278 
- derived analog images (e.g. stereo-orthophotos, array camera records 
converted into pictorial form) 
- derived digital images (e.g. digitized frame camera photographs) 
The photogrammetric instrumentation presently used in production is designed 
for processing of original and derived analog images and has the capability 
for the performance of processes with satisfactory accuracy and efficiency. 
In the last years the first steps have been taken towards the design. of 
photogrammetric digital image processing instrumentation for processing and 
analysis of original and derived digital images. The basic motivation for 
this development is the full exploitation of the potential offered by the 
advances in computer and digital image processing technologies (Case, 1982). 
It is expected that in the end, computing devices with appropriate display 
units may replace the conventional photogrammetric hardware for data 
processing, and shift the development of processing techniques and related 
functions entirely into the realm of software design. 
. This could be viewed as the natural extension of the concepts underlying the 
design of analytical instruments in which the digitizing of information 
stored on analog images occurs at the compilation stage and encompasses only 
the information about selected features. It is worth. noting that .the 
processing techniques of properly designed analytical instruments allow for 
the exploitation of all the imagery acquired by any kind of sensors from 
airborne or space platforms under the provision that the digitally acquired 
records are converted into an appropriate pictorial input form. The main 
deficiency of this approach is the incompatibility of conventional techniques 
for metric information processing with the image manipulation processes 
inherent in the techniques of digital image enhancement and analysis. Hence, 
the design of a digital photogrammetric system that would permit the 
unification of photogrammetric digital processing techniques with the 
techniques of digital image analysis seems to be a worthwhile objective. 
Such a system would allow for simultaneous exploitation of digital processes 
used in photogrammetry for the processing of metric information, of digital 
processes used in analysis of remotely sensed data (such as edge enhancement, 
contrast stretching and classification), and of digital processes used in 
image understanding, image matching and change detection (Rosenfeld, 1984). 
Consequently in a digital system of this type the potential for automation of 
processes should also be considerably increased. 
Instead of selective digitizing of information the concept of photogrammetric 
digital image processing implies the existence of original input information 
obtained by the conversion of an analog image into a numerical form 
represented by a two-dimensional array of digital gray level samples (Helava, 
1982), The development of linear array cameras capable of acquiring from 
space platforms stereo-images with good base to height ratios indicates the 
possibility of using original digital records for production and revision of 
maps. However the very small image scales, the limited attainable spatial 
resolution of sensors, the stringent requirements for the stability of the 
spatial attitude of the sensors and the continuity of forward movement of the 
platform combined with the relatively complex quasi-cilyndrical geometry of 
images ("pushbroom" mode of image formation) will impose limitations on the 
interpretability of desired features and on the extraction of metric 
information. Even with the anticipation of the improvements of spatial 
resolution of sensors these imagery may be most optimistically expected to be 
used for revision of maps in 1:100 000 and mapping in smaller scales (Welch, 
1982, Konecny et al., 1982, Chevral et al., 1981). Consequently for a long 
time to come, due to the requirement for the information of high metric 
quality, most of the source information will be acquired in analog form by