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17 
METHODS AND EQUIPMENTS FOR CALIBRATING 
PHOTOGRAMMETRIC CAMERAS 
by 
Officine Galileo of Florence. 
This note is intended to describe a camera testing device recently designed 
and constructed by the O.G. (Florence). By the use of this equipment it is 
possible to obtain the following calibration data: 
1) The equivalent focal length of the lens as set in the aerial camera. 
2) The radial lens distortion. 
3) The tangential lens distortion. 
4) The location of the principal point. 
The complete test data are obtained on a single photographic plate. As it 
is known, the tests may be of 
a~ 
17- 
the visual 
type. After 
or photographic 
the first experi 
ences the O.G. have selected 
the apparatus utilizing photo 
graphic principles: the visual 
method being less sensible 
owing to the parallaxes gene 
rated by the curvature of 
field which is unavoidable 
especially with wide-angle 
lenses. Besides the equipment 
in description, allows also the 
possibility of visual controls. 
The new camera testing devi 
ce, very simple in its whole, 
provides facilities for quickly 
and rigidly mounting most 
types of aerial cameras and 
has a high degree of accuracy. 
The device is placed in an 
underground, air conditioned, 
room, and lays on a mansonry building, about 70 cm high (see Fig. 1). This 
building supports the two parts of the equipment: i.e. a strong battlement (2) 
which holds the camera and a horizontal beam (3) turning around a vertical 
axis (4). A theodolite (5) lays on this beam and can run along it. 
The vertical axis can slide up and down and can be fastened by a lever (6). 
Its stability during the movement is assured by a cylindrical guide (7) solidly 
connected to the building, down into its depth. The horizontal beam can 
turn about the vertical axis, its rotation being measured by means of a gradua 
ted circle (9). The rectified plate (11) supporting the theodolite, slides on the 
upper rectified guides of the beam: the accuracy of the construction is checked 
Figure 1.