6 HISTORY OF PHOTOGRAMMETRY IN THE UNITED STATES
PHOTOGRAMMETRIC INSTRUMENTS AND PRO-
CEDURES DEVELOPED BY U.S.G.S.
Panoramic Camera?
The first panoramic camera Figure 1,
used by the U.S.G.S. was constructed by
C. W. Wright in 1904 and was improved in
1907. The improved model was a box type
Fic. 1. Panoramic camera.
in which the lens was revolved about a
vertical axis by a spring, with the rate of
revolution and, in part, the exposure being
regulated by detachable fans connected
by gearing with the lens shaft. Roll film
in 5- or 6-inch cartridges with several
exposures each was placed on a circular
film guide, so adjusted that when the film
was in position for exposure all elements
of the cylindrical surface of the film were
perpendicular to the level plane and paral-
lel to the lens shaft. The top of the camera,
being the reference plane for leveling, was
fitted with leveling-bubble slots at right
angles to each other. Three leveling screws
of the common type were used in connec-
tion with an adapter plate that fitted a
planetable tripod, thus avoiding the ne-
cessity of transporting two tripods. The
horizontal field of view was 126° for each
exposure; the vertical range was from 18°
to 22° above the horizon and from 26° to
30° below the horizon, depending on the
width of film used. The film was usually
developed in the field to check the quality
of exposure and the coverage of the area
to be mapped.
Panoramic Photoalidade?
The panoramic photoalidade Figure 2,
was developed between 1910 and 1916 for
use with panoramic photographs taken by
Bagley's parties in Alaska. Its purpose was
to transfer to the map the information ob-
tained from the photographs. It was so
designed that the operator could sight any
image point in the photograph and deter-
mine the horizontal direction from the
station point to the image point, in the
same way that the topographer operates
the telescopic alidade on a planetable. A
reading glass with a vertical hair, used with
a sighting vane, could be said to represent
the lens system in a field instrument. A
radial arm represented the plotting base
on an alidade, and directional lines were
plotted along this arm on the map sheet.
The reading glass, sighting vane, and
radial arm were controlled by a mechanism
of the rack-and-pinion type revolving
around a point representing both the op-
tical center of the lens and the camera sta-
tion.
To obtain differences of elevation for
contour sketching, measurements were
made of vertical distances of points above
or below the horizon line, which appeared
as shadowgraphs on the print. A simple
formula that used these distances with the
corresponding map distance and the prin-
Fic. 2. Panoramic photoalidade.
cipal distance of the photograph gave the
difference of elevation. A separate office
instrument, known as a rotary scale, was
constructed to expedite the measurement
of the vertical distance.
Tri-lens Camera?
The tri-lens camera Figure 3 was de-
signed in 1916-17 by J. W. Bagley, with
the assistance of J. B. Mertie, and F. H.
Moffitt, and was developed by the Corps
m
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