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PHOTOGRAMMETRIC ENGINEERING
U. S. Ars FoncE— WRIGHT FIELD
Ever since the inception of a photo-
graphic unit in the Engineering Division
of the U. S. Air Force, a detachment of
Corps of Engineer personnel has been as-
signed to cooperate in the development of
suitable aerial photographic equipment
and auxiliary accessories necessary to pro-
duce accurate tactical maps from aerial
photographs. The Corps of Engineer De-
tachment and the Photographic Unit,
now expanded to the Photo Reconnais-
sance Laboratory, have worked together
on this program since 1920 and the follow-
ing major items, which have contributed
considerably to the science of photogram-
metry have been developed by the U. S.
Air Force.
Early in 1921 the T-1 (tri-lens) camera
was developed as an accurate tactical map-
ping camera from which suitable maps
could be made. The basic design of this
camera was originated by James A. Bagley
of the Corps of Engineers and through
various stages it grew into a four-lens
camera (T-2A) and then into a five-lens
(T-3A) camera. This multiple-lens camera
culminated eventually into standardization
of the T-3A cameras as an operational
item in 1933 and was later used as a tan-
dem installation with two five-lens cam-
eras in a single mount, thereby producing
an octagonal picture. The tandem set-up
was used extensively until 1939. Asso-
ciated equipment, such as transforming
printers and alignment templets, were
also developed for use with this camera.
In 1934 a German RMP-10 camera
with a wide-angle 10 centimeter f/6.3
Topogon lens was imported. This wide-
angle lens opened up a new field in the
development of mapping cameras, and a
6-inch Metrogon was produced by the
Bausch and Lomb Optical Company; the
optical design of the Topogon was used
as a basis to provide a lens that would
cover a 9X9-inch format, thereby enabling
the use of 91 inch film which was Air Force
standard.
At a later date (1939-40) a 12-inch
Metrogon lens was produced and was used
in 18X 18-inch format. It has since been
used on the 9X 18-inch format to cover
large areas at small scale in a minimum of
flying time.
As a result of the development of the
6-inch Metrogon, the T-5 mapping camera
was produced in 1940 and was used as an
Air Force mapping camera until the end
of World War II. After this the T-9 and
later the T-11 cameras were developed.
The T-11 camera is now considered as the
standard tactical mapping camera for the
U. S. Air Force. A quantity is now being
procured for tactical mapping outfits.
To permit the production of more ac-
curate maps from aerial photographs and
to eliminate a considerable part of the
laborious work required, several attempts
have been made to stabilize the mapping
camera. As early as 1921 a stabilization
unit, controlled by a gyro, was geared into a
a standard camera so that it would achieve
a measure of stabilization and produce
more satisfactory photographs. However,
due to a lack of accurate and powerful
gyros the stabilization of cameras was
abandoned in 1925, and was not taken up
again until 1943. It was not until 1947, how
ever, that a satisfactory automatic stabi-
lized mount was developed that could be
used in conjunction with mapping cameras.
With the advent of the tactical mapping
camera it was necessary to provide suitable
processing, drying, printing, and projec-
tion equipment so that more accurate re-
sults could be obtained from exposed nega-
tives. Work along this line resulted in the
development of the E-2 (Steinman) proc-
essor in 1928, the B-5A in 1937, and the
B-6 in 1942. As requirements became more
exacting it was necessary to consider the
shrinkage of film used in aerial cameras.
After considerable tests, research, and
cooperation with industry a low-shrinkage
film base which eliminated considerable
inaccuracy was developed in 1932. This
development called for further develop-
ment of a low-shrink waterproof-base
printing paper in 1935, and later (in
1937) a white-pigmented base printing ma-
terial that was used extensively for the
assembly of the composite pictures from
the T-3A camera. All of these various de-
velopments have permitted greater ac-
curacy in the production of maps made
from aerial photographs.
There was a great need for a suitable
type of aircraft which would carry aerial
photographic equipment to the most de-
sirable altitude at constant level, which
would have sufficient range, and also be
reasonably stable during flight. While