und die denkbar größte Flexibilität. Sie werden deshalb für die weitere Ent-
wicklung des photogrammetrischen Instrumentariums von zentraler Bedeutung
sein. Ein experimentelles System wird am Fachgebiet Photogrammetrie und Kar-
tographie der Technischen Universität Berlin aufgebaut.
1. Introduction
Conventional stereoplotters were set up of optical and mechanical parts ex-
clusively. But during the last three decades more and more digital components
were integrated in stereophotogrammetric systems.
In an early period the mapping systems became digitized, i.e. the manufac-
turers equipped photogrammetric instruments with digital components and
computer-controlled drawing tables. By this development great flexibility,
high quality and complexity of the graphical output and a large amount of
operators comfort was achieved.
The latest state of development is the analytical plotter which was proposed
as a future concept already in 1957 by HELAVA (3). Today analytical plotters
are the standard in photogrammetric instrumentation. As is well known, in this
type of plotters the relationships between the two-dimensional image coordi-
nates and the three-dimensional model coordinates are solved by digital real-
time computation. The analytical plotter concept introduces a large number
of advantages, especially higher accuracy, greater flexibility and reduction
of orientation time. These advantages combined with the benefits of compu-
ter-controlled drawing tables improved the applicability and efficiency of
stereophotogrammetric systems to an extent which was inconceivable before.
But in all analytical plotters the data input is still achieved by means of
photographic images, i.e. in analog form. Because digitization was a tremen-
dous success so far, it suggests itself to continue this development and to
replace the photographs by digital image memories. This results in a fully
digital stereophotogrammetric system which is nothing else than the combi-
nation of photogrammetric principles with digital image processing techniques.
2. Design of a Digital Stereophotogrammetric System
Digital image processing has grown up to an efficient technique outside the
photogrammetrists field of view. Its purpose is to transform a given matrix
of densities which represents the input image to another matrix forming the
output image. The transformation parameters can be chosen arbitrarily where-
by the geometrical properties of the image as well as the radiometry, i.e.
the densities or colors, may be changed. Furthermore one can combine data
from several images in many ways with each other.
A great number of image processing systems is on the market and used for
many different purposes of this type. But the periphery of these image pro-
cessing systems is not sufficient for stereophotogrammetry. Three options
must be added to the standard equipment.
In the first place the data of two images have to be displayed in such a
way that stereoscopic vision is made possible. This can be achieved by many
different methods as PEIRIE (4) recently surveyed. The cheapest and never-
theless very effective solution is the application of an anaglyphic system.
This principle, which is well known to photogrammetrists from optical pro-
jection plotters, can easily be realized by means of a color monitor, in
