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.