265 
SENSOR CALIBRATION AND GEOMETRIC CALIBRATION OF A THREE LINE STEREO CAMERA 
Reinhard Schuster 
DLR, Institute for Space Sensor Technology, Rudower Chaussee 5, D-12489 Berlin, Germany 
Tel: +49-30-69545 583, Fax: +49-30-69545 572, E-mail: ws2e@arzpsv.rz.ba.dlr.de 
KEY WORDS: Sensor Calibration, Geometric Camera Calibration, Point Spread Function, Modulation Transfer Function 
ABSTRACT 
The calibration of digital cameras with a sensor modul consisting of 3 or more CCD-lines is a own field of considerable extent.The 
technical and time spending expense is often underestimated by the development of such camera systems. The paper deals with the 
precalibration of the sensor starting in the phase of design and ends with the geometric calibration of a complete camera system. 
The work was done with a camera of the type WAOSS (Sandau et al. 1994) which was developed for the Russian Mars mission but 
the techniques and methods are also valid for any other systems. 
ZUSAMMENFASSUNG 
Die Kalibrierung digitaler Zeilenkameras mit 3 oder mehr CCD-Zeilen als Empfänger ist eine eigenständige Aufgabe von 
erheblichem Umfang. Bei der Entwicklung solcher Systeme wird der dafür notwendige Aufwand in technischer und zeitlicher 
Hinsicht meist unterschátzt . Dieser Beitrag bescháftigt sich mit der Kalibration des Sensors beginnend wáhrend der 
Entwicklungsphase der Kamera und berichtet über die geometrische Kalibrierung eines kompletten Kamerasystems. Die 
Untersuchungen wurden an einer Kamera des Typs WAOSS (Sandau et al. 1994) durchgeführt, die für die russische Mars Mission 
96 entwickelt wurde. Die Techniken und Methoden sind jedoch auf andere Kamerasysteme übertragbar. 
1. INTRODUCTION 
The consequent application of modern digital image processing techniques in photogrammetry needs camera systems with direct 
digital image acquisition. The development of CCD sensors with pixel sizes below 10um and their use in aerial and space 
photogrammetry can perform the requirements of high resolution and direct digital data aquisition. The most advanced camera 
concept makes use of 3 CCD lines which are located in the image plane of the camera telescope. While the camera on their platform 
is moving about the ground three images can take from the same terrain quasi simultaneously. For the stereo reconstruction it is 
necessary to coincide these pictures automatically. This requires high accuracy for the geometric calibration process because the 
accuracy of the camera interior orientation determines the error of photogrammetric point determination. Additionaly point accuracy 
is determined by the Point Spread Function (PSF) of the camera system depending of optics, pixel size, CCD read out and cordinates 
of geometric calibration. In the last few years the 3-line camera concept has been realized for experimental airborne as well as 
spaceborn projects and is now coming in an operational phase. The main known camera systems basing on this concept are: 
e. the Monocular Electro-Optical Stereo Scanner (MEOSS) (Lanzl 1986) 
the Modular Optoelectronic Multispectral Scanner (MOMS-02) (Ackermann et al. 1989) 
the High Resolution Stereo Camera (HRSC) (Neukum et al. 1990) 
the Wide Angle Optoelectronic Stereo Scanner (WAOSS) (Oertel et al. 1991) 
e other new 3-line scanner for aerial and space application are under development 
The author was participated in the development of the wide angle camera WAOSS from the selection of sensors, optics and filters 
and responsible for sensor calibration and calibration of the whole camera system under laboratory and space simulating condition. 
The paper deals with sensor calibration and some geometric calibration results of the camera. The radiometric calibration results of 
the camera system will be a topic of a later publication. 
2. GENERAL CAMERA CALIBRATION PROCEDURES AND CALIBRATION FACILITY 
The necessary camera calibration procedures can summarized to the following topics 
e Sensor Calibration 
e Adjustment and Alignment of the Camera or Camera-head 
IAPRS, Vol. 30, Part 5W1, ISPRS Intercommission Workshop “From Pixels to Sequences”, Zurich, March 22-24 1995