The checked devices are: 
a) the plotting coordinatograph 
b) the plate-holders 
c) the lower ends and the upper extension of the space rods. 
The AA. have firstly taken in consideration the ideal adjustment conditions 
of the above-mentioned devices and they have tried to single out, to localize 
and if possible, to measure the irregularities of the mechanical construction. 
Every measurement has necessitated very sensitive experimental methods, 
sometimes original too. 
On the plotting coordinatograph the A.A. have checked: 
1) if the tree carriages run along stright-lines and if the bridge does not rotate 
during its movements 
2) if the above mentioned stright-lines are mutually perpendicular lines 
3) if eccentricity exists between the rotating axes of the cardan joints which 
connect the rods to the bridge of the base. 
All the checkovers of these devices performed with high precision, have given 
very good results and attested the excellence and the accuracy of the instrument 
mechanical devices. 
In checking the plate-holders and the plate movement (in this instrument the 
plates shift freely in its own plane, so that all optical devices may remain at 
a fixed position) it has been necessary to verify the following conditions for a 
correct working: 
1) No back lash in the plate-holders junction to the upper ends of the rods, 
which is realised by a spherical coupling 
2) The plate centre shall lie, during its movement, on a plane surface 
3) the plate-holders shall move without rotating round the x and y axes of the 
plate and the camera axis. 
It is proper to remark the perfect realization of the plate holders movements, 
fundamental condition for a correct working. 
The check of the space rod, which in the Stereocartograph is divided in two 
parts, one in the model side, and the other, a small sliding bar, placed above 
the camera, has required a particular study with many difficulties. 
The theoretic adjustment conditions of the rod, which rotates round a cardan 
joint, are the following ones: 
1) the rod shall be a rectilinear rod 
2) the above-mentioned small sliding bar shall be a rectilinear one, and no 
irregularities shall exist in its movement 
3) no reciprocal eccentricity shall exist among the axes which converge to the 
cardan joint centre: the primary and the secondary axes of rotation, the rod 
axis and that of the small sliding bar 
4) the rod axis and the small sliding bar axis shall be parallel ones 
5) no bending shall exist between the rod axis and the small sliding bar one 
whatever position and tilt they will take up. 
Except this last checkover, which is not yet performed, the other checks 
were achieved at least for one camera only, by using a method which is reputed 
an original one and which allows to single out the effects of every anomaly of 
cardan joint and to measure the linear and angular eccentricities among the 
above mentioned four axes. 
Etude expérimentale de la précision du Stéréocartographe Santoni mod. IV 
Le Stéréocartographe Santoni IV a été soumis à une étude très détaillée, pour déterminer sa 
précision intérieure. 
L’examen a été porté surtout sur: a) le coordinatomètre restituteur et le chariot de la base; 
b) le porte plaques et le pantographe; c) le système de projection formé par la tige inférieure, la 
petite tige supérieure et le cardan.