THE STEREO-PUSH-BROOM SCANNER SYSTEM DPS AND ITS ACCURACY
Otto Hofmann
Messerschmitt-Boelkow-Blohm GmbH, Dept. ZTA 2
FRG, 8000 Muenchen 80, P.B. 801149, Phone 089-60002030
ABSTRACT
Messerschmitt-Boelkow-Blohm (MBB) developed a new concept for a digi-
tal stereo-scanner with three line sensor arrays working on the push-
broom principle and a suitable, rigorous compilation process.
It delivers the orientation data of the camera in selectable update
points along the flight path of aircraft, spacecraft, or missiles, the
three-dimensional coordinates of the digital elevation model (DEM),
ortho- and stereo-orthophotos, digital elements for line maps and
rectified multispectral images.
The accuracy of the results is influenced by the focal length and the
sensor configuration of the camera, the flight altitude, the length
and width of the strip, the movements of the carrier, the arrangements
of the DEM-points, control points for absolute orientation and the
intervals between the camera update points.
By computer simulated models the influence of all these parameters have
been tested and the main results are presented.
1. INTRODUCTION
In the past years the opto-electronic scan technology, known under the
name "push-broom principle", has made remarkable progress and is ap-
plied and involved in present and future programs, for example in the
German space camera MOMS (Modular Opto-electronic Multispectral Scan-
' ner) and the French SPOT-program. The MOMS has been carried twice into
the orbit by the space shuttle "Challenger" in 1983 and 1984.
The outstanding features of this technology are known, they are founded
on the immediate conversion of radiation into electric signals and
yield among other important advantages instantaneous and unlimited
data transmission, direct digital image processing and precise measure-
ment of radiation in a wide spectral band.
These advantages have to be traded off against a severe disadvantage
that becomes apparent particularly in the production of maps: the loss
of geometrically exact stereocompilation as a consequence of the loss
of the central-perspective geometry. The push-broom principle forms the
image strip in a dynamic mode line by line and each image cycle has
its own set of orientation parameters, influenced by the movements of
the camera carrier. Therefore the reproduced image strip is distorted
and up to now no really practicable process for rectification was
known. MBB solved this problem by a purely analytical photogrammetric
process. Solely image data are used, external measurements or aids are
not necessary. The whole hard- and software equipment to be developed
is called "Digital Photogrammetry System, DPS".
- 345 -
