Abstract: A magnetic sensor of an electronic instrument has a circular or substantially circular component that assumes magnetism in the vicinity of its circumference. An X axis magnetic sensor detects a magnetic field component in the X axis direction that is arranged in a position inside the vicinity of the circumference of the component, or is arranged such that a detection axis of the magnetic sensor overlaps an X axis passing through the center of the component in an arbitrary position on the X axis or on its extended line. A Y axis magnetic sensor detects a magnetic component in a Y axis direction that is arranged inside the vicinity of the circumference of the component, or is arranged such that a detection axis of the magnetic sensor overlaps a Y axis passing through the center of the component and perpendicular to the X axis in an arbitrary position on the Y axis or on its extended line. A correcting circuit corrects the signals outputted from the X axis magnetic sensor and the Y axis magnetic sensor.

Abstract: 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 x2+y2+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).

Abstract: An improved method, system, and device for a compass combining an electronic magnetic compass and an angular velocity sensing gyroscope. One aspect of the invention integrates an angular velocity output signal from an angular velocity sensor or rate gyroscope to determine the angle of motion. An initial magnetic heading is obtained from a geomagnetic sensor and used as a reference for the integrated angular velocity signal. A geomagnetic heading signal is blended with the angular velocity output signal at an adaptive time interval. The adaptive time interval is increased if the reliability of the magnetic field improves and decreased if the reliability of the magnetic field degenerates. Additionally, dynamic calibration of the angular velocity sensor may be performed to correct for gyroscope bias (zero offset), and/or gyroscope scale factor or gain.

Abstract: A tilt-compensated electronic compass can be realized by calculating rather than measuring Earth's magnetic field component Z in a direction orthogonal to the two measurement axes of a 2-axis magnetic sensor. The orthogonal component Z can be calculated using a stored value for the Earth's magnetic field strength applicable over a wide geographic region. The calculation also requires using measured field values from the 2-axis sensor. Once Z is known, and using input from a 2-axis tilt sensor, compensated orthogonal components X and Y can be calculated by mathematically rotating the measured field strength values from a tilted 2-axis sensor back to the local horizontal plane. Thus, a very flat and compact tilt-compensated electronic compass is possible.

Abstract: In an electronic device, a method of measuring an external field and displaying indicia related to the measurement, wherein the electronic device generates a first internal field and at least a second internal field, wherein the method comprises the steps of measuring the external field when the electronic device is generating the first internal field; and only displaying indicia related to measurements taken while the electronic device is generating the first internal field. In the preferred embodiment, the first internal field is generated by a rotor of a stepping motor being in a first orientation, and the at least second internal field is generated by the rotor of the stepping motor being in a second orientation, wherein the method comprises the steps of determining whether the rotor is in the first orientation before measuring the external field; and if not, causing the rotor to rotate into the first orientation prior to measuring the external field.

Abstract: A method for measuring a directional of a body in a three-dimensional space defined by an X-axis (magnetic north), a Y-axis, and a Z-axis is proposed. An x-axis tilt angle, which is an angle between a horizontal plane and an x-axis, which is the direction towards which the body points, and a y-axis tilt angle, which is an angle between a y-axis orthogonal to the x-axis and the horizontal plane, are detected. The x-axis and the y-axis are converted so as to be in the horizontal plane using the x-axis tilt angle and the y-axis tilt angle. A primary azimuth between the X-axis and the x-axis converted is calculated. An azimuth error angle included in the primary azimuth is extracted based on the x-axis tilt angle, the y-axis tilt angle, and the primary azimuth.

Abstract: A compass system includes a platform defining an x-axis, a y-axis and an xy-plane, wherein a z-axis is orthogonal to the xz-plane. A beam is rotatably coupled to the platform such that the beam rotates about the y-axis. An accelerometer including a flexure plate perpendicular to the y-axis is coupled to the beam a distance from the y-axis. The accelerometer generates an accelerometer signal in response to movement of the flexure plate. An angular position sensor senses angular position of the beam relative to the x-axis and y-axis, the angular position sensor generating an angular position signal therefrom. A processor receives the accelerometer signal and the angular position signal and generates an East-West signal therefrom.

Abstract: A correcting mechanism for an electronic azimuth meter has an X-direction magnetic sensor and a Y-direction magnetic sensor for detecting a magnetic field in two orthogonal directions X and Y and for calculating an azimuth of a main body of an electronic azimuth meter. An azimuth change inducing unit provides a display of an induction mark to induce a continuous change of the azimuth of the electronic azimuth meter main body over a range of rotation of at least 360 degrees.

Abstract: A method and system for continuously and automatically calibrating the settings of an electronic compass, as needed, while a vehicle moves from place to place is shown. The calibration technique of the present invention measures the ocal magnetic field while the vehicle moves from place to place and determines points on a reference Cartesian coordinate system. Each such point defines the endpoint for a vector corresponding with the measured field intensity and orientation of the local magnetic field. Any three such points are used to calculate the center of a circle that extends through all of those points. A vector that begins at the origin of the reference Cartesian coordinate system and terminates at the calculated center of the circle is thereafter subtracted from subsequent field measurement vectors that correspond to the field intensity and direction of the local magnetic field.

Abstract: 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 x2+y2+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).

Abstract: An Improvement to enhance the usability of magnetic compasses by eliminating acceleration and turning errors, especially in aviation applications, without compromising simplicity and reliability. The improvement includes the addition of a weightless mass to the bar magnet of a conventional magnetic compass to counteract undesirable inertial forces on the bar magnet.

Abstract: Arranging a magnetic sensor in a position within 2−1/2 of the radius from the center of a component in a circular shape assuming magnetism, and correcting deflection by deflection amount correcting circuit of an output from the magnetic sensor in accordance with the relative position between the magnetic sensor and the component.

Abstract: A method for adjusting an electronic azimuth meter comprising the steps of performing a magnetic field generating sequence by generating a sequence of magnetic fields used for adjusting the electronic azimuth meter, the sequence of magnetic fields commencing with generation of a strong magnetic field having a magnitude larger than that of the Earth's geomagnetism, and providing, within the strong magnetic field, an electronic azimuth meter having a magnetic detector and a control unit for performing a data acquisition and adjustment process in response to detection of the strong magnetic field, so that the control unit commences the data acquisition and adjustment process when the strong magnetic field is detected and the electronic azimuth meter is not electrically connected to a magnetic field generating apparatus which generates the sequence of magnetic fields.

Abstract: An autocalibration method for use within an electronic compass in a vehicle is disclosed. The method includes steps of initializing variables and then retrieving sensor readings from at least two axis. The method then compares the compass tilt to a predetermined threshold. Next the method will determine if the sensor reading is a minimum or maximum for the current calibration cycle. Next the method will determine if the maximum value of the sensor readings is greater than the predetermined minimum spread. Then the method will calculate an offset value for each axis and calculate a sensor value for each axis. Then the method will calculate an azimuth value with the new sensor values and determine the heading using the azimuth.

Abstract: 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 2+y2+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).

Abstract: Arranging a magnetic sensor in a position within 2−1/2 of the radius from the center of a component in a circular shape assuming magnetism, and correcting deflection by deflection amount correcting circuit of an output from the magnetic sensor in accordance with the relative position between the magnetic sensor and the component.

Abstract: An electronic compass system includes a magnetic sensor circuit having at least two sensing elements for sensing perpendicular components of the Earth's magnetic field vector. A processing circuit is coupled to the sensor circuit to filter, process, and compute a heading. The processing circuit further selects an approximating geometric pattern, such as a sphere, ellipsoid, ellipse, or circle, determines an error metric of the data points relative to the approximating pattern, adjusts the pattern to minimize the error, thereby obtaining a best fit pattern. The best fit pattern is then used to calculate the heading for each successive sensor reading provided that the noise level is not noisy and until a new best fit pattern is identified. The electronic compass system is particularly well suited for implementation in a vehicle rearview mirror assembly.

Abstract: An electronic azimuth meter includes an electronic azimuth meter main body and X-direction and Y-direction magnetic sensors for detecting magnetic field components in orthogonal two directions of the main body, the main body includes a magnetic part magnetized by geomagnetism B0 for forming a magnetic field having components in oblique directions relative to directions of the geomagnetism at locations of the magnetic sensors, approximate equation storing means for storing pluralities with regard to respective directions X, Y, of approximate equations calculated based on magnetic field detected values Vx and Vy of the magnetic sensors with regard to a number of azimuths of the azimuth meter in geomagnetism having magnetic field components Bx and By, which are approximate equations representing relationships between the detected values Vx and Vy of the magnetic sensors and the magnetic field components Bx and By of the geomagnetism, and azimuth calculating means for calculating azimuth by selecting specific app

Abstract: A compass compensation system is provided for automatically and continuously calibrating an electronic compass for a vehicle, without requiring an initial manual calibration or preset of the vehicle magnetic signature. The system initially adjusts a two axis sensor of the compass in response to a sampling of at least one initial data point. The system further calibrates the compass by sampling data points that are substantially opposite to one another on a plot of a magnetic field and averaging an ordinate of the data points to determine a respective zero value for the Earth magnetic field. The system also identifies a change in magnetic signature and adjusts the sensor assembly.

Abstract: A method for dynamic auto-calibration of a multi-sensor tracking system and apparatus incorporating it therein are presented. The method and apparatus utilize information from complementary sensors, filtered by a simultaneously running filter that combines the sensor data into an estimate of the state of the monitored system to iteratively tune the bias estimate. To track a dynamic system, complimentary or redundant sensors may be combined with a model of the system so that the uncertainty in the estimated state of the dynamic system is less than the noise in the individual sensors. In addition to noise, the sensors may have bias, which has the same value whenever the system is in a particular state. While estimating the actual value of the state, the present invention allows the estimator to determine the bias. The present invention, in its most general embodiment requires complex computations.

Abstract: A three-axis algebraic model is used to numerically compensate for magnetic errors in measured magnetic field values in an electronic compass for any orientation of the compass. This model is based on physical principles and uses a linear algebra approach that facilitates computation of the parameters needed for compensation. During a calibration procedure of the electronic compass, magnetic and gravity fields are measured in three axes at each of a variety of combinations of orientations and azimuths. This set of measured magnetic and gravity fields is used to calculate a matrix compensation coefficient and a vector compensation coefficient using a system of equations. These compensation coefficients are stored and then used during normal operations of the electronic compass to correct all subsequently measured magnetometer data to obtain corrected values for the Earth's magnetic field, from which the correct azimuth can be calculated.

Abstract: A three-axis physical model is used to numerically compensate for errors in measured magnetic field values in an electronic compass for operation at any orientation. This compensation method generates certain quantities that characterize the magnetic field of the Earth in the vertical plane. These quantities are used to monitor the accuracy of the electronic compass during normal operation by comparing their current values either with values obtained during the calibration procedure or with values obtained from historical averages. Significant departure from the calibration values or from the historical averages indicates a probable loss of accuracy of the compass, and the user is so alerted.

Abstract: A hybrid three-axis magnetic sensor for calculating the accurate direction of the earth magnetism. The hybrid three-axis magnetic sensor includes: a flux gate type magnetic sensor which is so formed that a base serves as a main member and detects two axis components of a magnetic vector defined by a plane parallel to the base; a Hall element which detects another component of the magnetic vector orthogonal to the base; a tilt sensor which detects a tilt angle of the base; and a CPU, wherein the flux gate type magnetic sensor and the Hall element are integrally structured together as a hybrid IC. The thus detected three dimensional magnetic vector is corrected in the light of inclination of the base, so that the direction of the earth magnetism is accurately calculated.

Abstract: To provide an electronic equipment having a built-in electronic compass that detects terrestrial magnetism using a magnetic sensor, which is drivable with efficiency, and displays a compass direction (north). In this electronic wrist watch, a comparison means compares a detection value obtained by the first detection with a detection value obtained by the second detection, for instance. The reproducibility judgment means judges whether there exists reproducibility using a result of the comparison. In the case where there exists reproducibility, a pulse width setting means sets a short pulse width for a magnetic field. This makes it possible for a reset means to reset a magnetic sensor using electromagnetic energy that is required to reset the magnetic sensor.

Abstract: To reduce a dispersion in a sensitivity of a magnetism detecting circuit driving, by current, a magnetism sensor comprising magnetism resistance elements in a bridge constitution to a dispersion in a sensitivity of a magnetism sensor. An electronic azimuth meter is provided with EEPROM and drive current set values are previously stored to EEPROM. The drive current set values are calculated by a predetermined calculation by measuring bridge resistance of a magnetism sensor of the electronic azimuth meter. In detecting magnetism by the magnetism sensor, CPU controls a sensor drive circuit based on the drive current set values stored to EEPROM. Thereby, the sensor drive circuit supplies a magnetism sensor with optimum drive current in accordance with a bridge resistance value thereof.

Abstract: A compass compensation system is provided for automatically continuously calibrating an electronic compass for a vehicle, without requiring an initial manual calibration or preset of the vehicle magnetic signature. The system initially adjusts a two axis sensor of the compass in response to a sampling of at least one initial data point. The system further calibrates the compass by sampling data points that are substantially opposite to one another on a plot of a magnetic field and averaging an ordinate of the data points to determine a respective zero value for the Earth magnetic field. The system also identifies a change in magnetic signature and adjusts the sensor assembly.

Abstract: A method for drilling a wellbore to assure the avoidance of a substantially adjacent known magnetic source comprising the steps of obtaining survey data for the path or trajectory of a known magnetic source; preparing a wellplan comprising a path or trajectory for a second wellbore to be drilled, from the survey data and the wellplan, computing expected values of one or more parameters of the magnetic field to be encountered along a second wellbore during drilling operations, in association with drilling a second wellbore, measuring components of a magnetic field encountered and computing one or more magnetic field parameters at a series of survey points along the wellbore path or trajectory; and determining if measured values differ systematically from expected values, thereby indicating a deviation from the planned wellpath.

Abstract: The present invention relates to a control circuit for controlling the driving stability of a vehicle where the input quantities determining the course of track are input in a vehicle model circuit which determines at least on nominal value for a control quantity subject to parameters memorised in the vehicle reference model on the basis of a vehicle reference model reproducing the characteristics of the vehicle.

Abstract: The invention relates to an electronic compass adapted for providing users with an audible indication of direction. The compass includes a housing assembly having a speaker for providing a user with information concerning the orientation of the housing assembly relative to the earth's magnetic field. The compass further includes a Hall Effect detector for determining the orientation of the housing assembly relative to the Earth's magnetic field and a translator for translating the orientation data relating to the position of the housing assembly relative to the earth's magnetic field into an auditory signal which is transmitted to the speaker assembly for translation into an audible signal providing a user with audible instructions regarding the orientation of the housing assembly.

Abstract: A method for calibrating the attitude of a compass in relation to the platform on which the compass is installed. The compass includes an attitude determining device and an optical sighting device and the compass is integrally mounted on a platform. The method includes the steps of determining the angle between the optical sighting device and the attitude determining device, determining the attitude between the optical sighting device and the platform, and determining the attitude between the attitude determining device and the platform.

Abstract: An electronic compass is described for use in vehicles. The compass employs a magnetoresistive sensor for sensing the earth magnetic field and the sensor is operated in alternate set/reset bias modes. In a first embodiment, the compass is provided with deviation compensation by a closed loop system including measurement of the sensor output signals and an offset current strap for nullifying the vehicle deviation field. In a second embodiment, deviation compensation is provided by operation in an initial calibration mode and by operation in a normal compensation mode to adjust compensation, as needed, on a long term basis during normal operation of the compass. In the initial calibration mode, while the vehicle is being driven, the signal peak values are adjusted to a nominal earth field level by changing the offset current. Then, compensating signal reference values for each axis are determined as each peak for that axis is determined.

Abstract: A three-axis algebraic model is used to numerically compensate for magnetic errors in measured magnetic field values in an electronic compass for any orientation of the compass. This model is based on physical principles and uses a linear algebra approach that facilitates computation of the parameters needed for compensation. During a calibration procedure of the electronic compass, magnetic and gravity fields are measured in three axes at each of a variety of combinations of orientations and azimuths. This set of measured magnetic and gravity fields is used to calculate a matrix compensation coefficient and a vector compensation coefficient using a system of equations. These compensation coefficients are stored and then used during normal operations of the electronic compass to correct all subsequently measured magnetometer data to obtain corrected values for the Earth's magnetic field, from which the correct azimuth can be calculated.

Abstract: A three-axis physical model is used to numerically compensate for errors in measured magnetic field values in an electronic compass for operation at any orientation. This compensation method generates certain quantities that characterize the magnetic field of the Earth in the vertical plane. These quantities are used to monitor the accuracy of the electronic compass during normal operation by comparing their current values either with values obtained during the calibration procedure or with values obtained from historical averages. Significant departure from the calibration values or from the historical averages indicates a probable loss of accuracy of the compass, and the user is so alerted.

Abstract: An electronic compass is described for use in vehicles. The compass employs a magnetoresistive sensor for sensing the earth magnetic field and the sensor is operated in alternate set/reset bias modes. In a first embodiment, the compass is provided with deviation compensation by a closed loop system including measurement of the sensor output signals and an offset current strap for nullifying the vehicle deviation field. In a second embodiment, deviation compensation is provided by operation in an initial calibration mode and by operation in a normal compensation mode to adjust compensation, as needed, on a long term basis during normal operation of the compass. In the initial calibration mode, while the vehicle is being driven, the signal peak values are adjusted to a nominal earth field level by changing the offset current. Then, compensating signal reference values for each axis are determined as each peak for that axis is determined.

Abstract: An electronic compass system using information on a communications bus to eliminate magnetic noise which is integrated with an instrument cluster. A vehicle accessory, such as a blower motor, generates a known, consistent, magnetic field of intensity sufficient to cause a static magnetic offset in the electronic compass for each of its' electrical states. An electronic controller commands the vehicle accessory to change electrical states and transmits a vehicle event message on a communications bus. A magnetic field sensor detects a combination of Earth's magnetic field and the stray magnetic field produced by the vehicle accessory. A controller is coupled to the communications bus and uses the vehicle event message to look up a predetermined correction factor, corresponding to the electrical state, to eliminate the effect of the static magnetic offset. The controller then displays a heading unaffected by the static magnetic offset.

Abstract: A hybrid three-axis magnetic sensor for calculating the accurate direction of the earth magnetism. The hybrid three-axis magnetic sensor includes: a flux gate type magnetic sensor which is so formed that a base serves as a main member and detects two axis components of a magnetic vector defined by a plane parallel to the base; a Hall element which detects another component of the magnetic vector orthogonal to the base; a tilt sensor which detects a tilt angle of the base; and a CPU, wherein the flux gate type magnetic sensor and the Hall element are integrally structured together as a hybrid IC. The thus detected three dimensional magnetic vector is corrected in the light of inclination of the base, so that the direction of the earth magnetism is accurately calculated.

Abstract: 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 X2+y2+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).

Abstract: A system for calibrating an electronic compass for a vehicle of the type employing a Forward and Lateral magnetoresistive magnetic field sensor. As the vehicle changes headings, the system periodically samples and digitally stores the peaks of the sensor outputs. When the stored peaks indicate a minimum change in the output of the sensors, the system microcomputer calculates a “box” surrounding the subscribed arc of heading changes and computes the center of the “box” as the center of the locus of anticipated peaks for all quadrants and shifts the locus (i.e., “box”) to be within the domain of the A/D converter to prevent saturation, which could otherwise occur in the presence of strong remnant magnetic fields in the vehicle. The “box” is updated with each sampling of sensor outputs until the vehicle is eventually headed through all four cardinal compass headings, and the compass is then considered to be fully modeled in the microcomputer.

Abstract: To provide an adjusting method of an electronic azimuth meter capable of properly adjusting the electronic azimuth meter and an apparatus used for the method. According to an adjusting method of an electronic azimuth meter having a magnetic detector, magnetic fields including strong magnetic field for starting adjustment are generated at a magnetic field generating apparatus capable of generating the magnetic field stronger than the geomagnetism by an adjusting magnetic field generating sequence, the electronic azimuth meter for acquiring output data of magnetic sensors by adjusting a data acquisition sequence in correspondence with the magnetic field generating sequence, is arranged in a magnetic field region produced by the magnetic field generating apparatus by the magnetic field generating sequence and an adjusting data acquisition sequence of the electronic azimuth meter is started by step of sensing the strong magnetic field for starting adjustment by the magnetic detector.

Abstract: An arrangement for measuring the direction of the geomagnetic field {right arrow over (B)}E, in the proximity of a magnetic jamming device with a magnetic field direction variable as a function of time, which is distinguished by the fact that at least two magnetic field measuring devices are provided, each of which measures all three vector components of the total magnetic field ({right arrow over (B)}1,{right arrow over (B)}2), the magnetic field measuring devices have a position, ({right arrow over (r)}0,{right arrow over (r)}1,{right arrow over (r)}2) which is invariable as a function of time and is fixed relative to one another and relative to the jamming device, and the measured values can be called up synchronously and can be evaluated according to {right arrow over (B)}E=({right arrow over (B)}1+{right arrow over (B)}2)/2+P·({right arrow over (B)}1−{right arrow over (B)}2), P({right arrow over (r)}0,{right arrow over (r)}1,{right arrow over (r)}2) describing the geometric

Abstract: A method for determining azimuth in well bore hole where the well is being drilled utilizing Measurement-While-Drilling (MWD) equipment, including gravitometer and magnetometer instruments in the presence of an adjacent well. Interference fields introduced by adjacent wells are modeled as a single or series of magnetic dipoles. The interference fields axial interference field IBz is tracked and a position determined where the IBz component is at its maximum, minimum or a zero value. The total magnetic field is then measured at that point and the magnetic inclination and therefrom, the azimuth may be determined. Alternately, the interference field in the x,y plane (IB(x,y)) may be tracked and a position determined where the IB(x,y) component is equal to a minimum, maximum or zero value. The azimuth may then be determined by an alternate numeric or curve fitting methods.

Abstract: A correcting mechanism of an electronic azimuth meter includes a storing unit for storing maximum values and minimum values with regard to magnetic field detecting values by X- and Y-direction magnetic sensors, an updating unit for updating the magnetic field detecting values when newly detected magnetic field detecting values exceed maximum values/minimum values of the storing unit, an azimuth change inducing unit for providing display for inducing continuous change of azimuth of an electronic azimuth meter main body in a range larger than 360 degree, a predicting unit for predicting whether maximum value/minimum value are true when maximum/minimum magnetic field detecting values are not updated during a predetermined time period even by rotating the azimuth meter main body in accordance with induction display and canceling true prediction when maximum value/minimum value are updated and a stop control unit for stopping updating processing when all of maximum values/minimum values in X- and Y-directions are

Abstract: 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 x2+y2+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).

Abstract: An electronic compass system using magnetic signatures to detect a vehicle event which is integrated with an instrument cluster. A vehicle accessory, such as a rear defrost grid, generates a known, consistent, magnetic field of intensity sufficient to cause a static magnetic offset in the electronic compass for each of its' electrical states. This known consistent, magnetic field has a magnetic signature. A magnetic field sensor detects a combination of Earth's magnetic field and the stray magnetic field produced by the vehicle accessory. A controller is coupled to the magnetic field sensor and searches the magnetic field signal for the magnetic signature. The controller then looks up a predetermined correction factor, or uses an algorithm to determine a correction factor, corresponding to the magnetic signature, to eliminate the effect of the static magnetic offset. The controller then displays a heading unaffected by the static magnetic offset.

Abstract: An electronic compass system for eliminating magnetic noise which is integrated with an instrument cluster. A vehicle accessory, such as a stepper motor, also located in the instrument cluster, generates a known, consistent, magnetic field of intensity sufficient to cause a static magnetic offset in the electronic compass for each of its' electrical states. A magnetic field sensor detects a combination of The Earth's magnetic field and this stray magnetic field. A controller uses a predetermined correction factor, corresponding to the electrical state, to eliminate the effect of the static magnetic offset. The controller then displays a heading unaffected by the static magnetic offset.

Abstract: A self calibrating zero compensation circuit for a fluxgate compass comprising a toroidal core; a drive winding coupled to said core, and at least one and preferably two secondary sensing windings coupled to said core comprises a continuously operating demodulator coupled to the sensing windings and an intermittently operated drive signal fed to the drive winding. A microprocessor is coupled to the demodulator output through an analog to digital converter. The microprocessor provides alternatingly to the drive winding a drive signal for a first period of time and prevents transmission of the drive signal for a second, preferably equal period of time. During the second period of time, the sensing windings and the demodulator provide an output signal to said microprocessor representing the zero signal reference. The demodulator output during the first period of time represents the magnetic field signal from the compass.

Abstract: A method for correcting yaw in a DGPS (global positioning system) based guidance system mounted on a vehicle. The method corrects for a yaw induced heading/cross track error due to a DGPS antenna being mounted a significant distance from the point of operation (e.g., the vehicle operator's location, the center of the vehicle, etc.). The method determines a ground track of a vehicle using a DGPS system and a coupled antenna mounted on the vehicle. A heading of the vehicle is also determined using a compass mounted on the vehicle. The heading and the ground track are compared to determine whether a difference exits and the magnitude of the difference. Using the difference, the DGPS determined position is adjusted to be the position of the operator/center of the vehicle. Using this guidance information, an indication is generated operable for directing the vehicle to maintain a desired ground track.

Abstract: An electronic compass is described for use in vehicles. The compass employs a magnetoresistive sensor for sensing the earth magnetic field and the sensor is operated in alternate set/reset bias modes. In a first embodiment, the compass is provided with deviation compensation by a closed loop system including measurement of the sensor output signals and an offset current strap for nullifying the vehicle deviation field. In a second embodiment, deviation compensation is provided by operation in an initial calibration mode and by operation in a normal compensation mode to adjust compensation, as needed, on a long term basis during normal operation of the compass. In the initial calibration mode, while the vehicle is being driven, the signal peak values are adjusted to a nominal earth field level by changing the offset current. Then, compensating signal reference values for each axis are determined as each peak for that axis is determined.

Abstract: A technique for determining a gyro zero voltage is provided. A gyroscope ("gyro") is installed in an automobile as a component of an on-board navigation system. The gyro outputs a voltage representing an angular velocity of the vehicle. The gyro output voltage representing zero angular velocity ("gyro zero voltage") is determined by first determining when the vehicle is stationary based upon the amount of noise in the output voltage of the gyro. When the vehicle is determined to be stationary, the gyro zero voltage is measured.

Abstract: A rearview mirror assembly is disclosed for use in a vehicle that includes a mirror housing, a mounting structure for pivotally mounting the mirror housing to the vehicle such that the mirror housing may be both vertically and horizontally tilted, a compass sensor disposed in the mirror housing and coupled to a compass processing circuit, and a tilt detector for detecting when the mirror housing has been tilted from a prior position and for generating and transmitting a tilt detection signal to the compass processing circuit. The compass processing circuit may then respond to the reception of the tilt detecting signal by compensating the compass reading and/or display or by recalibrating the compass.