PHOTOGRAMMETRIC ENGINEERING 
poses; a straight-line distance routine, a 
punch coordinate routine, and an X-Y plotter 
program. Possible extensions of these stand 
ard programs are a path-length routine and 
area-measuring routines. Possible new pro 
grams would include a complete analytical 
aerial triangulation system, cut and fill cal 
culations, structural design problems, reduc 
tion and checking of ground-survey data, 
and the conversion of coordinates. The full 
versatility of the AP-C is still to be realized. 
Turning from the commercial to the mili 
tary version of the analytical plotter (the 
AP-2 is shown in Figure 5), a proposal for the 
automation of the stereoimage correlation 
function in the AP-2 has been advanced, 
“Image Correlation System for Analytical 
Stereoplotters,” by Dr. E. C. Johnson, Ben- 
dix Corporation, and A. Di Pentima, U. S. 
Air Force. This proposal makes full use of the 
versatile decision-making and control ability 
of the computer. To provide an automated 
stereomapping capability an image correla 
tion system is being added which will include 
a viewing unit, scan generator, and correla 
tion circuits. The viewing unit integrates two 
flying spot scanners into the standard AP-2 
equipment for stereo viewing. Two cathode 
ray tubes scan conjugate areas on the two 
photographs with two photomultipliers as 
the light sensing devices. The scan genera 
tors produce scan patterns for each photo 
graph and control the size and shape of the 
pattern by information from the computer. 
The scan pattern is placed in the local co 
ordinate system for each photograph and is 
compensated for local terrain slope. These 
signals are processed in the video correlator 
to produce X- and T-parallax, X- and Y- 
terrain slope errors, and correlation quality. 
These outputs are utilized by the computer 
to control overall operation and thus to 
generate the required plotting motions. The 
computer, in turn, furnishes scan size com 
mands and scan correction information to the 
scan generator to control the size and shape 
of the scan patterns. The computer and cor 
relator form a closed loop system which 
optimizes the operation of the correlator by 
continuously computing the average terrain 
slope and compensating the scanning pat 
tern. 
The usual modes of operation will be pro 
vided; relative orientation, automatic pro 
filing, and automatic contouring. However, 
in addition, automation of the analytical 
plotter will allow semi-automatic determina 
tion of interim orientation and absolute 
orientation. The provision of automatic 
stereo perception of the AP-2 will extend the 
capabilities of this instrument for the rapid 
production of contour and profile chartsHrom 
many types of photography. 
Fig. 5. Analytical Plotter AP-2.