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merits almost obsolete. They also started with the simple technical aspect of being equipped
with a digital computer and of realizing the geometrical image projection by computation and
by computer-controlled image positioning. However, they soon evolved, beyond original expec
tation, into most versatile photogrammetric workstations which have completely revolutionized
the conventional photogrammetric stereo-restitution. In the same way orthophotomaps and
digital terrain models, the latter originally intended for automating the derivation of contour
lines, developed into new general products which have gained independent standing of their own.
I do not have to trace the details of the actual development. All photogrammetrists know how
much analytical pliotogrammetry has influenced most thoroughly our working methods, has
changed our tools, has pushed accuracy, economy and versatility of pliotogrammetry to new lev
els of performance, has led to new conditions of operation, and has resulted in new applications
and new products.
2.3 The same type of evolution as with analytical pliotogrammetry we recognize in a second
line of development which concerns mapping, the classical field of photogrammetric applica
tion. The introduction of computerized methods also in this field started simple enough by
computer assisted plotting based on quite simple graphical functions. But again, tliis w r as only
the beginning of a revolutionary development. Fig. 1 traces how the photogrammetric plotting
instrument with its plotting table has evolved, step by step, towards a system for digital map
ping, with the help of interactive graphical workstations, reprojection into the stereo-plotter,
up to a system with full command and manipulation of complex graphical functions, linked up
with data bases and external information systems. With regard to the cartographic side all
channels are open to digital and automated cartography.
We see again the general trend of development. Due to the continuously increasing power
of computer performance the early simple efforts of improving previous working methods and
tools mushroom out into the full exploitation of new technical possibilities. The results are
breakthroughs into new performance, new methods, new products, new application, and to in
terfacings with other disciplines and other classes of information.
2.4 The third major line of development to be mentioned concerns the complex of remote
sensing. The relations and interactions,of remote sensing with pliotogrammetry proper are
still relatively weak, because of different product orientation (image interpretation/geometry),
different types of data, and different accuracy standards. Nevertheless, there is no doubt that
remote sensing and pliotogrammetry converge towards each other as they cover similar enough
objectives and operate on the common basis of imaging the same types of objects.
From that point of view remote sensing certainly constitutes a great extension of photogramme-
try, which has brought in new qualities. The extension concerns first a vastly extended physical
range of image data and image information. Special sensors provide infra-color images, multi-
spectral image data, thermal infrared and microwave data and images.
The second extension is represented by continuously orbiting earth observation siitellites which
continuously and globally provide image data from optical and other sensors.
The third innovative feature of remote sensing concerns the fact that image data are provided in
digital form. Remote sensing has certainly opened the path for digital image processing, even if
iemote sensing has been mainly oriented towards multi-spectral classification and digital image
interpretation, whilst the geometrical exploitation of image data has kept a low profile for a long
