electronic circuitry, made appropriate orientation and height 
changes to keep the scanning disc at the proper slope and in 
contact with the surface of the stereomodel. Tests showed that 
the orthophotograph and line drop contour manuscript could be 
produced for a stereopair in approximately 5 hours, with a 'C" 
factor of approximately 350. Because of its inability to correlate 
certain types of terrain and inherent weaknesses of the design 
resulting in slow response time during profile scanning, further 
development of this approach was not pursued. This system has 
the distinction of being the first system to produce simultaneously, 
line drop contours and orthophotographs from electronically 
correlated imagery. 
13. Prior to this latter contract, another development 
sponsored by the U, S, Army, also directed at modifying conventional 
stereoplotters, produced in 1959, the "Integrated Mapping System" 
under a contract with Fairchild Camera and Instrument Company, 
Syosset, New York. Subsequent modification under contract with 
Atlantic Research Corporation, Alexandria, Virginia, produced in 
1961, an instrument satisfactory as a test bed. This instrument 
utilized a Nistri Photomapper and required an operator to manually 
raise and lower the tracing table while the instrument was driven 
at a selectable speed to traverse the model. Each profile was 
temporarily recorded on magnetic tape. At the end of each profile, 
the operator could repeat the profile for checking or refinement 
until satisfied with its accuracy, and then record this profile 
permanently in three forms simultaneously or independently, 
line drop contour manuscript, orthophotography, and permanent tape 
recording. During each subsequent profile, the temporarily stored 
profile information was used to position approximately the height 
of the tracing table platen, which then could be overridden by 
the operator to produce the new profile data. This experimental 
development first demonstrated the feasibility of the line drop 
technique, the feasibility of producing an orthophotograph 
electronically, the digital recording of the profile information, 
and the applicability of the previous profile memory assist. While 
the instrument proved to be neither an economical nor a production 
efficient system, it proved very useful for testing those procedures 
and techniques which did not depend upon electronic correlation 
to establish the match between homologous images. 
14. While employed by the Photographic Survey Corporation 
of Canada, Mr. Gilbert L. Hobrough automated the contouring function 
of a Kelsh plotter in 1958. This was the first of the Stereomat 
series and was initially called "Auscor'" for Automating Scanning 
and Correlation. Electronic image scanning of the projected 
dispositives was accomplished by a flying spot scanner, located 
in the position of the standard tracing table platen, with dichroic 
mirrors and photomultiplier tubes located above the di&positive 
plates. Using signals from the photomultiplier tubes, correlation 
devices provided means for automatically detecting x and y parallax 
within a stereomodel. By means of servos connected to the appropriate 
^,Y,U axes of the projectors, y parallax could be automatically nulled 
in accomplishing relative orientation. The x parallax signal was used 
to drive the tracking unit in an X-Y coordinate system in order to 
trace contours automatically on plotting paper placed under the 
tracing unit.