Baseline calibration method and device for space-borne distributed interferometric synthetic aperture radar

Abstract

This application provides a baseline calibration method for a spaceborne distributed interferometric synthetic aperture radar (DSAR). The method includes: acquiring initial baseline vector parameters, baseline calibration parameters, and elevation parameters corresponding to a ground control point; determining a baseline error update amount for the baseline calibration parameters based on the initial baseline vector parameters and the elevation parameters; and correcting the baseline vector of the baseline calibration parameters based on the baseline error update amount if the baseline error update amount satisfies calibration conditions, thereby obtaining the final baseline vector parameters of the ground control point. This application also provides an apparatus that can solve the baseline calibration problem for all spaceborne distributed InSAR systems, including L-band, and achieve high-precision DEM production.

Description

Technical Field

[0001] This invention belongs to the field of radar signal processing technology, specifically relating to a baseline calibration method and apparatus for a spaceborne distributed interferometric synthetic aperture radar. Background Technology

[0002] Spaceborne distributed InSAR (Interferometric Synthetic Aperture Radar) technology refers to the technique of using multiple SAR satellites in a specific formation to observe the same area, obtaining multi-channel echo data, and then using interferometric processing to obtain a high-precision DEM (Digital Elevation Model). Spaceborne distributed InSAR systems are stable, have high data availability, and a wide swath width, possessing the capability for long-term stable monitoring of global DEMs. However, obtaining an accurate baseline is a prerequisite for forming a high-precision DEM, as elevation is highly sensitive to baseline length, sometimes by orders of magnitude 10. 2 This means that a baseline error at the millimeter level can introduce a height error at the meter level. For example, in an L-band InSAR system with an ambiguity height of 75m, a baseline error of 15mm in the radar line-of-sight direction will introduce a height error of 5.4m. Therefore, baseline calibration technology plays a crucial role in the generation of high-precision DEMs for spaceborne distributed InSAR.

[0003] Research on spaceborne distributed InSAR baseline calibration has been carried out both domestically and internationally. Currently, there are two main methods for spaceborne distributed InSAR baseline calibration: the first method uses the distributed target DEM obtained by lidar as a reference and employs two adjacent scenes acquired from two (different) wave positions to jointly calculate the two-dimensional baseline error; the second method uses the RD (Range-Doppler) equation to establish a calibration model and uses least squares to solve for the baseline error.

[0004] The current technical solution has the following shortcomings:

[0005] (1) Calibration methods based on distributed target reference elevation are not applicable to L-band systems. Current calibration methods based on distributed target reference elevation are designed for X-band spaceborne distributed InSAR systems and do not consider the influence of penetration depth. The L-band, compared to the X-band, is characterized by its longer wavelength and stronger penetration, especially in water content below 0.01m. 3 / m 3 In arid soil conditions, L-band electromagnetic waves can penetrate to depths exceeding 3 meters. The additional elevation error caused by the penetration depth of electromagnetic waves reduces baseline calibration accuracy due to the influence of the distributed target reference elevation on the baseline. Therefore, baseline calibration methods based on distributed target elevations cannot be applied to L-band spaceborne distributed InSAR systems.

[0006] (2) The requirements for using the dual-wavelength baseline calibration method are high. First, the dual-wavelength viewing angle difference is large, the calibration field range is wide, and the cost and difficulty of setting up ground control points are high. Second, the echo data of the dual-wavelength are not acquired simultaneously, and it cannot be guaranteed that the baseline configuration of the spaceborne distributed InSAR will not change during the dual-wavelength imaging process.

[0007] (3) The baseline calibration model established based on the RD equation has low accuracy. First, the slant range, as an observation parameter, is affected by atmospheric delay and internal thermal noise of the system, resulting in inherent system slant range error. Although slant range calibration can eliminate some of the slant range error, residual slant range error remains, causing coupling between baseline error and slant range error and reducing the accuracy of baseline calibration. Second, when using the least squares method to solve the calibration model established based on the RD equation, the condition number of the parameter matrix used for solving is large, and ill-conditioned problems are obvious, resulting in low stability and accuracy of baseline calibration. Summary of the Invention

[0008] In view of this, the purpose of this application is to overcome the shortcomings of existing technologies and propose a satellite-borne InSAR baseline calibration method and apparatus. This method and apparatus utilize the relationship between InSAR baseline and elevation to establish a baseline calibration model, and use the least squares method to solve the baseline error, thereby solving the baseline calibration problem of L-band satellite-borne distributed InSAR and achieving high-precision DEM production.

[0009] To achieve the above objectives, the technical solution of this application is implemented as follows:

[0010] According to one aspect of this application, a baseline calibration method for a spaceborne distributed interferometric synthetic aperture radar is provided, characterized in that the method comprises:

[0011] Obtain the initial parameters, baseline vector calibration parameters, and elevation parameters corresponding to the ground control points;

[0012] The baseline error update amount of the baseline vector calibration parameters is determined based on the initial parameters of the baseline vector and the elevation parameters;

[0013] If the baseline error update amount meets the calibration conditions, the baseline vector calibration parameters are corrected based on the baseline error update amount to obtain the final baseline vector parameters of the ground control point.

[0014] In the above scheme, determining the baseline error update amount of the baseline vector calibration parameters based on the initial parameters of the baseline vector and the elevation parameters includes:

[0015] Determine the elevation difference between the elevation parameter and the elevation reference parameter;

[0016] Based on the elevation difference, the baseline vector initial parameters are calculated using the least squares method to obtain the baseline error update.

[0017] In the above scheme, the baseline error update amount satisfies the calibration conditions, including:

[0018] The baseline error update amount is compared with a threshold.

[0019] If the comparison result indicates that the baseline error update amount is less than the threshold, it is determined that the baseline error update amount meets the calibration condition.

[0020] The method in the above scheme further includes:

[0021] If the comparison result indicates that the baseline error update amount is greater than or equal to the threshold, the initial parameters of the baseline vector are iteratively calculated based on the least squares method to update the baseline error update vector and the baseline vector until the baseline error update amount is less than the threshold.

[0022] In the above scheme, updating the baseline error update amount and the baseline vector includes:

[0023] The updated Nth baseline error vector is determined based on the iterative calculation results, where N is greater than or equal to 1;

[0024] The elevation parameters are updated based on the Nth baseline vector;

[0025] Based on the updated elevation parameters, the Nth baseline error update amount and the initial value of the baseline vector are calculated using the least squares method to determine the (N+1)th baseline error update amount;

[0026] The baseline vector is updated based on the N+1 baseline error update amounts until the baseline error update amounts are less than the threshold.

[0027] In the above scheme, obtaining the initial parameters of the baseline vector corresponding to the ground control point includes:

[0028] Determine the antenna phase center position parameters of the primary and secondary satellites corresponding to the ground control points;

[0029] The initial parameters of the baseline vector are determined based on the antenna phase center position parameters of the primary and secondary satellites.

[0030] In the above scheme, obtaining the baseline vector calibration parameters corresponding to the ground control points includes:

[0031] Determine the X-axis and Z-axis baselines of the primary and secondary satellites corresponding to the ground control points;

[0032] The X-axis baseline and the Z-axis baseline are determined as the baseline vector calibration parameters.

[0033] In the above scheme, obtaining the elevation parameters corresponding to the ground control points includes:

[0034] Determine the initial value of the baseline error;

[0035] The initial parameters of the baseline vector are corrected based on the initial value of the baseline error to obtain the corrected baseline vector parameters;

[0036] The elevation parameters are determined based on the geometric relationship between the ground control points and the primary and secondary satellites, using the corrected baseline vector parameters, the satellite slant range parameters corresponding to the ground control points, and the interferometric phase parameters.

[0037] In the above scheme, the elevation parameters are determined based on the corrected baseline vector parameters, the satellite slant range parameters corresponding to the ground control points, and the interferometric phase parameters, utilizing the geometric relationship between the ground control points and the primary and secondary satellites. This includes:

[0038] Determine the electromagnetic wave wavelength parameters and geocentric latitude parameters emitted by the satellite corresponding to the ground control point;

[0039] The elevation parameters are determined based on the geometric relationship between the ground control points and the primary and secondary satellites, the corrected baseline vector parameters, the satellite slant range parameters corresponding to the ground control points, the interferometric phase parameters, the electromagnetic wave wavelength parameters, and the geocentric latitude parameters.

[0040] According to another aspect of this application, a baseline calibration device for a spaceborne distributed interferometric synthetic aperture radar is provided, characterized in that the device comprises:

[0041] The acquisition unit is used to acquire the initial parameters of the baseline vector, the baseline vector calibration parameters, and the elevation parameters corresponding to the ground control points;

[0042] The determining unit is used to determine the baseline error update amount of the baseline vector calibration parameters based on the initial parameters of the baseline vector and the elevation parameters;

[0043] The correction unit is used to correct the baseline vector calibration parameters based on the baseline error update amount if the baseline error update amount is less than a threshold, so as to obtain the final baseline vector parameters of the ground control point.

[0044] The spaceborne InSAR baseline calibration method and apparatus provided in this application utilize the relationship between InSAR baseline and elevation and the least squares method to solve the baseline error. This method can solve the baseline calibration problem of spaceborne distributed InSAR in all bands, including the L-band, and achieve high-precision DEM production. Attached Figure Description

[0045] Figure 1 This document illustrates the implementation flow of the spaceborne distributed InSAR baseline calibration method in this application. Figure 1 ;

[0046] Figure 2 This is a schematic diagram showing the geometric relationship between the ground control points and the primary and secondary satellites in this application;

[0047] Figure 3 This document illustrates the implementation flow of the spaceborne distributed InSAR baseline calibration method in this application. Figure 2 ;

[0048] Figure 4 This is a schematic diagram of the elevation error of the baseline vector of the ground control points in this application before calibration.

[0049] Figure 5 This is a schematic diagram of the elevation error of the baseline vector of the ground control points in this application after calibration.

[0050] Figure 6 This is a schematic diagram of the elevation error of the whole scene image before calibration relative to SRTM in this application;

[0051] Figure 7 This is a schematic diagram showing the elevation error of the calibrated full-view image relative to SRTM in this application.

[0052] Figure 8 This is a histogram of the elevation error of the whole-view image before calibration relative to SRTM in this application;

[0053] Figure 9 This is a histogram of elevation error of the calibrated whole-view image relative to SRTM in this application;

[0054] Figure 10 This is a schematic diagram of the structural composition of the spaceborne distributed InSAR baseline calibration device in this application;

[0055] Figure 11 This is a schematic diagram of the structural composition of the electronic device in this application. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application 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 this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other. The steps shown in the flowcharts can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowcharts, in some cases, the steps shown or described may be performed in a different order than that shown here.

[0057] The technical solution of this application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] Figure 1 This document illustrates the implementation flow of the spaceborne distributed InSAR baseline calibration method in this application. Figure 1 ,like Figure 1 As shown, it includes:

[0059] Step 101: Obtain the initial parameters of the baseline vector, the calibration parameters of the baseline vector, and the elevation parameters corresponding to the ground control points;

[0060] Here, this method can be applied to electronic devices that have a baseline calibration system for spaceborne distributed interferometric synthetic aperture radar. Specifically, it can have an L-band spaceborne distributed InSAR system.

[0061] In this application, the electronic device can determine the antenna phase center position parameters of the primary and secondary satellites corresponding to the ground control point; based on the antenna phase center position parameters of the primary and secondary satellites, the initial parameters of the baseline vector can be determined.

[0062] Figure 2 This is a schematic diagram illustrating the geometric relationship between ground control points and the primary and secondary satellites in this application. For example... Figure 2 As shown, this electronic device can use the antenna phase center position of the main satellite imaging the ground control point as the origin S. AEstablish a coordinate system. The tangent to the primary satellite's track is defined as the Y-axis; the line connecting the center O of the WGS84 (World Geodetic System 1984) ellipsoid to the primary satellite is defined as the Z-axis; and the line orthogonal to the Y and Z axes is defined as the X-axis. Then, input the antenna phase center coordinates corresponding to the ground control points for the primary and secondary satellite imaging. Subtract the secondary satellite's three-dimensional coordinates from the primary satellite's three-dimensional coordinates to obtain the baseline vector. Rotate the baseline vector in the ECEF (Earth-Centered, Earth-Fixed) coordinate system to the primary satellite antenna phase center coordinate system to obtain the baseline vector. The unit vectors corresponding to the X, Y, and Z axes in the antenna phase center coordinate system are respectively... and The components of the baseline vector on each axis in the antenna phase center coordinate system are B. X B Y and B Z ,Right now Where T represents transpose.

[0063] In this application, the visiting electronic equipment can also determine the X-axis baseline and Z-axis baseline of the primary and secondary satellites corresponding to the ground control point; and then determine the X-axis baseline and the Z-axis baseline as the baseline vector calibration parameters.

[0064] In one implementation, the electronic device can set the baseline vector calibration parameters according to the calibration requirements. Where T represents transpose. ΔB represents the baseline error, bias represents the error, and ΔB represents the baseline error. X and ΔB Z These are the baseline corrections for the X and Z axes, respectively (referring to the final baseline error update). The reason for not correcting the Y-axis baseline here is that the Y-axis baseline error can be resolved by image registration.

[0065] In this application, the electronic device can also set the initial parameter of the baseline error as follows: Where T represents transpose. Based on the initial parameters of the baseline error, the initial parameters of the baseline vector can be corrected to obtain the corrected baseline vector parameters. Here, the corrected baseline vector parameters are: Among them, B Xcor and B Zcor These represent the components of the corrected baseline vector on the X and Z axes, respectively. T indicates transpose, cor indicates correction, and 0 indicates the initial value.

[0066] In this application, after determining the initial value of the baseline error and correcting the initial parameters of the baseline vector based on the initial value of the baseline error, the electronic device can also use the geometric relationship between the ground control point and the main and auxiliary satellites to determine the elevation parameters based on the corrected baseline vector parameters, the satellite slant range parameters corresponding to the ground control point, and the interferometric phase parameters.

[0067] In this application, when the electronic device determines the elevation parameter based on the corrected baseline vector parameter, the satellite slant range parameter corresponding to the ground control point, and the interferometric phase parameter using the geometric relationship between the ground control point and the primary and secondary satellites, it can also determine the electromagnetic wave wavelength parameter and geocentric latitude parameter emitted by the satellite corresponding to the ground control point; and determine the elevation parameter based on the corrected baseline vector parameter, the satellite slant range parameter, the interferometric phase parameter, the electromagnetic wave wavelength parameter, and the geocentric latitude parameter using the geometric relationship between the ground control point and the primary and secondary satellites.

[0068] In one implementation, the electronic device can determine the position S of the auxiliary satellite. B Projected onto the primary star's imaging plane S′ B At this point, the baseline after error correction. The projection vector is The projection angle from the modified 3D baseline to the projection plane is ψ1, and the projection angle from the auxiliary star slant distance to the projection plane is ψ2.

[0069] The method for obtaining the projection vector from the original vector is as follows:

[0070]

[0071] in, This is the original vector.

[0072] here,

[0073] Among them, R B The slant range of the auxiliary satellite is the straight-line distance from the auxiliary satellite to the ground control point.

[0074] here,

[0075] Among them, R A Main satellite S A The slant range is the straight-line distance from the main satellite to the ground control point; λ is the wavelength of the electromagnetic wave. It is an absolute interference phase.

[0076] Here, R A =R0+nΔx;

[0077] Where R0 is the nearest slant range after slant range calibration; n is the range pixel corresponding to the pixel in the primary star image. Calculate the secondary star S′ in the projection plane. B Slant distance R′ to ground target B The distance R from the primary star to the center of the WGS84 ellipsoid H The Earth's radius of curvature R corresponding to the ground target e .

[0078]

[0079]

[0080]

[0081] Where (X,Y,Z) represents the three-dimensional coordinates of the phase center of the main satellite antenna in the ECEF coordinate system; a and b are the major and minor semi-axis defined by the WGS84 ellipsoid, respectively, which are 6378137m and 6356752.314m; φ is the geocentric latitude.

[0082] In this application, the electronic device can also calculate the baseline direction angle α and the angle θ below the primary star based on the law of cosines;

[0083] in,

[0084] This application is based on Figure 2 The geometric relationship between the ground control points and the primary and secondary satellites is shown, combined with the distance R from the primary satellite to the geocenter of the WGS84 ellipsoid calculated above. H Slant distance R from the main satellite to the ground control point A The slant distance R from the auxiliary satellite to the ground control point B The main satellite's downward viewing angle θ, the baseline orientation angle α, and the Earth's radius of curvature R corresponding to the ground control point. e Calculate the elevation of control points using parameters:

[0085]

[0086] Step 102: Determine the baseline error update amount of the baseline vector calibration parameters based on the initial parameters of the baseline vector and the elevation parameters;

[0087] In this application, the electronic device can determine the baseline error update amount of the baseline vector calibration parameters based on the initial parameters of the baseline vector and the elevation parameters;

[0088] In one implementation, the electronic device can establish a baseline calibration solution model based on the relationship between the elevation parameter and the baseline vector:

[0089]

[0090] Among them, h ref The elevation reference parameter representing the ground control point, i.e., the actual elevation of the ground control point;

[0091] Here, if there are N calibration points on the ground, the elevation reference parameter for the ground control points can be h. ref =[h ref1 ,h ref2 ,...,h refN ] T By using the elevation parameters of this ground control point The error matrix can be obtained by subtracting the elevation reference parameter. The baseline error update γ can be calculated from this error matrix:

[0092] γ=(Η T PH) -1 H T PL;

[0093] Where P is the weight matrix. H is the parameter matrix, and... The first column of the parameter matrix The third column represents the rate of change of elevation with respect to the X-axis component of the baseline. B represents the elevation relative to the baseline Z-axis component. Z The rate of change, and

[0094]

[0095]

[0096] Among them, B PXZ For intermediate calculation parameters and β is the complementary angle of the lower viewpoint and

[0097] Step 103: If the baseline error update amount meets the calibration conditions, the baseline vector calibration parameters are corrected based on the baseline error update amount to obtain the final baseline vector parameters of the ground control point.

[0098] In this application, the electronic device can also compare the baseline error update amount with a threshold; obtain a comparison result; if the comparison result indicates that the baseline error update amount is less than the threshold, determine that the baseline error update amount meets the calibration condition.

[0099] If the comparison result indicates that the baseline error update amount is greater than or equal to the threshold, and it is determined that the baseline error update amount does not meet the calibration condition, the electronic device can also iteratively calculate the initial parameters of the baseline vector based on the Newton iterative least squares method to update the baseline error update vector and the baseline vector until the baseline error update amount is less than the threshold.

[0100] In this application, to ensure the speed and accuracy of the algorithm, the threshold can be set to 10. -9 m.

[0101] When updating the baseline error update amount and the baseline vector, the electronic device can further determine the updated Nth baseline error vector based on the iterative calculation results, where N is greater than or equal to 1; update the elevation parameter based on the Nth baseline vector; calculate the Nth baseline error update amount and the initial value of the baseline vector using Newton's iterative least squares method based on the updated elevation parameter to determine the (N+1)th baseline error update amount; update the baseline vector based on the (N+1)th baseline error update amount until the baseline error update amount is less than the threshold.

[0102] In this application, the updated baseline error and baseline vector can be:

[0103]

[0104]

[0105] The final baseline calibration yielded a baseline error of 0.0137m on the X-axis and 0.0179m on the Z-axis. Specifically, the elevation error distribution and histogram of the entire image before and after baseline error compensation are as follows: Figure 8 and Figure 9 As shown.

[0106] Since the baseline calibration method for spaceborne distributed interferometric synthetic aperture radar provided in this application only uses the range vector image data corresponding to the pixels on the main satellite image, and can be applied to all electromagnetic wave bands including the L-band, this application is an L-band spaceborne InSAR baseline calibration method based on a single-position target. Its advantages compared to existing experimental methods are:

[0107] (1) It can solve the problem of reference elevation error caused by the penetration of L-band electromagnetic waves.

[0108] (2) It can solve the problem of baseline configuration changes under dual-wavelength conditions and can be applied to all spaceborne InSAR baseline configurations. At the same time, it only requires the deployment of control points within a small calibration field, reducing the cost and difficulty of ground deployment of control points.

[0109] (3) In the process of solving the baseline error using the least squares method, the condition number of the matrix is ​​small, which avoids the occurrence of ill-conditioned problems, the algorithm is robust, and the baseline calibration accuracy is high.

[0110] Figure 3 This is a flowchart illustrating the baseline calibration method for spaceborne distributed interferometric synthetic aperture radar in this application. Figure 2 ,like Figure 3 As shown, the method includes:

[0111] Step 301: Input the position coordinates of the phase center of the primary and secondary satellite antennas corresponding to the ground control points, establish the coordinate system of the phase center of the primary satellite antenna, and obtain the initial parameters of the baseline vector;

[0112] Step 302: Determine the baseline vector calibration parameters and set the initial parameters of the baseline error. Establish a baseline calibration model based on the baseline vector calibration parameters, the initial parameters of the baseline error, and the initial parameters of the baseline vector.

[0113] Step 303: Based on the spaceborne InSAR satellite-to-ground geometry, calculate the elevation of the ground control points using the corrected baseline vector parameters, slant range, and interferometric phase.

[0114] Step 304: Establish the baseline calibration solution model and calculate the baseline error update using Newton's iterative least squares method. Then, correct the baseline vector based on this error update.

[0115] Step 305: Determine whether the baseline error update amount is less than the threshold. If not, proceed to step 306; if yes, proceed to step 305.

[0116] Step 305: If the baseline error update amount is less than the threshold, output the baseline error result to complete the baseline calibration of spaceborne distributed InSAR.

[0117] Step 306: If the baseline error update amount is greater than or equal to the threshold, then correct the baseline error update amount and the baseline vector. The corrected baseline vector is then used in step 303 for iterative calculation.

[0118] It should be noted that the calibration method provided in the above embodiments is different from... Figure 1 The provided calibration method implementations belong to the same concept, and their specific implementation process can be found by referring to [reference needed]. Figure 1 The method implementation examples are not described in detail here.

[0119] Figure 4 This is a schematic diagram showing the elevation error of the baseline vector of the ground control points in this application before calibration, as shown below. Figure 4 As shown, the elevation error is distributed on average between 7 and 7.4 m.

[0120] Figure 5 This is a schematic diagram showing the elevation error of the baseline vector of the ground control points in this application after calibration, as shown below. Figure 5 As shown, the average elevation error decreased from 7-7.4m to -0.3-+0.3m, meeting the elevation requirements.

[0121] Figure 6 This is a schematic diagram illustrating the elevation error of the entire scene image before calibration relative to SRTM in this application, as shown below. Figure 6As shown:

[0122] Here, SRTM stands for Shuttle Radar Topography Mission. As can be seen from the diagram, the elevation error is distributed on average between 0 and 15m.

[0123] Figure 7 This is a schematic diagram illustrating the elevation error of the calibrated full-view image relative to SRTM in this application, as shown below. Figure 7 As shown,

[0124] The elevation error is distributed on average between -5 and +5m.

[0125] Figure 8 This is a histogram of the elevation error of the whole-view image before calibration relative to SRTM in this application, such as... Figure 8 As shown, the average error is around 7m.

[0126] Figure 9 This is a histogram of the elevation error of the calibrated whole-view image relative to SRTM in this application, such as... Figure 9 As shown: First, the elevation error follows a Gaussian distribution with only one thermal noise error, indicating that the systematic error has been corrected; Second, the elevation accuracy required for surveying and mapping can be met after baseline calibration. The standard deviation of the elevation error of the entire image after baseline calibration is 1.4m, which can meet the elevation accuracy requirement of 5m for a 1:50000 topographic map.

[0127] The spaceborne distributed InSAR baseline calibration method provided in this application can be applied to all bands (X-band), including the L-band, and can solve the reference elevation error problem caused by the penetration of L-band electromagnetic waves. It can also solve the problem of baseline configuration changes under dual-position conditions and can be applied to all spaceborne InSAR baseline configurations. Furthermore, it only requires the deployment of control points within a relatively small calibration field, reducing the cost and difficulty of ground-based control point deployment. Secondly, because the input parameters for the least squares method are few, the condition number of the matrix is ​​small during the baseline error solution using least squares, avoiding ill-conditioned problems, resulting in a robust algorithm and high baseline calibration accuracy.

[0128] Figure 10 This is a schematic diagram of the structural composition of the spaceborne distributed InSAR baseline calibration device in this application, as shown below. Figure 10 As shown, the device includes:

[0129] The acquisition unit 1001 is used to acquire the initial parameters of the baseline vector, the baseline vector calibration parameters, and the elevation parameters corresponding to the ground control points;

[0130] The determining unit 1002 is used to determine the baseline error update amount of the baseline vector calibration parameters based on the initial parameters of the baseline vector and the elevation parameters;

[0131] The correction unit 1003 is used to correct the baseline vector calibration parameters based on the baseline error update amount if the baseline error update amount is less than a threshold, so as to obtain the final baseline vector parameters of the ground control point.

[0132] In a preferred embodiment, the device further includes a computing unit 1004;

[0133] Specifically, the determining unit 1002 is also used to determine the elevation difference between the elevation parameter and the elevation reference parameter;

[0134] The calculation unit 1004 is used to calculate the initial parameters of the baseline vector based on the elevation difference using the least squares method, and obtain the baseline error update amount.

[0135] In a preferred embodiment, the device further includes:

[0136] Comparison unit 1005 is used to compare the baseline error update amount with a threshold.

[0137] The determining unit 1002 is further configured to determine that the baseline error update amount satisfies the calibration condition if the comparison result indicates that the baseline error update amount is less than the threshold.

[0138] Output unit 1006 is used to output the baseline error update amount that meets the calibration conditions.

[0139] In a preferred embodiment, the calculation unit 1004 is further configured to perform iterative calculations on the initial parameters of the baseline vector based on the least squares method if the comparison result indicates that the baseline error update amount is greater than or equal to the threshold, so as to update the baseline error update vector and the baseline vector until the baseline error update amount is less than the threshold.

[0140] In a preferred embodiment, the correction unit 1003 is specifically used to determine the updated Nth baseline error vector based on the iterative calculation results, where N is greater than or equal to 1; update the elevation parameters based on the Nth baseline vector; calculate the Nth baseline error update amount and the initial value of the baseline vector using the least squares method based on the updated elevation parameters to determine the (N+1)th baseline error update amount; and update the baseline vector based on the (N+1)th baseline error update amount until the baseline error update amount is less than the threshold.

[0141] In a preferred embodiment, the determining unit 1002 is further configured to determine the antenna phase center position parameters of the primary and secondary satellites corresponding to the ground control point; and to determine the initial parameters of the baseline vector based on the antenna phase center position parameters of the primary and secondary satellites.

[0142] In a preferred embodiment, the determining unit 1002 is further configured to determine the X-axis baseline and Z-axis baseline of the primary and secondary satellites corresponding to the ground control point; and to determine the X-axis baseline and the Z-axis baseline as the baseline vector calibration parameters.

[0143] In the preferred embodiment, the determining unit 1002 is also used to determine the initial value of the baseline error;

[0144] Correction unit 1003 is used to correct the initial parameters of the baseline vector based on the initial value of the baseline error, so as to obtain the corrected baseline vector parameters;

[0145] The determining unit 1002 is also used to determine the elevation parameters based on the corrected baseline vector parameters, the satellite slant range parameters and the interferometric phase parameters corresponding to the ground control points, by utilizing the geometric relationship between the ground control points and the primary and secondary satellites.

[0146] In a preferred embodiment, the determining unit 1002 is further configured to determine the electromagnetic wave wavelength parameters and geocentric latitude parameters emitted by the satellite corresponding to the ground control point; and to determine the elevation parameters based on the corrected baseline vector parameters, the satellite slant range parameters, the interferometric phase parameters, the electromagnetic wave wavelength parameters, and the geocentric latitude parameters, using the geometric relationship between the ground control point and the primary and secondary satellites.

[0147] It should be noted that the above embodiments of the device, when correcting the baseline vector error of ground control points, are only illustrated by the division of the above-described program modules. In practical applications, the above processing can be assigned to different program modules as needed, that is, the internal structure of the device can be divided into different program modules to complete all or part of the processing described above. Furthermore, the device provided in the above embodiments and the calibration method embodiments provided above belong to the same concept; the specific implementation process is detailed in the method embodiments and will not be repeated here.

[0148] This application also provides an electronic device, which includes: a processor and a memory for storing a computer program capable of running on the processor.

[0149] When the processor runs the computer program, it executes any one of the method steps in the above processing method.

[0150] Figure 11This is a schematic diagram of the structure of the electronic device in this application. The electronic device 1100 can be a computer or an information transceiver terminal. Figure 11 The illustrated electronic device 1100 includes at least one processor 1101, a memory 1102, at least one network interface 1104, and a user interface 1103. The various components in the electronic device 1100 are coupled together via a bus system 1105. It is understood that the bus system 1105 is used to implement communication between these components. In addition to a data bus, the bus system 1105 also includes a power bus, a control bus, and a status signal bus. However, for clarity, ... Figure 11 The general labeled all buses as Bus System 1105.

[0151] The user interface 1103 may include a monitor, keyboard, mouse, trackball, click wheel, buttons, touchpad, or touch screen.

[0152] It is understood that memory 1102 can be volatile memory or non-volatile memory, or both. Non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), ferromagnetic random access memory (FRAM), flash memory, magnetic surface memory, optical disc, or compact disc read-only memory (CD-ROM); magnetic surface memory can be disk storage or magnetic tape storage. Volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as Static Random Access Memory (SRAM), Synchronous Static Random Access Memory (SSRAM), Dynamic Random Access Memory (DRAM), Synchronous Dynamic Random Access Memory (SDRAM), Double Data Rate Synchronous Dynamic Random Access Memory (DDRSDRAM), Enhanced Synchronous Dynamic Random Access Memory (ESDRAM), SyncLink Dynamic Random Access Memory (SLDRAM), and Direct Rambus Random Access Memory (DRRAM).The memory 1102 described in the embodiments of this application is intended to include, but is not limited to, these and any other suitable types of memory.

[0153] In this embodiment, the memory 1102 is used to store various types of data to support the operation of the electronic device 1100. Examples of such data include: any computer program used to operate on the electronic device 1100, such as the operating system 11021 and application program 11022; contact data; phonebook data; messages; pictures; audio, etc. The operating system 11021 includes various system programs, such as the framework layer, core library layer, driver layer, etc., used to implement various basic services and handle hardware-based tasks. The application program 11022 may include various applications, such as a media player, browser, etc., used to implement various application services. Programs implementing the methods of this embodiment may be included in the application program 11022.

[0154] The methods disclosed in the embodiments of this application can be applied to processor 1101, or implemented by processor 1101. Processor 1101 may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method can be completed by the integrated logic circuit of the hardware in processor 1101 or by instructions in the form of software. The processor 1101 may be a general-purpose processor, a digital signal processor (DSP), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Processor 1101 can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. A general-purpose processor may be a microprocessor or any conventional processor, etc. The steps of the methods disclosed in the embodiments of this application can be directly manifested as being executed by a hardware decoding processor, or being executed by a combination of hardware and software modules in the decoding processor. The software modules may be located in a storage medium, which is located in memory 1102. Processor 1101 reads the information in memory 1102 and completes the steps of the aforementioned method in conjunction with its hardware.

[0155] In an exemplary embodiment, the electronic device 1100 may be implemented by one or more application-specific integrated circuits (ASICs), DSPs, programmable logic devices (PLDs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), general-purpose processors, controllers, microcontrollers (MCUs), microprocessors, or other electronic components to perform the aforementioned method.

[0156] In an exemplary embodiment, this application also provides a computer-readable storage medium, such as a memory 1102 including a computer program, which can be executed by the processor 1101 of the electronic device 1100 to complete the steps described in the aforementioned method. The computer-readable storage medium may be a memory such as FRAM, ROM, PROM, EPROM, EEPROM, Flash Memory, magnetic surface memory, optical disc, or CD-ROM; it may also be various devices including one or any combination of the above-mentioned memories, such as mobile phones, computers, tablet devices, personal digital assistants, etc.

[0157] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs any of the method steps in the above-described processing method.

[0158] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or units can be electrical, mechanical, or other forms.

[0159] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the units may be selected to achieve the purpose of this embodiment according to actual needs.

[0160] The methods disclosed in the several method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments.

[0161] The features disclosed in the several product embodiments provided in this application can be arbitrarily combined without conflict to obtain new product embodiments.

[0162] The features disclosed in the several method or device embodiments provided in this application can be arbitrarily combined without conflict to obtain new method or device embodiments.

[0163] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A baseline calibration method for a spaceborne distributed interferometric synthetic aperture radar, characterized in that, The method includes: Obtain the initial parameters, baseline vector calibration parameters, and elevation parameters corresponding to the ground control points; The baseline error update amount of the baseline vector calibration parameters is determined based on the initial parameters of the baseline vector and the elevation parameters; If the baseline error update amount meets the calibration conditions, the baseline vector calibration parameters are corrected based on the baseline error update amount to obtain the final baseline vector parameters of the ground control point; The process of determining the baseline error update amount of the baseline vector calibration parameters based on the initial parameters of the baseline vector and the elevation parameters includes: Determine the elevation difference between the elevation parameter and the elevation reference parameter; Based on the elevation difference, the initial parameters of the baseline vector are calculated using the least squares method to obtain the baseline error update amount; The baseline error update satisfies the calibration conditions, including: The baseline error update amount is compared with a threshold. If the comparison result indicates that the baseline error update amount is less than the threshold, it is determined that the baseline error update amount meets the calibration condition. If the comparison result indicates that the baseline error update amount is greater than or equal to the threshold, the initial parameters of the baseline vector are iteratively calculated based on the least squares method to update the baseline error update amount and the baseline vector until the baseline error update amount is less than the threshold. Updating the baseline error update amount and the baseline vector includes: The updated Nth baseline vector is determined based on the iterative calculation results, where N is greater than or equal to 1; The elevation parameters are updated based on the Nth baseline vector; Based on the updated elevation parameters, the Nth baseline error update amount and the initial value of the baseline vector are calculated using the least squares method to determine the (N+1)th baseline error update amount; The baseline vector is updated based on the N+1 baseline error update amounts until the baseline error update amounts are less than the threshold.

2. The method according to claim 1, characterized in that, The process of obtaining the initial parameters of the baseline vector corresponding to the ground control point includes: Determine the antenna phase center position parameters of the primary and secondary satellites corresponding to the ground control points; The initial parameters of the baseline vector are determined based on the antenna phase center position parameters of the primary and secondary satellites.

3. The method according to claim 1, characterized in that, The acquisition of baseline vector calibration parameters corresponding to ground control points includes: Determine the X-axis and Z-axis baselines of the primary and secondary satellites corresponding to the ground control points; The X-axis baseline and the Z-axis baseline are determined as the baseline vector calibration parameters.

4. The method according to claim 1, characterized in that, The process of obtaining the elevation parameters corresponding to the ground control points includes: Determine the initial value of the baseline error; The initial parameters of the baseline vector are corrected based on the initial value of the baseline error to obtain the corrected baseline vector parameters; The elevation parameters are determined based on the geometric relationship between the ground control points and the primary and secondary satellites, using the corrected baseline vector parameters, the satellite slant range parameters corresponding to the ground control points, and the interferometric phase parameters.

5. The method according to claim 4, characterized in that, The process of determining the elevation parameters based on the corrected baseline vector parameters, the satellite slant range parameters corresponding to the ground control points, and the interferometric phase parameters, utilizing the geometric relationship between the ground control points and the primary and secondary satellites, includes: Determine the electromagnetic wave wavelength parameters and geocentric latitude parameters emitted by the satellite corresponding to the ground control point; The elevation parameters are determined based on the geometric relationship between the ground control points and the primary and secondary satellites, the corrected baseline vector parameters, the satellite slant range parameters corresponding to the ground control points, the interferometric phase parameters, the electromagnetic wave wavelength parameters, and the geocentric latitude parameters.

6. A baseline calibration device for a spaceborne distributed interferometric synthetic aperture radar, characterized in that, The device includes: The acquisition unit is used to acquire the initial parameters of the baseline vector, the baseline vector calibration parameters, and the elevation parameters corresponding to the ground control points; The determining unit is used to determine the baseline error update amount of the baseline vector calibration parameters based on the initial parameters of the baseline vector and the elevation parameters; The correction unit is used to correct the baseline vector calibration parameters based on the baseline error update amount if the baseline error update amount is less than a threshold, so as to obtain the final baseline vector parameters of the ground control point. The determining unit is used to determine the elevation difference between the elevation parameter and the elevation reference parameter; The calculation unit is used to calculate the initial parameters of the baseline vector based on the elevation difference using the least squares method, and obtain the baseline error update amount; The comparison unit is used to compare the baseline error update amount with a threshold. A determining unit is configured to determine that the baseline error update amount satisfies the calibration condition if the comparison result indicates that the baseline error update amount is less than the threshold. A calculation unit is configured to perform iterative calculations on the initial parameters of the baseline vector based on the least squares method if the comparison result indicates that the baseline error update amount is greater than or equal to the threshold, so as to update the baseline error update amount and the baseline vector until the baseline error update amount is less than the threshold. The correction unit is configured to determine the updated Nth baseline vector based on the iterative calculation results, where N is greater than or equal to 1; update the elevation parameters based on the Nth baseline vector; calculate the Nth baseline error update amount and the initial value of the baseline vector using the least squares method based on the updated elevation parameters to determine the (N+1)th baseline error update amount; and update the baseline vector based on the (N+1)th baseline error update amount until the baseline error update amount is less than the threshold.

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