To study the feasibility of CS, a prototype system was developed, 
under the condition that equipment components available at ITC in 
1975 should be integrated. At that time we did not have an analyti- 
cal plotter. To meet the specific requirements, the following hard- 
ware components were chosen: The precision analogue stereoplotter 
Zeiss Planimat D2 and the minicomputer PDP 11/45. The latter sup- 
ports several other instruments. The Planimat was fitted with rotary - 
encoders and step motors for the three model coordinate axes. The 
feed-back loop interfacing of computer and stereoplotter was reali- 
zed by the "Planimat Controller”, which was built in-house. Commu- 
nication between the operator and the system is via an alphanumeric 
terminal and a foot/hand switch. Software had to be developed for 
the following functions: 
- I/O handling of the terminal 
- control of recording in stationary mode operation 
- control of recording in dynamic mode operation with a preselected 
time or distance interval 
- control of positioning the X,Y,(Z) carriages of the Planimat 
- data collection and storage in SS 
- vector to raster conversion 
- data analysis, synthesis, and storage in PS 
- error detection 
- data conditioning for the data base and further processing. 
An overview of the system architecture is given in fig.l 
HARDWARE 
The essential elements of the three subsystems, i.., PDP, Planimat, 
and Controller, are listed in table 1. 
  
PDP 11/45 system Planimat system Controller 
Monitor DOS Planimat Counter cards 
Memory 56k bytes Encoders Rotary Motor drivers 
Console VT100 Motors Step Control cards 
Disk unit RK05 Terminal VT100 I/O registers 
Magtape unit Kennedy Foot/Hand switch 
Interface DR11-C 
  
  
  
  
  
Table 1: Hardware components 
The terminal is placed next to the Planimat. It is used to select 
the mode of operation, enter sampling parameters, encode features, 
and interrupt/restart and stop operation. Both the foot switch and 
the hand switch have the same function and can be used optionally. 
They release coordinate recording. The X and Y encoders provide a 
least count of lOum in model space. The least count of the Z encoder 
depends on the height gears inserted in the Planimat. With a gear 
ratio of 1:1, the Z-count is 5yum in the model system. 
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