receiving the video signal from the ortho flying spot scanner will expose a basically correct 
orthogonal picture. 
The image scanned and exposed in the orthophoto link is the same scanned and used for 
the correlation, so that all the corrections extracted and applied to the x and y correlation 
scan can be applied to the orthophoto scan. This will assure optimum adaptation of the ortho 
scan to the image on the diapositive, and consequently help to improve the printed out 
image. 
Due to the independent nature of the scan it is now possible to have the operator select 
the optimum orthophoto scan size for the terrain conditions of the diapositive used. 
A selection of from one to four mm. in swath width is available. 
Because the scan speed is controlled by the correlation signal, which varies continuously 
depending on terrain detail, the profiling speed changes between 1 mm to 6 mm/sec. This 
made an exposure control dependent on profiling speed mandatory in order to obtain an 
orthophoto of uniform exposure. This is realized by multiplying a signal proportional to 
the X motor speed with the video signal from the orthophoto flying spot scanner. The 
multiplied output is then corrected for cathode ray tube non-linearity such that a gamma 
of one will be obtained. 
Operational Modes 
The operational modes available are: 
Standby Mode: In this mode the x, y or z can be either moved with an accurate positioning © e 
control or slewed proportionally with independent controls on the front panel. 
The orientation drives can be selectively driven by a proportional control from the front 
panel. 
All drives are protected against damage by limit switches, a manual override allows removal 
of the movement out of limit only. 
The manual mode can be used for the initial orientation of the model or for manual opera- 
tion of the plotter.