An autonomous vehicle comprises at least one image sensor to provide measurements of landmark position for a plurality of landmarks; and processing functionality to estimate the position of the plurality of landmarks in a global frame and in the autonomous vehicle's frame, and to estimate the kinematic state of the autonomous vehicle in a global frame based, at least in part, on the measurements of landmark position from the at least one image sensor. The processing functionality is further operable to calculate errors in the estimated positions of the plurality of landmarks in the global frame and in the estimate of the kinematic state of the autonomous vehicle in the global frame by using a plurality of unit projection vectors between the estimated positions of the plurality landmarks in the autonomous vehicle's frame and a plurality of unit projection vectors between the estimated positions of the plurality of landmarks in the global frame.