Camera Calibration using the Damped Bundle Adjustment Toolbox
Keywords: Camera calibration, Bundle adjustment, Focal length, Convergent, Initial values, Close Range
Abstract. Camera calibration is one of the fundamental photogrammetric tasks. The standard procedure is to apply an iterative adjustment to measurements of known control points. The iterative adjustment needs initial values of internal and external parameters. In this paper we investigate a procedure where only one parameter – the focal length is given a specific initial value. The procedure is validated using the freely available Damped Bundle Adjustment Toolbox on five calibration data sets using varying narrow- and wide-angle lenses.
The results show that the Gauss-Newton-Armijo and Levenberg-Marquardt-Powell bundle adjustment methods implemented in the toolbox converge even if the initial values of the focal length are between 1/2 and 32 times the true focal length, even if the parameters are highly correlated. Standard statistical analysis methods in the toolbox enable manual selection of the lens distortion parameters to estimate, something not available in other camera calibration toolboxes.
A standardised camera calibration procedure that does not require any information about the camera sensor or focal length is suggested based on the convergence results.
The toolbox source and data sets used in this paper are available from the authors.