Abstract: An electronic vehicle accessory includes a non-volatile memory, and a controller coupled to the non-volatile memory and to a speed sensor of the vehicle for receiving speed data representing the vehicle's current speed. The controller determines when the vehicle's current speed falls below a predetermined threshold and stores variable data in the non-volatile memory when the vehicle's speed is below the predetermined threshold. The electronic vehicle accessory may be an instrument panel, an electronic compass, and/or a mini-trip computer, which may be housed in an overhead housing. By storing variable data in the non-volatile memory as a function of the vehicle's speed, the present invention ensures that the most up-to-date data is stored in the non-volatile memory before the vehicle's ignition is turned off while eliminating excessive stores that shorten the lifetime of the non-volatile memory.

Abstract: A Micro-Powered Flux-Gate Magnetometer is provided for measuring the strength and direction of external magnetic fields. The magnetometer includes a saturable core inductor, or flux-gate positioned in an area where the magnetic flux due to external magnetic fields will enter the inductor core and alter the inductance of the coil. The flux-gate inductor is driven by an alternating input signal sufficient to magnetically saturate the inductor core during each cycle. A saturation detecting circuit determines when the flux-gate core reaches saturation, and provides an saturation output signal indicating when, relative to the input signal, the core reaches saturation on each cycle of the input waveform. A comparison circuit compares the saturation signal and the alternating input signal and measures a propagation delay through the flux-gate inductor. Finally, an output circuit provides an analog output voltage signal proportional to the propagation delay through the flux-gate inductor.

Abstract: 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.

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 calibration 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 magnetic detection apparatus is disclosed, the size and cost of which can easily be reduced and with which excellent sensitivity can be obtained. The magnetic detection apparatus according to the present invention has a magnetic sensor formed by winding a coil around a magnetic member, wherein change in a response waveform of an electric current allowed to flow in the coil of the magnetic sensor occurring when time-varying voltage is applied to the coil is detected. Since the response waveform of the electric current allowed to flow in the coil is changed in accordance with the intensity of an external magnetic field, the external magnetic field can be detected.

Abstract: An electronic audio/visual direction indicator for underwater or other types of navigation which gives unobtrusive and continuous directional feedback without the need for manual manipulation.

Abstract: A tri-axial fluxgate magnetometer and housing therefor that includes elements which facilitate a small sized, relatively low cost magnetometer assembly without sacrificing accuracy and reliability. The assembly includes a unitary sensor substrate capable of orthogonally positioning each of the three fluxgate axes and their respective coils and sensors. The assembly positions the unitary substrate on a circuit board that contains the appropriate harmonic amplifiers, phase detectors, and integrators for signals from each of the three fluxgate axes. A second circuit board positioned parallel to, but apart from, the first, incorporates an appropriate frequency oscillator, frequency divider, and, if necessary, an appropriate voltage regulator. The circuit boards, positioned in parallel as described, are mounted to an end plate that incorporates a signal/control connector and which positions and holds the components of the magnetometer assembly in a generally rectangular configuration.

Abstract: An electronic audio/visual direction indicator for underwater or other types of navigation which gives unobtrusive and continuous directional feedback without the need for manual manipulation.

Abstract: Digital logic comprising a high speed analog to digital converter, a high speed analog to digital converter, a digital multiplier, and an infinite impulse response filter and decimation circuit are used to digitize a magnetic signal that is subsequently processed by magnetic data processing algorithms. The high resolution digital to analog converter is directly incorporated in a feedback loop of a magnetometer sensor, and an expensive precision analog to digital converter is replaced by a less expensive, lower power digital to analog converter. The improvement provided by the present invention includes a high speed analog to digital converter coupled between the oscillator and a first input of a multiplier, and a second analog to digital converter that is coupled between the sense coil of the sensor and a second input of the multiplier. The output of the multiplier is coupled to an infinite impulse response filter and decimation circuit that produces the digital output signal from the magnetometer.

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 calibration 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 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 calibration 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: Process for compensating a magnetic interference field in a vehicle having a navigation installation. During a calibration run for initial compensation, a first set of interference field parameters is determined from the measurements of the magnetic field probe (interference field vector V1, axes a, b of the elliptical locus curve E1, oblique position) and transformed onto points of a circular locus curve with the radius a about the origin (0); the distance from the origin (0) and the angle are calculated for each pair of measurements. The calculated radius values and the circularly transformed pairs of measurements (MP) are averaged and entered in their appropriate memory cell in a segmented memory for 360.degree. with a plurality of memory ceils (predetermined angular region). Variant 1: for each segment, the radius difference (.DELTA.

Abstract: A geomagnetic direction sensor has a substrate, at least two magneto-resistive effect devices and a coil for generating the bias magnetic field. The substrate retains shape symmetry when rotated through 90.degree. and includes plural magnetic cores for converging the geomagnetism. The magnetic cores are arrayed circumferentially of the substrate and interconnected with one another by a non-magnetic material. At least two magneto-resistive effect devices are provided in register with the magnetic gaps so as to be substantially at right angles to one another and to the direction of the magnetic field of the geomagnetism in the magnetic gap region. The substrate also includes a coil for generating a bias magnetic field for impressing a bias magnetic field to each of the magneto-resistive effect devices.

Abstract: An apparatus for mounting a magnetometer including a frame and a platform mounted for rotation within the frame. The magnetometer and one or more counterweights are mounted within the platform such that gravity acting on the counterweights maintains the magnetometer in a horizontal orientation. A first coil is coupled in parallel with the magnetometer and is wound around the perimeter of the platform. A second coil is wound around the perimeter of the frame such that the first and second coils form an air core transformer. The second coil terminates in two terminals which provide a communication port. A sensing circuit coupled to the port electrically communicates with the magnetometer via the inductive coupling provided by the transformer. In alternative embodiments, each of the first and second coils is implemented as two coils with associated diodes.

Abstract: A device for determining the orientation of a vehicle includes a magnetic field sensor (3) which is arranged in the vicinity of a ferromagnetic outer wall of the body of the vehicle and which is rigidly connected to the wall. External magnetic fields could unpredictably magnetize the wall portion (1) of the body, in the vicinity of which the magnetic field sensor (3) is provided, so that the measurements would become inaccurate. In order to achieve a substantial reduction of these adverse effects of external magnetic fields, the relevant wall portion is magnetically stabilized, preferably by including it in a magnetic circuit which also includes at least a magnet (11; 23, 27).

Abstract: An electronic stereo clino-compass which can be targeted directly at the discontinuous surface of a soil layer and in particular, where the running direction (azimuth) and inclination of a target surface can be measured quickly and easily without the necessity of specialized knowledge.

Abstract: An apparatus for determining the direction of a magnetic field is provided with a plurality of magnetically sensitive components arranged with their sensing axes equally spaced around a circular configuration. Each magnetically sensitive component is capable of providing a binary signal representing the resolution of the direction of a magnetic field along one of the two possible directions aligned with its sensing axis. The binary signals from each of the plurality of magnetically sensitive components is arranged to provide a grey code output that can be used to directly determine the direction that the apparatus is pointing toward. The compass points that can be resolved is related to the number of magnetically sensitive components by a ratio of two to one. For example, the use of four magnetically sensitive components permits the resolution of eight compass directions.

Abstract: A triaxial AC magnetic field analyzer/dosimeter instrument measures the field strength of three mutually orthogonal AC magnetic field components at a plurality of different frequencies in a frequency range of interest and stores corresponding data which may be processed to indicate the field strength at each of the frequencies and/or the sum of the field strengths over the frequency range of interest. The instrument is computer controlled and comprises three measurement channels corresponding to respective magnetic field components, each channel including a sensor coil, a clock controlled, switched capacitor, bandpass filter, and a TRMS detector. The passband of each filter is swept across the desired frequency range by a varying frequency clock.

Abstract: The Geomagnetic Orientation Sensor is a device used to determine the orientation of objects with respect to the magnetic field surrounding the earth. The sensor may also be used to determine orientation with respect to a local magnetic field, a local attenuation of the earth's magnetic field, or used as a pointer to track moving magnetic potentials. The device incorporates three mutually orthogonal Hall effect generator pairs, the output voltage differentials of which are directly proportional to the magnetic field intensity and direction relative to each generator pair. A set of three differential amplifier circuits detect and amplify the small voltages induced by the geomagnetic field. The resulting voltages, V.sub.X, V.sub.Y, and V.sub.Z, are multiplied by a constant to acquire three orthogonal angular displacement values with a range of 0 degrees to 180 degrees.

Abstract: An electronic audio/visual direction indicator for underwater or other types of navigation which gives unobtrusive and continuous directional feedback without the need for manual manipulation.

Abstract: A shifting compensation circuit which employs a ranging circuit having a variable direct voltage source, to compensate for abnormally large vehicle magnetic fields. A ranging circuit is coupled between a microcomputer and a flux-gate. The microcomputer monitors the output of an integrator through a buffer amplifier to minimize variations in the integrator output caused by temperature variations, and directs the variable direct voltage source to add a direct voltage reference, in opposition to the vehicle's magnetic field signal and within the output voltage range of the integrator, to the output signal of the flux-gate, such that the combination of the two signals is within the output voltage range of the integrator for all vehicle headings.

Abstract: A magnetic sensor mounting assembly embodying the present invention includes a base plate having cradles for pivotally receiving and adjustably locking a sensor supporting platform thereto. The base plate can be attached to an existing rearview mirror mounting member. The assembly further includes a cover providing access for adjusting the platform to a horizontal position and for allowing the rearview mirror mounting stem to extend therethrough.

Abstract: A solid-state omni range incline-compass having a gravity sensor and a geomagnetic flux sensor provided on, each of three orthogonal axes established on a moving body a unit for generating a mathematic horizontal plane by making a gimbal mechanism as a mathematic equation on the basis of outputs from the gravity sensor located on each of the three orthogonal axes and a unit for calculating an azimuth angle of the moving body on the basis of two orthogonal axes on the mathematic horizontal plane.

Abstract: An electronic compass (10) having at least two sense windings (11, 12) is mounted in a vehicle. The outputs (x(h), y(h)) of the windings are measured for a number of compass directions (headings). From this data an error difference angle (.phi.), from a nominal angle, which actually exists between the output windings is calculated. Preferably a look-up table (21, 39) is created relating actual compass heading (h) to measured sense winding outputs by utilizing the calculated error difference angle (.phi.). This table is then utilized for calculating actual compass heading based on actual measured sense winding outputs. The calculated error angle (.phi.) can also be used to calibrate the compass without creating a look-up table. The calibrated compass compensates for misalignment of the sense windings and provides a more accurate electronic compass without requiring creating a calibration table by orienting the compass in a very large number of exactly known directions.

Abstract: A position sensor has a ring of a material of high permeability that is floated on a liquid within a hermetically sealed toroid, so as to hold the ring in a horizontal position. Exciting coils are distributed uniformly about the ring to enclose the cross section thereof, and receiving coils are distributed uniformly about the circumference of the ring.

Abstract: A compass wherein positional information regarding a predetermined terrestrial location is stored; present time, corresponding to the terrestrial location whose positional information is stored, is measured and displayed; and constellation data is stored. A geomagnetism-detector is provided for detecting the direction of geomagnetism and for deriving azimuthal data therefrom. A constellation data display device is provided for reading out stored constellation data in accordance with the derived azimuthal data, the stored positional information, and the measured present time, and for displaying the readout constellation data.

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. 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.

Abstract: A flux-gate sensor orientation method which minimizes display jitter in electronic compasses which employ an n-point display or which calculate headings using the arctangent method. The method entails orienting the flux-gate sensor in a direction of plus or minus .+-.360.degree./2n relative to actual magnetic direction, so that instability points occur at display point boundaries. The method of the present invention finds application in microprocessor-based electronic compass systems but also makes possible the construction of a simple electronic compass employing small scale integration logic instead of a microprocessor.

Abstract: A Hall effect device with appropriate electronic circuits can sense a very weak magnetic field and it is thus useful to be used as a compass. It can also be configured as two or more directional indicators as desired.

Abstract: A thin film magnetic fluxgate compass having a supporting substrate on which a layer of high permeability material, and at least two layers of nonmagnetic conducting materials are deposited; the high permeability material is fabricated to form a magnetic core or cores; a portion of the non-magnetic conducting layers is fabricated to form an excitation coil, magnetically coupled to the core or cores, which is to be connected to a pulse generator; the remainder of the non-magnetic conducting layers is fabricated into at least two sensing coils, or two pairs of sensing coils wound around the core or cores in opposite pairs, which are used to generate output signals. A method for the fabrication of the thin film compass is disclosed. The compass can be used for the determination of the direction of the geomagnetic field, and, because of its miniature size, for instrumentation that requires a very small magnetic field sensor.

Abstract: An electronic compass can store azimuth data of points to be passed by a user in a plurality of registers, and the stored azimuth data are sequentially displayed on a display device every time an external operation switch is operated. The compass includes a magnetic sensor for detecting a geomagnetism, thereby obtaining north azimuth data on the earth. The north azimuth data obtained by the magentic sensor is displayed simultaneously with the stored azimuth data. Therefore, the user can know at each point a direction to go on the basis of the two displayed azimuth data, i.e., the stored azimuth data, and the north azimuth data on the earth.

Abstract: An improved fluxgate instrument for measuring heading as well and pitch and roll angles is disclosed. A plurality of fluxgate sensors are continuously energized with a DC feedback signal derived from the reading of each sensor so as to minimize magnetic cross-coupling between the sensors. In addition while two sensors are gimbally mounted to sense the horizontal components of the earth's magnetic field, the vertical field is sensed by two sensors strapped down relative to the instrument casing for sensing the earth's vertical magnetic field in order to compensate for latitude. Finally, sine and cosine coils surround the gimbally mounted sensors and generate AC fields which are sensed by the gimbally mounted sensors and are used to calculate the pitch and roll angles.

Abstract: An electronic compass for use in a vehicle includes compensation for attaining a high degree of accuracy without operator intervention or the need to drive the vehicle in a deliberate circular path. An automatic method for accurately determining maximum and minimum voltage values from a flux gate sensor having orthogonal sensing windings is provided that operates continuously to adjust for required changes in both the offset and gain compensation factors. The flux gate sensor is further mounted within the vehicle such that the axis of one of the sensing windings is positioned approximately 45.degree. with respect to the vehicle's longitudinal direction. The angled mounting of the sense winding axis results in strong sensing signals when travelling on most roads. The electronic compass further provides visual representation on the outer peripheral segments of an alphanumeric display to prompt the operator to drive in a circle during a manual compensation mode.

Abstract: The invention is a motion sensitive, battery operated compass utilizing Hall effect digital switches to sense the orientation of the compass in relation to the earth's magnetic field. A vibration sensing circuit serves to turn the compass on when it is in motion, and to turn the compass off when it is at rest. A chopper circuit is provided to interrupt the power supply at a predetermined frequency to conserve battery power. The Hall effect switches are mounted in a known relationship to a rotating magnet allowing selection and decoding of the sensor outputs to provide signals for the operation of an alpha numberic display.

Abstract: An apparatus and method for measuring a forward direction of a vehicle in which to derive a coordinate position of a center (O.sub.x, O.sub.y) of a directional circle derived from an output of a geomagnetic direction sensor after a magnetization on a vehicle body occurs, the magnetization on the vehicle body is determined from the output of the geomagnetic direction sensor installed in the vehicle and each parameter of a peak quantity (X.sub.max, Y.sub.max), peak direction (D.sub.x, D.sub.y), and a center value of an output circle before the present disturbance occurs is calculated, optimum coefficients are selected and set according to each parameter from among the previously derived coefficients, a magnetization quantity is calculated from each parameter and each optimum coefficient using a linear combination technique, and the coordinate position of the center of the output circle after the magnetization on the vehicle body occurs from the derived magnetization quantity.

Abstract: A magnetometer having only a single coil winding for sensing the magnetic field along a single axis. Functionally, the invention comprises an oscillator, an integrator, and a voltage-controlled current source. The oscillator uses a saturating inductor which also serves as the magnetic-field-sensing element. The inductor is driven with a positive voltage and when the current through the inductor exceeds a value which indicates that the core is saturated, the driving voltage switches to an equal-magnitude negative value. This negative drive is maintained until the current again indicates the core to be saturated, at which point the driving voltages switches back to the positive value. With no externally applied field, the inductor current averages to a zero value. An externally applied field helps the core saturate in one direction and hinders it in the other, resulting in a change in average inductor current.

Abstract: Apparatus and method for determining the azimuth (heading), pitch and roll which include a magnetometer-type sensor providing signals measured in three axes relative to a reference frame, and coil elements wound around the magnetometer which selectively impose specific magnetic fields about the sensor. Three axes field components of the magnetic field are measured from the sensor with and without the selective energization of the magnetic coils and stored, from which the azimuth, pitch and roll are calculated. Furthermore, quadrant correction is applied such that a unique reading is produced for all angles through 360.degree. of azimuth, pitch or roll.

Abstract: Disclosed is an electronic magnetic compass which is to be mounted on a small ship and which is reduced in cost and improved in performance. The electronic magnetic compass is provided with an angle sensor interlocked with a compass card so as to produce a code signal at every predetermined angle, a code converter for converting the code signal into a compass indication angle, and a signal conversion circuit for producing a deviation signal indicating a deviation between an azimuth angle signal and an indication angle signal. The compass azimuth measurement is performed with a simple configuration of an open loop system, so that the structure of an encoder for the angle sensor is so simple that the cost can be reduced so much. The azimuth angle signal and the indication angle signal can be automatically calibrated so that the measurement accuracy can be improved.

Abstract: An electronic compass system for determining the heading of an armored vehicle containing a large mass of ferromagnetic material, which system comprises a plurality of sensors, and for real-time computation of the corrections required of actual magnetometer measurements. Part of the values used for the computation are computed in advance, and part in real-time. Some of the computations are based on the perturbation of the earth magnetic field based on an algorithm which takes into account one or two rotational prolate ferromagnetic ellipsoids which have certain dimensions and which are at a predetermined distance from each other either represent the body of an armored vehicle, or when two ellipsoids are used, they represent the hull and turret of a tank.

Abstract: A magnetometer and method for measuring magnetic field strength particularly adapted for use in an electronic flux gate compass. A core of magnetic material in the shape of a toroid is coupled to a drive coil and to two sense coils oriented along orthogonal axes. A current limited, current source coupled to the drive coil periodically saturates the core, drives the core out of saturation at an intermediate current level, and saturates the core again. Each sense coil is coupled to a sense circuit which measures the current in the sense coil induced by the periodically changing flux density in the coil resulting from an external magnetic field coupled to the sense coil, produces a dc feedback signal to cancel out the external magnetic field, and provides the dc signal as an output representative of the external magnetic field strength along the axis of the sense coil. The dc signal is produced by synchronously detecting the amplified ac current in the sense coil.

Abstract: A digital compass system for use in a wide variety of motor vehicle models, especially in the automotive aftermarket, and including various features which simplify installation and calibration by non-professionals. A knowledge of magnetic direction is not required. During calibration, only true geographic directions are used throughout. While searching for a suitable location within the vehicle to mount the magnetic sensor, the installer is advised by the digital display unit of the system as to whether or not a given location contains excessively strong magnetic components.

Abstract: A magnetic compass calibration system used in areas of magnetic disturbance. The invention allows the aircraft to remain in the hangar or hangar area while the aircraft's compass is compensated. The invention compensates for time variances in ambient magnetic field, as well as magnetic variances caused by hard and soft iron found in the hangar area, ramp area or aircraft.

Abstract: A method of measuring an azimuth by detecting the earth's magnetism by using two perpendicular coils to detect the azimuth according to the outputs of the coils, including the steps of converting the outputs of the coils by multiplying them by a constant so as to vary in a range determined by a reference value, dividing the converted signal by the reference value, and measuring the azimuth at each coil output according to an inverse trigonometric function, with the divided result as a variable. An azimuth measuring apparatus for executing the method is also provided. Thus, the method and apparatus can accurately detect the azimuth and can further detect an error due to a disorder of the earth's magnetism or the inclination of the apparatus.

Abstract: In an electronic compass having a plurality of sensors (1, 2, 3), each reacting to a component of the earth field (Hy), it is desired to prevent errors based on variations in the signal amplification and to improve the accuracy of measurement. In accordance with the invention, three identical sensors (1, 2, 3) are disposed at an angle of 120.degree.. The compass may be used, in particular, for the navigation of vehicles.

Abstract: The effects of non-equal saturation spikes in a magnetic oscillator magnetometer utilizing a magnetic core sensing inductor are compensated by adding the average inductor current to both the high and low current magnitude limits. In particular, each of the current limits is selected to be a fixed current (which is greater than that required to saturate the core) offset by the average current flowing in the core.The effects of magnetic core hysteresis and series resistance between the inductor and its drive sources are compensated by controlling the drive voltage levels so that the time during which the inductor is driven by current in one direction is equal to the time during which it is driven by current in the other direction.

Abstract: Apparatus and method for determining the azimuth (heading), pitch and roll which include a magnetometer-type sensor providing signals measured in three axes relative to a reference frame, and coil elements wound around the magnetometer which selectively impose specific magnetic fields about the sensor. Three axes field components of the magnetic field are measured from the sensor with and without the selective energization of the magnetic coils and stored, from which the azimuth, pitch and roll are calculated. Furthermore, quadrant correction is applied such that a unique reading is produced for all angles through 360.degree. of azimuth, pitch or roll.

Abstract: A roll-independent magnetometer which may be used for example in a towed array magnetometer system comprises a first magnetic field sensor having iso-angular flux sensitivity about a roll axis and a second magnetic field sensor having sensitivity along the roll axis, the arrangement being such that a component of a magnetic field along the roll axis is measured by the second unidirectional sensor and the component of the field lateral to the roll axis is measured by the first sensor. Corrections may be applied for the inclination of the sensor and the angle of dip of the Earth's field. The angle of dip may be measured either in the towing vessel, in the towed body, or provided in look-up tabulated form.

Abstract: A method for determining the direction of the earth field, the north direction and the travelling direction of a vehicle by way of a magnetometer mounted in the vehicle is based on dynamic compensation or updating of interfering field changes. For this purpose, a resultant vector (v.sub.K) is formed from the magnetic field vector (V.sub.M) effective at the magnetometer, the previous hard-magnetic interfering field vector (H.sub.H) and the nominal vector (V.sub.P) determined from the circle diagram (O) of the magnetic field, as interfering field change in accordance with the equation v.sub.K =V.sub.M -v.sub.B -H.sub.H and this vector is weighted with a factor (k<1). The weighted resultant vector (K.times.v.sub.K) is then added to the previous interfering field vector (H.sub.H). Using the new hard-magnetic interfering field vector (H.sub.H'), thus determined, the direction of the earth field is then calculated in known manner and evaluated for navigation.

Abstract: In an azimuth signal generator for an automobile navigation system a change in the rotational rate of an inertia rotary member, which has its rotary shaft held vertically and is driven at substantially a constant speed, is detected as a direction changing rate of the car and the direction changing rate is integrated by an integrator to obtain an azimuth signal. On the other hand, the azimuth of geomagnetism is detected by a geomagnetic azimuth sensor and a correcting signal is produced based on an error between the azimuth signal and the geomagnetic azimuth signal. The correcting signal is negatively feedback to the input side of the integrator, causing the azimuth signal to follow the geomagnetic azimuth signal.

Abstract: The present invention is a magnetic field measuring system and method for generating a magnetic field signal representative of the Earth's undistorted magnetic field at any given spatial location over a measurement period. The measured undistorted magnetic field is substantially independent of distortions due to any magnetically susceptible material within the measuring system and is substantially independent of internal magnetic fields generated by magnetic field sources within the system.