1
THE 1960 ORTHOPHOTOSCOPE
by Roland H. Moore
U. S, Geological Survey
ABSTRACT
The Orthophotoscope is a photogrammetric instrument for converting
conventional perspective photographs into uniform-scale orthophotographs
in which the imagery is in true planimetric position. The conversion is
accomplished by scanning an anaglyphic stereomodel in narrow bands, and
enlarging the projected images inversely according to their scale. The
restituted imagery is printed photographically on a film which is exposed
differentially as the model is scanned.
The 1960 Orthophotoscope, described here, is the third in a
series of such instruments developed during the past decade in the research
laboratory of the U. S. Geological Survey. The design of the latest model
has benefited from experience with the two earlier versions, and it in-
corporates a number of substantial improvements, as follows:
1. Accommodates both Kelsh-type projectors and ellipsoidal-reflector
type projectors.
2. Provides for adjusting the scanning direction to permit scanning
parallel to major terrain features.
3. Replaces the flat film-supporting platform with a 12-inch diameter
cylinder that rotates and translates automatically.
4. Provides self-synchronizing mechanisms for the transmission of
X-, y-, and z-motions to the scanning assembly.
Ul
Provides means of using the profile data from each scan, simul-
taneously or subsequently, to operate other image-restitution
equipment or model-carving equipment, or to extract hypsometric
information in digital or analog form.
In redesigning the instrument the comfort of the operator has
been kept in mind as a major consideration. He is seated in a^position
where he has a nearly constant viewing angle during the entire scanning
operation. The response to controls is smooth and automatic, requiring
a minimum of physical effort. Experience has demonstrated that operator
fatigue is a major factor affecting the accuracy of photogrammetric
operations and that careful attention should be given to this factor.
Orthophotography is a promising new implement of photogrammetry,
and it can be the core of a new mapping system. Experience has shown that
the extent of its use depends on the geometry and image quality of the
product. With the 1960 Orthophotoscope, substantial improvements in ortho-
photograph quality and reduction in the cost of preparation can be expected.
presented at Ninth International Congress on Photogrammetry, London,
England, September 1960.
“publication authorized by the Director, U. S. Geological Survey,
Washington, D. C.
