that only the unknowns for orientations of photos (and 
additional parameters for self-calibration) are left, the 
following processes can be recognized 
- formation of observation equations 
- computation of the contribution of each observation 
equation on the normal equation system 
- pointwise triangular decomposition 
- pointwise reduction of the system 
These processes can be run in parallel. Buffers are 
required between the processes (or within them) to 
accumulate the necessary data. As a matter of fact, the 
Pipe concept from Unix is suitable for connecting the 
subsequent processing phases. 
The benefits of the approach emerge from the fact that many 
details of the solution are hidden from the main module. 
Also, if proper implementation techniques are used, the 
computer system can utilize parallel processing. The task 
concept in Ada language can be used beneficially for 
implementation. 
7. OTHER ASPECTS ON PORTABILITY 
With portability of software is usually ment that .a piece 
Of software can be transfered from one hardware environment 
to another without considerable reprogramming. Sometimes 
reprogramming that is limited to well-defined parts of the 
system is required. A use of standardized programming 
language is mandatory when general portability is desired. 
However, it is not sufficient to guarantee portability. For 
example, if FORTRAN language is used, differences in the 
word length can make a program practically  importable, if 
not proper consideration is given to the use of variables 
Of different types, especially if bits are addressed 
directly. Also limitations Of capacities of different 
components of the computer and differences in peripherial 
devices can hinder the portability. : 
Portability has to be considered also with respect to the 
organisational environment. From production point of view, 
a system should be standardized as much as possible. From 
the user’s point of view, a system has to be tailored to 
fit for specific needs and static working habits prevailing 
in the environment. 
There are several means for tailoring. One of the most 
crude ways is to supply the user with source code and let 
him modify the Program as much as he will. This is 
inadequate because it becomes totally impossible to update 
the user’s system with later revisions supplied by the 
software vendor. As a matter of fact, a "new" system is 
born at the delivery moment of the system. It has its own 
maintenance problems that are similar to the ones of the 
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