A polarization orientation method based on Rayleigh point information

Abstract

This invention discloses a polarization-oriented light method based on Rayleigh point information, comprising: acquiring a sky polarization image and calculating the measured polarization angle of each measurement point in the sky polarization image; calculating the ideal polarization angle of each measurement point in the sky polarization image, and obtaining the polarization angle error of each measurement point based on the measured polarization angle and the ideal polarization angle; selecting Rayleigh points from all measurement points based on the polarization angle error, and performing polarization-oriented light orientation based on all Rayleigh points to obtain the heading angle of the carrier. This invention is applied to the field of polarization-oriented light navigation. By comparing the measured polarization angle with the theoretical polarization angle of each measurement point before polarization-oriented light orientation, and selecting Rayleigh points in the sky polarization image based on the polarization angle error between the measured and theoretical polarization angles, and then performing polarization-oriented light orientation only using the selected Rayleigh points, the accuracy of polarization-oriented light orientation is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of polarized light navigation technology, specifically a polarized light orientation method based on Rayleigh point information. Background Technology

[0002] Accurate positioning information is the foundation for autonomous navigation of long-endurance unmanned platforms. However, in environments with limited satellite coverage or complex electromagnetic interference, existing inertial navigation systems suffer from error accumulation, and geomagnetic navigation is susceptible to interference, failing to meet the high-precision navigation requirements of unmanned platforms.

[0003] Sunlight, during its propagation, is absorbed and scattered by atmospheric particles, producing polarized light. A large amount of polarized light converges in the sky, forming an atmospheric polarization pattern with a certain distribution. This atmospheric polarization pattern contains directional information. Based on the geometric characteristic of the Rayleigh scattering model—that the polarized light vector E is perpendicular to the scattering surface—the azimuth of the carrier can be estimated by measuring atmospheric polarization information. Therefore, Rayleigh scattering is an important theoretical method for characterizing atmospheric polarization patterns. However, it only occurs when the particle size is much smaller than the incident light wavelength, making it difficult for Rayleigh scattering theory to explain the influence of other particles such as water vapor and aerosols on the scattering process. Furthermore, due to the complexity of weather, a single scattering model cannot describe all types of weather. Even in clear weather, other scattering besides Rayleigh scattering exists, especially in clear weather with obstructions, few clouds, cloudy skies, or overcast conditions, leading to increased orientation errors. Summary of the Invention

[0004] To address the shortcomings of the prior art, this invention provides a polarization orientation method based on Rayleigh point information, which can effectively improve the accuracy of polarization orientation.

[0005] To achieve the above objectives, the present invention provides a polarization orientation method based on Rayleigh point information, comprising the following steps:

[0006] Step 1: Acquire a sky polarization image based on the polarization compass on the carrier, and calculate the measured polarization angle of each measurement point in the sky polarization image;

[0007] Step 2: Calculate the ideal polarization angle of each measurement point in the sky polarization image, and obtain the polarization angle error of each measurement point based on the measured polarization angle and the ideal polarization angle;

[0008] Step 3: Based on the polarization angle error, select Rayleigh points from all measurement points, and perform polarization light orientation based on all Rayleigh points to obtain the heading angle of the carrier.

[0009] In one embodiment, the calculation process for the measured polarization angle in step 1 is as follows:

[0010] The Stokes vector S0 contains four parameters S0 = [S1 S2 S3 S4], where S1 represents the total light intensity, S2 is the light intensity difference between the 0° and 90° directions, S3 is the light intensity difference between the 45° and 135° directions, and S4 is the circular polarization component. Therefore, the light intensity of the polarized light after passing through the polarizer is:

[0011]

[0012] Where θ1 is the polarization angle, It is the angle between the polarization direction of the sensor and the optical axis of the system;

[0013] Omitting the S4 component, we obtain the simplified Stokes intensity equation as follows:

[0014]

[0015] When the polarization angle θ1 is taken as 0°, 45°, and 90° respectively, the Stokes parameters of the measurement point are obtained as follows:

[0016]

[0017] Neglecting circularly polarized light, the measured polarization angle at the measurement point can be obtained as φ. a = (1 / 2)·arctan(S3 / S2).

[0018] In one embodiment, the calculation process for the ideal polarization angle in step 2 is as follows:

[0019] The projection v of the observation direction vector v of the measurement point onto the optical compass coordinate system is calculated. c ,for:

[0020] v c =[sinγ v ·cosα v sinγ v ·sinα v -cosγ v ] T

[0021] Where T is the transpose of the matrix, α v γ is the azimuth angle of the measured point in the optical compass coordinate system. v The zenith angle of the measurement point in the optical compass coordinate system;

[0022] The projection s of the solar direction vector s onto the optical compass coordinate system is calculated. c ,for:

[0023]

[0024] in, This is the transformation matrix from the carrier coordinate system to the optical compass coordinate system. The transformation matrix from the navigation coordinate system to the optical compass coordinate system is s. n The sun's direction vector in the navigation coordinate system;

[0025] Based on the projection of the observation direction vector v and the solar direction vector s onto the optical compass coordinate system. c s c The projection e of the measurement point's vector E on the optical compass coordinate system is calculated. c ,for:

[0026] e c =k·v c ×s c

[0027] Where k is a constant that makes both sides of the equation equal;

[0028] Project the vector E of the measurement point onto the optical compass coordinate system. c Transform to the coordinate system of the measurement point, as follows:

[0029]

[0030] in, Let e1, e2, and e3 be the transformation matrix from the optical compass coordinate system to the measurement point coordinate system, where e1, e2, and e3 are vectors. v The three elements; Furthermore, the E vector e of the measurement point in the coordinate system of the measurement point can also be represented by the polarization angle, as:

[0031]

[0032] Therefore, the ideal polarization angle of the measurement point is φ. b =arctan(e2 / e1).

[0033] In one embodiment, the transformation matrix distance from the carrier coordinate system to the optical compass coordinate system is:

[0034]

[0035] The transformation matrix from the navigation coordinate system to the optical compass coordinate system is specifically as follows:

[0036]

[0037] Among them, r0, θ0, and Ψ0 are provided by other sensors to measure the carrier's roll angle, pitch angle, and yaw angle, respectively.

[0038] The solar direction vector in the navigation coordinate system is specifically:

[0039]

[0040] in, This represents the azimuth angle of the solar direction vector in the navigation coordinate system. The elevation angle of the solar direction vector in the navigation coordinate system.

[0041] In one embodiment, the constant k that makes both sides of the equation equal is specifically:

[0042]

[0043] Where τ is the scattering angle.

[0044] In one embodiment, in step 2, the polarization angle error specifically refers to:

[0045] Δφ=|φ a -φ b |

[0046] Where Δφ is the polarization angle error, φ a For the measured polarization angle, φ b This is the ideal polarization angle.

[0047] In one embodiment, step 3, the process of selecting Rayleigh points from all measurement points based on the polarization angle error, is as follows:

[0048] For any measurement point, determine whether its polarization angle error satisfies Δφ≤φ thres If so, the measurement point is a Rayleigh point; otherwise, it is a non-Rayleigh point, where φ thres The threshold value is used.

[0049] In one embodiment, the threshold φ thres =5°.

[0050] In one embodiment, step 3, the process of polarization orientation based on all Rayleigh points, is as follows:

[0051] Obtain the Rayleigh point set E consisting of all Rayleigh points. c ,for:

[0052]

[0053] in, i = 1 to L is the projection of the E vector of the i-th Rayleigh point onto the optical compass coordinate system, and L is the total number of Rayleigh points;

[0054] Rayleigh Points E c Each Rayleigh point satisfies the polarization vector orthogonality, that is:

[0055]

[0056] in, i = 1 to l is the projection of the observation direction vector of the i-th Rayleigh point onto the optical compass coordinate system, s c This is the projection of the solar direction vector onto the optical compass coordinate system;

[0057] At the same time and location, different Rayleigh points correspond to different E vectors and different observation direction vectors, but the corresponding solar direction vector is consistent. Therefore, by solving a system of equations for all Rayleigh points and using the Lagrange multiplier method, the projection s of the solar direction vector onto the optical compass coordinate system can be obtained. c ;

[0058] Furthermore, the projection of the solar direction vector onto the optical compass coordinate system can also be expressed as:

[0059]

[0060] Where, α s h is the azimuth angle of the solar direction vector in the optical compass coordinate system. s The zenith angle of the solar direction vector in the optical compass coordinate system;

[0061] Right now:

[0062]

[0063] Among them, s c (1), s c (2) Divided into vectors s c The first and second elements in;

[0064] Based on the azimuth angle α of the solar direction vector in the optical compass coordinate system s and the azimuth angle of the solar direction vector in the navigation coordinate system The heading angle of the carrier can then be obtained as follows:

[0065]

[0066] or

[0067]

[0068] Where Ψ is the heading angle of the carrier, and π is the ambiguity of the polarization direction.

[0069] Compared with the prior art, the present invention has the following beneficial technical effects:

[0070] This invention significantly improves the accuracy of polarization light orientation by comparing the measured polarization angle with the theoretical polarization angle at each measurement point before polarization light orientation, and by selecting Rayleigh points in the sky polarization image based on the polarization angle error between the measured and theoretical polarization angles, and then performing polarization light orientation only using the selected Rayleigh points. Attached Figure Description

[0071] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0072] Figure 1 This is a flowchart of the polarization orientation method based on Rayleigh point information in an embodiment of the present invention;

[0073] Figure 2 This is a schematic diagram of the scattering process of sunlight in the sky in an embodiment of the present invention;

[0074] Figure 3 This is a schematic diagram illustrating the influence of the Rayleigh point ratio on orientation error in an embodiment of the present invention.

[0075] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0076] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0077] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0078] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0079] This embodiment discloses a polarization light orientation method based on Rayleigh point information. Before polarization light orientation, the measured polarization angle and theoretical polarization angle of each measurement point are compared. Based on the polarization angle error between the measured and theoretical polarization angles, Rayleigh points in the sky polarization image are selected. Then, polarization light orientation is performed only using the selected Rayleigh points, thereby significantly improving the accuracy of polarization light orientation.

[0080] refer to Figure 1 The polarization orientation method based on Rayleigh point information in this embodiment specifically includes the following steps:

[0081] Step 1: Acquire sky polarization images based on the polarization compass on the carrier, and calculate the measured polarization angles of each measurement point in the sky polarization images;

[0082] Step 2: Calculate the ideal polarization angle of each measurement point in the sky polarization image, and obtain the polarization angle error of each measurement point based on the measured polarization angle and the ideal polarization angle;

[0083] Step 3: Based on the polarization angle error, Rayleigh points are selected from all measurement points, and polarization light orientation is performed based on all Rayleigh points to obtain the heading angle of the carrier.

[0084] refer to Figure 2 This is a schematic diagram illustrating the scattering process of sunlight in the sky, where O c V represents the observer on the ground, S represents the measuring point in the sky, Z represents the zenith, N represents geographic north, τ represents the scattering angle, and γ represents the scattering angle. s α s These represent the solar zenith angle and azimuth angle, respectively; φ represents the polarization angle of the measurement point; α v γ represents the azimuth angle of the measurement point. v α v These represent the zenith angle and azimuth angle of the measurement point V in the polarized compass coordinate system, respectively.

[0085] In this embodiment, the right-front-up coordinate system is defined as the polarization compass coordinate system (hereinafter referred to as the "c system"), X c axis and Y c The axes point to the horizontal and vertical axes of the polarizing compass, respectively. c The Z-axis is the direction of the optical axis of the polarizing compass, after leveling. c The axis points towards the zenith. The North-East-Earth coordinate system is defined as the navigation coordinate system (hereinafter referred to as the "n-system"), using O... n -X n Y n Z n It indicates that O n With O c coincide, Figure 2 For the sake of brevity, Y is omitted.n Axis and Z n Axis, X n The axis is oriented north. Figure 2 In this context, N is used to represent the coordinate system. The front-right-bottom coordinate system is defined as the carrier coordinate system (hereinafter referred to as the "b system"), denoted by O. b -X b Y b Z b Let O represent this. b With O c coincide, Figure 2 For the sake of brevity, Y is omitted. b Axis and Z b The axis, the heading angle Ψ of the carrier is X b The angle between the axis and N. Define O. v -X v Y v Z v Let Z be the coordinate system of the measurement point (hereinafter referred to as "v system"). v The axis points in the direction of the measurement point, X v The axis lies in the observation plane ΔO v Inside VV', Y v The axis can be determined by the right-hand rule. Figure 2 For the sake of brevity, Y is omitted. v The axes are: e is the unit vector of the polarized light E vector vibration direction at measurement point V, v is the unit vector of the observation direction, and s is the unit vector of the solar direction.

[0086] In this embodiment, the measured polarization angle of the measurement point can be calculated using the Stokes vector method. The Stokes vector contains four parameters S0 = [S1 S2 S3 S4], where S1 represents the total light intensity, S2 is the light intensity difference between the 0° and 90° directions, S3 is the light intensity difference between the 45° and 135° directions, and S4 is the circular polarization component. Therefore, the light intensity of the polarized light after passing through the polarizer is:

[0087]

[0088] Where θ1 is the polarization angle, It is the angle between the polarization direction of the sensor and the optical axis of the system;

[0089] Since circular polarization components are rare in nature, the S4 component is generally omitted in practical calculations, resulting in the simplified Stokes intensity equation:

[0090]

[0091] When the polarization angle θ1 is 0°, 45°, and 90° respectively, the Stokes parameter of each pixel in the image is obtained as follows:

[0092]

[0093] Neglecting circularly polarized light, the measured polarization angle at each measurement point is:

[0094]

[0095] Where, φ a The measured polarization angle is the actual polarization angle at the measurement point.

[0096] In this embodiment, the ideal polarization angle of the measurement point is calculated based on a simulation model of the ideal atmospheric polarization mode. The specific implementation process is as follows:

[0097] Depend on Figure 2 It can be seen that the projection of the observation direction vector v onto the c-frame is v c for:

[0098] v c =[sinγ v ·cosα v sinγ v ·sinα v -cosγ v ] T (5)

[0099] T is the transpose of the matrix, and γ is the zenith angle of the measurement point in the c-frame. v and azimuth α v Specifically:

[0100]

[0101] Among them, (x v y v (x) represents the coordinates of the observation point in the atmospheric polarization image. c y c f represents the coordinates of the center point of the atmospheric polarization image. c The focal length of the polarization compass obtained through calibration;

[0102] The solar direction vector s in the n-frame can be expressed as:

[0103]

[0104] in, This represents the azimuth angle of the solar direction vector in the navigation coordinate system. Let the elevation angle of the solar direction vector in the navigation coordinate system be given the time and geographical location. It can be obtained through the solar ephemeris;

[0105] s n When converted to the C-family system, the following are available:

[0106]

[0107] The transformation matrix from the b-system to the c-system is expressed as:

[0108]

[0109] Let be the transformation matrix from the n-system to the c-system, expressed as:

[0110]

[0111] Among them, r0, θ0, and Ψ0 are provided by other sensors (such as satellite dual antennas) to measure the carrier's roll angle, pitch angle, and yaw angle, respectively.

[0112] According to Rayleigh scattering theory, in the same coordinate system, the E vector of polarized light is perpendicular to the scattering surface. Therefore, the projection of the E vector e at the measurement point onto the optical compass coordinate system is e. c for:

[0113] e c =k·v c ×s c (12)

[0114] k is a constant that makes both sides of the equation equal, expressed as:

[0115]

[0116] Where τ is the scattering angle;

[0117] The projection of the measurement point's vector e, obtained from equation (12), onto the c-system is e c Converting to the V-series, we get:

[0118]

[0119] e1, e2, and e3 are vectors e v The three elements; The transformation matrix from the optical compass coordinate system to the measurement point coordinate system is expressed as:

[0120]

[0121] Furthermore, the E vector e of the measurement point in the coordinate system of the measurement point can also be represented by the ideal polarization angle, as follows:

[0122]

[0123] Combining equations (15) and (17), the ideal polarization angle of the measurement point can be obtained as φ. b=arctan(e2 / e1).

[0124] According to the calculation process of the ideal polarization angle, given a fixed geographical location, time, and carrier attitude angle, the ideal polarization angle of the measurement point under the current condition can be obtained.

[0125] After calculating the measured polarization angle and the ideal polarization angle at the measurement point, the polarization angle error can be calculated. In this embodiment, the polarization angle error is specifically as follows:

[0126] Δφ=|φ a -φ b | (18)

[0127] Where Δφ is the polarization angle error.

[0128] In step 3, the process of selecting Rayleigh points from all measurement points based on polarization angle error is specifically as follows: For any measurement point, determine whether its polarization angle error satisfies:

[0129] Δφ≤φ thres (19)

[0130] Where, φ thres For the threshold;

[0131] If so, the measurement point is a Rayleigh point; otherwise, it is a non-Rayleigh point. In this embodiment, a threshold φ is set. thres =5°.

[0132] After completing the selection of Rayleigh points, polarization orientation can be performed based on all Rayleigh points. The specific implementation process is as follows:

[0133] Assuming there are L Rayleigh points selected, we first obtain the Rayleigh point set E consisting of all Rayleigh points. c ,for:

[0134]

[0135] in, i = 1 to L is the projection of the E vector of the i-th Rayleigh point onto the optical compass coordinate system;

[0136] Rayleigh Points E c Each Rayleigh point satisfies the polarization vector orthogonality, that is:

[0137]

[0138] in, i = 1 to L is the projection of the observation direction vector of the i-th Rayleigh point onto the optical compass coordinate system;

[0139] As shown in equation (20), at the same time and location, different Rayleigh points correspond to different E vectors and different observation direction vectors, but the corresponding solar direction vector is the same. Therefore, by solving the system of equations for all Rayleigh points and using the Lagrange multiplier method, the projection s of the solar direction vector on the optical compass coordinate system can be obtained. c ;

[0140] Furthermore, the projection of the solar direction vector onto the optical compass coordinate system can also be expressed as:

[0141]

[0142] Where, α s h is the azimuth angle of the solar direction vector in the optical compass coordinate system. s The zenith angle of the solar direction vector in the optical compass coordinate system;

[0143] Then, according to equation (20), s can be calculated. c Then we can obtain the azimuth angle of the solar direction vector in the c system, that is:

[0144]

[0145] Among them, s c (1), s c (2) Divided into vectors s c The first and second elements in;

[0146] Finally, by combining the time and the solar ephemeris, the azimuth of the solar direction vector in the n-system is obtained. The heading angle of the carrier can then be obtained as follows:

[0147]

[0148]

[0149] or

[0150]

[0151] Where Ψ is the heading angle of the carrier, and π is the ambiguity of the polarization direction.

[0152] In practice, the ambiguity π of polarized light orientation can be removed by the quadrant position of the solar meridian projection or the difference in heading angle between adjacent frames.

[0153] The polarization orientation method based on Rayleigh point information in this embodiment will be further explained below with specific examples.

[0154] Assume there are M measurement points in the acquired sky polarization image, and the measured polarization angles of these measurement points are:

[0155] P1=[φ1,φ2,…,φ M (26)

[0156] The theoretical polarization angle at each measurement point is:

[0157] P2=[φ1',φ2',…,φ M '] (27)

[0158] Therefore, the polarization angle error at these measurement points is:

[0159] P3=[Δφ1,Δφ2,…,Δφ M (28)

[0160] When the horizontal attitude angle of the carrier is 0°, the measurement error of the polarization angle will be proportionally transferred to the heading angle estimation error. Therefore, the orientation error ΔΨ caused by the polarization angle measurement error at this time... error for:

[0161]

[0162] Equation (28) shows that the polarization angle error of each measurement point will affect the orientation error, and their weights are all 1 / M. If the polarization angle error of some measurement points is large, it will affect the final orientation accuracy.

[0163] Assuming the first measurement point to m (m≤M) measurement points are Rayleigh points satisfying equation (19), then the orientation error is calculated using only Rayleigh points. for:

[0164]

[0165] Since the Rayleigh points used for orientation are all measurement points with small polarization angle errors, therefore:

[0166]

[0167] Equation (31) demonstrates that the orientation error using only Rayleigh points is less than or equal to the orientation error using all measurement points. To more intuitively illustrate that using only Rayleigh points improves orientation accuracy, let's assume an extreme case: the first to the mth measurement points are Rayleigh points, each with a polarization angle error of a1, while the (m+1)th to the Mth measurement points are non-Rayleigh points, each with an error of a2, where a1 and a2 are both definite constants. If only the polarization angle measurement error is considered, then the orientation error ΔΨ calculated using all measurement points would be... error for:

[0168]

[0169] Let K1 be the proportion of Rayleigh points to all measurement points and K2 be the proportion of non-Rayleigh points to all measurement points. Then equation (32) can be rewritten as:

[0170] ΔΨ error =K1·a1+K2·a2 (33)

[0171] Taking a1 = 3° and a2 = 15°, the orientation error is:

[0172] ΔΨ error =3a1+15a2 (34)

[0173] The diagram illustrating the impact of Rayleigh point percentage on orientation error is shown below. Figure 3 As shown. From Figure 3 It is known that the proportion of Rayleigh points directly affects the polarization direction accuracy. The higher the proportion of Rayleigh points, the smaller the direction error, while the higher the proportion of non-Rayleigh points, the larger the direction error.

[0174] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A polarization orientation method based on Rayleigh point information, characterized in that, Includes the following steps: Step 1: Acquire a sky polarization image based on the polarization compass on the carrier, and calculate the measured polarization angle of each measurement point in the sky polarization image; Step 2: Calculate the ideal polarization angle at each measurement point in the sky polarization image, and obtain the polarization angle error at each measurement point based on the measured polarization angle and the ideal polarization angle. The ideal polarization angle is then calculated based on a simulation model of the ideal atmospheric polarization mode. The observation direction vector of the measurement point is calculated. Projection on the optical compass coordinate system ,for: in, This is the transpose of the matrix. To measure the azimuth of the point in the optical compass coordinate system, The zenith angle of the measurement point in the optical compass coordinate system; The solar direction vector was calculated. Projection on the optical compass coordinate system ,for: in, This is the transformation matrix from the carrier coordinate system to the optical compass coordinate system. This is the transformation matrix from the navigation coordinate system to the optical compass coordinate system. The sun's direction vector in the navigation coordinate system; Based on the observation direction vector Solar direction vector Projection on the optical compass coordinate system , The E vector of the measurement point is calculated. Projection on the optical compass coordinate system ,for: in, A constant that makes both sides of the equation equal; The E vector of the measurement point Projection on the optical compass coordinate system Transform to the coordinate system of the measurement point, as follows: in, This is the transformation matrix from the optical compass coordinate system to the measurement point coordinate system. , , For vectors The three elements; In addition, the E vector of the measurement point In the coordinate system of the measurement point, expressed by the polarization angle, it is: Therefore, the ideal polarization angle of the measurement point is: ; Step 3: Based on the polarization angle error, select Rayleigh points from all measurement points, and perform polarization light orientation based on all Rayleigh points to obtain the heading angle of the carrier; the constant that makes both sides of the equation equal. Specifically: in, The scattering angle is denoted by .

2. The polarization orientation method based on Rayleigh point information according to claim 1, characterized in that, In step 1, the calculation process for the measured polarization angle is as follows: Stokes vector Includes four parameters ,in, Represents the total light intensity. It is the difference in light intensity at 0° and 90°. It is the difference in light intensity at 45° and 135°. If the polarization component is circular, then the intensity of the polarized light after passing through the polarizer is: in, It is the polarization angle. It is the angle between the polarization direction of the sensor and the optical axis of the system; Will By omitting the components, the simplified Stokes intensity equation is obtained as follows: When the polarization angle When the angles are 0°, 45°, and 90° respectively, the Stokes parameters of the measurement point are as follows: Neglecting circularly polarized light, the measured polarization angle at the measurement point can be obtained as follows: .

3. The polarization orientation method based on Rayleigh point information according to claim 2, characterized in that, The transformation matrix distance from the carrier coordinate system to the optical compass coordinate system is: The transformation matrix from the navigation coordinate system to the optical compass coordinate system is specifically as follows: in, , , The roll angle, pitch angle, and yaw angle of the carrier are provided by other sensors, respectively. The solar direction vector in the navigation coordinate system is specifically: in, This represents the azimuth angle of the solar direction vector in the navigation coordinate system. The elevation angle of the solar direction vector in the navigation coordinate system.

4. The polarization orientation method based on Rayleigh point information according to any one of claims 1 to 3, characterized in that, In step 2, the polarization angle error specifically refers to: in, For polarization angle error, For the measured polarization angle, This is the ideal polarization angle.

5. The polarization orientation method based on Rayleigh point information according to claim 4, characterized in that, In step 3, the process of selecting Rayleigh points from all measurement points based on the polarization angle error is as follows: For any measurement point, determine whether its polarization angle error satisfies the following conditions. If so, the measurement point is a Rayleigh point; otherwise, it is a non-Rayleigh point. The threshold value is used.

6. The polarization orientation method based on Rayleigh point information according to claim 5, characterized in that, The threshold .

7. The polarization orientation method based on Rayleigh point information according to any one of claims 1 to 3, characterized in that, In step 3, the process of polarizing light orientation based on all Rayleigh points is as follows: Obtain the set of Rayleigh points consisting of all Rayleigh points. ,for: in, For the first The projection of the E vector of a Rayleigh point onto the optical compass coordinate system The total number of Rayleigh points; Rayleigh Points Each Rayleigh point satisfies the polarization vector orthogonality, that is: in, For the first The projection of the observation direction vector of each Rayleigh point onto the optical compass coordinate system This is the projection of the solar direction vector onto the optical compass coordinate system; At the same time and location, different Rayleigh points correspond to different E vectors and different observation direction vectors, but the corresponding solar direction vector is consistent. Therefore, by solving a system of equations for all Rayleigh points and using the Lagrange multiplier method, the projection of the solar direction vector onto the optical compass coordinate system can be obtained. ; Furthermore, the projection of the solar direction vector onto the optical compass coordinate system is expressed as: in, This is the azimuth angle of the solar direction vector in the optical compass coordinate system. The zenith angle of the solar direction vector in the optical compass coordinate system; Right now: in, , Divided into vectors The first and second elements in; Based on the azimuth angle of the solar direction vector in the optical compass coordinate system and the azimuth angle of the solar direction vector in the navigation coordinate system The heading angle of the carrier can then be obtained as follows: or in, The heading angle of the carrier. Ambiguity for the orientation of polarized light.

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