Sensitivity of the pose refinement problem to accurate estimation of camera parameters

A study is made of the effect of errors in estimates of the image center and focal length on pose refinement and other related (3-D inference from 2-D images) problems/algorithms. The authors show that for `small´ field of view imaging systems, incorrect knowledge of the camera center does not affect the determination of the location of the camera significantly. Incorrect estimates of the focal length only significantly affect the determination of the z-component (i.e. parallel to the optical axis) of the translation in camera coordinates. The output of the pose refinement algorithm is used to calculate the relative orientation between the coordinate frames of the same camera in two or more different positions as a prelude to computation of 3-D depths of new points by pseudo-triangulation. A model of error for this depth based on the amount of error in placing the image center conforms to the errors obtained for experiments with synthetic and real data. New points are located to an average accuracy of 1.5 mm and 0.3 ft for the two real image sequences respectively