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ANALOG OR DIGITAL MAPPING FROM AERIAL PHOTOGRAPHS ? 
A Contribution to the Conception of Digital Mapping Systems 
0. Kòlbl 
Ecole polytechnique fédérale de Lausanne 
Photogrammétrie, GR-Ecublens, 1015 Lausanne / Switzerland 
Summary 
Digital methods offer great flexibility for image processing; however, for visual 
measurements, these techniques do not enable one to obtain performances simi 
lar to those achieved by analog means for image presentation. Consequently, 
digital mapping is preferable for largely automated operations like image 
enhancement, the derivation of digital terrain models or the production of ortho 
photos, whereas digital instruments do not currently provide performance 
comparable to good analytical plotters. 
New procedures will be added to the current photogrammétrie activities, like the 
use of aerial photographs in geographic information systems or the reproduction 
of maps based on pictorial information. This will result in instruments made up 
of components such as : scanners, parallel processors, geographic information 
systems with underlayed aerial photographs, stereoscopic measuring instru 
ments and electrostatic plotters. 
The author anticipates this evolution of photogrammétrie instruments, based on 
his own experience, consisting mainly in the development of a system for the 
automatic derivation of digital terrain models, including a high-speed processor 
based on Transputer technology. 
Keywords : Digital photogrammetry, Digital terrain models, Image processing, 
Instruments, Land information systems, Photogrammetry 
1 . Introduction 
During the last few years, photogrammetry has drastically changed. The classi 
cal procedures for image measurements on analog instruments are gradually 
being replaced by analytical techniques and already partly by digital methods. For 
sure, this development has not yet reached its final stage and more and more 
interesting possibilities are arising concerning the automatization of image proc 
essing and data management in information systems. In particular, the inter 
relation between a photogrammetric plotter and an information system requires 
good facilities for dialogue between the plotter and the database. 
Most of the recent realizations depend on the progress in electronic data process 
ing, and the desired speed and efficiency of computer processors is as yet only 
partially available. A good part of this paper deals with future developments and 
it is always a bit hazardous to extrapolate too far, as there is a risk of overesti 
mating technological progress. The author, conscious of this danger, has tried to