A. Meid (1991) reports on the integration of knowledge based 
techniques for the measurement of image coordinates. With his 
approach error sources can be kept minimum or remaining 
errors will be eliminated. 
The digital orthophoto is meanwhile a standard tool of 
photogrammetry (H.P. Baehr/T. Voegtle, 1991) - a cost- 
benefit analysis was given by H.P. Baehr/J. Wiesel (in H. 
Ebner et al, 1991) It is no isolated product of 
photogrammetry; in GIS it serves as orientation map for vector 
data in which it is handled as an additional layer. Using these 
orthoprojections of image data in postprocessing bottom-up 
procedures nodes and segments of edges can be extracted, 
which are the basis in further vectorisation processes (D. 
Fritsch in H. Ebner, 1991). 
Image matching was also deepened in the period of 1988 - 
1992. While R. Li (1990) investigates area and edge matching 
techniques the research work carried out by C. Heipke (1991), 
B. Straub (1991) and C.T. Schneider (1991) give first 
experiences when using object space image matching. The 
same approach is under investigation at the Institute of 
Photogrammetry and Cartography, Technical University of 
Darmstadt (B.P. Wrobel et al. in W. Foerstner/S. Ruwiedel, 
1992). One main problem in this matching definition is the 
computer effort for the solution of large linear equation 
systems which might be overcomed by adequate solution 
strategies such as multigrid and by regularisation techniques; 
furthermore the progress in computer architectures (e.g. 
Advanced RISC) gives its full support. J. Piechel (1991) points 
out an increase in accuracy for automatic digital terrain model 
generation if matching is solved area-based. 
Image matching is not only interesting from a theoretical point 
of view: F. Ackermann/M. Hahn (in H. Ebner et al., 1991) and 
R. Krzystek/D. Wild (in W. Foerstner/S. Ruwiedel, 1992) 
present an operational program package for image matching 
which uses a chain of several algorithms in a multiresolution 
mode. The chain consists of the setup of the image pyramide, 
image normalization, feature detection and location, and the 
matching process itself. In this sense, large scale aerial 
photographs can be processed leading to very accurate DTM's. 
Problems still unsolved are the location and elimination of 
man-made constructions and other natural phenemena for 
example trees, bushes etc.. But it should be noted that today 
image matching techniques represent also standard tools of 
digital photogrammetry. 
Using the reseach and experience in image matching one 
further step forward is image understanding which extracts 
geometry and semantics from digital images. Also here some 
research activities were initiated by german scientists - a good 
review of existing techniques can be found in W. Foerstner 
(1991). Other contributions to this subject are given by the 
proceedings of the workshop on Robust Computer Vision 
which was organized by WG III/2 (W. Foerstner/S. Ruwiedel, 
1992). Image understanding will become more and more 
important; it is expected that for future periods 
photogrammetric research is deepened here. 
3. Development of Remote Sensing 
Reserach carried out in remote sensing belongs to the work 
coordinated by Commission VII ISPRS. But also for 
Commission III some references will be cited in particular 
those dealing mostly with algorithmic aspects. One important 
topic is the radiometric adjustment of different image sceneries 
also called mosaicing which is a problem to be overcomed not 
38 
only in processing of remote sensing data but also in digital 
orthoprojections. The contribution given by M. Kaehler (1989) 
shows radiometric corrections for satellite imagery -the 
textbook of J. Albertz (1991) points out furthermore this 
problem. 
Within data analysis of remote sensing the classification 
remains still a problem which is not yet sufficiently solved. 
Classification algorithms structure pixel oriented remote 
sensing images according to objects introduced before. This 
object oriented approach is the basis for an integration of 
remote sensing data in GIS. J. Albertz (1991) and W. Goepfert 
(1991) present classical algorithms for supervised and 
unsupervised classification; a new model for supervised 
classification can be found in H. Schumacher (1991). The 
application of aerial image matching techniques has been 
transferred to SPOT data by C. Heipke/W. Kornus (in H. 
Ebner et al., 1991); it shows that matching problems in aerial 
photogrammetry and remote sensing might be solved using the 
same software. 
4. Development of GIS and Digital Mapping 
Progress in GIS is concentrated on several topics: first it is 
well-known that photogrammetry delivers three-dimensional 
coordinates nowadays to be handled by two-dimensional GIS- 
products. The task is the extension of GIS theory by at least 
the third dimension in geometry. A review and solution 
strategies of this problem are given by D. Fritsch (1991) - it is 
pointed out that interfacing a DTM with GIS is one of three 
solutions. In this context further DTM research can be seen: H. 
Kuhn (1989) deals with visualization aspects, and W. 
Reinhardt (1991) proposes strategies for an interactive DTM 
setup. 
The integration of image data in GIS presupposes a DTM as 
reference surface. Thus, not only image data can be rectified 
but also image understanding will have some profits 
integrating the third dimension. D. Fritsch (in M. Schilcher/D. 
Fritsch, 1989) presents a three level approach for image 
integration: the lowest level is given by rectified image data, 
the medium level manages object oriented raster data, and the 
top level extracts vectorial geometry which is semantically 
structured. The dissertation of H. Yang (1992) fits exactly into 
the medium level, because homogeneous raster objects can be 
coded very efficiently by quadtree structures. 
But only with the highest (top) level of image data integration 
spatial databases of GIS can be filled and updated. Therefore 
we have an analogy to the image understanding task which 
should not be seen as inverse problem but as information 
fusion using GIS data. 
5. Education and Presentation of Research 
Within the period 1988 - 1992 several new textbooks in 
photogrammetry, remote sensing and GIS have been published 
written by german scientists. These books could fill 
deficiencies in scientific literature and help to improve the 
education considerably. The following textbooks should be 
named: H.P. Baehr/T. Voegtle (1991) and W. Goepfert (1991) 
in digital image processing, J. Albertz (1991) in interpretation 
of aerial photographs and satellite images, and R. Bill/D. 
Fritsch (1991) with introductory readings in GIS. As further 
progress in education some tutorials were organized. Not only 
the intercommission WG III/VI did education work here; also 
the WG' s itself introduced some workshops with tutorials. The 
situation in education within 1988 - 1992 was much better than 
in the quadrennium before: it started with a tutorial on 
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