the mobile optical unit, are placed, as well as the 
mounting for the observation optical unit. 
It is also necessary to remember that the Analytical Plotter is 
basically, from the cinematic point of view, a stereocomparator in 
which the movement according to the two co-ordinates X and Y are 
distributed respectively between the mobile optical unit and the film 
piate-holders. 
The operations involved in calibration and adjustment can be 
schematically subdivided into the following four phases: 
(1) General preliminary calibration in the workshop, 
(2) Operations involving‘levelling and correcting, 
(3) General optical calibration, 
(4) Trials testing the accuracy of the instrument. 
These four phases are clearly distinct and the respective necessary 
tuning operations are not disturbed by the successive operations.