an electronic flux gate compass calibration method and apparatus . an electronic flux gate compass mounted on a terrestrial vehicle is first rotated 360 degrees by driving the vehicle in a circle to determine four reference points where the locus of points representing the orthogonal outputs of the compass crosses over the x and y axes of a reference cartesian coordinate system . these four reference points are employed to calibrate the orthogonal outputs of the compass and compute a calibrated compass heading . thereafter , as the vehicle moves from place to place , the output of the compass is monitored . if the output is within a predetermined region around one of the reference points , the reference point is modified to be closer to that output point . when the vehicle has moved through a closed loop , i . e ., rotated a net 360 degrees , the compass is recalibrated .