A NEW MATCHING APPROACH FOR THREE-LINE SCANNER IMAGERY
C. Wiedemann !, L. Tang?, T. Ohlhof*
* Chair for Photogrammetry and Remote Sensing
Technical University Munich, D-80290 Munich, Germany
Phone: +49-89-2892 2676, Fax: +49-89-280 95 73
E-Mail: wied@photo.verm.tu-muenchen.de
? Technical Consulting & Software Development for
Photogrammetry, Remote Sensing and Geoinformatics
Riesstr. 65, D-80993 Munich, Germany
Phone, Fax: +49-89-140 50 34
E-Mail: 101377.3562@compuserve.com
Commision III, Working Group 2
KEY WORDS: Photogrammetry, Matching, CCD, Extraterrestrial, Method, Three-Line Imagery, HRSC, WAOSS
ABSTRACT
This paper deals with the automatic determination of conjugate points in multiple 3-line images of different resolution for
the task of image orientation. A program for digital image matching was developed as part of the photogrammetric data
processing chain in the context of the planned Mars’96 mission. The matching approach contains three phases: First, a
few highly reliable conjugate points are found on the higher levels of image pyramids using feature based matching. In
the second phase — also on a higher image pyramid level — a regular distribution of conjugate points is obtained by
least squares matching. Finally, the points are tracked down through the image pyramid to the original resolution. The
program was tested with terrestrial and extraterrestrial data provided by 3-line scanners as well as by a frame camera.
The test results show the applicability of the approach.
KURZFASSUNG
Der vorliegende Beitrag behandelt die automatische Bestimmung homologer Punkte für die Orientierung mehrerer 3-
Zeilen-Bilder unterschiedlicher Auflösung. Dazu wurde ein Programm für die digitale Bildzuordnung als Teil der pho-
togrammetrischen Verarbeitungskette im Rahmen der geplanten Mars’96 Mission entwickelt. Der Zuordnungsansatz bein-
haltet drei Phasen: Zuerst werden einige sehr zuverlässige homologe Punkte mittels merkmalsbasierter Zuordnung auf
einer höheren Bildpyramidenebene gefunden. In der zweiten Phase — ebenfalls auf der höheren Pyramidenebene — wird
eine gleichmäßige Punktverteilung durch Kleinste-Quadrate-Zuordnung erreicht. Schließlich werden die Punkte durch
die Bildpyramide bis zur Originalauflösung verfolgt. Das Programm wurde mit terrestrischen und extraterrestrischen
Bilddaten getestet, die von 3-Zeilen-Scannern sowie einer Flächenkamera stammen. Die Ergebnisse der Tests zeigen die
Anwendbarkeit des Ansatzes.
1 INTRODUCTION conjugate points are needed for both the reconstruction of
the exterior orientation of the images and the generation
This paper deals with the automatic determination of con- of Digital Terrain Models (DTM). In this contribution an
jugate points in multiple 3-line images of different resolu- image matching algorithm is presented for the image ori-
tion in the context of the planned Russian Mars'96 mis- entation task only.
sion. In this mission, two different 3-line scanners, the
High Resolution Stereo Camera (HRSC) and the Wide- Both HRSC and WAOSS are based on the 3-line CCD
Angle Optoelectronic Stereo Scanner (WAOSS), will be concept, in which stereo images are acquired nearly si-
flown on board a Russian spacecraft towards planet Mars, multaneously (Hofmann et al. 1982). Note that 3 linear
to be launched in November 1996. The quality of the im- CCD arrays are imaging different terrain at the same time,
agery and the stereoscopic coverage of Mars by the com- whereas the 3 CCD arrays image the same terrain at differ-
bination of HRSC and WAOSS is expected to be superior ent times, as the sensor platform moves. HRSC consists of
to the images taken from the former Mariner and Viking 9 CCD arrays with 5184 active sensor elements each, and
missions. WAOSS contains 3 CCD arrays with also 5184 active sen-
sor elements each. HRSC will operate in the near periapsis
The scientific objectives of the two camera experiments in region of the orbit around Mars (22300 km orbital height),
the field of photogrammetry are concentrated on the ac- whereas WAOSS will work also in more distant orbit seg-
quisition of 3-dimensional information of Mars' topogra- ments (up to 223,000 km orbital height). The ground track
phy in local, regional and global scales. For fulfilling these of both cameras in periapsis is depicted in Figure 1. A
objectives digital image matching is an essential step, as detailed description of the cameras and its operations is
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996
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