Method for obtaining RR polarimetric mirror reflectivity and polarimetric GNSS-R inversion method

Abstract

The application provides a RR polarization mirror reflectivity acquisition method, which is used for a polarization GNSS-R inversion method, and the method comprises the following steps: establishing a Mueller matrix for determining RR polarization mirror reflectivity, so that the RR polarization mirror reflectivity increases with the increase of soil moisture; acquiring an incident angle, a dielectric constant and a surface roughness in GNSS-R satellite data; and determining the RR polarization mirror reflectivity by using the Mueller matrix according to the incident angle, the dielectric constant and the surface roughness. The RR polarization mirror reflectivity acquisition method determines the parameters under the conditions of vv, hh and hv, and determines the RR polarization mirror reflectivity according to the Mueller matrix, so that the accuracy of the acquired effective reflectivity of the RR polarization is higher, and the accuracy of the polarization GNSS-R inversion method is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of GNSS-R technology, specifically relating to a method for obtaining RR polarization mirror reflectivity and a polarization GNSS-R inversion method. The method for obtaining RR polarization mirror reflectivity is specifically used in a simplified polarization GNSS-R inversion method. Background Technology

[0002] GNSS-R technology is an emerging Earth observation method that utilizes navigation satellite reflected signals to remotely sense ground parameters. Because it does not require a dedicated transmitter, its significant advantages include small size, light weight, low power consumption, and high spatiotemporal resolution, making it an important emerging force in the field of navigation and remote sensing. In its initial applications, GNSS-R used LHCP polarized antennas to receive surface reflected signals; therefore, LR polarization was employed for surface parameter inversion studies.

[0003] With the development of GNSS technology, the reception and utilization of GNSS reflected signals are no longer limited to the original LR polarization. R and L represent RHCP (right-hand circular polarization) and LHCP (left-hand circular polarization), respectively. Using antennas with other polarizations to receive reflected signals other than LHCP has become an important trend in current and future receiver design. The reception and utilization of RR polarization has become a significant factor in improving the accuracy of GNSS-R technology inversion of surface parameters. For example, the HydroGNSS, planned for launch by ESA in 2024, employs a dual-polarization design, using both RHCP and LHCP receiver antennas to receive surface reflected signals. This means that during the inversion process, RR and LR polarization reflectivity data will be used together to improve the accuracy of surface parameter inversion.

[0004] Current formulas for calculating reflectivity in RR polarization suffer from significant discrepancies between theoretical calculations and actual data due to excessive assumptions in the models.

[0005] Therefore, in order to address the above problems, it is urgent to develop and establish a mirror reflectivity model for RR polarization applicable to random rough surface scattering, so as to achieve accurate prediction of mirror reflectivity for RR polarization. Summary of the Invention

[0006] The purpose of this invention is to provide a method for obtaining RR polarization mirror reflectivity and a polarization GNSS-R inversion method, so as to achieve accurate prediction of RR polarization mirror reflectivity.

[0007] To achieve the above objective, a method for obtaining RR polarized mirror reflectivity, used in polarized GNSS-R inversion methods, includes:

[0008] S1: Establish a Müller matrix for determining the RR polarization mirror reflectivity, wherein the Müller matrix causes the RR polarization mirror reflectivity to increase with increasing soil moisture;

[0009] S2: Obtain the incident angle, dielectric constant, and surface roughness from GNSS-R satellite data;

[0010] S3: Determine the RR polarization mirror reflectivity using the Müller matrix based on the incident angle, dielectric constant, and surface roughness.

[0011] The Müller matrix uses the scattering coefficients under the vv co-polarization condition, the hh co-polarization condition, and the hv cross-polarization condition as its basic elements; step S3 specifically includes:

[0012] S31: Determine the scattering coefficients under the following conditions: vv co-polarization, hh co-polarization, and hv cross-polarization, based on the incident angle, dielectric constant, and surface roughness.

[0013] S32: Based on the parameters under the vv co-polarization condition, the hh co-polarization condition, and the hv cross-polarization condition, the Müller matrix is ​​used to determine the RR polarization mirror reflectivity.

[0014] The parameters under the vv co-polarization condition, hh co-polarization condition, and hv cross-polarization condition include the scattering coefficients under the vv co-polarization condition, hh co-polarization condition, and hv cross-polarization condition; the Müller matrix WW is:

[0015]

[0016] in, It is the scattering coefficient under the same polarization condition. It is the scattering coefficient under the same polarization condition (hh). It is the scattering coefficient under hv cross-polarization conditions;

[0017] The RR polarized mirror reflectivity for:

[0018]

[0019] It is the matrix element in the first row and first column of the Müller matrix. It is the first row of the second line of the Müller matrix.

[0020] Column matrix elements, It is the matrix element in the 1st row and 2nd column of the Müller matrix. It is the second of the Müller matrix.

[0021] The matrix element in the second column of the row, U It is the matrix element in the 3rd row and 3rd column of the Müller matrix. U It is the matrix element in the 4th row and 4th column of the Müller matrix 33 44.

[0022] In step S2, the Fresnel reflection coefficient in the nadir direction, the vertical polarization and the horizontal polarization Fresnel reflection coefficient are determined, and then the scattering coefficients under the vv co-polarization condition, the hh co-polarization condition and the hv cross-polarization condition are determined using the Umich model.

[0023] According to the Umich model, the scattering coefficient under the same polarization condition is... hh homopolarization conditions

[0024]

[0025] in, It is the scattering coefficient under the same polarization condition. It is the scattering coefficient under the same polarization condition (hh). These are the scattering coefficients under the hv cross-polarization condition, θ, ε r ks represent the incident angle, dielectric constant, and surface roughness, respectively; the subscript h indicates horizontal polarization, and the subscript v indicates vertical polarization; g is an empirical constant; p and q are the first and second intermediate parameters, respectively; Γ v (θ), Γ h (θ) are the Fresnel reflection coefficients for vertical and horizontal polarization, respectively;

[0026] The first intermediate parameter p is:

[0027]

[0028] The second intermediate parameter q is:

[0029]

[0030] Where Γ0 is the Fresnel reflection coefficient in the nadir direction.

[0031] The parameters under the vv co-polarization condition, hh co-polarization condition, and hv cross-polarization condition include the scattering coefficient f under the vv co-polarization condition, hh co-polarization condition, and hv cross-polarization condition. vv f vh f vh ;

[0032] The Müller matrix for:

[0033]

[0034] Among them, f vv f vh f vh U0 is the scattering coefficient under the vv copolarization condition, the hh copolarization condition, and the hv cross-polarization condition; V is the Stokes vector, and U0 is the transformation matrix.

[0035] The RR polarized mirror reflectivity for:

[0036]

[0037] Among them, P 14 P is the matrix element in the 1st row and 4th column of the Müller matrix. 24 P is the matrix element in the 2nd row and 4th column of the Müller matrix. 11 P is the matrix element in the first row and first column of the Müller matrix. 21 P is the matrix element in the 2nd row and 1st column of the Müller matrix. 41 P is the matrix element in the 4th row and 1st column of the Müller matrix. 12 P is the matrix element in the 1st row and 2nd column of the Müller matrix. 22 P is the matrix element in the 2nd row and 2nd column of the Müller matrix. 42 P is the matrix element in the 4th row and 2nd column of the Müller matrix. 44 It is the matrix element in the 4th row and 4th column of the Müller matrix.

[0038] On the other hand, the present invention provides a polarized GNSS-R inversion method, comprising:

[0039] A1: Obtain the effective reflectivity SR of LR polarization pol1 The RR polarization mirror reflectance is obtained using the RR polarization mirror reflectance acquisition method described above, and is used as the effective reflectance SR of RR polarization. pol2 ;

[0040] A2: Effective reflectivity SR combined with RR polarization pol2 and the effective reflectivity SR of LR polarization pol1 To determine the desired inversion results.

[0041] Step A2 includes:

[0042] A21: Obtain the effective reflectivity SR of LR polarization pol1 Effective reflectivity SR with RR polarization pol2 Reflectivity dual polarization ratio The obtained reflectivity dual polarization ratio It is the square ratio of the Fresnel reflection coefficient modes of LR polarization and RR polarization;

[0043] A22: Soil moisture is obtained by inversion based on the square ratio of the Fresnel reflection coefficient moduli of LR polarization and RR polarization.

[0044] The RR polarization mirror reflectance acquisition method of the present invention determines the scattering coefficients under vv co-polarization conditions, hh co-polarization conditions, and hv cross-polarization conditions, and determines the RR polarization mirror reflectance based on the Müller matrix, thus improving the accuracy of the obtained effective reflectance of the RR polarization. Furthermore, the RR polarization mirror reflectance acquisition method of the present invention utilizes the aforementioned RR polarization mirror reflectance acquisition method to obtain the RR polarization mirror reflectance as the effective reflectance of the RR polarization, and combines the effective reflectance of the RR polarization with the effective reflectance of the LR polarization to determine the required inversion result. Because the obtained effective reflectance of the RR polarization is more accurate, the accuracy of the polarization GNSS-R inversion method, especially the simplified polarization GNSS-R inversion method, is effectively improved. Attached Figure Description

[0045] Figure 1 This is a flowchart of the RR polarization mirror reflectivity acquisition method of the present invention.

[0046] Figure 2A and Figure 2B These are schematic diagrams showing the changes in LR polarization reflectance and RR polarization reflectance as soil moisture increases. Detailed Implementation

[0047] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0048] The RR polarization mirror reflectivity acquisition method of the present invention is mainly based on the following principles:

[0049] The Umich model is an experimental model based on polarimetric radar measurements (see reference [JA Kong, RTShinand L. Tsang, "Theory of Microwave Remote Sensing", vol. 2, Wiley-Interscience, Jul. 3, 1985]). The Umich model can only calculate the specular reflectivity of linearly polarized surfaces. This invention improves the Umich model to enable it to calculate the specular reflectivity of RR-polarized surfaces. The developed model is named Umich4PolR.

[0050] The specific contents of the Umich4PolR model include: the calculation models of scattering coefficients under the same polarization conditions of vv and hh and the scattering coefficients under the cross polarization condition of hv in the existing Umich model, as well as the Müller matrix WW, which is unique in this invention for determining the RR polarization mirror reflectivity.

[0051] According to the existing Umich model, the scattering coefficients under the same polarization conditions of vv and hh and the scattering coefficients under the cross-polarization condition of hv are as follows:

[0052]

[0053]

[0054]

[0055] in, It is the scattering coefficient under the same polarization condition. It is the scattering coefficient under the same polarization condition (hh). These are the scattering coefficients under the hv cross-polarization condition, θ, δ r ks represent the incident angle, dielectric constant, and surface roughness, respectively, and θ and δ represent the surface roughness. r These parameters (ks) can be obtained from GNSS-R satellite data. The subscript h represents horizontal polarization, and the subscript v represents vertical polarization; g is an empirical constant that can be specified later based on the inversion algorithm; p and q are the first and second intermediate parameters, respectively; Γ v (θ), Γ h (θ) are the Fresnel reflection coefficients for vertical and horizontal polarization, respectively.

[0056] Wherein, the first intermediate parameter p is:

[0057]

[0058] The second intermediate parameter q is:

[0059]

[0060] Where Γ0 is the Fresnel reflection coefficient in the nadir direction, calculated using the following formula:

[0061]

[0062] Among them, the Fresnel reflection coefficients Γ for vertical and horizontal polarization v (θ), Γ h (θ) are respectively:

[0063]

[0064]

[0065] From formulas (7) and (8), it can be seen that the Fresnel reflection coefficient Γ for vertical polarization and horizontal polarization... v (θ), Γ hThe dielectric constant ε in (θ) r It is a function of soil moisture, so the RR polarization reflectance obtained by combining formula (4) and formula (5) is also a function of soil moisture and will increase with the increase of soil moisture.

[0066] First embodiment: A method for obtaining RR polarization mirror reflectivity based on the Umich4PolR model

[0067] According to a first embodiment of the present invention, the RR polarization mirror reflectivity acquisition method of the present invention is used in polarization GNSS-R inversion algorithms, especially simplified polarization GNSS-R inversion algorithms. Simplified polarization refers to the fact that the navigation satellite transmits RHCP, and the receiver receives RHCP / LHCP or H or V polarization. That is, the polarization information of the transmitter is fixed, but the polarization of the receiver is various. This is simplified polarization.

[0068] The method for obtaining the reflectivity of an RR polarized image in this invention mainly includes the following steps:

[0069] Step S1: Using the scattering coefficient under the same polarization condition vv Scattering coefficient under the same polarization condition Scattering coefficient under hv cross-polarization conditions Using these as basic elements, a Müller matrix is ​​established to determine the reflectivity of RR polarized images;

[0070] The Müller matrix used to determine the RR polarization mirror reflectance is original to this invention and has not been disclosed in any other literature. The design of the Müller matrix ensures that the RR polarization mirror reflectance increases with increasing soil moisture.

[0071] The Müller matrix WW is:

[0072]

[0073] in, It is the scattering coefficient under the same polarization condition. It is the scattering coefficient under the same polarization condition (hh). It is the scattering coefficient under the hv cross-polarization condition.

[0074] In other words, These are the basic elements of the Müller matrix WW.

[0075] The formula for the Müller matrix WW above can be simplified as follows:

[0076]

[0077] Among them, U 11 It is the matrix element in the first row and first column of the Müller matrix, i.e., the one mentioned above. U 21 It is the matrix element in the 2nd row and 1st column of the Müller matrix, i.e., the one mentioned above. U 12 It is the matrix element in the 1st row and 2nd column of the Müller matrix, i.e., the one mentioned above. U 22 It is the matrix element in the 2nd row and 2nd column of the Müller matrix, i.e., the one mentioned above. U 33 It is the matrix element in the 3rd row and 3rd column of the Müller matrix, i.e., the one mentioned above. U 44 It is the matrix element in the 4th row and 4th column of the Müller matrix, i.e., the one mentioned above.

[0078] Step S2: Obtain the incident angle θ and dielectric constant ε from GNSS-R satellite data. r and surface roughness ks;

[0079] For detailed methods on calculating the dielectric constant, please refer to the reference [Hallikainen, MT, et al.,

[0080] Microwave dielectric behavior of wet soil-part 1:empirical models and experimental observations.Geoscience and Remote Sensing,IEEE Transactions on, 1985.GE-23(1):p.25-34] and [Dobson, MC, et al., Microwave dielectric behavior of wet soil-Part II: Dielectric mixing models.Geoscience and Remote Sensing, IEEETransactions on,1985.GE-23(1):p.35-46].

[0081] Step S3: Based on the incident angle θ and dielectric constant ε r The surface roughness ks is used to determine the RR polarization mirror reflectivity using the Müller matrix;

[0082] Step S3 specifically includes:

[0083] Step S31: Based on the incident angle θ and the dielectric constant ε r Based on the surface roughness ks, determine the Fresnel reflection coefficient Γ0 in the nadir direction, and the Fresnel reflection coefficients Γ for vertical and horizontal polarization. v (θ), Γh (θ), and then the scattering coefficient under the same polarization condition of vv is determined using the Umich model. Scattering coefficient under the same polarization condition Scattering coefficient under hv cross-polarization conditions

[0084] Among them, the Fresnel reflection coefficient Γ0 in the nadir direction, and the Fresnel reflection coefficients Γ for vertical and horizontal polarization. v (θ), Γ h The formulas for calculating (θ) are as described above, and the scattering coefficient under the same polarization condition is... Scattering coefficient under the same polarization condition Scattering coefficient under hv cross-polarization conditions The specific calculation formula is as described above.

[0085] Step S32: Determine the RR polarization mirror reflectivity using the Müller matrix based on the parameters under the vv co-polarization condition, the hh co-polarization condition, and the hv cross-polarization condition.

[0086] RR polarized mirror reflectivity for:

[0087]

[0088] U 11 It is the matrix element in the first row and first column of the Müller matrix, i.e., the one mentioned above. U 21 It is the matrix element in the 2nd row and 1st column of the Müller matrix, i.e., the one mentioned above. U 12 It is the matrix element in the 1st row and 2nd column of the Müller matrix, i.e., the one mentioned above. U 22 It is the matrix element in the 2nd row and 2nd column of the Müller matrix, i.e., the one mentioned above. U 33 It is the matrix element in the 3rd row and 3rd column of the Müller matrix, i.e., the one mentioned above. U 44 It is the matrix element in the 4th row and 4th column of the Müller matrix, i.e., the one mentioned above.

[0089] The obtained RR polarized mirror reflectance increases with increasing soil moisture.

[0090] It should be noted that the reason this invention proposes a method for calculating RR polarization reflectance is that current domestic and international formulas for calculating RR polarization reflectance are linear combinations of the Fresnel reflectance formulas for v-polarization and H-polarization. A significant problem with this method is that the calculated RR polarization reflectance decreases with increasing soil moisture, but experimental data does not confirm this. Therefore, this invention provides a new method for calculating RR polarization reflectance. Any improved model of RR polarization reflectance that increases with increasing soil moisture falls within the scope of this invention.

[0091] Second embodiment: A method for obtaining RR polarization mirror reflectivity based on the SPM4Pol model

[0092] In the second embodiment, the RR polarized mirror reflectance model that increases reflectance with increasing soil moisture can be the SPM4Pol model.

[0093] In this embodiment, the method for obtaining RR polarized mirror reflectivity based on the SPM4Pol model includes:

[0094] Step S1': Establish a Müller matrix for determining the RR polarization mirror reflectivity, wherein the Müller matrix causes the RR polarization mirror reflectivity to increase with increasing soil moisture;

[0095] In this embodiment, the developed model is the SPM4Pol model, which includes the Müller matrix.

[0096] The Müller matrix established in this SPM4Pol model as follows:

[0097]

[0098] Among them, f vv f vh f vh U0 is the scattering coefficient under the vv copolarization condition, the hh copolarization condition, and the hv cross-polarization condition, where V is the Stokes vector and U0 is the transformation matrix.

[0099] The above Müller matrix The method for obtaining each parameter in the formula is as follows: [Y. Oh, K. Sarabandi and FTUlaby, "An empirical model and an inversion technique for radar scattering from bare soil surfaces," IEEE Transactions on Geoscience and Remote Sensing, vol. 30, no. 2, pp. 370-381, Mar 1992. doi: 10.1109 / 36.134086].

[0100] The above Müller matrix The formula simplifies to:

[0101]

[0102] Among them, P 11 P is the matrix element in the first row and first column of the Müller matrix. 21 P is the matrix element in the 2nd row and 1st column of the Müller matrix. 31 P is the matrix element in the 3rd row and 1st column of the Müller matrix. 41 P is the matrix element in the 4th row and 1st column of the Müller matrix. 12 P is the matrix element in the 1st row and 2nd column of the Müller matrix. 22 P is the matrix element in the 2nd row and 2nd column of the Müller matrix. 32 P is the matrix element in the 3rd row and 2nd column of the Müller matrix. 42 P is the matrix element in the 4th row and 2nd column of the Müller matrix. 13 P is the matrix element in the 1st row and 3rd column of the Müller matrix. 23 P is the matrix element in the 2nd row and 3rd column of the Müller matrix. 33 P is the matrix element in the 3rd row and 3rd column of the Müller matrix. 43 P is the matrix element in the 4th row and 3rd column of the Müller matrix. 14 P is the matrix element in the 1st row and 4th column of the Müller matrix. 24 P is the matrix element in the 2nd row and 4th column of the Müller matrix. 34 P is the matrix element in the 3rd row and 4th column of the Müller matrix. 44 It is the matrix element in the 4th row and 4th column of the Müller matrix.

[0103] Step S2': Obtain the incident angle, dielectric constant, and surface roughness from GNSS-R satellite data;

[0104] Step S3': Based on the incident angle θ and dielectric constant ε rThe surface roughness ks is used to determine the RR polarization mirror reflectivity using the Müller matrix.

[0105] In this embodiment, step S3' specifically includes:

[0106] Step S31': Based on the incident angle θ and the dielectric constant ε r Based on the surface roughness ks, determine the scattering coefficient f under the vv co-polarization condition, hh co-polarization condition, and hv cross-polarization condition. vv f vh f vh ;

[0107] Step S32': Based on the vv co-polarization condition, the hh co-polarization condition, and the hv cross-polarization condition, the scattering coefficient f vv f vh f vh The Müller matrix is ​​used to determine the RR polarization mirror reflectivity.

[0108] RR polarization mirror reflectivity calculated by the SPM4Pol model The calculation formula is as follows:

[0109]

[0110] Experimental results:

[0111] Figures 2A-2B This is a schematic diagram showing the distribution of RR polarization reflectance as soil moisture increases. The experimental data used are from SMAP-R (a type of GNSS-R). Figure 2A This is a distribution diagram of LR polarization reflectance as a function of soil moisture. Figure 2B This is a distribution diagram of RR polarization reflectance as a function of soil moisture. Figure 2B The diagram illustrates the increase in RR polarization reflectance with increasing soil moisture. Therefore, the Müller matrix established in the first and second embodiments for determining RR polarization mirror reflectance does indeed better reflect the relationship between RR polarization mirror reflectance and soil moisture compared to the prior art (in the prior art, RR polarization mirror reflectance decreases with increasing soil moisture).

[0112] Third embodiment: Polarized GNSS-R inversion method

[0113] Based on the RR polarization mirror reflectance acquisition method of the present invention, a polarization GNSS-R inversion method can be proposed. This inversion method utilizes the RR polarization mirror reflectance acquisition method to obtain the RR polarization mirror reflectance as the effective reflectance SR of the RR polarization. pol2 And combined with the effective reflectivity SR of RR polarization pol2 and the effective reflectivity SR of LR polarizationpol1 This is used to determine the required inversion results. Since the accuracy of the effective reflectivity of the obtained RR polarization is higher, the accuracy of the polarization GNSS-R inversion method is effectively improved.

[0114] Therefore, polarization GNSS-R inversion methods based on the RR polarization mirror reflectivity acquisition method include:

[0115] Step A1: Obtain the effective reflectivity SR of LR polarization pol1 The RR polarization mirror reflectance is obtained using the RR polarization mirror reflectance acquisition method described above, and is used as the effective reflectance SR of RR polarization. pol2 ;

[0116] Among them, the effective reflectivity SR of LR polarization is obtained. pol1 The method is based on existing technology.

[0117] In this embodiment, the polarization GNSS-R inversion method takes the bare soil parameter inversion of a single-frequency dual-polarization receiver as an example, where the effective reflectivity SR of LR polarization is... pol1 and the effective reflectivity SR of RR polarization pol2 All satisfy the theoretical model for effective reflectivity SR(θ) as follows:

[0118]

[0119] k0=2π / λ

[0120] Wherein, exp(-4k 2 s 2 cos 2 (θ) is the roughness factor, s is the surface roughness coefficient in SMAP, θ is the incident angle, and SR(θ) is the effective reflectance, which can be substituted into the effective reflectance SR of LR polarization. pol1 and the effective reflectivity SR of RR polarization pol2 .

[0121] Step A2: Combine the effective reflectivity SR of RR polarization pol2 and the effective reflectivity SR of LR polarization pol1 To determine the desired inversion results.

[0122] In this embodiment, step A2 includes:

[0123] Step A21: Obtain the effective reflectivity SR of LR polarization pol1 Effective reflectivity SR with RR polarization pol2 Reflectivity dual polarization ratio Based on the reflectivity dual polarization ratio To obtain the square ratio of the Fresnel reflection coefficient modes for LR and RR polarization;

[0124] As mentioned above, the effective reflectivity SR of LR polarization... pol1 and the effective reflectivity SR of RR polarization pol2 All satisfy the theoretical model of the effective reflectivity SR(θ) as follows. Therefore, when using a single-frequency dual-polarization receiver, the reflectivity dual-polarization ratio is used. The roughness factor can be eliminated, that is, the reflectivity bipolarization ratio. It is the ratio of the square of the Fresnel reflection coefficient modulus.

[0125] Reflectivity dual polarization ratio for:

[0126]

[0127] Among them, SR pol1 and SR pol2 These are the LR polarization reflectance and the RR polarization reflectance, respectively.

[0128] Step A22: Soil moisture is obtained by inversion based on the square ratio of the Fresnel reflection coefficient moduli of LR polarization and RR polarization.

[0129] In this embodiment, the square ratio of the Fresnel reflection coefficient moduli of LR polarization and RR polarization is related to soil moisture, so the inversion result is soil moisture.

[0130] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. All simple and equivalent changes and modifications made in accordance with the claims and description of this application fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A method for obtaining RR polarized mirror reflectivity, used in polarized GNSS-R inversion methods, characterized in that, include: Step S1: Establish a Müller matrix for determining the RR polarization mirror reflectivity, wherein the Müller matrix causes the RR polarization mirror reflectivity to increase with increasing soil moisture. Step S2: Obtain the incident angle, dielectric constant, and surface roughness from GNSS-R satellite data; Step S3: Determine the RR polarization mirror reflectivity using the Müller matrix based on the incident angle, dielectric constant, and surface roughness; The Müller matrix uses the scattering coefficients under the vv copolarization condition, the hh copolarization condition, and the hv cross-polarization condition as its basic elements; Step S3 specifically includes: Step S31: Determine the scattering coefficients under the vv co-polarization condition, the hh co-polarization condition, and the hv cross-polarization condition based on the incident angle, dielectric constant, and surface roughness; Step S32: Based on the scattering coefficients under the vv co-polarization condition, the hh co-polarization condition, and the hv cross-polarization condition, determine the RR polarization mirror reflectivity using the Müller matrix; The Müller matrix WW is: ， in, It is the scattering coefficient under the same polarization condition. It is the scattering coefficient under the same polarization condition (hh). It is the scattering coefficient under hv cross-polarization conditions; The RR polarized mirror reflectivity for: ， It is the matrix element in the first row and first column of the Müller matrix. It is the matrix element in the 2nd row and 1st column of the Müller matrix. It is the matrix element in the 1st row and 2nd column of the Müller matrix. It is the matrix element in the 2nd row and 2nd column of the Müller matrix. It is the matrix element in the 4th row and 4th column of the Müller matrix.

2. The method for obtaining RR polarized mirror reflectivity according to claim 1, characterized in that, In step S2, the Fresnel reflection coefficient in the nadir direction, the vertical polarization and the horizontal polarization Fresnel reflection coefficient are determined, and then the scattering coefficients under the vv co-polarization condition, the hh co-polarization condition and the hv cross-polarization condition are determined using the Umich model. According to the Umich model, the scattering coefficient under the same polarization condition is... Scattering coefficient under the same polarization condition Scattering coefficient under hv cross-polarization conditions for: ， ， ， in, It is the scattering coefficient under the same polarization condition. It is the scattering coefficient under the same polarization condition (hh). It is the scattering coefficient under the hv cross-polarization condition. These are the incident angle, dielectric constant, and surface roughness, respectively. The subscript h indicates horizontal polarization, and the subscript v indicates vertical polarization; g is an empirical constant; p and q are the first and second intermediate parameters, respectively. , These are the Fresnel reflection coefficients for vertical and horizontal polarization, respectively; The first intermediate parameter p is: ， The second intermediate parameter q is: ， in, It is the Fresnel reflectance in the nadir direction.

3. The method for obtaining RR polarized mirror reflectivity according to claim 2, characterized in that, The parameters under the vv co-polarization condition, hh co-polarization condition, and hv cross-polarization condition include the scattering coefficients under the vv co-polarization condition, hh co-polarization condition, and hv cross-polarization condition. , , ; The Müller matrix for: ， in, , , U0 is the scattering coefficient under the vv copolarization condition, the hh copolarization condition, and the hv cross-polarization condition; V is the Stokes vector, and U0 is the transformation matrix. The RR polarized mirror reflectivity for: ， in, It is the matrix element in the 1st row and 4th column of the Müller matrix. It is the matrix element in the 2nd row and 4th column of the Müller matrix. It is the matrix element in the first row and first column of the Müller matrix. It is the matrix element in the 2nd row and 1st column of the Müller matrix. It is the matrix element in the 4th row and 1st column of the Müller matrix. It is the matrix element in the 1st row and 2nd column of the Müller matrix. It is the matrix element in the 2nd row and 2nd column of the Müller matrix. It is the matrix element in the 4th row and 2nd column of the Müller matrix. It is the matrix element in the 4th row and 4th column of the Müller matrix.

4. A polarization GNSS-R inversion method, characterized in that, include: Step A1: Obtain the effective reflectivity of LR polarization The RR polarization mirror reflectance is obtained using the RR polarization mirror reflectance acquisition method according to any one of claims 1-3, and is used as the effective reflectance of RR polarization. ; Step A2: Effective reflectivity combined with RR polarization and the effective reflectivity of LR polarization To determine the desired inversion results.

5. The polarization GNSS-R inversion method according to claim 4, characterized in that, Step A2 includes: Step A21: Obtain the effective reflectivity of LR polarization Effective reflectivity with RR polarization Reflectivity dual polarization ratio The obtained reflectivity dual polarization ratio It is the square ratio of the Fresnel reflection coefficient modes of LR polarization and RR polarization; Step A22: Soil moisture is obtained by inversion based on the square ratio of the Fresnel reflection coefficient moduli of LR polarization and RR polarization.

Images