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Corps OF ENGINEERS
Photogrammetric activities of the
United States Army Corps of Engineers
began in 1920 when Major James W. Bag-
ley, Corps of Engineers, was assigned to
cooperate with the Army Air Corps in
carrying out tests of aerial photos for use in
topographic mapping. The first research
was in development of suitable aerial
mapping cameras. Major Bagley's tri-
lens camera, invented in 1916, formed the
basis for a series of multiple-lens cameras
culminating in the five lens T-3A camera
having one vertical chamber and four ob-
lique chambers. This camera remained the
standard precision mapping camera of the
U. S. Army until 1940.
A tandem T-3A camera arrangement
was also evolved, made up of two five-lens
T-3A cameras mounted so that their hori-
zontal axes were at 45 degrees to each
other. The oblique photographs when
transformed by a special printer into the
plane of the vertical photography, may
be assembled with one vertical photo-
graph to provide a near vertical 9-lens
composite photograph.
In 1935, the stereocomparagraph was
invented by Captain Benjamin B. Talley,
of the Corps of Engineers, and standard-
ized for use of field photomapping units.
In 1937, vertical and oblique multiplex
projectors (normal-angle) were developed
by the Bausch and Lomb Optical Com
pany, under a contract with the Corps of
Engineers, in order to provide a stereo-
compilation instrument capable of utiliz-
ing T-3A vertical and oblique photography
for topographic mapping. During the same
period experiments were begun with single
lens wide-angle cameras. After testing
various lenses the 6 inch metrogon lens
with 93 degree angular coverage was adopt-
ed in 1940 for use in the standard military
mapping camera.
In 1938, the Corps of Engineers issued
a specification for wide-angle Multiplex in
order to utilize mapping photography
taken with wide-angle cameras; it con-
tracted for a limited quantity. In 1939,
these instruments were standardized for
U. S. Army use, and in 1940 further pro-
curement of normal-angle equipment
ceased.
The use of the metrogon lens neces-
sitated the development of a distortion
compensating reduction printer; develop-