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SOFTWARE SIMULATIONS OF ON-LINE ANALYTICAL SYSTEMS 
Dr. V. Kratky 
Photogrammetric Research 
National Research.Council of Canada 
Ottawa, Ontario, CANADA, KIA OR6 
Commission II 
ABSTRACT 
The software for on-line analytical systems is generally not portable from 
system to system due to many differences in their hardware and interface 
structure. The efforts in developing more universal software would greatly 
benefit if the programming and testing work could be carried out independently 
of the system hardware. An analysis demonstrates how to simulate the 
analytical plotter and interface functions by software, using a suitable 
interactive terminal. Two examples of experiments document a successful 
simulation of an analytical plotter using either a computer graphics terminal 
via a lightpen interaction, or a regular computer video terminal with 
interaction achieved in a split screen mode by a moving cursor. 
INTRODUCTION 
Most analytical plotters are controlled with a minicomputer support, sometimes 
in combination with an additional microprocessor power programmed to perforn 
some routine, real-time functions. The program for one system is not 
compatible with another one even when the same minicomputer is used. Software 
is generally not portable due to many differences in the system architecture, 
in the effective control of individual components and in the design of the 
interface. As a consequence, any on-line software development is useful only 
for a particular instrument which must be available for testing. Efforts 
aimed at the higher standardization of on-line analytical systems and the 
development of more universal software are rather restricted. 
The sítuation would improve if some programming and testing work could be 
carried out without the presence of the system hardware. It is feasible that 
the hardware functions be computer simulated and programs run with a simulated 
interaction just through the computer with no plotter hardware involved. This 
approach may stimulate more independent software development and also provide 
an excellent tool for training and demonstrations. 
Obviously, simulations do not generate any meaningful measurements, as no 
photographs are involved, and thus the accuracy and reliability of real 
systems cannot be evaluated. However, most other practical aspects, such as 
programming structures, the organization of interaction, the efficiency of 
computations etc. can not only be tested, but also refined through 
simulations. 
FUNCTION OF ON-LINE SYSTEMS 
Before starting to analyze how to proceed with hardware simulations it is 
useful to review the basic functions of on-line systems, with reference to 
more detail in (Jaksic, 1973, 1980). Generally, on-line digital 
photogrammetric systems are photograph measuring devices (comparators, 
plotters) interfaced with a computer which can process measured information 
on-line with its collection. Of interest here are only closed-loop systems