System Description 
The features described above allow the system to operate as 
a simple stereo scanning device, shown in Plate 1, with full three 
dimensional model scanning and zoom. The system has a menu 
indicating the other facilities available: 
  
  
  
  
| Output | | TRACKBALL | Image | I Terminate! 
| Coords | | Z | Correlation | | Function | 
| to file | | CONTROL | on/off | | | 
| MED Em is qi A pa 
| Increment !Revert to lDigital | For'd/Rev I IData I 
| Zoom | zero IData | Model | ICapture | 
| | zoom lOverlay | on/off I Istart/ I 
| | I | I | stop | 
| | | | | |--—-—-—-——— | 
| Pen | Change IDisplay | Display | | | 
| up/down | Parameters | Index | Coords on | |IDTM | 
| | | Image | Screen I Istart I 
  
Parameter Modification 
The first group of options give the system features usually 
implemented in the hardware of an analytical plotter,such as altering 
Y-squint, XYZ model scanning speeds and the size of the floating 
mark. Other options allow a Z value to be input (for contouring), 
image correlation window enlargement, direct movement to an input 
control point, and a fast scroll across the model area. 
Graphical Overlays 
Two options are available; firstly an overview display of the 
whole disk image with the current model area outlined, and secondly, 
digital data overlay. This option allows one or more ground data 
files to be projected onto the left or right image. Files generated on 
a previous occasion or during the current session can be overlaid to 
check for missing or inaccurate detail. As the graphics planes of the 
I2S do not have the independent scroll capability, data cannot at 
present be overlaid during digitising. 
Data output 
Three methods of data output are available. Firstly, 
continuous XYZ coordinate output onto the display monitor. Secondly, 
digital terrain models can be recorded. Using this option, a grid is 
specified by digitising two corners of a rectangle and a grid node 
interval. The model is automatically driven to the plan points, and Z 
is adjusted by the operator. The third data output method is by a 
string data file. This operates similarly to any digital mapping 
system - the operator moves to a point with the 'pen' up or down 
and vectors are recorded in a file. 
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