期刊名称：ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
印刷版ISSN：2194-9042
电子版ISSN：2194-9050
出版年度：2006
卷号：XXXVI Part 5
出版社：Copernicus Publications
摘要：This paper reports on the camera calibration procedure developed at CycloMedia and its modification for the reduction of chromatic aberration for further improvement of CycloMedia's main product: 360o panoramic images called Cycloramas. For the construction of Cycloramas, images are taken every 10 meter from all public roads in The Netherlands with a rotating fisheye camera system mounted on a car (Figure 1). These images are used for a variety of applications for a wide range of clients including municipalities, provinces, housing corporations, estate agents, and insurance companies. CycloMedia develops the techniques and software for the production of Cycloramas and their applications in-house. This also is true for the camera calibration procedure and for the conversion of two overlapping fisheye images into a single high-resolution omni- directional panoramic image. The adopted fisheye camera model and the procedure for camera calibration are presented in the paper. The procedure involves the semi-automatic measurement of artificial targets in multiple images. The calibration software performs a least-squares adjustment for the estimation of the camera parameters that describe the relation between the spatial direction of a ray and its projection in the image plane, i.e. the interior orientation. With an example calibration the measurement precision is estimated to be 0.16 pixel standard deviation which is equivalent to an angular precision of 0.014o or better than 3 mm at 10 m. The calibration procedure has been applied for each colour band of a test data set in order to reduce chromatic aberration. Two methods for target localisation have been tested and compared. With both localisation methods the systematic shifts between target positions of different bands do not exceed 1 pixel. Colour artefacts were still present in the Cyclorama constructed using the per band calibration parameters. The conclusion is that the colour aberrations in the images under consideration cannot be reduced significantly with this approach and that not only lateral chromatic aberration plays a role. However, the visual appearance of chromatic aberration could be reduced significantly by manually adjusting the magnification of the red and blue band. It is concluded that the nature of this chromatic aberration is to be studied in more detail in order to come to a final solution for its elimination
关键词：Camera calibration; fisheye; panorama; chromatic aberration; mobile mapping; omni-directional imaging
