title: Extrinsic Calibration of Camera Networks Based on Pedestrians.
abstract: In this paper, we propose a novel extrinsic calibration method for camera networks by analyzing tracks of pedestrians. First of all, we extract the center lines of walking persons by detecting their heads and feet in the camera images. We propose an easy and accurate method to estimate the 3D positions of the head and feet w.r.t. a local camera coordinate system from these center lines. We also propose a RANSAC-based orthogonal Procrustes approach to compute relative extrinsic parameters connecting the coordinate systems of cameras in a pairwise fashion. Finally, we refine the extrinsic calibration matrices using a method that minimizes the reprojection error. While existing state-of-the-art calibration methods explore epipolar geometry and use image positions directly, the proposed method first computes 3D positions per camera and then fuses the data. This results in simpler computations and a more flexible and accurate calibration method. Another advantage of our method is that it can also handle the case of persons walking along straight lines, which cannot be handled by most of the existing state-of-the-art calibration methods since all head and feet positions are co-planar. This situation often happens in real life.
authors.affiliation: Image Processing and Interpretation, TELIN, Ghent University/iMinds, Sint Pietersnieuwstraat 41, 9000 Gent, Belgium. Junzhi.Guan@telin.ugent.be.
authors.forename: Junzhi
authors.initials: J
authors.lastname: Guan
authors.affiliation: Image Processing and Interpretation, TELIN, Ghent University/iMinds, Sint Pietersnieuwstraat 41, 9000 Gent, Belgium. Francis.Deboeverie@telin.ugent.be.
authors.forename: Francis
authors.initials: F
authors.lastname: Deboeverie
authors.affiliation: Image Processing and Interpretation, TELIN, Ghent University/iMinds, Sint Pietersnieuwstraat 41, 9000 Gent, Belgium. Maarten.Slembrouck@telin.ugent.be.
authors.forename: Maarten
authors.initials: M
authors.lastname: Slembrouck
authors.affiliation: Image Processing and Interpretation, TELIN, Ghent University/iMinds, Sint Pietersnieuwstraat 41, 9000 Gent, Belgium. dirk.vanhaerenborgh@telin.ugent.be.
authors.forename: Dirk
authors.initials: D
authors.lastname: Van Haerenborgh
authors.affiliation: Image Processing and Interpretation, TELIN, Ghent University/iMinds, Sint Pietersnieuwstraat 41, 9000 Gent, Belgium. Dimitri.VanCauwelaert@telin.ugent.be.
authors.forename: Dimitri
authors.initials: D
authors.lastname: Van Cauwelaert
authors.affiliation: Image Processing and Interpretation, TELIN, Ghent University/iMinds, Sint Pietersnieuwstraat 41, 9000 Gent, Belgium. peter.veelaert@ugent.be.
authors.forename: Peter
authors.initials: P
authors.lastname: Veelaert
authors.affiliation: Image Processing and Interpretation, TELIN, Ghent University/iMinds, Sint Pietersnieuwstraat 41, 9000 Gent, Belgium. philips@telin.UGent.be.
authors.forename: Wilfried
authors.initials: W
authors.lastname: Philips
keywords: camera network; extrinsic calibration; orthogonal Procrustes; pedestrians