- 4 - 
of 1000 lines per inch exists, but is not yet being used. Approximately 40 square inches 
of each stereophoto area are simultaneously scanned, converted point by point to den 
sity-level digits, and recorded on magnetic tapes. All survey data associated with 
aerial stereo photographs must also be digitized, including precise control data, 
obtained from ground-control and control measurements on the IBM digitizing stereo 
comparator (Fig. 1) and camera and other distortion measurements. The details of 
the System’s operation are described in a contributed paper, ’’Automatic Map Com 
pilation Using Digital Techniques”, as part of paper II - 1 on Automatic Mapping Instru 
ments. 
The control data measurements made at this same time are also usable for aero- 
triangulation, including strip and block adjustment. These digital techniques are 
well established and require little comment. The latest progress in these techniques 
is being reported by Dr. Helmud Schmid in his Commission II paper on ’’Analytical 
Instruments.” 
The photo (Fig. 3) and control data are processed in the IBM 7094 system (Fig. 2). 
The following computer operations are being performed from this input digitized 
data: 
• Resection and orientation from stereo photographic control data measurements. 
• Rectification of photographic data. 
• Scaling of photographic data to printout scale. 
• Correction of photographs for all measured distortions in X and Y. 
• Orthographic correction of photographs. 
• Production of contours of various widths. 
• Preparation of profiles for a digital terrain model for engineering design 
applications. 
Printing map compilation manuscripts for editing is performed by the computer from 
output data stored on magnetic tape. A precise CRT printer is provided by the digi 
tizing stereo-comparator operating in essentially a reverse mode. This instrument 
converts this data into one of several photographic forms, as desired by the user. 
Present outputs generated from this digital mapping system are printed onto film 
or diapositives; those which have proven feasible are: 
• Rectified and scaled photographs 
• Ortho-corrected photographs (Fig. 4) 
t Ortho-photographic maps with contours 
• Contour maps (Figs. 5 compared with 6A and 6B) 
• A grid (for printer calibration or map overlay; Fig. 7) 
• A checkerboard pattern (to show range of tonal printing)