HISTORY OF PHOTOGRAMMETRY IN THE UNITED STATES
TENNESSEE VALLEY AUTHORITY
Shortly after the Tennessee Valley
Authority was created in 1933, there was
an immediate demand for topographic
coverage of the Tennessee Valley water-
shed, some 42,000 square miles in extent.
Photogrammetry was in its infancy in
America at that time, and such a large and
immediate need for topographic coverage,
cadastral surveys, land use studies, etc.,
created a demand for investigation into
new ideas and processes.
Realizing that topographic mapping of
such an area through any method would
take a number of years, the topographic
program was temporarily postponed and
the effort of the TVA’s mapping forces,
with the cooperation of the U. S. Geolog-
ical Survey, was directed toward prepara-
tion of a 1:24,000 7i-minute quadrangle,
planimetric series, of the entire Valley. This
was produced in less than four years by
means of 5-lens photography, controlled
horizontally by basic triangulation and
traverse, and radial line photogrammetric
solution. This radial line work was one of
the. early photogrammetric efforts in
America. Compilation of this series was
completed in 1936.
Prior to this, a few Multiplex aero pro-
jectors had been received by the Air Force
at Wright Field for experimental purposes.
In view of the success of the photogram-
metric approach to the planimetric series,
the possibilities of the Multiplex were im-
mediately investigated by representatives
of the Tennessee Valley Authority and the
U. S. Geological Survey. A few bars of
normal-angle equipment were acquired,
and were installed in the offices of the
Tennessee Valley Authority at Chatta-
nooga.
The topography obtained was thor-
oughly checked; the results indicated that
the Multiplex held possibilities as an eco-
nomical means for producing maps of
standard accuracy. The Tennessee Valley
soon became the great proving ground of
American photogrammetry. During the
next few years, continual study and re-
search, designed to isolate probable errors,
was undertaken. It is believed that the
TVA-USGS cooperative endeavor in Chat-
tanooga can be credited with much of the
development of the Multiplex as a pro-
ductive and economical tool for the Ameri-
can mapping profession.
The research included the analysis of
lens distortion and the design of a dia-
positive printer to compensate for these
distortions. Under the leadership of T. P.
Pendleton and R. K. Bean much of the
preliminary work leading to the American
design of multiplex equipment was ac-
complished during this cooperative pro-
gram.
During this time, R. O. Anderson, re-
cently deceased, engaged in considerable
research and developed a number of
photogrammetric principles and formulas,
the most notable of these being the scale-
point method for tilt calculation of the
aerial photograph. The Flynn Projection
Plotter was developed by Abe T. Flynn
for drawing map projection lines. The
Photo Triangulator was constructed by
the Branch in 1937.
Since 1933 the Tennessee Valley Author-
ity has made cadastral surveys of more
than 2,000,000 acres of privately-owned
property, representing some 40,000 indi-
vidual ownerships in the Valley area.
Aerial photography was used in practically
all of these surveys. In the surveys of ap-
proximately 1,500,000 acres enlarged ae-
rial photographs were used as a planetable
sheet in the field; on this cultural features
which served as property lines and im-
provements were identified and were later
converted to true map position by radial
line methods in the office. It is believed
that this was the first large undertaking
for which such a procedure was used for
property surveys. Later, as the topo-
graphic program of the Authority ad-
vanced and Multiplex manuscripts at
rather large scale were available on which
fence lines, woods lines, hedgerows,
streams, and other features likely to repre-
sent property lines were shown, facsimile
copies of the manuscript were made into
planetable sheets and used as a base for
property surveys.
Tennessee Valley Authority Technical
Report, No. 23, "Surveying, Mapping
and Related Engineering," covers prac-
tically all mapping activities of the Maps
and Surveys Branch; it is just off the
press.
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