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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.