If it should now be impossible, because of the limitations of the A 7 Autograph,
to make an absolute orientation of ¢' and ¢, " the plotting of the building must be
performed as shown in Figure 3, also of Congress Hall in Philadelphia. Plotting is
in both plan and elevation. It is part of the usefulness of the A 7 Autograph for
architectural photogrammetry that a change of the gear system, from "aerial, '" with
which architectural elevations are plotted, to "terrestrial, " with which architectural
floor and ceiling plans and horizontal sections are plotted, also provides correction
of plotting distortions of common architectural cylindrical forms, as described in
"Architectural Photogrammetry at Ohio State University" in the December,1957 issue
of Photogrammetric Engineering.
The resulting plottings, which require the plan drawing for the rotation of the
foreshortened elevations into full frontal projection, as shown in Figure 4, provide
the best determination of inaccessible dimensions on the buildings, necessary for the
final drawings and for the control of plotting of more nearly frontal stereopairs.
A comparison of vertical dimensions of the inaccessible tower of Saint Paul's
Chapel on Lower Broadway in New York City, shown in Figure 5 - as determined
from various diagonal stereopairs of the building and before full development of the
system of survey control and orientation described herein - indicated an accuracy to
within 1 part in 1300 on the height of the tower. This degree of accuracy is satisfactory
for the recording of historic architecture. Other applications of photogrammetry to
architecture can utilize the ultimate degree of accuracy possible with the science of
photogrammetry.
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