Practical PTZ camera calibration using Givens rotations

Due to their ease of use and availability, pan-tilt-zoom (PTZ) cameras are everywhere. However, in order to utilize these cameras for a meaningful application, it is necessary that these cameras be calibrated. In this paper, we address the problem of calibrating such a rotating and zooming camera and present a simple yet novel solution. We show that in the case of a general rotation the problem can be solved in closed- form by applying a series of Givens rotations, providing five intrinsic parameters from only a minimum set of two images. Whereas other methods use orthogonality of the rotation matrix as a constraint, our approach applies direct decomposition of the infinite homography As a result, we are able to obtain four constraints for estimating camera parameters. We rigourously test our method on synthetic data by introducing very large noise. We also compare our method with the state- of-the-art PTZ camera calibration method. Our solutions and analysis are thoroughly validated on both synthetic and real data.