4 1 Introduction
orbits oriented towards the area which was to be photographed in stereo. MOMS-
02 was the first sensor system to use the three-line stereo method (In-Track-Stereo)
patented by Otto Hofmann in 1979 (Hofmann, 1982). In 1993 MOMS-02 was flown
on the Space Shuttle Mission STS 55 and in 1996 it was installed in the PRIRODA-
Module of the MIR Space Station. MOMS-02 used one objective lens for each
stereo channel. The first space-based mission of a Three-Line Stereo System, which
had the three stereo lines arranged on the focal plane behind one single wide-angle
objective lens, was achieved with BIRD (Bi-Spectral Infrared Detection) in 2001
(Briess, 2001). WAOSS-B (Wide-Angle Optoelectronic Stereo Scanner-BIRD) is
the modified version of WAOSS, a sensor system on the Russian Mars 96 Mission
that was designed to observe the dynamics in the atmosphere and on the sur-
face of Mars (Sandau, 1998). Unfortunately this mission failed in its initial launch
stage.
Most of the sensor systems which were developed for space-based applications
gave rise also to versions developed for use in aircraft [for example, Sandau and
Eckardt (1996)]. As a result they have been used for test purposes or/and for scien-
tific or commercial applications. Examples of a number of different German sensor
systems are:
• MEOSS: the satellite version was also used on aircraft
• MOMS-02: DPA (Digital Photogrammetry Assembly) as the airborne version
• WAOSS: WAAC (Wide-Angle Airborne Camera) as the airborne version
• HRSC: HRSC-A and HRSC-AX as airborne versions (HRSC – High Resolution
Stereo Camera – was the second German stereo camera for the failed Mars 96
Mission; it is now part of the ESA-Mission Mars Express, launched in 2003).
The development of these different techniques and sensors evolved in parallel
with the increased utilisation of aerial photographs in digital map production. If
film images are to be entered into digital databases, they must be converted into
digital form using photogrammetric scanners. Owing to the development of space-
based sensor technologies as mentioned above and the strong development trends
in other high technology fields essential to this application, it eventually became
practicable and economically feasible to go beyond scanning and replace the con-
ventional film used in aerial photography with direct digital imagery. Owing to the
many significant advances in key technological disciplines such as optics, mechan-
ics, critical materials, micro-electronics, micro-mechanics, detector and computer
technologies, signal processing, communication and navigation, we now have
financially realistic solutions for digital airborne camera systems accepted on the
market.
One concept considered for a digital camera system is to replace the conventional
film by suitable digital matrices or blocks of matrices. Another is to implement sin-
gle or multiple detector lines to create the digital image data. The first ideas along
these lines were indicated in a dissertation at the University of New Brunswick
(Derenyi, 1970). Independently from this, Otto Hoffmann developed and patented
the Three Line Concept of a Digital Airborne Camera system (Hofmann, 1982,