Abstract: A method for estimating the location and orientation of a mobile robot with respect to landmarks whose positions are given using a sensor for measuring bearings of the landmarks with respect to the robot, where bias errors are present. The method comprises using the sensor to obtain bearings the landmarks. The location and orientation of the robot with respect to the landmarks is estimated, based on the measured bearings, and bias errors associated with the measured bearings are corrected to obtain corrected bearings. A correction function is used to finds the minimal sum of squared errors between measured bearings and the corrected bearings. The location and the orientation of the robot is determined to be where the sum of squared errors between measured bearings and the corrected bearings is minimal.