A SIMULATION STUDY ON POINT DETERMINATION FOR THE MOMS-02/D2 SPACE
PROJECT USING AN EXTENDED FUNCTIONAL MODEL
H. Ebner, W. Kornus, T. Ohlhof
Chair for Photogrammetry and Remote Sensing
Technical University Munich
Arcisstr. 21, D-8000 Munich 2, Germany
Tel: + 49-89-2105 2671; Fax: + 49-89-280 95 73; Telex: 522854 tumue d
E-mail: ebner@photo.verm.tu-muenchen.de
Commission IV
ABSTRACT:
In the course of the 2nd German Spacelab mission D2, scheduled for launch in 1993, the MOMS-02 camera is
intended to acquire digital threefold stereo imagery of the earth's surface from space. In former simulations the
influence of certain mission parameters on the attainable geometric accuracy has already been examined. With
regard to the future compilation of real data, the functional model was extended with respect to the special
MOMS-02 camera geometry and the actual orbit.
After a brief description of the extended model, the results of new simulations are presented. They show the
influence of the precision of observed exterior orientation parameters, the type and density of ground control,
the camera inclination across flight direction and the simultaneous adjustment of two crossing strips with
different intersection angles on the theoretical accuracy of the point determination. Because of the improved
functional model the obtained accuracy estimates are expected to be representative for the practical project.
Finally conclusions are drawn from these results.
KEY WORDS: Accuracy, Aerotriangulation, Space Imagery, 3-D.
1. INTRODUCTION
MOMS-02/D2 is a digital camera project in the framework
of the second German Spacelab mission D2 scheduled to be
launched in early 1993. The optical system of the MOMS-02
camera consists of a stereo module with three panchromatic
channels and a multispectral module with four colour chan-
nels. The stereo data acquisition will be performed by three
linear arrays of CCD detectors.
From the photogrammetric point of view the scientific ob-
jectives of the mission are (Ackermann et al., 1990):
» the generation of a Digital Terrain Model (DTM) with a
standard deviation of 5 m,
» the production of high quality topographic and orthoima-
ge maps and
» the development of a softcopy (digital) photogrammetric
workstation.
With respect to the digital nature of the primary informa-
tion, the data processing of three-line-camera imagery has
to be performed completely in the digital domain. The con-
cept for a fully digital photogrammetric data acquisition and
evaluation is shown in (Heipke et al., 1990).
Within the MOMS-02/D2 science team the Chair for Photo-
grammetry and Remote Sensing of the Technical University
Munich is responsible for the threedimensional point
determination by bundle adjustment including the recon-
struction of the exterior orientation. The functional model
was adopted step by step according to the geometric
specifications of the mission. The latest extensions are
described in detail. Results of computer simulations using
the extended model are presented, which verify the theore-
tical accuracy. Finally, conclusions are drawn and recom-
mendations for future line camera missions are given.
2. EXTENSION OF THE FUNCTIONAL MODEL
The forthcoming evaluation of practical MOMS-02 imagery
is to be carried out using the bundle block adjustment pro-
gram CLIC, developed at the Chair for Photogrammetry
and Remote Sensing (TU Munich, 1992). The functional
model of CLIC has to be adopted according to the geo-
metric specifications of the MOMS-02/D2 project. The most
important extensions, concerning the camera geometry, the
reconstruction of the exterior orientation and the
introduction of offset and drift parameters are described in
the following.
2.1 Camera geometry
The 3 lenses of the MOMS-02 stereo module provide a
threefold along track stereo scanning with different ground
resolutions. The focal length cy of the nadir (N) looking
high resolution (HR) lens amounts to 660.0 mm, the
forward (F) and backward (B) looking lenses are inclined
with respect to the HR lens by +21.9° and have a focal
length of 237.2 mm each (cz, Cp).
Figure 1 schematically shows the optical system of the
MOMS-02 camera. The inclined stereo lenses are represen-
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