an example some prototypes of digital photogrammetric 
workstations (DPW) have been developed in the last few 
years. The characteristics and advantages of such systems 
in comparison to analytical instruments can be expressed 
(Ref. 1 and 2) by the following items: 
- no need for high precision opto-mechanical parts 
- robust measurements system 
- stable image geometry 
- automatic, semi-automatic or manual operation 
- high degree of interactivity 
- data acquisition, storage and processing in one system 
- on-line and real-time capabilities 
- direct 3 dimensional graphic superimposition possiblities 
- possible use as data acquisition and processing instrument 
in GIS 
Recognizing decreasing hardware costs, the possible advan 
tages of such systems for the processing of digital images 
are the increase in accuracy, the high degree of automation 
yielding in a faster availability of the results. A classification 
of the existing systems shows the existance of 3 major 
groups: 
- Custom build systems, which are of great functionality 
and have a high performance, but are generally very 
expensive. 
- Systems based on conventional image processing systems, 
where image processing function may be directly used, 
but which generally have a lack of openess with respect 
to hard- and software. 
- Modular systems, which are open with respect to the 
integration of hard- and software and generally can be 
considered very flexible, but which require a high effort 
in developing adequate user interfaces and data manage 
ment software. 
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