Camera auto-calibration using pedestrians and zebra-crossings

Abstract

In this paper we present a novel camera self-calibration technique to automatically recover intrinsic and extrinsic parameters of a static surveillance camera by observing a traffic scene. The scene must consist of one or more pedestrians and a zebra-crossing. We first extract a horizontal vanishing point and a vanishing line from a zebra-crossing. The observation of pedestrians allows calculating a so called vertical line of mass. All lines of mass are parallel in 3D space and therefore the vertical vanishing point can be estimated. The second horizontal vanishing point can be calculated by introducing the triangle spanned by three orthogonal vanishing points. All three vanishing points are then taken to gather the intrinsic parameters. The extrinsic parameters are calculated after the determination of the camera's height from the distance between two zebra-crossing edges. By combining static and dynamic calibration objects, the method gets robust against outliers. This robustness in combination with the practicability is shown in our experiments, which are carried out by using synthetic and real data of different application scenarios.