PHOTOGRAMMETRIC CALIBRATION AND POINT DETERMINATION USING A DIGITAL CCD CAMERA
C. Heipke*, M. Stephani’, G. Strunz*, R. Lenz?
1 Chair for Photogrammetry and Remote Sensing
? Chair for Telecommunications
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: heipke@photo.verm.tu-muenchen.de
Commission V
ABSTRACT:
Digital CCD cameras are increasingly being used for
photogrammetric applications, mainly for digitizing film
hardcopies and in close range environments (robot vi-
sion, machine vision). À prerequisite for these tasks is a
sufficient geometric and radiometric accuracy of the
camera.
In this paper we assess the geometric accuracy potential
of a digital CCD camera, the ProgRes 3000, for photo-
grammetric point determination using the selfcalibra-
tion approach in conjunction with a small testfield. 8
images of this testfield with 29 well defined points were
recorded. Measurement of the image coordinates of
these points was carried out using two different me-
thods: a chain code algorithm and least squares mat-
ching. The results are reported and discussed.
Furthermore, the impact of the camera calibration on
object point determination is demonstrated. Achieved
empirical standard deviations of the control points lie in
the range of 30 um or 1:20.000 in object space.
Key words: Robot vision, digital CCD camera, calibra-
tion, close range photogrammetry.
1. INTRODUCTION
Charge Coupled Device (CCD) cameras are increasing-
ly being used in photogrammetry for direct image acqui-
sition and for digitization of hardcopy film. In general
the interior orientation of these cameras is not known, it
changes, when the focusing is changed, and lens distor-
tion has to be taken into account. Therefore, the cameras
must be calibrated to meet photogrammetric accuracy
requirements. A complete calibration includes radiome-
tric aspects (e.g. the compensation of different sensitivi-
ty of CCD sensor cells) as well as geometric ones.
Geometric calibrations of CCD cameras with video out-
put (analogue signal) are reported from a number of
authors. Gülch /1984/, Dähler /1987/, and Luhmann,
Wester-Ebbinghaus /1987/ investigated the image quali-
ty (line jitter, blooming etc.). Beyer /1987/ treated vario-
us aspects of the geometric calibration using a three
dimensional testfield. Lenz /1987/ presented a fast mul-
ti-step calibration procedure for applications at televi-
sion field rate. However, major problems were observed
in conjunction with the necessary A/D conversion of the
video signal. Dáhler concludes, that "it is ... strongly
recommended to transfer the information from CCD
cameras digitally" /Dáhler 1987, p. 59/. Only few reports
on a photogrammetric calibration of such digital CCD
cameras exist /Bósemann et al. 1990; Beyer 1991; Ed-
mundson et al. 1991; Heipke et al. 1991/.
This paper deals with the geometric accuracy potential
of the ProgRes 3000 /Lenz 1989/, a digital CCD camera.
Our approach using selfcalibration in conjunction with
a small testfield is explained. 8 images of this testfield
with 29 well defined points were recorded. Measure-
ment of the image coordinates of these points was car-
ried out using two different methods: a chain code algo-
rithm and least squares matching. The results are repor-
ted and discussed. Finally an example for the photo-
grammetric evaluation of three dimensional objects is
given. Achieved empirical standard deviations of the
control points lie in the range of 30 jm or 1:20.000 in
object space.
