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6 
having all the desired geometric characteristics, by introducing a corrective ] 
new photographs can come out completely free from distorsions or with a a S 
ferent distortion, as, for example, that of the plotting cameras, if they had mie 
— which, naturally, would be already known. In this way the advantage is a 
there are no residual differences in distorsion among the printed photographs a by 
which is inevitably the case when the distorsion is corrected separately by d elfe 
means applied to the plotter cameras. Furthermore printing by the optical system de 
with the orthoscopie Photoprinter, is preferable to contact printing, since the i s * 
fectly plane plates is not necessary. x 
The comparatively low cost of the orthoscopie Photoprinter, one of which can sy 
several plotters, and its usefulness make it a valuable aid in doing M 
work, and it is to be hoped that its use will become general with all the advantage m 
simplicity and uniformity of the photogrammetric plotters. 
A few years ago I conceived and designed a plotter, based on the Porro-Koppe vi 
ciple, which I called “telescopic”, and which solved all the problems noted i 
This plotter makes possible even the preventative rectification of the Photogrags 
accordance with the complete transformation of all the geometric characteristics oe 
most orthodox way, as if the new photograph were made with a new camera of dite 
geometric characteristics and with a different exterior orientation. This plotter Ny 
| 
1 
did not meet with favor, probably because its importance was not understood. Now, iy} 
» Now, i 
new design, it is being presented to this Congress by my colleague, Dr. Gino Parent] al 
I am certain that it will meet with a greater amount of well deserved attention om fi 
part of those interested in photogrammetry, since it is possible, with it, to attain fi 
hoped-for simplification of the photogrammetric plotters. 
But the great novelty of my plotters, the one which arouses the most interest — ai 
alas, the most diffidence is that of the replacement of the mechanical transmis 
with electro-magnetic ones, thus permitting the simplification of the structure oi ik 
plotters and conferring upon them a valuable complex of advantages in their practical i 
What is the reason for this diffidence? It is certainly not a misunderstood infolera 
which cannot be attributed to or blamed upon us who are the creators and designers 
instruments that have overthrown the old surveying practices. It must be attributed fia 
to the doubt that the new transmissions are not such as to assure the perfect and sem 
synchronization between the mark and the pencil tracing the drawing. 
The principle on which these electro-magnetic devices are based is a known ong, 
the devices find broad application today wherever it is a matter of transmitting ani 
movement between two or more shafts with strong approximations that in some us 
as in fire control centers on ships for example, don't go beyond a few seconds of at 
which is more than enough for their use in photogrammetric plotters. 
In the Photostereograph model Beta/2 they are applied in such a way that 
revolution of their rotor corresponds to a displacement of one millimeter of the mai: 
the direction of the desired co-ordinate and of an amount corresponding t0 the "i 
introduced among the axes involved for the pencil. It follows that when this ni 
one to three, a ratio that must be considered as among the highest employable in pta 
with this type of plotters, it is then necessary that there comes about a want of Ji 
of at least 12 degrees between the rotors of the corresponding devices, 0 that the je 
deviates from its exact position in relation to the position of the mark by a teni! 
millimeter, i.e., by half of the line drawn. 
Since the torque gradient in the electro-magnetic device 
36 grams for each degree of rotation of the rotor, when the w 
rotors of the electro-magnetic devices reach the 12 degrees, we have 
390 grams, a torque which is about twice that necessary to overcome th 
entire mechanical complex that provides for the movement of the mark and the i 
The transmission of the value of the coordinate corresponding to the position 6^ 
  
s used in the plotter is ie 
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