JP2008107102A - Electronic compass and azimuth measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic compass and an azimuth measuring method capable of calibrating easily a three-dimensional azimuth measurement error, and measuring precisely a three-dimensional azimuth. <P>SOLUTION: This electronic compass 10 has a geomagnetic azimuth detector 11 having three magnetic detection parts, an azimuth operation means 32 for calculating the attitude azimuth of a measuring object from triaxial component data, a magnetic field determination means 31 for determining normality/abnormality of a magnetic field, and a calibration means 33 for calibrating the center of an azimuth sphere drawn by the triaxial component data by an attitude change of the measuring object when determined to be abnormal by the magnetic field determination means 31. The calibration means 33 includes a center operation means 331 for operating the center of the azimuth sphere from at least four triaxial component data, and a least-squares-method operation means 332 for calculating the azimuth sphere by using a least-squares method from a prescribed number of the triaxial component data. The azimuth operation means 32 calculates and outputs the attitude azimuth successively by using the center of the azimuth sphere calibrated by the calibration means 33, when determined to be abnormal by the magnetic field determination means 31. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electronic compass and an azimuth measuring method for detecting a three-dimensional geomagnetism and measuring a three-dimensional azimuth of a measurement object, and in particular, azimuth measurement caused by a disturbance magnetic field due to magnetization of the measurement object. The present invention relates to an electronic compass that corrects errors and a direction measurement method.

Conventionally, an electronic compass has been developed that detects geomagnetism in two axial directions and measures the two-dimensional orientation of a measurement object.
In such an electronic compass, the biaxial component of the geomagnetic vector is detected, and the orientation is displayed with reference to the center of the orientation circle. This azimuth circle is a circle drawn by biaxial component data by turning the object to be measured. In order to measure the azimuth, it is necessary to first obtain the center of the azimuth circle. And when an azimuth | direction circle has shifted | deviated, it is necessary to calibrate this.

  For example, in Cited Document 1, a bisector connecting two pieces of data is calculated, classified into a plurality of sectors according to the slope of the calculated vertical bisector, and data is stored in all sectors. Then, a technique for calculating the center of the circle by calculating the point at which the sum of squares of the distance from the representative of each sector is minimum is disclosed.

Also, in Cited Document 2, a parameter for determining an ellipse as an output circle using the least square method is obtained based on a predetermined number of measurement values obtained by a geomagnetic azimuth sensor. It is stated that the center is requested.
However, these methods have a problem that calibration of the azimuth circle takes time and accurate azimuth measurement cannot be performed appropriately.

Reference 3 discloses an electronic compass having a calibration unit that calibrates the center of the azimuth circle, which includes a center calculation unit and a least-squares calculation unit. According to this, the center of the azimuth circle can be calibrated quickly by the center computing means, and more accurately, calibration can be performed by the least square method computing means in the long term.
The details of the azimuth circle are described in Citation 3.

However, the above-mentioned electronic compass can only measure the orientation by detecting the biaxial component of the geomagnetic vector and can only measure the orientation in two dimensions. Therefore, for example, the electronic compass cannot be mounted on a portable electronic device or the like to perform three-dimensional orientation measurement.
In order to perform such a three-dimensional azimuth measurement, it can be considered that three magnetic detectors (magnetic sensors) are arranged in three orthogonal directions to detect a geomagnetic component.

  However, when calibrating the measurement error, it is necessary to obtain the center of a three-dimensional “azimuth sphere” as shown in FIG. 6 instead of obtaining the center of the azimuth circle described above. Here, the azimuth sphere is a sphere drawn by three-axis component data by a three-dimensional posture change of the measured object, and the center thereof is a reference for azimuth measurement.

  In obtaining the center of this azimuth sphere, when trying to use the same method as the invention of Patent Document 3, the azimuth circles in three planes orthogonal to each other are obtained, the respective centers are obtained, and these are overlapped. You have to find the center of the azimuth sphere. Then, there is a problem that it becomes a very complicated calibration method.

JP-A-6-58758 JP-A-9-68431 JP 2006-234581 A

  The present invention has been made in view of such conventional problems, and can easily calibrate a three-dimensional azimuth measurement error and can accurately measure a three-dimensional azimuth. It is intended to provide an orientation measurement method.

In the first invention, triaxial component data (X1, Y1, Z1), (X2, Y2, Z2),... (Xi, which are orthogonal to the triaxial components of the geomagnetic vector that changes with the orientation of the measured object. Yi, Zi), a geomagnetic bearing detector having three magnetic detectors arranged orthogonally,
Azimuth calculating means for calculating the posture azimuth of the measured object from the three-axis component data (Xi, Yi, Zi);
Magnetic field determination means for determining normality / abnormality of the magnetic field;
Calibration means for calibrating the center of the azimuth sphere drawn by the three-axis component data (Xi, Yi, Zi) according to the change in posture of the object to be measured when the magnetic field determination means determines that it is abnormal;
The calibration means includes center calculation means for calculating the center of the azimuth sphere from at least four of the three-axis component data (Xi, Yi, Zi),
A least-squares calculation means for calculating the azimuth using a least-squares method from a predetermined number of the three-axis component data (Xi, Yi, Zi),
The azimuth calculating means outputs the posture azimuth calculated from the three-axis component data (Xi, Yi, Zi) when the magnetic field determining means determines normal, and when the magnetic field determining means determines abnormal, The electronic compass is characterized in that the posture azimuth is calculated and output sequentially using the center of the azimuth calibrated by the calibrating means.

Next, the effects of the present invention will be described.
In the electronic compass, only when it is determined that the magnetic field determination means is abnormal and the center of the azimuth sphere needs to be calibrated, the center calculation means uses at least four three-axis component data (Xi, Yi, Zi). Since the center of the azimuth sphere is calculated, and the azimuth is calculated by the azimuth calculating means using the center as the provisional center of the azimuth sphere, it is possible to display an azimuth with relatively little error in a short time.

Thereafter, the least square method computing means obtains the center of the azimuth sphere from a predetermined number of three-axis component data, and the azimuth computing means obtains the azimuth, so that a highly accurate azimuth can be finally displayed. Accordingly, it is possible to measure an accurate three-dimensional azimuth while suppressing generation of a measurement error due to magnetization.
As described above, the center calculation means in the calibration means calculates the center of the azimuth sphere from the four three-axis component data (Xi, Yi, Zi), thereby accurately correcting the three-dimensional azimuth measurement error in a short time. The center of the azimuth sphere can be calibrated.

  As described above, according to the present invention, it is possible to easily calibrate a three-dimensional orientation measurement error and provide an electronic compass capable of accurately measuring a three-dimensional orientation.

In the second invention, three-axis component data (X1, Y1, Z1), (X2, Y2, Z2) orthogonal to the three-axis components of the geomagnetic vector that changes with the orientation of the measured object, (Xi, Yi, Zi) is detected as a triaxial component data detection step;
An azimuth calculation step for calculating the posture azimuth of the measured object from the three-axis component data (Xi, Yi, Zi) detected in the three-axis component data detection step;
A magnetic field determination step for determining normality / abnormality of the magnetic field;
A calibration step for calibrating the center of an azimuth sphere drawn by the three-axis component data (Xi, Yi, Zi) according to a change in posture of the measured object when the magnetic field determination step is determined to be abnormal;
Have
The calibration step includes a center calculation step for calculating the center of the azimuth sphere from at least four of the three-axis component data (Xi, Yi, Zi);
A least-squares method calculating step for calculating the azimuth sphere using a least-squares method from a predetermined number of the three-axis component data (Xi, Yi, Zi),
The azimuth calculating step outputs the posture azimuth of the measured object calculated from the three-axis component data (Xi, Yi, Zi) when the magnetic field determining step is determined to be normal, and the magnetic field determining step is abnormal. In the azimuth measuring method, the posture azimuth is calculated and output sequentially using the center of the azimuth sphere calibrated in the calibration step.

  ADVANTAGE OF THE INVENTION According to this invention, the calibration of a three-dimensional azimuth | direction measurement error can be performed easily, and the azimuth | direction measurement method which can measure a three-dimensional azimuth | direction accurately can be provided.

  In the first invention (invention 1) and the second invention (invention 5), examples of the object to be measured include portable electronic devices such as cellular phones. The orientation orientation is a three-dimensional orientation determined by the orientation of the object to be measured, and corresponds to, for example, a three-dimensional orientation in which the vertical direction of the display screen of the mobile phone is oriented.

Moreover, it is preferable that the said magnetic detection part has a detection accuracy of +/- 3mG (Claim 2).
In this case, the three-axis component of the geomagnetic vector can be detected with sufficient accuracy. Thereby, it is possible to accurately measure the posture orientation. In addition, since the center of the central sphere can be accurately calibrated, accurate measurement can be ensured.
Considering that the magnitude of geomagnetism is 300 to 350 mG, when the azimuth is shifted by 1 °, the detection error in the specific azimuth is 3 to 4 mG. Therefore, when the magnetic detection unit has a detection accuracy of ± 3 mG, a detection accuracy of ± 1 ° can be obtained as the direction detection.

In addition, it is preferable to perform azimuth measurement at intervals of 1 msec or less (claims 3 and 6).
In this case, the calibration means can calibrate the center of the bearing sphere sufficiently accurately. In other words, when performing calibration, it is necessary to acquire four or more triaxial component data and obtain the center of the azimuth sphere, but the fact that azimuth measurement can be performed at intervals of 1 msec or less means that the triaxial component This means that a large number of data can be acquired in a short time, and the center of the azimuth sphere can be calibrated in a short time. Therefore, accurate calibration can be performed, and accurate three-dimensional posture orientation can be detected.
Considering that the time required to change the posture of the object to be measured by 1 ° by normal human movement is about 1 msec or more, if azimuth measurement can be performed at intervals of 1 msec or less, 1 ° A change in posture can be sufficiently detected.

Moreover, it is preferable that the said magnetic detection part is a magnetoimpedance magnetic sensor.
The magneto-impedance magnetic sensor is very small, and the geomagnetic orientation detector can be miniaturized. Therefore, it becomes easy to incorporate the geomagnetic orientation detector in, for example, a portable electronic device. In addition, since the magneto-impedance magnetic sensor can be a highly sensitive magnetic sensor, the triaxial component data (Xi, Yi, Zi) of the geomagnetic vector can be measured with particularly high accuracy. As a result, it is possible to accurately detect the three-dimensional posture orientation and to accurately calibrate the three-dimensional orientation measurement error in the calibration means.

An electronic compass and an orientation measurement method using the same according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the electronic compass 10 of this example includes the following geomagnetic azimuth detector 1, azimuth calculation means 32, magnetic field determination means 31, and calibration means 33.

  As shown in FIG. 2, the geomagnetic azimuth detector 1 has three-axis component data (X1, Y1, Z1), (X2, Y2, Z2) orthogonal to the three-axis components of the geomagnetic vector that changes with the orientation of the measured object. ,..., (Xi, Yi, Zi), and three magnetic detectors 11x, 11y, 11z arranged orthogonally.

The azimuth calculating means 32 calculates the posture azimuth of the measured object from the three-axis component data (Xi, Yi, Zi).
The magnetic field determination means 31 determines normality / abnormality of the magnetic field.
When the magnetic field determination unit 31 determines that the magnetic field determination unit 31 is abnormal, the calibration unit 33 calibrates the center of the azimuth sphere (FIG. 6) drawn by the three-axis component data (Xi, Yi, Zi) according to the posture change of the measured object. FIG. 6 is a diagram showing how the azimuth sphere shifts due to a disturbance magnetic field, etc., where the sphere represented by the solid line is the azimuth sphere before the shift, and the sphere represented by the broken line is It is an azimuth sphere after shifting.

The calibration means 33 includes a center calculation means 331 for calculating the center of the azimuth sphere from at least four of the three-axis component data (Xi, Yi, Zi), and a predetermined number of the three-axis component data (Xi, Yi, Zi). And a least square method computing means 332 for calculating the azimuth sphere using the least square method.
When the magnetic field determination means 31 determines that the magnetic field determination means 31 is normal, the azimuth calculation means 32 outputs the posture direction calculated from the triaxial component data (Xi, Yi, Zi). Using the center of the azimuth sphere calibrated by the calibration means 33, the orientation azimuth is calculated and output sequentially.

  Specifically, as shown in FIG. 1, the electronic compass 10 of the present example has triaxial component data (X1, Y1, Z1) in which the sensitivity axes are orthogonally arranged and the X component and Y component of the geomagnetic vector are orthogonal. , (X2, Y2, Z2),... (Xi, Yi, Zi) of the geomagnetic azimuth detector 1 having three magnetic detectors 11x, 11y, 11z, and the magnetic detectors 11x, 11y, 11z An AD converter 2 that converts an output into a digital signal at a predetermined frequency, a microcomputer 3 that receives the digital signal and calculates the direction of the moving object by software, and a display unit 4 that displays the calculated direction are provided. Yes.

As the geomagnetic azimuth detector 1, a conventional detector in which two coils wound perpendicularly to the permalloy core are used as the magnetic detectors 11x, 11y, and 11z may be used, but the magneto-impedance magnetic sensor is used as the magnetic detector. It is preferable to use magnetic detectors having 11x, 11y, and 11z. A magneto-impedance magnetic sensor (hereinafter referred to as “MI sensor”) is composed of, for example, an amorphous (FeCoSiB) wire having a diameter of 20 μm and a length of 1 mm and a detection coil wound around the wire, and is proportional to the strength of the magnetic field. It is an ultra-compact, high-sensitivity magnetic sensor that outputs an analog voltage. Therefore, as shown in FIG. 2, the geomagnetic orientation detector 1 has two MI sensors arranged at right angles to each other (11x, 11y, and 11z), together with the drive circuit 12, about 3.5 mm in length and about 3 in width. It can be enclosed in a 5 mm IC package.
Further, the magnetic detection units 11x, 11y, and 11z have a detection accuracy of ± 3 mG.

As the AD converter 2, one having a resolution of about 14 bits may be used. Thereby, the azimuth measurement resolution of the measured object can be satisfied, and the signal does not saturate even if the magnetic field around the geomagnetic direction detector 1 due to the magnetization of the measured object becomes larger than the geomagnetism.
The microcomputer 3 determines the center of the azimuth circle when the magnetic field determination means 31 for determining the normality / abnormality of the magnetic field, the azimuth calculation means 32 for calculating the posture azimuth of the measurement object, and the magnetic field determination means 31 determine that the magnetic field determination means 31 is abnormal. And calibration means 33 for calibrating. The calibration unit 33 includes a center calculation unit 331 and a least square method calculation unit 332. The magnetic field determination unit 31, the azimuth calculation unit 32, and the calibration unit 33 are configured by software.

In the three magnetic detectors 11x, 11y, and 11z, triaxial component data (Xi, Yi, Zi) are sequentially acquired at predetermined time intervals and input to the microcomputer 3 via the AD converter 2. The magnetic field determination means 31 of the microcomputer 3 uses, as a threshold value, the sum of the squares of the change amounts of each component (ΔX ² + ΔY ² + ΔZ ² ) from two triaxial component data acquired at a predetermined time interval. Compare. Here, the threshold value can be set to 100 mG, for example. This 100 mG is a threshold that can be derived in consideration of the measurement accuracy of the triaxial component data.
That is, the magnetic field determination means 31 determines whether or not the following inequality holds, and determines that the above is true if it is true, and judges that it is normal if it is not true.

The operation of the magnetic field determination unit 31 will be described with reference to the flowchart of FIG. In step S11, triaxial component data (Xi, Yi, Zi) is acquired, ΔX ² + ΔY ² + ΔZ ² is calculated in step S12, the magnitude relationship with 100 mG is compared, and ΔX ² + ΔY ² + ΔZ ² ≧ 100 mG At this time, it is determined as Y (abnormal), and when ΔX ² + ΔY ² + ΔZ ² <100 mG, it is determined as N (normal). If determined to be abnormal, the process proceeds to step S13.

In step S13, the coordinates of the center of the azimuth sphere are obtained using four or more three-axis component data (Xi, Yi, Zi) stored in the microcomputer 3 for a predetermined time. Here, four three-axis component data are used, and the respective three-axis component data are (X1, Y1, Z1), (X2, Y2, Z2), (X3, Y3, Z3), (X4, Y4, Z4). Will be described.
The above three-axis component data is substituted into the sphere equation shown in the following (Equation 2) to obtain four equations, and by solving these simultaneous equations, the center of the azimuth sphere after the shift (a, b, c) ). In (Expression 2), R is the radius of the azimuth sphere.

However, here, in order to reduce the variables, the origin is moved to the fourth point (X4, Y4, Z4) in the four three-axis component data, and the coordinates of the four points are respectively (X1-X4, Y1-Y4, Z1-Z4), (X2-X4, Y2-Y4, Z2-Z4), (X3-X4, Y3-Y4, Z3-Z4), (0, 0, 0).
These coordinates are newly defined as (X1, Y1, Z1), (X2, Y2, Z2), (X3, Y3, Z3), (0, 0, 0). These coordinates are newly substituted into the equation of the sphere shown in the following (Equation 3), and the following three equations shown in (Equation 4) are obtained.

  When these equations are rewritten into a matrix, the following (Formula 5) is obtained.

(Equation 5) becomes (Equation 7) below.

The following (Equation 8) is obtained by multiplying both sides of (Equation 7) by the inverse matrix M ⁻¹ .

Then, by obtaining this inverse matrix M ⁻¹ , the solutions (a ′, b ′, c ′) of the simultaneous equations can be calculated.
Then, the coordinate origin is returned to the original, and the solution (a, b, c) is obtained by (a ′ + X4, b ′ + Y4, c ′ + Z4).

Next, in step S14, a three-dimensional shift amount (Δa ² + Δb ² + Δc ² ) ^{1 /} between this solution and the center coordinates (a, b, c) of the azimuth sphere set from the beginning. ² is compared with a predetermined threshold. For example, the threshold is 20 mG. That is, it is determined whether or not the following inequality (Equation 9) holds. This 20 mG is a threshold value that can be derived in consideration of errors due to the geomagnetic measurement environment. Further, since the detection accuracy of the MI sensor is ± 3 mG, the amount of deviation 20 mG can be sufficiently detected.

If the above inequality is satisfied, it is determined as abnormal and the process proceeds to the calibration means 33. If the inequality is not satisfied, it is determined as normal and the process proceeds to the direction calculation means 32.
Then, the calibration means 33 resets the center coordinates (a, b, c) of the azimuth sphere that were originally set to the newly obtained center coordinates of the azimuth sphere.
Then, the azimuth calculation is performed.

The function of the operation of the central calculation means 331 is performed by software according to the flowchart of FIG. This flowchart is activated when the magnetic field determination means 31 determines that there is an abnormality. In step S21, a data point (Xi, Yi, Zi) is acquired, and in step S22, the data is sequentially stored. Next, in step S23, four data points separated from each other by a predetermined distance or more are extracted. Here, as a condition of data points that are separated by a predetermined distance or more, for example, the distance between the three data points is 200 mG or more away from each other, and the distance from the plane that the fourth data point is determined by the three data points is, for example, It can be set in a state of being separated by 50 mG or more.
Next, in step S24, the center of the azimuth sphere is obtained from the above four three-axis component data by the calculation method described above, and the result is passed to the azimuth calculation means 32 in step S25.

  The function of the least squares method calculation means 332 is performed by software according to the flowchart of FIG. This flowchart is activated simultaneously with the center calculation means 331 when the magnetic field determination means 31 determines that there is an abnormality. In step S31, a data point is acquired, and in step S32, the data point is sequentially stored. Next, in step S33, a predetermined number of data points are taken out, and in step S34, an azimuth sphere is estimated by a least square method calculation, and the center position (a, b, c) of this azimuth sphere is calculated. Here, the predetermined number of data points to be extracted is 40. The center position (a, b, c) obtained here is transferred to the azimuth calculating means 32 in step S35.

  The calculation of the center position (a, b, c) by the least square method calculation means 332 requires a certain amount of time until a predetermined number of data points are collected, and is completed later than the center calculation means 331. As shown in FIG. 1, when the center position (a, b, c) data is passed from the least square method calculator 332, the azimuth calculator 32 replaces this with the center position of a new azimuth sphere, The azimuth is calculated, and the display unit 4 displays the azimuth with high accuracy.

Further, the calibration means 33 has the center position (a, b, c) of the azimuth sphere determined by the center calculation means 331 and the center position (a, b, c) of the azimuth sphere determined by the least squares calculation means 332. You may further have an average calculating means which calculates the average of.
An accurate azimuth calculation can be performed by calculating the average of the center positions of the azimuth spheres obtained by the two means and using the average value in the azimuth calculation means 32 by the average calculation means.

In addition, the electronic compass of this example can be used for portable electronic devices, such as a mobile telephone, for example. For example, when the portable electronic device is moved three-dimensionally, the calibration by the calibration unit 33 can be performed.
Further, as the operating condition of the magnetic field determining means 31, for example, it can be operated according to conditions such as when a predetermined acceleration occurs or when a telephone call is made.
That is, the geomagnetic azimuth detector 1 continues to acquire the triaxial component data and stores the data in the memory, but the unused data is sequentially deleted. In the magnetic field determination means 31, when the above operating conditions are satisfied, the data can be compared retroactively to predetermined past data to determine whether the magnetic field is normal or abnormal. The predetermined acceleration can be detected by installing an acceleration sensor on the measured object. In addition, this acceleration sensor can also employ a small and highly accurate sensor using an MI sensor.

Next, the function and effect of this example will be described.
In the electronic compass 10, only when it is determined that the magnetic field determination unit 31 is abnormal and the center of the azimuth sphere needs to be calibrated, the center calculation unit 331 uses at least four three-axis component data (Xi, Yi, Zi). Since the center of the azimuth sphere is calculated and the azimuth is calculated by the azimuth calculating means 32 using the center as the temporary center of the azimuth sphere, it is possible to display an azimuth with relatively little error in a short time.

Thereafter, the least square method computing means 332 obtains the center of the azimuth sphere from a predetermined number of three-axis component data, and the azimuth computing means 32 obtains the azimuth, so that a highly accurate azimuth can be finally displayed. Accordingly, it is possible to measure an accurate three-dimensional azimuth while suppressing generation of a measurement error due to magnetization.
As described above, the center calculation means 331 in the calibration means 33 calculates the center of the azimuth sphere from the four three-axis component data (Xi, Yi, Zi), thereby reducing the three-dimensional azimuth measurement error in a short time. The center of the azimuth sphere can be calibrated accurately.

  As described above, according to this example, it is possible to easily calibrate a three-dimensional orientation measurement error, and to provide an electronic compass capable of accurately measuring a three-dimensional orientation.

The block diagram of the electronic compass in an Example. The schematic block diagram of the geomagnetic direction detector using MI sensor in an Example. The flowchart of the magnetic field determination means in an Example. The flowchart of the center calculating means in an Example. The flowchart of the least squares method calculating means in an Example. The figure which showed a mode that the orientation sphere shifted by the disturbance magnetic field in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Geomagnetic direction detector 10 Electronic compass 11a, 11b, 11c Magnetic detection part (Magnet impedance magnetic sensor)
31 Magnetic field determination means 32 Direction calculation means 33 Calibration means 331 Center calculation means 332 Least squares calculation means

Claims (6)

Detects the three-axis component of the geomagnetic vector that changes with the orientation of the measured object as three-axis component data (X1, Y1, Z1), (X2, Y2, Z2), ... (Xi, Yi, Zi) A geomagnetic azimuth detector having three magnetic detectors arranged orthogonally;
Azimuth calculating means for calculating the posture azimuth of the measured object from the three-axis component data (Xi, Yi, Zi);
Magnetic field determination means for determining normality / abnormality of the magnetic field;
Calibration means for calibrating the center of the azimuth sphere drawn by the three-axis component data (Xi, Yi, Zi) according to the change in posture of the object to be measured when the magnetic field determination means determines that it is abnormal;
The calibration means includes center calculation means for calculating the center of the azimuth sphere from at least four of the three-axis component data (Xi, Yi, Zi),
A least-squares calculation means for calculating the azimuth using a least-squares method from a predetermined number of the three-axis component data (Xi, Yi, Zi),
The azimuth calculating means outputs the posture azimuth calculated from the three-axis component data (Xi, Yi, Zi) when the magnetic field determining means determines normal, and when the magnetic field determining means determines abnormal, An electronic compass characterized by sequentially calculating and outputting the posture orientation using the center of the orientation sphere calibrated by the calibration means.   The electronic compass according to claim 1, wherein the magnetic detection unit has a detection accuracy of ± 3 mG.   3. The electronic compass according to claim 1, wherein the azimuth measurement is performed at intervals of 1 msec or less.   The electronic compass according to claim 1, wherein the magnetic detection unit is a magneto-impedance magnetic sensor. Detects the three-axis component of the geomagnetic vector that changes with the orientation of the measured object as three-axis component data (X1, Y1, Z1), (X2, Y2, Z2), ... (Xi, Yi, Zi) A three-axis component data detecting step,
An azimuth calculation step for calculating the posture azimuth of the measured object from the three-axis component data (Xi, Yi, Zi) detected in the three-axis component data detection step;
A magnetic field determination step for determining normality / abnormality of the magnetic field;
A calibration step for calibrating the center of an azimuth sphere drawn by the three-axis component data (Xi, Yi, Zi) according to a change in posture of the measured object when the magnetic field determination step is determined to be abnormal;
Have
The calibration step includes a center calculation step for calculating the center of the azimuth sphere from at least four of the three-axis component data (Xi, Yi, Zi);
A least-squares method calculating step for calculating the azimuth sphere using a least-squares method from a predetermined number of the three-axis component data (Xi, Yi, Zi),
The azimuth calculating step outputs the posture azimuth of the measured object calculated from the three-axis component data (Xi, Yi, Zi) when the magnetic field determining step is determined to be normal, and the magnetic field determining step is abnormal. And determining and outputting the orientation orientation sequentially using the center of the orientation sphere calibrated in the calibration step.   6. The azimuth measuring method according to claim 5, wherein the azimuth measurement is performed at intervals of 1 msec or less.

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