The bridging function of the Anaplot is supported and greatly facilitated by 
a combination of some unique hardware and software features. They allow for 
a versatile use of manual or computer control of the real-time positioning 
operation applied either to the left or right photo stage, alternately 
considered to be dependent as the bridging proceeds.  Essentiall ; there are 
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three different controls of positioning operations as sketched in Fig gure 1, 
In the parallax mode, activated by a special footswitch, x- and y-paraliaxes 
are generated and measured in the currently dependent picture. Both 
parallaxes are then applied together with the manual positioning of the old, 
independent photograph, thus typically representing the stereocomparator mode 
of operation. During the computer controlled positioning which provides the 
plotter mode of operation, only calculated values are applied. 
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{ Position 
a calculation 
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| 1 
| | PARALI AX 
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positioning 
  
  
measurement 
  
  
  
Fig. 1. Control of real-time positioning 
Stereocomparator Mode. The manual control of measurements is achieved by 
handwheels X and Y which position the measuring marks in both photographs. 
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By engaging the parallax switch the same handwheels operate in the parallax 
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mode, transferring changes px and py to a single photograph only, either left 
or right, depending on the status of bridging. A standard footwheel Z is a 
substitute for the px operation and its change is also projected to a single 
picture. The function of handwheels can be assumed by a joystick, which 
enables a single-hand fast planimetric positioning. From the operational 
point of view the Anaplot is here used as a Stereocomparator.