Calibration of a stereo system with small relative angles

The authors present an algorithm for the calibration of a stereo system with small relative angles in an uncontrolled environment. This algorithm has two advantages: (1) it is more accurate than the existing algorithms in the computer vision and photogrammetry literatures; and (2) it provides useful insight into the problem of camera calibration and relative orientation. This is done by deriving explicit analytical solutions for the relative pan, tilt, and roll angles in terms of the world pan angle (gaze angle) and the coordinates of the feature points used in their computations. These solutions allow a better understanding of the problem of calibration in general by providing insight as to how errors due to quantization and uncertainty in the location of image centers affect the computation of rotation angles. The findings are likely to be of use even when the relative rotation angles are not small