Differential interference SAR constellation three-dimensional earth surface deformation field measurement precision analysis method and system

Abstract

The invention provides a differential interference SAR constellation three-dimensional surface deformation field measurement precision analysis method and system, and the method comprises the steps: inputting the orbital elements and load observation capabilities of all satellites in a constellation, and setting a to-be-analyzed observation region; simulating and calculating the observation time of each satellite in the observation area to be analyzed in a strict regression period; calculating observation sight vectors of the satellites to the simulation grid points in the observation area; analyzing and estimating the sight deformation measurement precision of each satellite to the observation area; and establishing an observation equation, and analyzing and estimating the three-dimensional deformation measurement precision of the whole constellation on the observation area. According to the method, the problem of differential interference SAR constellation three-dimensional surface deformation monitoring precision analysis is successfully solved, and important technical support can be provided for construction of a subsequent differential interference SAR surface deformation monitoring system.

Description

Technical Field

[0001] The present invention relates to the technical field of spaceborne radar, and in particular, to a method and system for analyzing the measurement accuracy of a three-dimensional surface deformation field of a differential interferometric synthetic aperture radar (SAR) constellation. Background Art

[0002] The three-dimensional deformation measurement technology of differential interferometric SAR (D-InSAR) is a method that uses the data obtained by synthetic aperture radar (SAR) to extract the minute surface deformation information through interferometric processing. By analyzing the phase differences between two or more SAR images, this technology can accurately measure the surface deformation, which is of great significance for the monitoring of natural disasters such as earthquakes, landslides, urban subsidence, and volcanic activities. However, it should be noted that a single pass of a differential interferometric SAR system can only measure the deformation along the radar line of sight. To obtain the three-dimensional deformation, it is necessary to form a constellation network to obtain the deformations in different lines of sight directions and jointly solve for the three-dimensional deformation of the surface. Conducting research on the analysis of the measurement accuracy of the three-dimensional surface deformation of differential interferometric SAR is of great significance for improving the accuracy of three-dimensional deformation monitoring and reducing the constellation scale.

[0003] The patent document "Method and System for Analyzing and Calculating the Measurement Accuracy of the Deformation Rate of a Differential Interferometric SAR Satellite" (CN202311236266.1) introduces a method and system for analyzing and calculating the measurement accuracy of the deformation rate of a differential interferometric SAR satellite along the line of sight direction under a single pass, but this patent only analyzes the measurement accuracy of the surface deformation rate along the line of sight direction of differential interferometric SAR under a single pass and does not involve the analysis of the measurement accuracy of the three-dimensional surface deformation.

[0004] The patent document "Method and System for Analyzing the Influencing Factors of the Measurement Accuracy of the Deformation Quantity of a Differential Interferometric SAR Satellite" (CN202311204908.X) introduces a method and system for analyzing the influencing factors of the measurement accuracy of the deformation quantity of a differential interferometric SAR satellite, but this patent only analyzes the measurement accuracy of the surface deformation quantity along the line of sight direction of differential interferometric SAR under a single pass and does not involve the analysis of the measurement accuracy of the three-dimensional surface deformation.

[0005] The literature "Extracting the Three-Dimensional Surface Deformation Velocity Field Based on Permanent Scatterer Radar Interferometry with Multiple Satellite Platforms" (Liu Guoxiang, Zhang Rui, Li Tao, et al. Chinese Journal of Geophysics, 2012, 55(8): 2598-2610.) proposed a model and algorithm for extracting the three-dimensional surface deformation velocity field based on permanent scatterer radar interferometry with multiple platforms. The vertical displacement velocity field and the horizontal displacement velocity components in the north-south and east-west directions of the observation area were obtained through joint solution and verified with ground leveling and existing GPS observation results. However, this paper only gives the method for inverting the three-dimensional deformation rate and does not involve the analysis of the accuracy of the three-dimensional surface deformation of the constellation.

[0006] The literature "Adaptive Fusion Deformation Measurement of Multi-source InSAR Data Based on Variance Component Estimation" (Ao Meng, Zhang Lu, Liao Mingsheng, et al. Chinese Journal of Geophysics, 2020, 63(8): 2901-2911.) improved the classical Small Baseline Subset (SBAS) time-series InSAR analysis method. East-west and north-south deformation parameters were added to its deformation inversion model. The a posteriori variance of multi-source observation data was solved using the variance component estimation method, and the weight matrix was determined through iterative refinement to obtain the optimal estimation of the deformation parameters. However, the paper did not involve the analysis of the surface three-dimensional deformation accuracy of the differential interferometric SAR constellation.

[0007] The literature "Extraction and Analysis of Three-dimensional Co-seismic Deformation of the Ms 6.9 Menyuan Earthquake Based on Sentinel-1" (Pu Songwen, Wen Xin, Zhou Zhiwei, et al. Geospatial Information, 2024, 22(6): 109-112, 117.) based on Sentinel-1 ascending and descending orbit synthetic aperture radar (SAR) data, used SAR differential interferometry (D-InSAR) and pixel offset tracking (POT) techniques to obtain multi-angle surface deformations of the Ms 6.9 Menyuan earthquake in Qinghai on January 8, 2022, and extracted the three-dimensional co-seismic deformation field using a three-dimensional deformation estimation model. However, the paper did not involve the analysis of the surface three-dimensional deformation accuracy of the differential interferometric SAR constellation.

[0008] In summary, a method and system for analyzing the surface three-dimensional deformation accuracy of a differential interferometric SAR constellation have not been publicly reported, and the present invention is the first of its kind. Summary of the Invention

[0009] Aiming at the deficiencies in the prior art, the purpose of the present invention is to provide a method and system for analyzing the measurement accuracy of a three-dimensional surface deformation field of a differential interferometric SAR constellation.

[0010] According to a method for analyzing the measurement accuracy of a three-dimensional surface deformation field of a differential interferometric SAR constellation provided by the present invention, it includes:

[0011] Step S1: Input the orbital elements of each satellite in the constellation and the payload observation capabilities, and set the observation area to be analyzed;

[0012] Step S2: Simulate and calculate the observation time of each satellite for the observation area to be analyzed within a strict regression orbit period;

[0013] Step S3: Calculate the observation line-of-sight vectors of each satellite for the simulated grid points in the observation area;

[0014] Step S4: Analyze and estimate the line-of-sight deformation measurement accuracy of each satellite for the observation area;

[0015] Step S5: Establish an observation equation and analyze and estimate the three-dimensional deformation measurement accuracy of the entire constellation for the observation area.

[0016] Further, the step S2 includes:

[0017] Step S2.1: For each satellite in the constellation, simulate the satellite orbit position and velocity vector within a strict regression orbit period at a preset time interval.

[0018] Step S2.2: For each satellite in the constellation, set multiple equally spaced observation perspectives within its radar observation perspective range, and use the perspective equation, Doppler equation, and Earth model for target positioning.

[0019] Step S2.3: For each satellite, determine whether the target located in step S2.2 is within the simulation analysis scenario. If it is within the simulation scenario at all times, include the effective observation time of the satellite, thereby obtaining the observation time interval of each satellite for the observation area.

[0020] Further, in step S2.2, using the perspective equation, Doppler equation, and Earth model for target positioning includes:

[0021]

[0022] In the formula, p m (t a ) represents the position vector of the m-th satellite in the Earth-fixed coordinate system at azimuth time t a , v m (t a ) represents the velocity vector of the m-th satellite in the Earth-fixed coordinate system at azimuth time t a , θ is the lower viewing angle, p t is the position vector of the target in the Earth-fixed coordinate system, λ is the radar wavelength, f dc is the imaging Doppler center, and DEM is the external Earth model.

[0023] Further, the step S3 includes:

[0024] Step S3.1: Divide the observation area into grids, set the grid spacing according to requirements, and convert the coordinates of each grid point to the Earth-fixed coordinate system.

[0025] Step S3.2: For each grid point, use the Doppler equation to back-calculate the observation time of each satellite for this grid point.

[0026] Step S3.3: For each grid point, use the satellite orbit position corresponding to the observation time of each satellite after step S3.2 to calculate the line of sight and observation distance to the target. If the observation line of sight is within the radar beam and effective range, then regard this observation as an effective observation.

[0027] Step S3.4: Convert the effective observation line-of-sight vectors of each satellite to each grid point to the target local coordinate system.

[0028] Further, the said Step S5 includes:

[0029] Step S5.1: For each grid point, establish a three-dimensional surface deformation observation equation:

[0030] Ax = b

[0031] In the formula, A is the radar observation line-of-sight matrix of the target, b is the observation vector, and x is the vector composed of three-dimensional deformation amounts, and each element is the deformation in the east-west direction, the deformation in the north-south direction, and the vertical deformation respectively;

[0032] Step S5.2: Calculate the covariance matrix of the deformation vector inversion:

[0033] C x =(A H W H WA) -1 A H WC b W H A(A H W H WA) -1

[0034] In the formula, C x is the covariance matrix of the deformation vector estimation, A is the radar observation line-of-sight matrix of the target, W is the weighted value for solving the equation system, C b is the diagonal matrix composed of the variances of the radar line-of-sight direction deformations of each observation, the superscript H represents the matrix transpose, and the superscript -1 represents the matrix inversion;

[0035] Step S5.3: Take out the diagonal elements in C x and take the root mean square as the estimated accuracy of the deformation rate in the corresponding direction.

[0036] According to a differential interferometric SAR constellation three-dimensional surface deformation field measurement accuracy analysis system provided by the present invention, it includes:

[0037] Module M1: Input the orbital elements and payload observation capabilities of each satellite in the constellation, and set the observation area to be analyzed;

[0038] Module M2: Simulate and calculate the observation time of each satellite for the observation area to be analyzed within a strict regression orbit period;

[0039] Module M3: Calculate the observation line-of-sight vectors of each satellite for the simulated grid points in the observation area;

[0040] Module M4: Analyze and estimate the line-of-sight deformation measurement accuracy of each satellite for the observation area;

[0041] Module M5: Establish an observation equation and analyze and estimate the three-dimensional deformation measurement accuracy of the entire constellation for the observation area.

[0042] Furthermore, the module M2 includes:

[0043] Module M2.1: For each satellite in the constellation, simulate the satellite orbit position and velocity vector within a strict regression orbit period at a preset time interval;

[0044] Module M2.2: For each satellite in the constellation, set multiple equally spaced observation perspectives within its radar observation perspective range, and use the perspective equation, Doppler equation, and Earth model for target positioning;

[0045] Module M2.3: For each satellite, determine whether the target located in Module M2.2 is within the simulation analysis scenario. If it is within the simulation scenario at all times, include the effective observation time of the satellite, thereby obtaining the observation time interval of each satellite for the observation area.

[0046] Furthermore, in Module M2.2, using the perspective equation, Doppler equation, and Earth model for target positioning includes:

[0047]

[0048] where p m (t a ) represents the position vector of the mth satellite in the Earth-fixed coordinate system at azimuth time t a , v m (t a ) represents the velocity vector of the mth satellite in the Earth-fixed coordinate system at azimuth time t a , θ is the down-looking angle, p t is the position vector of the target in the Earth-fixed coordinate system, λ is the radar wavelength, f dc is the imaging Doppler center, and DEM is the external Earth model.

[0049] Furthermore, the module M3 includes:

[0050] Module M3.1: Divide the observation area into grids, set the grid spacing according to requirements, and convert the coordinates of each grid point to the Earth-fixed coordinate system;

[0051] Module M3.2: For each grid point, use the Doppler equation to back-calculate the observation time of each satellite for this grid point;

[0052] Module M3.3: For each grid point, calculate the line of sight to the target and the observation distance based on the satellite orbital positions corresponding to each satellite observation time after using Module M3.2. If the observation line of sight is within the radar beam and the effective range, then regard this observation as a valid observation.

[0053] Module M3.4: Convert the valid observation line of sight vectors of each satellite to each grid point to the local coordinate system of the target.

[0054] Furthermore, the said Module M5 includes:

[0055] Module M5.1: For each grid point, establish a three-dimensional surface deformation observation equation:

[0056] Ax = b

[0057] Where A is the radar observation line of sight matrix of the target, b is the observation vector, and x is the vector composed of three-dimensional deformation quantities, and each element is the deformation in the east-west direction, the north-south direction, and the vertical direction respectively.

[0058] Module M5.2: Calculate the covariance matrix of the deformation vector inversion:

[0059] C x =(A H W H WA) -1 A H WC b W H A(A H W H WA) -1

[0060] Where C x is the covariance matrix of the deformation vector estimation, A is the radar observation line of sight matrix of the target, W is the weighting value for solving the equation system, C b is the diagonal matrix composed of the variances of the deformation measurements in the radar line of sight direction for each observation. The superscript H represents the matrix transpose, and the superscript -1 represents the matrix inversion;

[0061] Module M5.3: Take out the diagonal elements in C x and take the root mean square as the estimated accuracy of the deformation rate in the corresponding direction.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] The present invention successfully solves the problem of the accuracy analysis of three-dimensional surface deformation monitoring by the differential interferometric SAR constellation, and can provide important technical support for the subsequent construction of the differential interferometric SAR surface deformation monitoring system. Description of the Drawings

[0064] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments read in conjunction with the accompanying drawings:

[0065] Figure 1 is a schematic diagram of the analysis process for the three-dimensional surface deformation monitoring accuracy of the differential interferometric SAR constellation of the present invention;

[0066] Figure 2 is a schematic diagram of the coverage times of the satellites in the first group of the Land Exploration-1;

[0067] Figure 3 is a schematic diagram of the coverage times of satellites with an inclination angle of 55°;

[0068] Figure 4 is a schematic diagram of the influencing factors of the deformation in the north-south direction;

[0069] Figure 5 is a schematic diagram of the influencing factors of the deformation in the east-west direction;

[0070] Figure 6 is a schematic diagram of the influencing factors of the vertical deformation. Specific Embodiments

[0071] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several changes and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0072] As Figure 1 shown, the present invention provides a method for analyzing the measurement accuracy of the three-dimensional surface deformation field of a differential interferometric SAR constellation, including:

[0073] Step S1: Input the orbital elements and payload observation capabilities of each satellite in the constellation, and set the observation area to be analyzed;

[0074] Step S2: Simulate and calculate the observation time of each satellite for the observation area to be analyzed within a strictly repeating orbit period;

[0075] Step S3: Calculate the observation line-of-sight vectors of each satellite for the simulated grid points in the observation area;

[0076] Step S4: Analyze and estimate the line-of-sight deformation measurement accuracy of each satellite for the observation area;

[0077] Step S5: Establish an observation equation and analyze and estimate the three-dimensional deformation measurement accuracy of the entire constellation for the observation area.

[0078] Specifically, in step S1, the orbital elements of each satellite in the input constellation and the payload observation capabilities are input, and the observation area to be analyzed is set. Here, it is assumed that the number of satellites in the constellation is M:

[0079] Specifically, in step S2, the observation time of each satellite for the observation area to be analyzed within a strict regression orbit period is simulated and calculated, including:

[0080] Step S2.1: For each satellite in the constellation, simulate the position and velocity vectors of the satellite in the Earth-fixed coordinate system within a strict regression orbit period at a certain time interval;

[0081] Step S2.2: For each satellite in the constellation, set multiple equally spaced observation perspectives within its radar observation perspective range, and use the perspective equation, Doppler equation, and Earth model for target positioning. The positioning equation is as follows:

[0082]

[0083] Where p m (t a ) represents the position vector of the mth satellite in the Earth-fixed coordinate system at azimuth time t a , v m (t a ) represents the velocity vector of the mth satellite in the Earth-fixed coordinate system at azimuth time t a , θ is the depression angle, p t is the position vector of the target in the Earth-fixed coordinate system, λ is the radar wavelength, f dc is the imaging Doppler center, and DEM is the external Earth model.

[0084] Step S2.3: For each satellite, determine whether the target located in step S2.2 is within the simulation analysis scenario. If it is within the simulation scenario at all times, include the effective observation time of the satellite, so as to obtain the observation time interval of each satellite for the observation area.

[0085] Specifically, in step S3, calculate the observation line-of-sight vectors of each satellite for the simulation grid points in the observation area, including;

[0086] Step S3.1: Divide the observation area into grids, set the grid spacing according to requirements, and convert the coordinates of each grid point to the Earth-fixed coordinate system;

[0087] Step S3.2: For each grid point, use the Doppler equation to inversely calculate the observation time of each satellite for this grid point;

[0088] Step S3.3: For each grid point, calculate the line of sight to the target and the observation distance using the satellite orbital positions corresponding to each satellite observation time after Step S3.2. If the observation line of sight is within the radar beam and the effective range, then this observation is regarded as a valid observation.

[0089] Step S3.4: Transform the valid observation line-of-sight vectors of each satellite to each grid point into the target local coordinate system (such as the northeast-up coordinate system).

[0090] Specifically, for Step S4 to analyze and estimate the line-of-sight deformation measurement accuracy of each satellite to the observation area, factors such as satellite orbit determination error and decorrelation phase error need to be comprehensively considered.

[0091] Specifically, in Step S5, establish an observation equation to analyze and estimate the three-dimensional deformation measurement accuracy of the entire constellation to the observation area, which specifically includes:

[0092] Step S5.1: For each grid point, establish a three-dimensional surface deformation observation equation

[0093] Ax = b

[0094] In the formula, A is the radar observation line-of-sight matrix of the target, b is the vector composed of the three-dimensional deformation quantities of the observation vector, x is the vector composed of the three-dimensional deformation quantities, and each element is the deformation in the east-west direction, the deformation in the north-south direction, and the vertical deformation respectively; then the weighted least-squares solution of the three-dimensional surface deformation observation quantity is:

[0095] x = (A H W H WA) -1 A H Wb

[0096] Step S5.2: Calculate the covariance matrix of the deformation vector inversion:

[0097] C x = (A H W H WA) -1 A H WC b W H A(A H W H WA) -1

[0098] In the formula, C x is the covariance matrix of the deformation vector estimation, A is the radar observation line-of-sight matrix of the target, W is the weighted value for solving the equation system, C b is the diagonal matrix composed of the radar line-of-sight deformation measurement variances of each observation, the superscript "H" represents the matrix transpose, and the superscript "-1" represents the matrix inversion.

[0099] Step S5.3: C x The elements on the diagonal are taken out and the root mean square is taken as the deformation rate estimation accuracy in the corresponding direction.

[0100] The present invention will be further described below with reference to the accompanying drawings.

[0101] Here, we use the payload parameters of the LuTan-1 satellite group 01 to conduct simulation experiments on a strictly regressive orbit with a 55° inclination. The payload simulation parameters are shown in Table 1. It is assumed that the accuracy of single deformation measurements is the same.

[0102] Table 1 Spaceborne SAR payload simulation parameters

[0103]

[0104] Depend on Figure 2 and Figure 3 It can be seen that the present invention can realize the analysis of the orbit coverage times of different satellites. Figure 4 , Figure 5 and Figure 6 It can be seen that the present invention can invert the north-south, east-west and vertical deformation measurement accuracy influencing factors. The larger the influence factor, the worse the accuracy in the corresponding direction.

[0105] The method of the present invention successfully solves the problem of accuracy analysis of three-dimensional surface deformation monitoring using differential interferometry SAR constellations, and can provide important technical support for the subsequent construction of differential interferometry SAR surface deformation monitoring systems.

[0106] The method of the present invention realizes the precision analysis of three-dimensional surface deformation monitoring using differential interferometry SAR constellation, which is the first of its kind in China and abroad.

[0107] The present invention also provides a differential interferometry SAR constellation 3D surface deformation monitoring and accuracy analysis system. The differential interferometry SAR constellation 3D surface deformation monitoring and accuracy analysis system can be implemented by executing the process steps of the differential interferometry SAR constellation 3D surface deformation monitoring and accuracy analysis method. That is, those skilled in the art can understand the differential interferometry SAR constellation 3D surface deformation monitoring and accuracy analysis method as a preferred embodiment of the differential interferometry SAR constellation 3D surface deformation monitoring and accuracy analysis system. The system includes:

[0108] Module M1: Input the orbital elements and payload observation capabilities of each satellite in the constellation, and set the observation area to be analyzed;

[0109] Module M2: Simulate and calculate the observation time of each satellite in the observation area to be analyzed within a strict regression orbit period;

[0110] Module M3: Calculate the observation sight line vector of each satellite to the simulation grid points in the observation area;

[0111] Module M4: Analyze and estimate the line-of-sight deformation measurement accuracy of each satellite for the observation area;

[0112] Module M5: Establish an observation equation and analyze and estimate the three-dimensional deformation measurement accuracy of the entire constellation for the observation area.

[0113] Those skilled in the art know that in addition to implementing the system and its various devices, modules, and units provided by the present invention in the form of pure computer-readable program code, the method steps can be logically programmed to enable the system and its various devices, modules, and units provided by the present invention to be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers, etc. to achieve the same functions. Therefore, the system and its various devices, modules, and units provided by the present invention can be regarded as a kind of hardware component, and the devices, modules, and units included therein for implementing various functions can also be regarded as the structure within the hardware component; the devices, modules, and units for implementing various functions can also be regarded as both software modules for implementing the method and the structure within the hardware component.

[0114] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other.

Claims

1. A method for analyzing the measurement accuracy of the three-dimensional surface deformation field of a differential interferometric SAR constellation, characterized in that, Including: Step S1: Input the orbital elements of each satellite in the constellation and the payload observation capabilities, and set the observation area to be analyzed; Step S2: Simulate and calculate the observation time of each satellite for the observation area to be analyzed within a strict regression orbit period; Step S3: Calculate the observation line-of-sight vectors of each satellite for the simulation grid points in the observation area; Step S4: Analyze and estimate the line-of-sight deformation measurement accuracy of each satellite for the observation area; Step S5: Establish an observation equation and analyze and estimate the three-dimensional deformation measurement accuracy of the entire constellation for the observation area.

2. The method for analyzing the measurement accuracy of the three-dimensional surface deformation field of a differential interferometric SAR constellation according to claim 1, wherein The said Step S2 includes: Step S2.1: For each satellite in the constellation, simulate the satellite orbit position and velocity vector within a strict regression orbit period at a preset time interval; Step S2.2: For each satellite in the constellation, set multiple equally spaced observation perspectives within its radar observation perspective range, and use the perspective equation, Doppler equation, and Earth model for target positioning; Step S2.3: For each satellite, determine whether the target located in Step S2.2 is within the simulation analysis scenario. If it is within the simulation scenario at all times, include the effective observation time of this satellite to obtain the observation time interval of each satellite for the observation area.

3. The method for analyzing the measurement accuracy of the three-dimensional surface deformation field of a differential interferometric SAR constellation according to claim 2, wherein In Step S2.2, using the perspective equation, Doppler equation, and Earth model for target positioning includes: where p m (t a ) represents the position vector of the m-th satellite at azimuth time t a in the Earth-fixed coordinate system, v m (t a ) represents the velocity vector of the m-th satellite at azimuth time t a in the Earth-fixed coordinate system, θ is the depression angle, p t is the position vector of the target in the Earth-fixed coordinate system, λ is the radar wavelength, f dc is the imaging Doppler center, and DEM is the external Earth model.

4. The method for analyzing the measurement accuracy of the three-dimensional surface deformation field of a differential interferometric SAR constellation according to claim 1, wherein The said Step S3 includes: Step S3.1: Divide the observation area into grids, set the grid spacing according to requirements, and convert the coordinates of each grid point to the Earth-fixed coordinate system; Step S3.2: For each grid point, use the Doppler equation to inversely calculate the observation time of each satellite for this grid point; Step S3.3: For each grid point, use the satellite orbit position corresponding to the observation time of each satellite after Step S3.2 to calculate the line-of-sight and observation distance to the target. If this observation line-of-sight is within the radar beam and effective action distance, then regard this observation as an effective observation; Step S3.4: Convert the effective observation line-of-sight vectors of each satellite for each grid point to the target local coordinate system.

5. The method for analyzing the measurement accuracy of the three-dimensional surface deformation field of a differential interferometric SAR constellation according to claim 1, wherein The said Step S5 includes: Step S5.1: For each grid point, establish a three-dimensional surface deformation observation equation: Ax = b In the formula, A is the radar observation line-of-sight matrix of the target, b is the observation vector, and x is the vector composed of three-dimensional deformation quantities, and each element is the deformation in the east-west direction, north-south direction, and vertical direction respectively. Step S5.2: Calculate the covariance matrix of the deformation vector inversion: C x = (A H W H WA) -1 A H WC b W H A(A H W H WA) -1 where C x is the covariance matrix of the deformation vector estimation, A is the radar observation line-of-sight matrix of the target, W is the weighting value for solving the equations, and C b is the diagonal matrix composed of the variances of the radar line-of-sight deformation measurements for each observation. The superscript H represents the matrix transpose, and the superscript -1 represents the matrix inverse; Step S5.3: Take out the elements on the diagonal of C x and take the root mean square as the estimated accuracy of the strain rate in the corresponding direction.

6. A three-dimensional surface deformation field measurement accuracy analysis system for a differential interferometric SAR constellation, characterized in that, Including: Module M1: Input the orbital elements of each satellite in the constellation and the payload observation capabilities, and set the observation area to be analyzed; Module M2: Simulate and calculate the observation time of each satellite for the observation area to be analyzed within a strict regression orbit period; Module M3: Calculate the observation line-of-sight vectors of each satellite for the simulation grid points in the observation area; Module M4: Analyze and estimate the line-of-sight deformation measurement accuracy of each satellite for the observation area; Module M5: Establish an observation equation and analyze and estimate the three-dimensional deformation measurement accuracy of the entire constellation for the observation area.

7. The differential interference SAR constellation three-dimensional surface deformation field measurement accuracy analysis system according to claim 6, characterized in that The said Module M2 includes: Module M2.1: For each satellite in the constellation, simulate the satellite orbit position and velocity vector within a strict regression orbit period at a preset time interval; Module M2.2: For each satellite in the constellation, set multiple equally spaced observation perspectives within its radar observation perspective range, and use the perspective equation, Doppler equation, and Earth model for target positioning; Module M2.3: For each satellite, determine whether the target located in Module M2.2 is within the simulation analysis scenario. If it is, include the effective observation time of this satellite at all times in the simulation scenario, so as to obtain the observation time interval of each satellite for the observation area.

8. The differential interferometric SAR constellation three-dimensional surface deformation field measurement accuracy analysis system according to claim 7, characterized in that In Module M2.2, using the perspective equation, Doppler equation, and Earth model for target positioning includes: where p m (t a ) represents the position vector of the m-th satellite at azimuth time t a in the Earth-fixed coordinate system, v m (t a ) represents the velocity vector of the m-th satellite at azimuth time t a in the Earth-fixed coordinate system, θ is the depression angle, p t is the position vector of the target in the Earth-fixed coordinate system, λ is the radar wavelength, f dc is the imaging Doppler center, and DEM is the external Earth model.

9. The differential interference SAR constellation three-dimensional surface deformation field measurement accuracy analysis system according to claim 6, wherein The said Module M3 includes: Module M3.1: Divide the observation area into grids, set the grid spacing according to requirements, and convert the coordinates of each grid point to the Earth-fixed coordinate system; Module M3.2: For each grid point, use the Doppler equation to back-calculate the observation time of each satellite for this grid point; Module M3.3: For each grid point, calculate the line of sight and observation distance to the target using the satellite orbital positions corresponding to the observation times of each satellite after Module M3.

2. If this observation line of sight is within the radar beam and effective range, then regard this observation as an effective observation; Module M3.4: Convert the effective observation line of sight vectors of each satellite for each grid point to the target local coordinate system.

10. The differential interferometric SAR constellation three-dimensional surface deformation field measurement accuracy analysis system according to claim 6, wherein The said Module M5 includes: Module M5.1: For each grid point, establish a three-dimensional surface deformation observation equation: Ax = b where A is the radar observation line of sight matrix of the target, b is the observation vector, and x is the vector composed of three-dimensional deformation quantities, and each element is the deformation in the east-west direction, north-south direction, and vertical direction respectively. Module M5.2: Calculate the covariance matrix of the deformation vector inversion; C x = (A H W H WA) -1 A H WC b W H A(A H W H WA) -1 where C x is the covariance matrix of the deformation vector estimation, A is the radar observation line-of-sight matrix of the target, W is the weighting value for solving the equations, and C b is the diagonal matrix composed of the variances of the radar line-of-sight deformation measurements for each observation. The superscript H represents the matrix transpose, and the superscript -1 represents the matrix inverse; Module M5.3: Take C x Take out the elements on the diagonal and take the root mean square as the estimation accuracy of the strain rate in the corresponding direction.

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