optical model would make it necessary to refer to the control points, thus rendering 
superfluous the first operation. 
But knowledge of the exterior orientation data of the photograph can make 
preparation of new photographs possible with the use of an auxiliary instrument, by 
which the long operations necessary today for the formation and absolute orienta- 
tion of the optical model would be reduced or absolutely eliminated, with great 
benefit in the cost and performance of the plotter, and, therefore, decisely, giving 
economic advtantage to the project. 
In fact, with the data furnished by the computer and new auxiliary instrument 
the following can be obtained: 
A. Photographs on which the position of the nadiral point will be indicated; 
B. Rectified photographs, that is made equivalent to photographs taken with 
vertical axis. 
The indication on the photograph of the nadiral point position can allow, as 
already stated (1), the formation of the optical model and its absolute orientation 
with extreme rapidity and practically without recourse to systematic attempts. 
Present plotters would be entirely able to adopt the new procedure which only 
requires bringing, at the beginning, the nadiral point on the perpendicular to the 
horizontal plane of the plotter. 
[t is better still if, in the new plotters, the camera supports are equipped with 
the rotation, which I have called o, that is, around an axis perpendicular to the 
horizontal reference plane of the plotter or nadiral axis of the photograph. Indeed, 
I adopted this rotation as far back as my first photocartograph (1924); in fact, in 
the photocartograph, besides the K rotation, there were the previously-mentioned 0 
rotation and only one tilt and tip of the camera, according to an axis which 
passed through the optical center of the camera and which was situated in a plane 
parallel to the horizontal reference plane of the instrument. 
Recently, in order to permit the use, both according to the method now uni 
versally accepted for the formation of the optical model and according to that 
sponsored by me, by means ot the nadiral point, in the Photomultiplex DIII, 
besides the indicated rotations, that is K and g, I also introduced the two rotations 
w and ¢, which, however, contrary to the design of ordinary plotters, vary their 
orientation in the plane, with the rotation g, to which they are slaved. 
The g rotation, as already stated, perfectly serves for orientation of the figure 
projected on the plane without varying either the geometric form or the magnifi- 
cation because it occurs around an axis perpendicular to the horizontal reference 
plane of the plotter. Rotations g and K are identical when the main axis of the 
camera is perpendicular to the horizontal reference plane of the plotter. 
Naturallv. in order to obtain the scale of the optical model, it is necessary to 
know the distance between two control points or set in the plotter the b, base 
(1) U. Nistri - « A Practical Procedure for Performing Spatial Aerial Triangulation », 
extract from the Bulletin of Geodesy and Related Sciences, Military Geographic Institute 
magazine, XIV Year, No. 3, July, August, September 1955. 
U. Nistri - « A Practically Procedure to Carry out Spatial Stereo-triangulation », 
reprinted from « Photogrammetric Engineering », March 1955. 
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