Camera calibration by vanishing point and cross ratio

The authors present a unified camera calibration method in which radial distortions can be considered or ignored. The usually tangled process of calibrating intrinsic and extrinsic camera parameters in the zero-distortion case is separated by using vanishing points as calibration points. By ignoring distortions, rough estimates for intrinsic camera parameters are solved linearly. Refinements are made on the basis of the invariance properties of the cross ratio and the collinearity of perspectivity, so that radial distortion can be considered. With the corrected image plane, the usual linear methods can be used to solve extrinsic camera parameters with low computational cost