324 
leading role, and this is the cause for the lower requirement im- 
posed on the manufacture of the optic-mechanical instrument. Now, 
the conception of "instrument" has given place to "system" and the 
user would also poke his nose into the development. Therefore, the 
monopolizing positions of the traditional instrument manufacturers 
have been shocked. Er 
For this othophotoprojector the precise programs are introduced to 
ensure the corrections to the orthogonality of the picture carriers, 
the nonlinearity of the ZOOM system, the eccentricity and the turn- 
ing of the drum and etc. The corrections can be carried out in two 
ways: functions and tables. The table would be adopted whenever an 
error pattern was difficult to be functionized. 
(6) System Configuration 
The grids, profiles, discrete points and digitized contours all 
could be used as inputs for the orthophoto production. The various 
formates of imputs made the orthophoto system larger and larger 
(shown in Figure 5). 
  
  
Disckette| Hard disk 
System controller 
CRT. 500K —AOrthophoto projector 
7 
Bg 
| Magnetic tape Printer) 
| unit | 
Parrallel 
  
  
  
  
  
  
  
  
  
  
  
  
  
Figure 5. 
Here, the system controller interferes directly in every step of 
the projector. This configuration costed more money, unreasonable 
and not neccessary. From the trend that modern computer technology 
experiences from the centralised to the distributed, this system 
should be configurated in the way shown in Figure 6.