Inversion and correction method for atmospheric refraction error of differential sky polarization compass

文档序号:1671137 发布日期:2019-12-31 浏览:24次 中文

阅读说明:本技术 一种差分天空偏振罗盘大气折射误差的反演及修正方法 (Inversion and correction method for atmospheric refraction error of differential sky polarization compass ) 是由 张霄 叶涛 郭雷 于 2019-10-09 设计创作,主要内容包括:本发明公开一种差分天空偏振罗盘大气折射误差的反演及修正方法,包括以下步骤:基准站测量天空偏振光,结合已知的位置、时间、航向等信息反演出当前天空下的大气折射误差角,并上传数据中心;天空偏振数据中心接收并存储多个基准站发送来的大气折射误差角数据;用户端天空偏振罗盘向天空偏振数据中心发送数据请求;天空偏振数据中心选取用户端邻近的多个基准站的大气折射误差角数据,加权后分配给用户端天空偏振罗盘;用户端天空偏振罗盘利用接收到的大气折射误差角数据进行导航修正,实现高精度的航向计算。本发明与现有技术相比具有如下优点:可减小随机变化的大气折射误差对天空偏振罗盘的影响,提高天空偏振罗盘航向计算精度。(The invention discloses an inversion and correction method of atmospheric refraction error of a differential sky polarization compass, which comprises the following steps: the method comprises the following steps that a reference station measures sky polarized light, inverts an atmospheric refraction error angle under the current sky by combining known information such as position, time and course, and uploads the atmospheric refraction error angle to a data center; the sky polarization data center receives and stores atmospheric refraction error angle data sent by a plurality of reference stations; a user side sky polarization compass sends a data request to a sky polarization data center; the sky polarization data center selects atmospheric refraction error angle data of a plurality of reference stations adjacent to a user side, and distributes the atmospheric refraction error angle data to a user side sky polarization compass after weighting; and the sky polarization compass at the user side carries out navigation correction by utilizing the received atmospheric refraction error angle data, so as to realize high-precision heading calculation. Compared with the prior art, the invention has the following advantages: the influence of randomly changed atmospheric refraction errors on the sky polarization compass can be reduced, and the calculation accuracy of the heading of the sky polarization compass is improved.)

1. an inversion and correction method for atmospheric refraction error of a differential sky polarization compass is characterized by comprising the following steps:

(1) each sky polarized light measuring reference station independently measures the state of sky polarized light, and the atmospheric refraction error angle under the current sky is inverted by the known position, time and heading information of the reference station and is uploaded to a sky polarized data center; the inversion calculation adopts a local atmospheric refraction error angle inversion algorithm, the atmospheric refraction error angle is inverted by using a course resolving method based on a Rayleigh scattering model and an inertial measurement unit based on the position, time and posture information of a reference station, the whole atmospheric refraction error item at a measurement end is calculated reversely from the result, the variation characteristic of the atmospheric refraction error is kept, and the establishment of a complex model of the atmospheric refraction error along with the variation of environmental parameters is avoided, and the method specifically comprises the following steps:

known reference station sky polarization compass heading Ψ0With time and position information, firstly calculating a sun altitude Hs and a sun azimuth As of a reference station, and then combining a roll angle gamma and a pitch angle theta output by an inertia measurement element on a sky polarization compass of the reference station and an actually measured polarization angle beta to invert an atmospheric refraction error angle phi under the sky where the current reference station is located:

Figure FDA0002226113630000011

the specific expression of each coefficient is as follows:

A1either cos γ cos β cos Hs sin As or sin β cos Hs cos As

B1=-sinγ cos β cos Hs sin As

A2=sinβ cos Hs sin As-cosγ cosβ cos Hs cos As

B2=sinγ cosβ cos Hs cos As

A3=sinγ cosβ sin Hs

B3=cosγ cosβ sin Hs

(2) The sky polarized data center receives and stores atmospheric refraction error angle data transmitted by each sky polarized light measurement reference station;

(3) a user side sky polarization compass sends a data request to a sky polarization data center;

(4) the sky polarization data center selects a plurality of atmospheric refraction error angle data of the sky polarization light measurement reference station adjacent to the user side sky polarization compass, and distributes the atmospheric refraction error angle data to the user side sky polarization compass after weighting;

(5) the user side sky polarization compass carries out navigation correction by utilizing the received atmospheric refraction error angle data, and the heading precision is improved.

2. The method of claim 1, wherein in the step (4), the atmospheric refraction error angle data of the plurality of sky polarized light measurement reference stations are selected to satisfy the following conditions: (a) the user side sky polarization compass is positioned in the effective radius of the reference station, namely positioned in the same local sky; (b) the difference between the uploading time of the atmospheric refraction error angle data of the reference station and the current time is within a defined threshold range, and the data is considered to be invalid when the time difference exceeds the threshold.

3. The method of claim 1, wherein the step (5) of inverting and correcting the atmospheric refraction error of the differential sky polarization compass comprises: firstly, information distribution is carried out on atmospheric refraction error angle data received by a user side sky polarization compass; then, acquiring a conversion matrix, and calculating an updated course angle by using a course calculation method based on a Rayleigh scattering model and an inertial measurement unit;

the concrete implementation steps are as follows:

a) the sky polarization compass at the user end takes the received atmospheric refraction error angle phi as a known random common error item and distributes error angle information based on the horizontal attitude of the user end, namely the atmospheric refraction error angle phi is mapped to a roll angle gamma and a pitch angle theta, the information distribution is determined according to the following two formulas,

Δ γ and Δ θ represent the errors of roll angle and pitch angle, respectively, caused by atmospheric refraction errors;

b) and then, taking the delta gamma and the delta theta as known quantities to carry out course angle updating calculation as follows:

first obtaining an updated transformation matrix

Figure FDA0002226113630000023

And then, utilizing the Rayleigh scattering vertical relation:

Figure FDA0002226113630000024

Epthe polarization angle beta is measured by a polarization compass at the user end to obtain SnThe position time information of the user end is used for calculating the solar altitude Hs and the solar altitude As, so that Sn=[cosHs sinAs cosHs cosAs sinHs]T;Ep=[cosβ sinβ 0]TThe equation only contains an unknown number, namely the heading angle psi, and the heading of the user-side polarization compass after atmospheric refraction error correction is obtained by solving the unknown number.

Technical Field

The invention relates to an inversion and correction method for atmospheric refraction error of a differential sky polarization compass, which can be used for high-precision navigation of the sky polarization compass.

Background

The polarized sky light has a relatively stable distribution mode, and the azimuth information contained in the polarized light can be determined by combining the real-time, geographical position and other information of the carrier. The moving carrier utilizes the sky polarization compass to detect and calculate the sky polarized light, can obtain the navigation parameter of body, realizes the polarized light navigation of full autonomy. Atmospheric refraction is a common optical phenomenon, and sunlight or other electromagnetic waves which originally go straight forward can be deflected due to environmental factors such as air density when passing through the atmosphere. In fact, we see the sun somewhat higher than its actual position. This effect is more pronounced the closer to the horizon. In the technical fields of satellite optical remote sensing, GPS navigation positioning, astronomical measurement and the like, observation errors caused by atmospheric refraction effects must be considered.

The magnus and the like in the granted Chinese patent CN102346252A provide an atmospheric refraction compensation method in the optical satellite remote sensing data geographic positioning, and the high-precision positioning is realized by compensating the earth radius and then calculating and acquiring the coordinates of a ground point corresponding to a certain pixel point in a satellite image by using a conventional imaging model. In granted Chinese patent CN102261921A, Libaohua et al propose a method for correcting the influence of atmospheric refraction on the accuracy of a star sensor, decompose the atmospheric refraction value into a component delta X in the X-axis direction and a component delta Y in the Y-axis direction under the image space coordinate system of the star sensor, and then subtract the deviation delta X and delta Y caused by the atmospheric refraction value from all successfully identified star images to calculate the attitude quaternion. Although techniques and methods for correcting atmospheric refractive error have been developed in these related arts, these methods do not take into account their random variation characteristics, and generally use their empirical values for correction. In fact, the atmospheric refraction effect is affected by various factors such as zenith distance, air temperature, air pressure and humidity, is a random variation process, and has a large difference under different meteorological conditions.

The university of great connecting workers' Brooku-Quel team discloses a positioning system based on a multidirectional polarized light navigation sensor in an authorized Chinese patent CN103822629A, wherein polarized light angle sensors for measuring the maximum polarization direction of incident light are respectively arranged on any two planes of a fixed frame body, and the polarized light angle sensors can measure sky polarized light information in multiple directions to realize a navigation function. A sky polarized light navigation method based on public error update is proposed by the guo lei team of the university of aerospace in beijing in patent CN 2018103918761. The common error proposed by the method is the difference between the theoretical value of the maximum polarization degree and the actual measured value, and the method only corrects the value of the maximum polarization degree. The influence of atmospheric refraction errors on the polarization angle measurement value is not considered, and the problem that the course precision is reduced due to randomly changed atmospheric refraction errors cannot be solved. In the process of measurement and navigation calculation of the existing sky polarization compass, the influence of atmospheric refraction on polarized light transmission is not considered, and the polarized light is considered to be transmitted along a straight line. There is therefore inevitably an error caused by atmospheric refraction, which, although small in an ideal clear sky, must be corrected if high-precision polarized light navigation is to be achieved.

In general, the existing sky polarization compass has the defect that atmospheric refraction error correction is not performed, and the existing atmospheric refraction error correction methods in other technical fields also do not consider the random variation characteristic of atmospheric refraction, so that the correction methods have defects.

Disclosure of Invention

The technical problem of the invention is solved: the method comprises the steps of quantitatively summing the influence of atmospheric refraction effect on a sky polarization compass into an atmospheric refraction error angle, acquiring polarization information by using sky polarized light measurement reference stations at different positions, reflecting the atmospheric refraction error angle in the current sky, and performing navigation correction by using the data as a basis to calculate an updated course value. The method uses the thought that a difference GPS system eliminates a common error item of a reference station and a user side for reference, and can effectively reduce the influence of an atmospheric refraction error angle which changes randomly on a user side sky polarization compass by establishing the sky polarization light measurement reference station, and improve the calculation precision of the user side sky polarization compass heading.

The technical solution of the invention is as follows: an inversion and correction method for atmospheric refraction error of a differential sky polarization compass comprises the following steps:

(1) each sky polarized light measurement reference station independently measures the state of sky polarized light, and atmospheric refraction error angle data under the current sky is calculated by inversion according to the known position, time and heading information of the reference station and is uploaded to a sky polarized data center; the inversion calculation adopts a local atmospheric refraction error angle inversion algorithm, the atmospheric refraction error angle is inverted by using a course resolving method based on a Rayleigh scattering model and an inertial measurement unit based on the position, time and posture information of a reference station, the whole atmospheric refraction error item at a measurement end is calculated reversely from the result, the variation characteristic of the atmospheric refraction error is kept, and the establishment of a complex model of the atmospheric refraction error along with the variation of environmental parameters is avoided, and the method specifically comprises the following steps:

known reference station sky polarization compass heading Ψ0With time and position information, firstly calculating a sun altitude Hs and a sun azimuth As of a reference station, and then combining a roll angle gamma and a pitch angle theta output by an inertia measurement element on a sky polarization compass of the reference station and an actually measured polarization angle beta to invert an atmospheric refraction error angle phi under the sky where the current reference station is located:

Figure BDA0002226113640000021

the specific expression of each coefficient is as follows:

A1=cosγcosβcos Hs sin As+sinβcos Hs cos As

B1=-sinγcosβcos Hs sin As

A2=sinβcos Hs sin As-cosγcosβcos Hs cos As

B2=sinγcosβcos Hs cos As

A3=sinγcosβsin Hs

B3=cosγcosβsin Hs

(2) the sky polarized data center receives and stores atmospheric refraction error angle data transmitted by each sky polarized light measurement reference station;

(3) a user side sky polarization compass sends a data request to a sky polarization data center;

(4) the sky polarization data center selects a plurality of atmospheric refraction error angle data of the sky polarization light measurement reference station adjacent to the user side sky polarization compass, and distributes the atmospheric refraction error angle data to the user side sky polarization compass after weighting;

(5) the user side sky polarization compass carries out navigation correction by utilizing the received atmospheric refraction error angle data, and the heading precision is improved by 0.05-0.6 degrees.

The atmospheric refraction error angle in the step (1) refers to: the included angle between the apparent direction of the polarization compass and the actual transmission direction of the polarized light, which is caused by the refraction effect of the atmosphere on the light transmission, changes with the environment.

In the step (4), the conditions that atmospheric refraction error angle data of a plurality of sky polarized light measurement reference stations need to be simultaneously met are: (a) the user side sky polarization compass is within the effective radius of the reference station, i.e. under the same local sky. (b) The difference between the uploading time of the atmospheric refraction error angle data of the reference station and the current time is within a defined threshold range, and the data is considered to be invalid when the time difference exceeds the threshold.

In the step (5), the navigation correction process includes: firstly, information distribution is carried out on atmospheric refraction error angle data received by a user side sky polarization compass; and then acquiring the conversion matrix, and calculating an updated course angle by using a course calculation method based on the Rayleigh scattering model and the inertial measurement unit.

The concrete implementation steps are as follows:

a) and the user side sky polarization compass uses the received atmospheric refraction error angle phi as a known random common error item and carries out error angle information distribution based on the self horizontal attitude, namely the atmospheric refraction error angle phi is mapped to a roll angle gamma and a pitch angle theta, and the information distribution is determined according to the following two formulas.

Figure BDA0002226113640000031

Figure BDA0002226113640000032

Δ γ and Δ θ represent the errors of roll angle and pitch angle, respectively, caused by atmospheric refraction errors;

b) and then, taking the delta gamma and the delta theta as known quantities to carry out course angle updating calculation as follows:

firstly, obtaining an updated transformation matrix:

Figure BDA0002226113640000041

and then, utilizing the Rayleigh scattering vertical relation:

Figure BDA0002226113640000042

Epthe polarization angle beta can be measured by a polarization compass at a user end to obtain SnThe position time information of the user end can be used for calculating the solar altitude Hs and the solar altitude As. Thus Sn=[cos Hs sin As cos Hs cos As sin Hs]T;Ep=[cosβ sinβ 0]TIn known amounts. The equation only contains an unknown number, namely the heading angle psi, and the solution of the unknown number is to obtain the heading corrected by the atmospheric refraction error.

Compared with the prior art, the invention has the advantages that: by taking the thought that a difference GPS system eliminates a common error item of a reference station and a user terminal, the inversion and correction method of the atmospheric refraction error is provided, the atmospheric refraction error which changes randomly can be effectively inverted in real time by establishing the sky polarized light measurement reference station, the influence of the atmospheric refraction error when the user terminal polarization compass moves at a large inclination angle can be effectively reduced through a course correction algorithm, and the course accuracy of the sky polarization compass is improved.

Drawings

FIG. 1 is a schematic view of the detection relationship of a sky polarization compass in accordance with the present invention;

FIG. 2 is a system flow diagram of the present invention;

fig. 3 is a schematic diagram of the system of the present invention.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and examples.

As shown in fig. 2, according to the workflow shown in fig. 2 and the coordinate relationship defined in fig. 1, the specific implementation steps of the present invention are as follows:

(1) and each sky polarized light measuring reference station independently measures the state of the sky polarized light by using a sky polarized compass to obtain the actually measured polarized angle beta. The polarization E vector in the carrier system (sky polarization compass coordinate system) is therefore denoted Eb=Ep=[cosβ sinβ 0]T

(2) Then, the solar calendar (with associated calculation formula) is consulted through the position and time information of the reference station to obtain the solar vector in the current geographic system, which is expressed as Sn=[cos Hs sin As cos Hs cos As sin Hs]TWherein Hs and As respectively represent the solar altitude and the solar azimuth (north is positive).

(3) And (3) carrying out inversion calculation on the randomly changed atmospheric refraction error angle phi, wherein the polarization E vector of the point P needs to be converted into a geographical system, and the attitude matrix of the sky polarization compass is processed to obtain a conversion matrix:

Figure BDA0002226113640000051

that is, error amounts Δ γ and Δ θ are added to the roll angle γ and the pitch angle θ, which are determined by the atmospheric refraction error angle φ. The inclined posture of the sky polarization compass of the reference station is set to four conditions: (γ ═ e, θ ═ 0); (γ ═ e, θ ═ 0); (γ ═ 0, θ ∈); where the absolute values of Δ γ and Δ θ are equal to Φ (γ is 0 and θ is ∈), respectively, Φ can be calculated by an inversion algorithm. For example, (γ ═ e, θ ═ 0):

Figure BDA0002226113640000052

substituting the vector coordinates into the following Rayleigh scattering vertical relation expression to solve the atmospheric refraction error angle:

Figure BDA0002226113640000053

thus, when the reference station sky polarization compass heading Ψ0And the time and position information is known, and by combining the roll angle gamma output by the inertia measurement element on the sky polarization compass of the reference station and the actually measured polarization angle beta, the atmospheric refraction error angle under the sky where the current reference station is located can be inverted according to the steps (1), (2) and (3) as follows:

Figure BDA0002226113640000054

wherein each coefficient is:

A1=cosγcosβcos Hs sin As+sinβcos Hs cos As

B1=-sinγcosβcos Hs sin As

A2=sinβcos Hs sin As-cosγcosβcos Hs cos As

B2=sinγcosβcos Hs cos As

A3=sinγcosβsin Hs

B3=cosγcosβsin Hs

(4) the reference station sky polarization compass is continuously sampled at a predetermined sampling period to ensure tracking of randomly varying atmospheric refraction errors. In each sampling period, sequentially collecting the data under the four postures in the step (3), and calculating four atmospheric refraction error angles phi through inversion1,φ2,φ3,φ4Finally, the atmospheric refraction error angle in the local sky near the reference station is taken as its average value phi (phi)1234)/4. And after each sampling period is finished, uploading the atmospheric refraction error angle data to a sky polarization data center by the reference station.

(5) In the navigation motion process of the user side sky polarization compass, the inclination angle of the polarization compass relative to the horizontal plane is calculated according to the roll angle gamma and the pitch angle theta of the user side sky polarization compass, which are output by the inertial measurement unit.

Ω=cos-1(cosγcosθ)

Omega is the angle between the viewing direction of the sky polarization compass and the vertical direction. And setting a threshold, and when the omega is larger than the threshold, taking refraction influence into consideration to carry out navigation correction. The user polarization compass sends an atmospheric refraction error data request to the sky polarization data center. The sky polarization data center distributes an appropriate atmospheric refraction error angle phi to the user side sky polarization compass in a weighting mode.

Taking the system of fig. 3 as an example, the process of assigning atmospheric refraction error angle data to the center of sky polarization is described. The whole system comprises a sky polarization data center, a user side sky polarization compass and N reference stations, and the effective coverage areas of the sky polarization compass and the user side sky polarization compass are represented by circles. Because the user-side sky polarization compass is within the effective radius of the reference stations 4 and 5, the reference stations 4 and 5 are first selected as the pending data sources. And then, the uploading time of the atmospheric refraction error angle data of the reference stations 4 and 5 is considered, and if only the difference between the uploading time of the reference station 4 and the current time is within the defined threshold range, the atmospheric refraction error angle data of the reference station 4 is selected, and the atmospheric refraction error angle data of the reference station 5 is discarded. Finally, the sky polarization data center distributes the atmospheric refraction error angle phi of the reference station 4 to the user side sky polarization compass in a weighting mode.

(6) And the user-side polarization compass performs information distribution according to the received random common error term of the atmospheric refraction error angle phi and the horizontal attitude angles (roll angle gamma and pitch angle theta) output by the self inertial measurement element. The larger the horizontal attitude angle of the carrier, i.e. the higher the degree of tilt, the greater the effect of refraction. The atmospheric refraction error angle information is distributed as follows.

Figure BDA0002226113640000061

Figure BDA0002226113640000062

(7) And after the information distribution is finished, performing navigation correction to obtain new course information, and firstly obtaining an updated conversion matrix as follows:

Figure BDA0002226113640000063

and then, utilizing the Rayleigh scattering vertical relation:

Figure BDA0002226113640000064

Epthe polarization angle beta can be measured by a polarization compass at a user end to obtain SnThe solar altitude Hs and the solar altitude As can be calculated from the position time information of the user end, and specific expressions are listed in steps (1) and (2). Defining:

Figure BDA0002226113640000065

then substituting into delta gamma, delta theta and Sn、EpThe expression of (a) is arranged to obtain:

(A cos Hs sin As+B cos Hs cos As)cosΨ+(B cos Hs cos As-A cos Hs sin As)sinΨ

=-C sin Hs

defining a system of equations:

K1cosΨ+K2sinΨ=K3

K1=[A cos Hs sin As+B cos Hs cos As]

K2=[B cos Hs cos As-A cos Hs sin As]

K3=-C sin Hs

solving the equation set to obtain an updated course angle:

Figure BDA0002226113640000071

the method is a specific implementation step of inverting the atmospheric refraction error angle through the relevant measurement data of the reference station and distributing the atmospheric refraction error angle to a sky polarization compass at a user side for heading correction.

Fig. 1 and related steps in the summary of the invention are described in additional detail below.

The atmospheric refraction error angle proposed in the step (1) is an error angle between the apparent direction of the sky polarization compass and the actual polarization light transmission direction, which is caused by the atmospheric refraction effect on light transmission, and changes continuously with the change of environmental parameters. Therefore, we propose the following local atmospheric refraction error angle inversion method using the reference station information to perform dynamic estimation.

The method for realizing the atmospheric refraction error angle inversion of the reference station comprises the following steps:

a) firstly, a sky polarization compass detection diagram as shown in FIG. 1 is defined, wherein a coordinate system ENU represents a geographical coordinate system of northeast, and a coordinate system X represents a geographical coordinate system of northeastmYmZmRepresenting the sky polarization compass coordinate system. OZmThe sight line direction of the sky polarization compass is shown, the intersection point M of the sky polarization compass and the celestial sphere is a nominal measured polarization point, and the point P below the nominal measured polarization point is an actual measured polarization point. S is a projection point of the sun on the celestial sphere, and omega is an included angle between the sight line direction and the vertical direction of the sky polarization compass and is equal to the horizontal inclination angle of the sky polarization compass. When the horizontal inclination angle omega of the sky polarization compass is more than or equal to 70 degrees, the refraction effect needs to be considered for the light transmission, the phenomenon of the gas masking difference in the statistic atmospheric optics is similar, the actual light transmission route is PO below the sight line direction MO, and the polarization E vector of the point P is Ep. And defining the angle MOP as the atmospheric refraction error angle to be considered and as the variation.

b) Definition Carrier system XbYbZbCoordinate system X of sky polarization compassmYmZmCoincidence, navigation coordinate system XnYnZnDefined as the geographic coordinate system of the ENU northeast. Defining the polarization angle as the measured value of β in FIG. 1, the P-point polarization vector of the carrier system can be expressed as Eb=Ep=[cosβ sinβ 0]T

c) The solar vector in the navigation coordinate system can be obtained by consulting the solar calendar (with related calculation formula) through the position and time information, and is expressed as Sn=[cos Hs sin As cos Hs cos As sin Hs]TWherein Hs and As respectively represent the solar altitude and the sun under the geography systemAzimuth (north is positive).

d) Since the point actually measured is P, the polarization vector of the P point needs to be transformed into the geographical system. Because the transformation matrix for transferring the polarization vector of the point M to the geographical system is the attitude matrix of the sky polarization compass, and the ═ MOP ═ φ, the attitude matrix is correspondingly processed to obtain the transformation matrix:

Figure BDA0002226113640000081

psi, theta and gamma are respectively the heading angle, roll angle and pitch angle of the sky polarization compass. OZ of OP and sky polarization compassmThe axis has a refraction error angle phi, the influence of which is expressed as the change of a horizontal attitude angle, so that a corresponding conversion matrix can be obtained only by adding the variables delta gamma and delta theta to the roll angle and the pitch angle respectively, and the sizes of the delta gamma and the delta theta are determined by the current sky atmosphere refraction error angle phi.

e) Since phi is unknown and varies randomly, direct forward estimation by physical parameters is difficult, so that it needs to be calculated by inversion in a certain method. The specific allocation between φ and Δ γ and Δ θ is also unknown, but φ can be considered as an inclination angle, which is below the view direction of the sky polarization compass, so it is simply inferred that the absolute values of Δ γ and Δ θ are equal to φ when only roll and pitch angles are present, respectively. The tilted attitude of the reference station sky polarization compass is thus set to four cases: (γ ═ e, θ ═ 0); (γ ═ e, θ ═ 0); (γ ═ 0, θ ∈); and (gamma is 0 and theta is epsilon), wherein epsilon is an angle which is more than or equal to 70 degrees. In this case, the absolute values of Δ γ and Δ θ are equal to φ, respectively, and φ can be calculated by an inversion algorithm.

Here, the inversion algorithm will be described by taking (γ ∈, θ ═ 0) as an example. Heading Ψ of the reference station0As is known, this time:

Figure BDA0002226113640000082

based on the property of the rayleigh scattering model that the solar vector is perpendicular to the polarization E vector, the vector coordinates described above are substituted into:

Figure BDA0002226113640000083

finishing to obtain:

[(cosγ-φsinγ)cosβcos Hs sin As+sinβcos Hs cos As]cosΨ+[sinβcos Hs sin As

-(cosγ-φsinγ)cosβcos Hs cos As]sinΨ=(sinγ+φcosγ)cosβsin Hs

thus, when the reference station sky polarization compass heading Ψ0And the time and position information are known, and by combining the roll angle gamma output by an inertia measuring element on a sky polarization compass of the reference station and the actually measured polarization angle beta, the atmospheric refraction error angle under the sky where the current reference station is located can be calculated by inversion according to the steps as follows:

wherein each coefficient is:

A1=cosγcosβcos Hs sin As+sinβcos Hs cos As

B1=-sinγcosβcos Hs sin As

A2=sinβcos Hs sin As-cosγcosβcos Hs cos As

B2=sinγcosβcos Hs cos As

A3=sinγcosβsin Hs

B3=cosγcosβsin Hs

the strategy of inverting atmospheric refraction error angle data of the reference station under the current sky in the step (1) and uploading the data to the sky polarization data center is as follows: in each sampling period of the base station sky polarization compass, data under four postures are sequentially collected, and the four atmospheric refraction error angles phi are calculated through inversion1,φ2,φ3,φ4Finally, the atmospheric refraction error angle in the current sky of the reference station is taken as the average value phi (phi)1234)/4. After each sampling period is completed, the reference station refracts the atmospheric errorThe angular data is uploaded to a sky polarization data center.

In the step (4), the rule for selecting the atmospheric refraction error angle data includes: a) the user side sky polarization compass is positioned in the effective radius of the reference station, namely positioned in the same local sky; b) the difference between the uploading time of the atmospheric refraction error angle data and the current time is within a defined threshold range, and the data is considered to be invalid when the time difference exceeds the threshold. Because the atmospheric composition varies with the distribution of the terrain, the refraction characteristics of the atmospheric composition are related to weather, temperature, particle characteristics and the like in the current sky range, the atmospheric environment of the same area is not fixed and constant, and the external atmospheric refraction error of the sky polarization compass also varies randomly, data which is within the effective radius of the reference station and the time difference of which meets the requirement of a threshold value needs to be selected.

In the step (5), the navigation correction method using the atmospheric refraction error angle means that information distribution is performed on a random common error item, which is received atmospheric refraction error angle data, based on roll angle and pitch angle data output by a user-side sky polarization compass inertia measurement element to obtain a corrected attitude matrix. And then the corrected attitude matrix is used for transferring the actually measured polarization vector to the geographical system. And based on a Rayleigh scattering model, calculating the updated course by utilizing the principle that the polarization vector is vertical to the sun vector under the geographic system. The specific implementation algorithm is as follows:

a) and the sky polarization compass at the user side distributes information according to the received atmospheric refraction error angle phi. That is, the atmospheric refraction error angle phi is mapped to the roll angle gamma and the pitch angle theta. According to the spherical trigonometric formula, there is the following equation:

cos(Ω+φ)=cos(γ+Δγ)cos(θ+Δθ)

because φ, Δ θ, Δ γ are small quantities, the trigonometric function is a bounded function with a value range of [ -1,1], which is obtained after simple processing:

cosφ≈cosΔγcosΔθ

i.e. the transfer of the angular variation is similar to the attitude rotation. The omission of higher order terms is developed using the Taylor formula:

φ2≈(Δγ)2+(Δθ)2

the larger the two horizontal attitude angles (roll angle gamma and pitch angle theta) of the user-side sky polarization compass are, namely the higher the inclination degree is, the larger the influence of randomly-changed atmospheric refraction is. Therefore, assuming that the distribution value of the atmospheric refraction error angle Φ on each axis is proportional to the magnitudes of the two horizontal attitude angles, it is obtained in the case where the above equation is satisfied:

Figure BDA0002226113640000091

Figure BDA0002226113640000092

for example, when θ is 0, Δ γ is Φ, which is consistent with the foregoing reasoning.

b) And then correcting the attitude matrix of the sky polarization compass at the user end by using the delta gamma and the delta theta as known random common error terms, and further performing heading updating calculation as described below.

Firstly, correcting the attitude matrix to obtain an updated transformation matrix:

Figure BDA0002226113640000101

and then, utilizing the Rayleigh scattering vertical relation:

Figure BDA0002226113640000102

Epthe polarization angle beta can be measured by a polarization compass at a user end to obtain SnThe solar altitude Hs and the solar altitude As can be calculated from the position time information of the user end, and the specific expression is given in the foregoing. Substitution into Sn、EpAfter finishing, define:

Figure BDA0002226113640000103

then derive the arrangement to

(A cos Hs sin As+B cos Hs cos As)cosΨ+(B cos Hs cos As-A cos Hs sin As)sinΨ

=-C sin Hs

Namely the following equation:

K1cosΨ+K2sinΨ=K3

K1=[A cos Hs sin As+B cos Hs cos As]

K2=[B cos Hs cos As-A cos Hs sin As]

K3=-C sin Hs

solving the equation set to obtain an updated course:

Figure BDA0002226113640000104

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