total 4 
cumu- 
lative 
costs 
software 
  
  
no. of units 
Figure 2 
This is doubly significant, because in order to exploit the 
potential of analytical plotters to the full considerable soft- 
ware efforts are necessary. These add presently heavily on the 
total system cost. In the future they can become negligible if 
software is produced in such a manner that it can be reused on 
other computers. There is a need for user oriented software 
documentation and standardization. 
Otherwise software may remain limited, forcing the analytical 
plotters either to be more substitutes for mechanical plotters; 
or the system costs will remain high because of constantly 
redesigning software. 
Three types of instruments can be considered as analytical 
instruments: 
1. The Helava Concept type "Analytical Plotters " 
They generate x, y, Z pulses and eompute photo shifts by 
4 servos plus table shifts by 2 servo-systems. 
The Digital Stereocartographs 
They digitize manually driven photo coordinates, compute 
from these x, y, z model and ground coordinates and calculate 
y'shifts for y-parallax-free observations and x'shifts for 
the following of contours. 
For this task only 2 servos are needed in addition to the 
2 table servos. Because of the slight movements involved, 
cheaper stepping motors can be used instead of servos. 
The Stereocords 
They only measure image coordinates with x'y' and px"; 
it is only possible to calculate x, y, z and to drive the 
plotting table by 2 controls. 
The progress made in analytical plotters im shown in this 
summary: