CN107340545A - A kind of earth magnetism total factor measuring system and method - Google Patents

Abstract

The present invention provides a geomagnetic element measurement system and method. The geomagnetic element measurement system includes a geomagnetic element sensor, an element magnetometer host and a connection unit. The geomagnetic element sensor includes a total field sensor and a uniform magnetic field generator. One end of the total field sensor is snapped and fixed on the inner center of the uniform magnetic field generator, and the other end is not connected to the uniform magnetic field generator. The element magnetometer host includes a measurement module and a constant current source system, and the measurement module includes an excitation Source, signal conditioning module and magnetic field measurement module, the excitation source drives the total field sensor to send a signal, the connection unit includes a signal transmission line and a power supply line, the signal transmission line connects the total field sensor and the measurement module, and the power supply line The uniform magnetic field generator is connected with a constant current source system, and the constant current source system supplies power to the uniform magnetic field generator through a power supply line.

Description

A system and method for measuring all elements of geomagnetism

technical field

The invention relates to the field of geomagnetic measurement, in particular to a system and method for measuring all elements of geomagnetism.

Background technique

The geomagnetic field is one of the basic physical fields reflecting the material distribution and geological structure of the earth, and it can reveal the physical and chemical processes inside the earth. The magnetometer is the main scientific instrument for measuring the geomagnetic field, and it is widely used in earth science research, geological and resource exploration, aerospace, military exploration and other fields. There are seven main elements of geomagnetic field information: total field, horizontal component, northward component, eastward component, vertical component, magnetic inclination and magnetic declination. The conventional total geomagnetic field measurement can only determine the distribution and structure of the magnetosphere, but the geomagnetic elements other than the total field contain more target information and have a wider application range.

At present, the measurement of geomagnetic elements can be divided into three categories: the first category is represented by fluxgate sensors, which can directly obtain geomagnetic three-component information, but there are orthogonality errors, temperature drift, and the inability to perform absolute observations, etc. Problem; the second category is the combined measurement of the fluxgate sensor and theodolite. This type of magnetometer is also called DI instrument and cannot be used for automatic observation. The third type is the combination measurement method of the total field sensor and the Helmholtz coil (uniform magnetic field generator). This kind of geomagnetism has a large volume, and most of the total field sensors selected are proton precession sensors, and the sensitivity is not high. And it is impossible to obtain the information of all geomagnetic elements.

Contents of the invention

In view of this, the embodiments of the present invention provide a geomagnetic all-element measurement system and method that can realize high-precision integrated vector measurement of all geomagnetic elements.

The present invention provides a geomagnetic element measurement system, the geomagnetic element measurement system includes a geomagnetic element sensor, an element magnetometer host and a connection unit, the geomagnetic element sensor includes a total field sensor and a uniform magnetic field generator, the total field sensor One end is snapped and fixed on the inner center of the uniform magnetic field generator, and the other end is not connected to the uniform magnetic field generator. The element magnetometer host includes a measurement module and a constant current source system, and the measurement module includes an excitation source, a signal conditioning module and a magnetic field measurement module, the connection unit includes a signal transmission line and a power supply line, the signal transmission line connects the total field sensor and the measurement module, the power supply line connects a uniform magnetic field generator and a constant current source system, and the constant current The source system supplies power to the uniform magnetic field generator through a power supply line. After the constant current source system supplies power to the uniform magnetic field generator, the excitation source drives the total field sensor to output FID signals, and the signal conditioning module The FID signal is received through the transmission line, the signal conditioning module amplifies, filters and shapes the signal, and outputs the shaped signal, and the magnetic field measurement module measures the shaped signal to obtain the current magnetic field value.

Further, the uniform magnetic field generator includes a first coil and a second coil that are orthogonal to each other, the size of the first coil is larger than the size of the second coil, and the second coil is engaged and fixed inside the first coil, so One end of the total field sensor is engaged and fixed at the inner center of the second coil, and the other end is not connected to the uniform magnetic field generator.

Further, the first coil and the second coil are spherical coils.

Further, the total field sensor is an overhauser sensor.

The present invention also provides a measurement method using a geomagnetic element measurement system, and the measurement method of the geomagnetic element measurement system includes the following steps:

S1: under the condition that the first coil and the second coil are not energized, the first total geomagnetic field F1 is measured by the magnetic field measurement module;

S2: Input current to the first coil and the second coil in sequence, and the magnetic field measurement module measures the bias magnetic fields I ₊ , I ₋ , D ₊ , D ₋ ,

S21: The constant current source system inputs a current I ₁ to the first coil, and the magnetic field measurement module measures a bias magnetic field I ₊ ;

S22: The constant current source system inputs a current I ₂ that is opposite in direction to the current I ₁ and equal in magnitude to the first coil, and the magnetic field measurement module measures a bias magnetic field I ₋ ;

S23: The constant current source system inputs a forward current I ₃ to the second coil, at this time the total geomagnetic field F deflects parallel to the axis of the second coil, and the magnetic field measurement module measures a bias magnetic field D ₊ .

S24: The constant current source system inputs a current I ₄ that is equal in size to the current I ₃ and opposite in direction to the second coil. At this time, the total geomagnetic field F is deflected antiparallel to the axis of the second coil, and the magnetic field The measurement module measures the bias magnetic field D _- ;

S3: According to the value of the total geomagnetic field F, the bias magnetic field I ₊ , the bias magnetic field I- _, the bias magnetic field D ₊ , and the bias magnetic field _D- , calculate the variation of the magnetic inclination I and the magnetic declination D;

S4: Calculate the horizontal component H, northward component X, eastward component Y, and vertical component Z values of the elements according to the geometric relationship of the seven geomagnetic elements and the known total geomagnetic field F, magnetic inclination I, and magnetic declination D.

Further, the step S3 includes the following steps:

S31: seek the value of the total geomagnetic field F;

S311: under the condition that the coil is not energized, measure the second total geomagnetic field F2;

S312: the value of the total geomagnetic field F under the total field without deflection is the average value of the first total geomagnetic field F1 and the second total geomagnetic field F2;

S32: according to the value of the total geomagnetic field F, the bias magnetic field I+, and the bias magnetic field I-, calculate the variation of the magnetic inclination angle I;

S33: According to the value of the total geomagnetic field F, the bias magnetic field D+, and the bias magnetic field D-, calculate the variation of the magnetic declination angle D;

S34: Calculate the current magnetic declination D and magnetic inclination I.

Further, said step S32: according to the value of the total geomagnetic field F, the bias magnetic field I+, and the bias magnetic field I-, calculate the variation of the magnetic inclination I, specifically include:

The first coil and the second coil are fed with currents of equal size and opposite directions, and the bias magnetic fields generated after being superimposed with the total geomagnetic field F are set as F ₊ and F _- ,

Suppose A is the bias magnetic field formed after the current passed through the first coil or the second coil, A can be the value of any one of I ₊ and D ₊ in step S2, and F- is the value _in step S2 The value of any one of I _- , D _- can be obtained by the law of cosines:

F ₊ ² = A _- ² + F ² -2A _- Fcosα ₀

F _- ² ＝A _- ² +F ² -2A _- Fcos(π-α ₀ )

but:

Because A ₊ ＝A _- ＝A, after operation, we can get

_Ai represents the bias field formed by the current passed into the first coil, and _Ad represents the bias field formed by the current passed into the second coil respectively, so:

After the total field deflection, the change of the total geomagnetic field F is in the magnetic meridian plane, and when the first coil and the second coil are placed according to the preset position, β _i represents the instantaneous change of the magnetic inclination angle I;

According to the triangular relationship of each magnetic field:

therefore:

also because:

α ₁ is the angle between the bias magnetic field and the current magnetic field to be measured, according to the relationship between the bias magnetic field can be:

make It can be obtained by Taylor series expansion:

so:

The value of β _i is the instantaneous variation ΔI of the magnetic inclination angle I.

Further, said step S33: according to the value of the total geomagnetic field F, the bias magnetic field D+, and the bias magnetic field D-, calculate the variation of the magnetic declination D, specifically include:

According to the cosine law, the value of the changing magnetic declination β _d is obtained. The magnetic declination β _d is the angle between the magnetic field to be measured and the magnetic meridian plane. The magnetic declination β _d is projected to the horizontal plane, so the variation of the magnetic declination D ΔD is:

Further, said step S34: calculate current magnetic declination D, magnetic inclination I, specifically include:

After obtaining the magnetic inclination I and magnetic declination D changes, according to the initial magnetic declination D ₀ and initial magnetic inclination I ₀ of the measurement site, the current magnetic declination D and magnetic inclination I are calculated. The calculation formula is as follows:

I＝I ₀ +ΔI

D=D ₀ +ΔD.

In the geomagnetic element analyzer of the present invention, the uniform magnetic field generator is a spherical coil, which facilitates the miniaturization of the instrument; the combined use of the uniform magnetic field generator and the total geomagnetic field sensor improves the accuracy of measurement; At the same time, the measurement method of magnetic inclination increment - magnetic declination increment is adopted to realize the integrated observation of the total magnetic field, three components, magnetic declination, and magnetic inclination, which overcomes the temperature of other geomagnetic measuring instruments. Problems such as large drift, low precision, few measurement parameters, and large volume, realize high-precision integrated measurement of geomagnetic all-element information, adapt to different magnetic measurement requirements in multiple fields and platforms, and conform to the future development trend of geomagnetic element sensor measurement .

Description of drawings

Fig. 1 is a structural schematic diagram of a geomagnetic all-element measurement system of the present invention.

Fig. 2 is a schematic diagram of the workflow of a geomagnetic all-element measurement system of the present invention.

Fig. 3 is a schematic workflow diagram of a geomagnetic all-element measuring method according to the present invention.

Fig. 4 is a schematic diagram of the geometric relationship of the seven elements of a geomagnetic all-element measurement system according to the present invention.

Fig. 5 is a schematic diagram of an integrated measurement model of a geomagnetic all-element measurement system according to the present invention.

Fig. 6 is a schematic flowchart of a magnetic inclination increment-magnetic declination increment measuring method of a geomagnetic all-element measuring system according to the present invention.

Fig. 7 is a schematic diagram of the relationship between the bias magnetic field and the total geomagnetic field to be measured of a geomagnetic all-element measurement system according to the present invention.

Fig. 8 is a diagram of instantaneous magnetic inclination angle variation after power-on of a geomagnetic all-element measuring system according to the present invention.

detailed description

In order to make the purpose, technical solution and advantages of the present invention clearer, the embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

Please refer to Fig. 1, the embodiment of the present invention provides a kind of geomagnetic element measurement system, described geomagnetic element measurement system comprises geomagnetic element sensor 10, element magnetometer main frame 20 and connection unit 30,

The geomagnetic element sensor 10 includes a total field sensor 11 and a uniform magnetic field generator 12, the total field sensor 11 is an overhauser sensor, and the uniform magnetic field generator 12 includes a mutually orthogonal first coil 121 and a second coil 122, The first coil 121 and the second coil 122 are spherical coils, the size of the first coil 121 is larger than the size of the second coil 122, and the second coil 122 is engaged and fixed inside the first coil 121, and the total field One end of the sensor 11 is engaged and fixed on the inner center of the second coil 122 , and the other end is not connected to the uniform magnetic field generator 12 .

The main element magnetometer 20 includes a measurement module 21 and a constant current source system 22, the measurement module 21 includes an excitation source 211, a signal conditioning module 212 and a magnetic field measurement module 213, and the constant current source system 22 is the first The coil 121 and the second coil 122 are powered.

The connection unit 30 includes a signal transmission line 31 and a power supply line 32, the signal transmission line 31 connects the total field sensor 11 and the measurement module 21, and the power supply line 32 connects the uniform magnetic field generator 12 and the constant current source system 22, so The constant current source system 21 supplies power to the uniform magnetic field generator 12 through the power supply line 32 .

When the constant current source system 21 supplies power to the uniform magnetic field generator 12, the excitation source 211 drives the output FID (Free Induction Decay, free induction decay) signal of the total field sensor 11; the FID signal passes through the transmission line 31 sent to the signal conditioning module 212 of the measurement module 21, the signal conditioning module 212 amplifies, filters and shapes the signal, and outputs a square wave signal, and the magnetic field measurement module 213 measures the square wave signal to obtain the current magnetic field value.

The geomagnetic field is a vector field, which consists of seven elements: the total field F, the horizontal component H, the northward component X, the eastward component Y, the vertical component Z, the magnetic inclination I, and the magnetic declination D.

Referring to FIG. 4 , along the direction of the geographic meridian, an x-axis of a coordinate system is set up, and the x-axis points to the geographic true north along the direction of the geographic meridian.

A y-axis is set at a position perpendicular to the x-axis, and the y-axis points to the geographical due east along the direction of the latitudinal circle.

At point O where the x-axis and the y-axis intersect, the z-axis is set vertically downward.

Let the vector direction of the total geomagnetic field F be OA, the projection of the total field F on the x-axis is the northward component X, and the projection of the total field F on the y-axis is the eastward component Y, and the total field F is in The projection on the z axis is the vertical component Z, and the projection of the total field F on the horizontal plane (xOy) plane is the horizontal component H;

The vertical plane (ZOB) where the total field F is located is the magnetic meridian plane, the angle (xOB) between the geographical meridian plane (xOZ) and the magnetic meridian plane is the magnetic declination D, and the angle between the horizontal plane (xOy) and the total field F (AOB) is the magnetic inclination I.

The geometric relationship of the seven geomagnetic elements is as follows:

Please refer to FIG. 2 , before the measurement of the geomagnetic element measurement system, the functional test is performed on each instrument component of the geomagnetic element measurement system to check whether the instrument can be used normally, and if there is a fault, it will be returned for maintenance.

In the case of normal use, at the selected test site, by observing whether there is a difference in the deflection components of the magnetic inclination angle I and the magnetic declination angle D, it is confirmed whether the instrument is leveled. After the instrument is leveled, test and record within a measurement cycle measured value.

Please refer to Figure 3, the geomagnetic measurement steps are as follows:

S1: under the condition that the first coil 121 and the second coil 122 are not energized, measure the first total geomagnetic field F1 by the magnetic field measurement module 213;

S2: Please refer to Fig. 3, measure the bias magnetic field I ₊ , I- _, D ₊ , _D- ;

S21: The constant current source system 22 inputs a current I ₁ to the first coil 121, and the magnetic field measurement module 213 measures a bias magnetic field I ₊ ;

S22: In the constant current source system 22, a current I ₂ that is opposite in direction to the current I ₁ and equal in magnitude is input to the first coil 121, and the magnetic field measurement module 213 measures a bias magnetic field I ₋ ;

S23: The constant current source system 22 inputs a forward current I ₃ to the second coil 122, and the magnetic field measurement module 213 measures a bias magnetic field D ₊ ;

S24: The constant current source system 22 inputs a current I ₄ that is equal in magnitude to the current I ₃ and opposite in direction to the second coil 122, and the magnetic field measurement module 213 measures a bias magnetic field D ₋ ;

S3: Please refer to Figure 6, according to the total geomagnetic field F, bias magnetic field I ₊ , bias magnetic field I- _, bias magnetic field D ₊ , bias magnetic field D _- values, calculate the value of magnetic inclination I and magnetic declination D ;

S31: seek the value of the total geomagnetic field F;

S311: under the condition that the coil is not energized, measure the second total geomagnetic field F2;

S312: the value of the total geomagnetic field F under the total field without deflection is the average value of the first total geomagnetic field F1 and the second total geomagnetic field F2;

S32: According to the value of the total geomagnetic field F, the bias magnetic field I+, and the bias magnetic field I-, the variation of the magnetic inclination I is calculated, and the steps are as follows:

The first coil 121 and the second coil 122 are fed with currents of equal size and opposite directions, and the bias magnetic fields generated after being superimposed on the total field F are set as F ₊ and F ₋ ,

Let A be the bias magnetic field formed after the current passed through the first coil 121 or the second coil 122, A can be the value of any one of I ₊ and D ₊ in step S2, and F- is the value _of step S2 The value of any one of I _- and D _- in S2, its relationship is shown in Figure 7, and can be obtained by the law of cosines:

F ₊ ² = A _- ² + F ² -2A _- Fcosα ₀

F _- ² ＝A _- ² +F ² -2A _- Fcos(π-α ₀ )

but:

Because A ₊ ＝A _- ＝A, after operation, we can get

A _i represents the bias field formed by the current passed in the first coil 121, and A _d represents the bias field formed by the current passed in the second coil 122 respectively, so:

Please refer to Fig. 5, Fig. 7 and Fig. 8, the change of the total geomagnetic field F after the total field deflection in Fig. The instantaneous magnetic inclination angle β _i changes after the first coil 121 and the second coil 122 are energized are shown in Figure 8, and the ef axis is the initial direction of the magnetic field, and the reference axis gh axis is set in the model direction of the ef axis with reference to Figure 5 , the plane formed by the ef axis and the gh axis is called the magnetic meridian plane.

F is the current direction of the magnetic field to be measured, and β _i represents the instantaneous change of the magnetic inclination angle I.

According to the triangular relationship of each magnetic field in Fig. 8, it can be obtained:

therefore:

also because:

α ₁ is the angle between the bias magnetic field and the current magnetic field to be measured, according to the relationship between the bias magnetic field can be:

make It can be obtained by Taylor series expansion:

so:

The value of β _i is the instantaneous variation ΔI of the magnetic inclination angle I;

S33: According to the value of the total geomagnetic field F, the bias magnetic field D+, and the bias magnetic field D-, the variation of the magnetic declination D is calculated, and the steps are as follows:

The method for calculating the magnetic declination D is consistent with the calculation method for the magnetic inclination. The reference axis ab is set in the vertical direction of the gh axis, and the reference axes ab and ef form a plane perpendicular to the magnetic meridian plane formed by ef and gh. According to the cosine Theorem, find the changing magnetic declination β _d .

The calculation of magnetic declination D is different from magnetic inclination I in that β _d is the angle between the magnetic field to be measured and the magnetic meridian plane, and the magnetic declination D is on the horizontal plane, so β _d must be projected to the horizontal plane, so the magnetic declination The variation ΔD of D is:

S34: calculate the value of current magnetic declination D, magnetic inclination I;

After obtaining the variation of magnetic inclination I and magnetic declination D, the current magnetic declination D and magnetic inclination I are calculated according to the initial magnetic declination D ₀ and initial magnetic inclination I ₀ of the measurement location. The specific calculation formula is as follows:

I＝I ₀ +ΔI

D＝D ₀ +ΔD

S4: Calculate the horizontal component H, the northward component X, the eastward component Y, and the value of the vertical component Z according to the known total geomagnetic field F, magnetic inclination I and magnetic declination D.

According to the geometric relationship of the seven geomagnetic elements and the known values of the total geomagnetic field F, magnetic declination D, and magnetic inclination I, the values of the horizontal component H, the northward component X, the eastward component Y, and the vertical component Z are calculated.

In this article, the orientation words such as front, rear, upper, and lower involved are defined by the parts in the drawings and the positions between the parts in the drawings, just for the clarity and convenience of expressing the technical solution. It should be understood that the use of the location words should not limit the scope of protection claimed in this application.

In the case of no conflict, the above-mentioned embodiments and features in the embodiments herein may be combined with each other.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (9)

1. A geomagnetic element measurement system, characterized in that: the geomagnetic element measurement system includes a geomagnetic element sensor, an element magnetometer host and a connection unit, and the geomagnetic element sensor includes a total field sensor and a uniform magnetic field generator, and the total One end of the field sensor is fastened and fixed on the inner center of the uniform magnetic field generator, and the other end is not connected to the uniform magnetic field generator. The element magnetometer host includes a measurement module and a constant current source system, and the measurement module includes an excitation source , a signal conditioning module and a magnetic field measurement module, the connection unit includes a signal transmission line and a power supply line, the signal transmission line connects the total field sensor and the measurement module, the power supply line connects a uniform magnetic field generator and a constant current source system, the The constant current source system supplies power to the uniform magnetic field generator through a power supply line, and when the constant current source system supplies power to the uniform magnetic field generator, the excitation source drives the total field sensor to output an FID signal, and the The signal conditioning module receives the FID signal through the transmission line, the signal conditioning module amplifies, filters and shapes the signal, and outputs the shaped signal, and the magnetic field measurement module measures the shaped signal to obtain the current magnetic field value. 2. A kind of geomagnetic elements measuring system as claimed in claim 1, characterized in that: said uniform magnetic field generator comprises a first coil and a second coil which are orthogonal to each other, and the size of said first coil is larger than that of the second coil The size of the second coil is engaged and fixed inside the first coil, one end of the total field sensor is engaged and fixed at the center of the inner side of the second coil, and the other end is not connected to the uniform magnetic field generator. 3. A system for measuring geomagnetic elements as claimed in claim 2, wherein the first coil and the second coil are spherical coils. 4. A geomagnetic element measurement system as claimed in claim 3, characterized in that: said total field sensor is an overhauser sensor. 5. apply the measuring method of a kind of geomagnetic element measuring system as claimed in claim 3 or 4, it is characterized in that comprising the steps: S1: under the condition that the first coil and the second coil are not energized, the first total geomagnetic field F1 is measured by the magnetic field measurement module; S2: Input current to the first coil and the second coil in sequence, and the magnetic field measurement module measures the bias magnetic fields I ₊ , I ₋ , D ₊ , D ₋ , S21: The constant current source system inputs a current I ₁ to the first coil, and the magnetic field measurement module measures a bias magnetic field I ₊ ; S22: The constant current source system inputs a current I ₂ that is opposite in direction to the current I ₁ and equal in magnitude to the first coil, and the magnetic field measurement module measures a bias magnetic field I ₋ ; S23: The constant current source system inputs a forward current I ₃ to the second coil, at this time the total geomagnetic field F deflects parallel to the axis of the second coil, and the magnetic field measurement module measures a bias magnetic field D ₊ . S24: The constant current source system inputs a current I ₄ that is equal in size to the current I ₃ and opposite in direction to the second coil. At this time, the total geomagnetic field F is deflected antiparallel to the axis of the second coil, and the magnetic field The measurement module measures the bias magnetic field D _- ; S3: According to the value of the total geomagnetic field F, the bias magnetic field I ₊ , the bias magnetic field I- _, the bias magnetic field D ₊ , and the bias magnetic field _D- , calculate the variation of the magnetic inclination I and the magnetic declination D; S4: Calculate the horizontal component H, northward component X, eastward component Y, and vertical component Z values of the elements according to the geometric relationship of the seven geomagnetic elements and the known total geomagnetic field F, magnetic inclination I, and magnetic declination D. 6. The measuring method of a kind of geomagnetic element measuring system as claimed in claim 5, is characterized in that: described step S3 comprises the steps: S31: seek the value of the total geomagnetic field F; S311: under the condition that the coil is not energized, measure the second total geomagnetic field F2; S312: the value of the total geomagnetic field F under the total field without deflection is the average value of the first total geomagnetic field F1 and the second total geomagnetic field F2; <mrow><mi>F</mi><mo>=</mo><mfrac><mrow><msub><mi>F</mi><mn>1</mn></msub><mo>+</mo><msub><mi>F</mi><mn>2</mn></msub></mrow><mn>2</mn></mfrac></mrow> S32: according to the value of the total geomagnetic field F, the bias magnetic field I+, and the bias magnetic field I-, calculate the variation of the magnetic inclination angle I; S33: According to the value of the total geomagnetic field F, the bias magnetic field D+, and the bias magnetic field D-, calculate the variation of the magnetic declination angle D; S34: Calculate the current magnetic declination D and magnetic inclination I. 7. the measuring method of a kind of geomagnetic elements measuring system as claimed in claim 6, is characterized in that: described step S32: according to the value of geomagnetic total field F, bias magnetic field I+, bias magnetic field I-, calculates Variation of magnetic inclination I, including: The first coil and the second coil are fed with currents of equal size and opposite directions, and the bias magnetic fields generated after being superimposed with the total geomagnetic field F are set as F ₊ and F _- , Suppose A is the bias magnetic field formed after the current passed through the first coil or the second coil, A can be the value of any one of I ₊ and D ₊ in step S2, and F- is the value _in step S2 The value of any one of I _- , D _- can be obtained by the law of cosines: <mrow><msup><msub><mi>F</mi><mo>+</mo></msub><mn>2</mn></msup><mo>=</mo><msup><msub><mi>A</mi><mo>-</mo></msub><mn>2</mn></msup><mo>+</mo><msup><mi>F</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msub><mi>A</mi><mo>-</mo></msub><mi>F</mi><mi></mi><msub><mi>cos&amp;alpha;</mi><mn>0</mn></msub></mi>mrow> <mrow><msup><msub><mi>F</mi><mo>-</mo></msub><mn>2</mn></msup><mo>=</mo><msup><msub><mi>A</mi><mo>-</mo></msub><mn>2</mn></msup><mo>+</mo><msup><mi>F</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><mi>A</mi><mo>-</mo><mi>F</mi><mi></mi><mi>c</mi><mi>o</mi><mi>s</mi><mrow><mo>(</mo><mi>&amp;pi;</mi><mo>-</mo><msub><mi>&amp;alpha;</mi><mn>0</mn></msub><mo>)</mo></mrow></mrow> but: Because A ₊ ＝A _- ＝A, after operation, we can get <mrow><msup><mi>A</mi><mn>2</mn></msup><mo>=</mo><mfrac><mrow><msup><msub><mi>F</mi><mo>+</mo></msub><mn>2</mn></msup><mo>+</mo><msup><msub><mi>F</mi><mo>-</mo></msub><mn>2</mn></msup><mo>-</mo><mn>2</mn><msup><mi>F</mi><mn>2</mn></msup></mrow><mn>2</mn></mfrac></mrow> _Ai represents the bias field formed by the current passed into the first coil, and _Ad represents the bias field formed by the current passed into the second coil respectively, so: <mrow><msub><mi>A</mi><mi>i</mi></msub><mo>=</mo><msqrt><mrow><mo>(</mo><msup><msub><mi>I</mi><mo>+</mo></msub><mn>2</mn></msup><mo>+</mo><msup><msub><mi>I</mi><mo>-</mo></msub><mn>2</mn></msup><mo>-</mo><mn>2</mn><msup><mi>F</mi><mn>2</mn></msup><mo>)</mo><mo>/</mo><mn>2</mn></mrow></msqrt></mrow> <mrow><msub><mi>A</mi><mi>d</mi></msub><mo>=</mo><msqrt><mrow><mo>(</mo><msup><msub><mi>D</mi><mo>+</mo></msub><mn>2</mn></msup><mo>+</mo><msup><msub><mi>D</mi><mo>-</mo></msub><mn>2</mn></msup><mo>-</mo><mn>2</mn><msup><mi>F</mi><mn>2</mn></msup><mo>)</mo><mo>/</mo><mn>2</mn></mrow></msqrt></mrow> After the total field deflection, the change of the total geomagnetic field F is in the magnetic meridian plane, and when the first coil and the second coil are placed according to the preset position, β _i represents the instantaneous change of the magnetic inclination angle I; According to the triangular relationship of each magnetic field: <mrow><mi>c</mi><mi>o</mi><mi>s</mi><mrow><mo>(</mo><msub><mi>&amp;alpha;</mi><mn>1</mn></msub><mo>)</mo></mrow><mo>=</mo><mfrac><mrow><msup><mi>F</mi><mn>2</mn></msup><mo>+</mo><msup><msub><mi>A</mi><mrow><mi>i</mi><mo>+</mo></mrow></msub><mn>2</mn></msup><mo>-</mo><msup><msub><mi>I</mi><mo>+</mo></msub><mn>2</mn></msup></mrow><mrow><mn>2</mn><msub><mi>FA</mi><mrow><mi>i</mi><mo>+</mo></mrow></msub></mrow></mfrac></mrow> therefore: <mrow><msub><mi>&amp;alpha;</mi><mn>1</mn></msub><mo>=</mo><mi>arc</mi><mi></mi><mi>c</mi><mi>o</mi><mi>s</mi><mrow><mo>(</mo><mfrac><mrow><msup><mi>F</mi><mn>2</mn></msup><mo>+</mo><msup><msub><mi>A</mi><mrow><mi>i</mi><mo>+</mo></mrow></msub><mn>2</mn></msup><mo>-</mo><msup><msub><mi>I</mi><mo>+</mo></msub><mn>2</mn></msup></mrow><mrow><mn>2</mn><msub><mi>FA</mi><mrow><mi>i</mi><mo>+</mo></mrow></msub></mrow></mfrac><mo>)</mo></mrow></mrow> also because: <mrow><msub><mi>A</mi><mi>i</mi></msub><mo>=</mo><msub><mi>A</mi><mrow><mi>i</mi><mo>+</mo></mrow></msub><mo>=</mo><msub><mi>A</mi><mrow><mi>i</mi><mo>-</mo></mrow></msub><mo>=</mo><msqrt><mrow><mo>(</mo><msup><msub><mi>I</mi><mo>+</mo></msub><mn>2</mn></msup><mo>+</mo><msup><msub><mi>I</mi><mo>-</mo></msub><mn>2</mn></msup><mo>-</mo><mn>2</mn><msup><mi>F</mi><mn>2</mn></msup><mo>)</mo><mo>/</mo><mn>2</mn></mrow></msqrt></mrow> α ₁ is the angle between the bias magnetic field and the current magnetic field to be measured, according to the relationship between the bias magnetic field can be: <mrow><msub><mi>&amp;alpha;</mi><mn>1</mn></msub><mo>=</mo><mi>arc</mi><mi></mi><mi>c</mi><mi>o</mi><mi>s</mi><mrow><mo>(</mo><mfrac><mrow><msup><msub><mi>I</mi><mo>-</mo></msub><mn>2</mn></msup><mo>-</mo><msup><msub><mi>I</mi><mo>+</mo></msub><mn>2</mn></msup></mrow><mrow><mn>4</mn><mi>F</mi><mrow><mo>(</mo><msqrt><mrow><mfrac><mrow><msup><msub><mi>I</mi><mo>+</mo></msub><mn>2</mn></msup><mo>+</mo><msup><msub><mi>I</mi><mo>-</mo></msub><mn>2</mn></msup></mrow><mn>2</mn></mfrac><mo>-</mo><mn>2</mn><msup><mi>F</mi><mn>2</mn></msup></mrow></msqrt><mo>)</mo></mrow></mrow></mfrac><mo>)</mo></mrow></mrow> make It can be obtained by Taylor series expansion: <mrow><msub><mi>&amp;alpha;</mi><mn>1</mn></msub><mo>&amp;ap;</mo><mi>arccos</mi><mrow><mo>(</mo><mn>0</mn><mo>)</mo></mrow><mo>+</mo><msup><mrow><mo>&amp;lsqb;</mo><mi>arccos</mi><mrow><mo>(</mo><mn>0</mn><mo>)</mo></mrow><mo>&amp;rsqb;</mo></mrow><mo>&amp;prime;</mo></msup><mo>&amp;CenterDot;</mo><mi>x</mi><mo>=</mo><mfrac><mi>&amp;pi;</mi><mn>2</mn></mfrac><mo>+</mo><mi>x</mi><mo>=</mo><mfrac><mi>&amp;pi;</mi><mn>2</mn></mfrac><mo>+</mo><mfrac><mrow><msup><msub><mi>I</mi><mo>+</mo></msub><mn>2</mn></msup><mo>-</mo><msup><msub><mi>I</mi><mo>-</mo></msub><mn>2</mn></msup></mrow><mrow><mn>4</mn><mi>F</mi><mrow><mo>(</mo><msqrt><mrow><mfrac><mrow><msup><msub><mi>I</mi><mo>+</mo></msub><mn>2</mn></msup><mo>+</mo><msup><msub><mi>I</mi><mo>-</mo></msub><mn>2</mn></msup></mrow><mn>2</mn></mfrac><mo>-</mo><mn>2</mn><msup><mi>F</mi><mn>2</mn></msup></mrow></msqrt><mo>)</mo></mrow></mrow></mfrac></mrow> so: The value of β _i is the instantaneous variation ΔI of the magnetic inclination angle I. 8. the measuring method of a kind of geomagnetic elements measuring system as claimed in claim 7, is characterized in that: described step S33: according to the value of geomagnetic total field F, bias magnetic field D+, bias magnetic field D-, calculates The variation of magnetic declination D, including: According to the cosine law, the value of the changing magnetic declination β _d is obtained. The magnetic declination β _d is the angle between the magnetic field to be measured and the magnetic meridian plane. The magnetic declination β _d is projected to the horizontal plane, so the variation of the magnetic declination D ΔD is: <mrow><mi>&amp;Delta;</mi><mi>D</mi><mo>=</mo><mfrac><msub><mi>&amp;beta;</mi><mi>d</mi></msub><mrow><mi>cos</mi><mi></mi><mi>I</mi></mrow></mfrac><mo>=</mo><mfrac><mrow><msup><msub><mi>D</mi><mo>+</mo></msub><mn>2</mn></msup><mo>-</mo><msup><msub><mi>D</mi><mo>-</mo></msub><mn>2</mn></msup></mrow><mrow><mn>4</mn><mi>F</mi><mrow><mo>(</mo><msqrt><mrow><mfrac><mrow><msup><msub><mi>D</mi><mo>+</mo></msub><mn>2</mn></msup><mo>+</mo><msup><msub><mi>D</mi><mo>-</mo></msub><mn>2</mn></msup></mrow><mn>2</mn></mfrac><mo>-</mo><mn>2</mn><msup><mi>F</mi><mn>2</mn></msup></mrow></msqrt><mo>)</mo></mrow><mo>&amp;CenterDot;</mo><mi>cos</mi><mi></mi><mi>I</mi></mrow></mfrac><mo>.</mo></mrow> 9. the measuring method of a kind of geomagnetic elements measuring system as claimed in claim 8, is characterized in that: described step S34: calculate current magnetic declination D, magnetic inclination I, specifically comprise: After obtaining the magnetic inclination I and magnetic declination D changes, according to the initial magnetic declination D ₀ and initial magnetic inclination I ₀ of the measurement site, the current magnetic declination D and magnetic inclination I are calculated. The calculation formula is as follows: I＝I ₀ +ΔI D=D ₀ +ΔD.