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Proceedings, XXth congress

Kazuya AOYAMA, Hirofumi CHIKATSU
Tokyo Denki University, Department of Civil and Environmental Engineering, 350-0394 Hatoyama Saitama, Japan
kazuya@chikatsu-lab.g.dendai.ac.jp, chikatsu@g.dendai.ac.jp
Commission Youth Forum
KEY WORDS: Photogrammetry, Calibration, Digital, Camera, Image, Cost, Software
The change in photogrammetry from analog to digital means a change from film to CCD or CMOS sensor, and real-time imaging
became possible. In particular, amateur digital cameras have been receiving attention as convenient equipment in digital
photogrammetric fields since the numbers of pixel for amateur digital cameras have been amazingly increased by modern
semiconductor and digital technology. As a result, convenient photogrammetry using amateur digital cameras are expected to
contribute enormously to digital photogrammetric field. However, ground control points are needed for camera calibration, which
requires huge labor and time for measuring ground control points.
Under these circumstances, the authors developed a calibration method without ground control points. However, some problems still
remain. For example, the above calibration method is necessary to calculate interior orientation parameters such as focal length, lens
distortion, principle points, and interior orientation should be performed previously using test target or test sheet.
[n order to resolve the above problems, effective calibration method which does not need ground control points nor previous interior
orientation procedures are discussed in this paper.

Amateur digital cameras are expected to contribute enormously In order to remove previous interior orientation procedures
to digital photogrammetric field, and there are various using test target or test sheet, triplet images are taken from left,
photogrammetric software on the market to perform 3D center, and right position. Figure 2 shows concept of imaging
measurement using amateur digital camera. However, ground for triple image, and detail calibration procedures are as
control points or previous interior orientation procedures are follows:
needed for camera calibration. (a) Relative orientation using left and right image is performed.
In order to evaluate amateur digital camera, performance The focal length is assumed to be a nominal value, and neglect
evaluation for armature digital camera were investigated by the lens distortion at this stage.
authors(Kunii & Chikatsu, 2001). Furthermore, in order to (b) The characteristic 9 points which are common points to
resolve the above restrict problems, the authors have been triplet images are selected, and these 9 points are defined as a
concentrating on developing the convenient photogrammetric temporal control points.
software, and software for low-cost digital photogrammery (c) Relative 3D coordinate to the temporal control points are
“3DiVision” was designed to perform convenient 3D calculated by using the calculated relative orientation
measurement using amateur digital cameras(Chikatsu & Kuni, parameters.
2002), and an application was discussed(Nakada & Chikatsu, (d) Self-calibration for the center image is performed using
2003). Figure 1 shows calibration concept of the 3DiVision. relative 3D coordinate.
However, previous interior orientation procedure is still issue (e) Exterior orientation parameters for the center camera in
for practical 3D measurement using amateur digital camera. relative coordinate system are calculated, but computed interior
Under theses circumstances, calibration method using triplet orientation parameters (f(focal length), xo,yo(principal point),
images are developed in this paper. a,,à>,03,04(scale factor) k,(lens distortion parameter)) are
[. Interior orientation | defined as common to the three images. :
(f) All of the calculated exterior orientation parameters for the
v : : left, center, right camera, 3D coordinates for the temporal
| Distance measurement between two points on object | control points and the interior orientation parameters are
assumed to be initial valus.
[. Relative orientation | As a next stage,
Y (g) Self-calibration for the three images are performed
[> Simultaneous adjustment ] simultaneously using collinearity condition. Ln
(h) Relative 3D coordinates to each measurement point within

Figure 1. Concept of 3DiVision the object field are calculated.