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3.1. Digital terrain models, digital mapping, cartographic 
automation, data banks 
The concept of digital terrain models has been linked with 
civil engineering applications for a long time. In the mean- 
time it has become a concept of its own, with potential app- 
lication in many fields, particularly so for topographic 
and cartographic purposes. 
Commission III is mainly concerned with the mathematical 
problems of interpolation, and with questions of accuracy 
and of suitable description of terrain surfaces. However, 
such questions cannot be considered independently. There is 
a strong interdependence with data acquisition and an equal 
strong influence from the objectives and conditions of appl 
cation. 
At present, a number of computer programs have been developed 
for interpolation of digital terrain models and for automatic 
derivation and plotting of contour lines. Such programs are 
Currently used for testing and experimenting, and for prac- 
tical application to some extent. The development has been 
rather quick. The previously sceptical attitude of potential 
users seems to be changing. 
The assessment of the interpolation principles in question 
remains still a major theoretical and experimental task. 
such investigations will have to consider that the results 
of various interpolation principles differ rather little, 
provided the data acquisition is adequate or even redundant. 
0n the other hand the sensitivity of the principles against 
poor or insufficient data acquisition is especially important 
as well as the means which computer programs provide for 
treating data omissions, terrain discontinuities, breaklines 
etc. 
9 
Independent of basic research the practical application of 
digital terrain models is expanding, even beyond the present 
application for civil engineering and digital contouring. 
Digital terrain models are subsets of topographical or more 
general data banks, and they are used for digital steering 
of orthoprojectors. There are also non-topographical appli- 
cations, for instance in medicine. 
The areas of digital planimetric mapping, of automation in 
cartography, and of data banks have not yet been adressed to 
Commission III. Evidently their dependence on hardware or the 
application aspects dominate over the methodical and mathe- 
matical aspects, for the time being. 
3.2. Digital image processing 
The subject of digital image processing has recently moved 
from a highly specialized topic of research to the general 
attention of photogrammetry and related fields. This is due 
to the success of research, but probably even more to the 
availability of vast quantities of Landsat imagery which 
demand means for automated photo-interpretation.