9 
3x 
3x 
3x 
3x 
1 
1 
Z 
Z 
3X , 
3 Y 
3X , 
3 Y 
8y i 
ay i 
8y 2 
8y 2 
3X , 
3 Y 
3X , 
3 Y 
The correlator uses these correction coefficients as multipliers in 
transforming the basic scan signals, which are generated in model 
coordinates, into the proper photo-coordinate system for each 
photograph. 
In the process, the scanning signals are corrected for two basic 
effects: (1 ) camera orientation and geometry, and (Z) terrain slope. 
Each of the eight partial derivatives above thus is a function of the 
local relation between model and photo coordinates and, also, the 
terrain slope. For example: 
3x^ 3Xj 3x^ 
3X “ 3X~ + 3E~ S x 
m m 
where X m , Y m , E m represent model coordinate displacements and S x 
represents terrain slope in the X direction. In determining the proper 
scanning pattern shapes, the computer must therefore generate sixteen 
partial derivatives. In this computation, advantage is taken of the fact 
that the computer in normal operation calculates changes in photo 
coordinates due to changes in model coordinates. The program for 
determining derivatives makes use of this capability by periodically 
inserting arbitrary known changes in model coordinates and detecting 
the resulting changes in photo coordinates. The ratios of the changes 
in photo coordinates to the changes in model coordinates are the de 
sired partial derivatives. 
DESCRIPTION OF OPERATION 
Set-up and orientation procedures for the automated system are 
similar to those for the AP-2, except that advantage is taken of the 
system's ability to measure and eliminate X and Y parallax automati 
cally at each orientation point. In the initial operation, the photographs 
are mounted on their carriages, and the proper program tapes are read