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TYPEWRITER 
  
VIDEO INPUT 
. EC INPUT SIGNALS +; 
/ ee EE 
T WOO 
CORRELATOR 
COMPUTER 
Na | re 
GT Y 
METER AND SLOPE | 
DISPLAY 1 
  
  
  
| RESEAU 
STORAGE 
— SIGNALS 
SCAN 
CORRECTION 
^ COFFICIENTS 
    
  
  
DIGITAL 
SERVO 
SERVO MOTOR MOTOR 
COMMANDS COMMANDS © 
| 
    
Figure 2 Functional Organization 
and Z in the model. The handwheels and footwheel 
are not connected mechanically to the photo stages. 
Instead, the digital computer uses electrical pulses 
supplied by the control wheels to increment the cur- 
rent values of model coordinates X, Y, and Z. The 
computer then calculates the three sets of comparator 
stage x, y coordinates which correspond to these X, 
Y, Z model coordinates, based on the camera geome- 
try. The three photo stages are driven by servo 
motors in x and y until the computed stages are cen- 
tered under the three measuring marks. The computer 
carries out this entire sequence 40 times per second. 
Thus, the operator sees no delay between the time he 
turns a handwheel or footwheel and the apparent 
movement of the floating mark in the stereo model. 
Analytical interior- and relative-orientation pro- 
cedures establish the camera geometry necessary for 
the digital computer to transform model coordinates. 
For interior orientation, the operator enters camera 
parameters for each stage by control panel switches 
or by typewriter keyboard, then he turns the hand- 
wheels to send the measuring mark to each of the 
fiducial marks in turn, where their stage coordinates 
are stored in the computer memory. The operator 
presses a switch to initiate the computer calculation 
of the transformation between photo and stage co- 
ordinates. 
Relative orientation is performed similarly. The 
operator enters approximate orientation elements by 
switches or keyboard and then moves the floating 
88 
mark through the overlap area with the control 
wheels, removing Y parallax at five or more points. 
At each point, the coordinates of the conjugate 
points are stored in the computer memory. When the 
operator presses a panel switch, the dependent rela- 
tive orientation of one of the observed photos with 
respect to the other is computed. A scale condition is 
computationally applied to the orientation to assure a 
common stereomodel scale in the triple overlap area. 
After relative orientation has been established for 
both “slave” photographs with respect to the third 
fixed, or “master,” photograph, pass-point measure- 
ments are made. The interior- and relative-orientation 
procedures may require a total of five minutes. This 
time is more than compensated by the increased 
speed in selecting, observing, and recording pass- 
points. 
As the operator moves the floating mark through 
the stereo model, the rotation and magnification of 
the two viewed images are automatically adjusted by 
computer-controlled optical adjustments. If he 
wishes, the operator can use the electronic correlation 
equipment to automatically adjust the Z model co- 
ordinate to remove X parallax. Thus, the floating 
mark is always on or near the model surface. Any 
residual Y parallax also is removed by the correlation 
circuitry. 
When an image is selected, the operator can make a 
manual or an automatic "'fine-pointing" adjustment. 
For manual adjustment, the operator locks the master 
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