A method for removing noise from data in an electronic compass system which discounts noise values or outliers (extreme headings far from average) by displaying median headings in the absence of a clear trend in the direction of change of sampled headings. If a clear trend is detected, extreme headings are displayed. Compass jitter is reduced by requiring two consecutive differences be on the same side of the displayed heading before the displayed heading is changed.
Mobile terminals, methods, and program products for generating a magnetic heading. A geographic position of the mobile terminal is determined. A magnetic field at the mobile terminal is sensed. A magnetic inclination and/or a magnetic declination of the magnetic field is determined based on the determined geographic position. A magnetic heading is determined for the mobile terminal based on the sensed magnetic field and based on the determined magnetic inclination and/or magnetic declination.
An electronic compass (10) for use in a boring tool (12) which will provide an orientation of the boring tool relative to the earth's magnetic field. In addition, a more straightforward left or right deviation from an initial bearing can be determined. The invention can correct for pitch angle and roll angle variation as well. The magnetic field is sensed by an axial magnetic field (12), a radial magnetic field sensor (18) and a plane-normal magnetic sensor (24) which are preferably magnetoresistive sensors.
An electrical system providing automatic calibration of a vehicle compass for abrupt and significant changes in vehicle magnetism. The system includes a magnetic field sensor providing signal information representing the magnetic field sensed within the vehicle. Coupled to the sensor is an electrical circuit for processing the signal information from the sensor to determine if a shift in vehicle magnetism has occurred and for calculating compensation signal information to provide a corrected heading display.
The compass system of the present invention utilizes an improved calibration routine in which a processing circuit of the compass recalibrates the compass each time three data points are obtained from a magnetic field sensor that meet predetermined criteria. One such criterion is that the three data points define corners of a triangle that is substantially non-obtuse. When three data points have been obtained that define a triangle meeting this criterion, the processing circuit calculates a center point for a circle upon which all three data points lie by solving the equation x.sup.2+y.sup.2+Ax+By+C=0 for A, B, and C, using the coordinate values (x,y) for the three data points and defining the center point as (-A/2, -B/2).
The compass system of the present invention utilizes an improved calibration routine in which a processing circuit of the compass recalibrates the compass each time three data points are obtained from a magnetic field sensor that meet predetermined criteria. One such criterion is that the three data points define corners of a triangle that is substantially non-obtuse. When three data points have been obtained that define a triangle meeting this criterion, the processing circuit calculates a center point for a circle upon which all three data points lie by solving the equation x.sup.2 +y.sup.2 +Ax+By+C=0 for A, B, and C, using the coordinate values (x,y) for the three data points and defining the center point as (-A/2, -B/2).
