and other systematic distortions. Electronic scanning of the 
photographic imagery provides the waveforms which are 
used in correlation for orientation purposes as well as in 
determining three dimensional map coordinates of the imagery. 
This approach permits considerable flexibility in terms of 
universal input compared to the conventional stereo compila- 
tion instruments, with respect to focal lengths, lens dis- 
tortion, type of camera, etc, The contour information is 
produced in conventional graphical form by means of a coordina- 
tograph, in line drop form as oriented segments or bands of 
several density levels, or digital data on magnetic tape. 
Automatic output of planimetric data is an orthophotograph form. 
11. The digital approach is characterized by the initial 
conversion of the photographic image, spot by spot, into 
digital values representing gray scale levels. The two main 
functions are the scanning and digitizing of the photographic 
data, and the analysis and manipulation of the data in a 
large digital computer to obtain the desired output products, 
contours and orthophotographs. In the manipulation of data, 
corrections can be made for lens distortion, film shrinkage, 
earth curvature, refraction, and other systematic distortions. 
Conjugate images are located by using statistical methods in 
the matching of spot densities. 
BACKGROUND 
12. It is interesting to note that the word "automation" 
appeared for the first time in 1955 in dictionaries and encyclo- 
pedias, but that first directed effort toward automation in 
photogrammetry was in 1950 when the U. S. Army Engineer Research 
and Development Laboratories, (ERDL - Now designated U. S. Army 
Mobility Equipment Research and Development Center, (MERDC)), 
Fort Belvoir, Virginia, awarded a contract to the Bausch and 
Lomb Optical Company, Rochester, New York, for ''A Study of an 
Automatic Scanning Device for Producing 3-D Topographic Maps." 
This initial study, which was based on some preliminary 
experimentation by Bausch and Lomb based on a suggestion from 
Dr. George Harrison of the Massachusetts Institute of Technology, 
employed a two projector multiplex bar and a scanning unit 
replacing the tracing table. In this first effort only high 
contrast, artificially produced diapositives could be matched to 
determine profiles when projected on the scanning unit. Successive 
developmental efforts were pursued by the U. S. Army under contract 
with Pickard and Burns, Inc., Needham, Massachusetts; Hycon Manu- 
facturing Company, Pasadena, California; Hogan Laboratories, New 
York, New York, and Bunker-Ramo Corporation, Canoga Park, California 
during the period from 1952 to 1962 based on modifying conventional 
stereoplotters to automate the contouring operation using projection 
type plotters of first, the Multiplex and then the Kelsh type. The 
last contract resulted in an instrument which was called the "Auto- 
matic Stereomapping System." This system mechanized the operation 
of a Kelsh stereoplotter so that it automatically scanned a stereo- 
model in successive profiles. The scanning unit utilized a Nipkow 
disc (a rotating disk with holes in a spiral pattern) to scan the 
stereoimage, and with the aid of tilt and height servo systems and