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

Abstract

The application provides a baseline estimation method of a spaceborne distributed interferometric synthetic aperture radar, comprising the following steps: determining delay scaling parameters of a main satellite and an auxiliary satellite; if the delay scaling parameters satisfy a scaling condition, determining main satellite track positions and auxiliary satellite track positions of a ground control point corresponding to imaging time of the main satellite and the auxiliary satellite based on the delay scaling parameters and fitting track parameters of the main satellite and the auxiliary satellite; and determining a baseline vector parameter of the ground control point based on the main satellite track positions and the auxiliary satellite track positions. Meanwhile, the application also provides a baseline estimation device of the spaceborne distributed interferometric synthetic aperture radar, which can correct system delay errors and improve baseline estimation precision.

Description

Technical Field

[0001] This application relates to radar signal processing technology, and more particularly to a baseline estimation method and apparatus for a spaceborne distributed interferometric synthetic aperture radar. Background Technology

[0002] Spaceborne distributed InSAR (Interferometric Synthetic Aperture Radar) is a spaceborne Earth observation system that combines InSAR technology with satellite formation technology. It is widely used in high-precision DEM (Digital Elevation Model) production and terrain deformation monitoring. The baseline is a crucial interferometric parameter affecting DEM generation; it not only determines the removal of the flat-ground phase during interferometry but also directly impacts the elevation accuracy of the DEM.

[0003] Currently, there are four main types of baseline estimation methods: methods based on image registration offset, methods based on external DEM, methods based on flat-land phase, and methods based on interferogram fringe rate. The drawback of current technical solutions is that they do not consider the impact of system delay errors, resulting in lower accuracy. Summary of the Invention

[0004] In view of this, the embodiments of this application aim to provide a baseline estimation method and apparatus for spaceborne distributed interferometric synthetic aperture radar, which can correct system delay errors and improve baseline estimation accuracy.

[0005] To achieve the above objectives, the technical solution of this application is implemented as follows:

[0006] According to one aspect of this application, a baseline estimation method for a spaceborne distributed interferometric synthetic aperture radar is provided, the method comprising:

[0007] Determine the delay calibration parameters for the primary and secondary satellites;

[0008] If the delay calibration parameters meet the calibration conditions, based on the delay calibration parameters and the fitted trajectory parameters of the primary and secondary satellites, the trajectory positions of the primary and secondary satellites corresponding to the imaging time of the primary and secondary satellites at the ground control points are determined.

[0009] The baseline vector parameters of the ground control point are determined based on the positions of the primary and secondary satellite trajectories.

[0010] In the above scheme, the delay calibration parameters satisfy the calibration conditions, including:

[0011] Based on the azimuth time parameter and range time parameter in the delay calibration parameters, determine the slant range parameters of the primary and secondary satellites corresponding to the ground control point;

[0012] Calculate the slant range difference between the slant range parameters of the primary and secondary satellites and the slant range reference parameters;

[0013] The delay error update amount is calculated using the slant distance difference;

[0014] The delay error update amount is compared with the threshold.

[0015] If the comparison result indicates that the delay error update amount is less than the threshold, it is determined that the delay calibration parameter meets the calibration condition.

[0016] The method in the above scheme further includes:

[0017] If the comparison result indicates that the delay error update amount is greater than or equal to the threshold, the azimuth time parameter and range time parameter are corrected using the least squares method until the delay error update amount is less than the threshold.

[0018] In the above scheme, determining the position of the main satellite trajectory corresponding to the imaging time of the main satellite at the ground control point based on the delay calibration parameters and the fitted trajectory parameters of the main and auxiliary satellites includes:

[0019] The azimuth sampling time corresponding to the ground control point is determined based on the azimuth time parameter and range time parameter of the main satellite in the delay calibration parameters.

[0020] Based on the correspondence between the time parameter and the position parameter in the fitted trajectory parameters, the target trajectory position corresponding to the azimuth sampling time is determined;

[0021] Based on the target location parameters, the position of the main satellite trajectory corresponding to the imaging time of the main satellite at the ground control point is determined.

[0022] In the above scheme, determining the auxiliary satellite trajectory position of the ground control point corresponding to the imaging time of the auxiliary satellite based on the delay calibration parameters and the fitted trajectory parameters of the primary and auxiliary satellites includes:

[0023] Based on the azimuth time parameter and range time parameter of the auxiliary satellite in the delay calibration parameters, the reception time and transmission time of the auxiliary satellite receiving the echo from the ground control point are determined.

[0024] Based on the correspondence between the time parameters and the position parameters in the fitted trajectory parameters, the target trajectory position corresponding to the receiving time and the transmitting time is determined;

[0025] Based on the target location parameters, the location of the auxiliary satellite trajectory corresponding to the imaging time of the auxiliary satellite at the ground control point is determined.

[0026] In the above scheme, before determining the primary and secondary satellite trajectory positions corresponding to the imaging time of the primary and secondary satellites based on the delay calibration parameters and the fitted trajectory parameters of the primary and secondary satellites, the method further includes:

[0027] Based on the first data from the primary and secondary satellites, determine the state vector parameters of the primary and secondary satellites;

[0028] The trajectory parameters of the primary and secondary satellites are fitted based on the state vector parameters to obtain the fitted trajectory parameters.

[0029] In the above scheme, determining the delay calibration parameters of the primary and secondary satellites includes:

[0030] Based on the second data from the primary and secondary satellites, the azimuth time parameters and range time parameters of the primary and secondary satellites are obtained.

[0031] The azimuth time parameter and range time parameter are determined as the delay calibration parameters for the primary and secondary satellites.

[0032] The method in the above scheme further includes:

[0033] Determine the rate of change of the baseline vector parameters over time;

[0034] The baseline vector parameters are fitted to the rate of change parameters to obtain the baseline vector parameters of the pixel points of the whole scene image of the main and auxiliary satellites.

[0035] The method in the above scheme further includes:

[0036] Obtain the geographic coordinate parameters of the ground control points;

[0037] Convert the geographic coordinate parameters to geographic coordinate parameters in the geocentric and geofixed coordinate system;

[0038] The determination of the slant range parameters of the primary and secondary satellites corresponding to the ground control point based on the azimuth time parameter and range time parameter in the delay calibration parameters includes:

[0039] The slant range parameters of the primary and secondary satellites are determined based on the azimuth time parameter, the range time parameter, and the geographic coordinate parameter in the geocentric-geofixed coordinate system.

[0040] According to another aspect of this application, a baseline estimation device for a spaceborne distributed interferometric synthetic aperture radar is provided, the device comprising:

[0041] The unit is configured to determine the delay calibration parameters of the primary and secondary satellites; and to determine the trajectory positions of the ground control points corresponding to the imaging time of the primary and secondary satellites based on the delay calibration parameters and the fitted trajectory parameters of the primary and secondary satellites, if the delay calibration parameters meet the calibration conditions; and to determine the baseline vector parameters of the ground control points based on the trajectory positions of the primary and secondary satellites.

[0042] The judgment unit is used to determine whether the delay calibration parameters meet the calibration conditions.

[0043] The baseline estimation method and apparatus for spaceborne distributed interferometric synthetic aperture radar provided in this application is a spaceborne distributed InSAR baseline estimation method based on bistatic delay effect correction, which can solve the problem of delay errors in the range and azimuth directions of the primary and secondary satellites in spaceborne distributed InSAR baseline estimation. Attached Figure Description

[0044] Figure 1 This document illustrates the implementation flow of the baseline estimation method for spaceborne distributed interferometric synthetic aperture radar in this application. Figure 1 ;

[0045] Figure 2 A schematic diagram of the primary star slant range corresponding to the control point before delay error correction;

[0046] Figure 3 This is a schematic diagram of the slant range of the primary star corresponding to the control point after the delay error correction;

[0047] Figure 4 A schematic diagram of the auxiliary satellite slant range corresponding to the control point before delay error correction;

[0048] Figure 5 This is a schematic diagram of the auxiliary satellite slant range corresponding to the control point after delay error correction.

[0049] Figure 6 This is a schematic diagram of the baseline obtained after correcting the delay error parameters in this application;

[0050] Figure 7 This document illustrates the implementation flow of the baseline estimation method for spaceborne distributed interferometric synthetic aperture radar in this application. Figure 2 ;

[0051] Figure 8 This is a schematic diagram of the baseline estimation device structure of the spaceborne distributed interferometric synthetic aperture radar in this application;

[0052] Figure 9 This is a schematic diagram of the structural composition of the electronic device in this application. Detailed Implementation

[0053] 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.

[0054] The technical solution of this application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] Figure 1 This document illustrates the implementation flow of the baseline estimation method for spaceborne distributed interferometric synthetic aperture radar in this application. Figure 1 ,like Figure 1 As shown, the method includes:

[0056] Step 101: Determine the delay calibration parameters for the primary and secondary satellites;

[0057] In this application, the method can be applied to electronic devices with InSAR systems. InSAR systems suffer from system delay errors due to internal device performance and external environmental influences. These system delay errors include range delay error and azimuth delay error. Range delay error refers to the deviation between the distance sampling delay of the first pixel in the range direction and the distance sampling delay corresponding to the actual nearest slant range; this directly reflects the slant range error. Azimuth delay error refers to the deviation between the sampling time of the first row in the image azimuth direction and the actual azimuth sampling time; this directly reflects the SAR trajectory coordinate error. The existence of system delay errors directly causes severe errors in slant range. However, current baseline estimation methods all rely on slant range, and slant range errors cause additional positioning errors, leading to reduced baseline estimation accuracy. Therefore, this electronic device can read first and second data from different devices on the primary and secondary satellites. The first data comes from the POS recording device, and the second data comes from the image acquisition device. Based on the first data, the electronic device can obtain the state vector parameters of the primary and secondary satellites; based on the second data, it can obtain the azimuth and range time parameters of the primary and secondary satellites. This electronic device can determine the azimuth time parameters and range time parameters of the primary and secondary satellites as the delay calibration parameters of the primary and secondary satellites.

[0058] Step 102: If the delay calibration parameters meet the calibration conditions, based on the delay calibration parameters and the fitted trajectory parameters of the primary and secondary satellites, determine the trajectory positions of the primary and secondary satellites corresponding to the imaging time of the primary and secondary satellites at the ground control points;

[0059] In this application, the state vector parameters include, but are not limited to, the three-dimensional position coordinates, velocity parameters, and corresponding time parameters of the primary and secondary satellites. Based on these state vector parameters, the trajectory parameters of the primary and secondary satellites can be fitted to obtain the fitted trajectory parameters of the primary and secondary satellites.

[0060] In this application, when fitting the trajectory parameters of the primary and secondary satellites, the electronic device can specifically establish a trajectory model and fit the satellite trajectory using polynomial equations. Specifically, the satellite position vector at time t... It can be represented as:

[0061]

[0062] In this formula, N k Let be the degree of the highest term of the polynomial; k is the degree of each term of the polynomial; a k ,b k and c k is the polynomial parameter; t is the time corresponding to the state vector. The satellite's velocity vector can be obtained by taking the derivative of the position vector polynomial with respect to time, thus ensuring the consistency between the position and velocity vectors.

[0063] Among them, velocity vector The polynomial form is as follows:

[0064]

[0065] In this formula, to balance the requirements of algorithm efficiency and accuracy, let N... k =3, input the v state vector parameters recorded in the onboard POS in the first data, i.e., the orbital position X POS =(X POS1 ,X POS2 ,...,X POSv ), Y POS =(Y POS1 ,Y POS2 ,...,Y POSv ) and Z POS =(Z POS1 Z POS2 ,...,Z POSv ) and its corresponding time t = (t POS1 ,t POS2 ,...,t POSvThe fitting polynomial parameters are a = (a3 a2 a1 a0), b = (b3 b2 b1 b0) and c = (c3 c2 c1 c0):

[0066]

[0067]

[0068]

[0069] in,

[0070] In this application, if both the azimuth time parameter and the range time parameter in the delay calibration parameter meet the calibration conditions, then based on the delay calibration parameter and the fitted trajectory parameters of the primary and secondary satellites, the position of the ground control point corresponding to the imaging time of the primary and secondary satellites is determined.

[0071] In one implementation, the electronic device can determine the slant range parameters of the primary and secondary satellites corresponding to the ground control point based on the azimuth and range time parameters in the delay calibration parameters; calculate the slant range difference between the primary and secondary satellite slant range parameters and the slant range reference parameters; calculate the delay error update using the slant range difference, and compare the delay error update with a threshold; if the comparison result indicates that the delay error update is less than the threshold, it is determined that the delay calibration parameter meets the calibration conditions. If the comparison result indicates that the delay error update is greater than or equal to the threshold, it is determined that the delay calibration parameter does not meet the calibration conditions. If the delay calibration parameter does not meet the calibration conditions, the electronic device can also use the least squares method to correct the azimuth and range time parameters until the delay error update difference is less than the threshold.

[0072] In this application, when the electronic device determines the position of the main satellite trajectory corresponding to the imaging time of the main satellite based on the delay calibration parameters and the fitted trajectory parameters of the main and auxiliary satellites, it can first determine the azimuth sampling time corresponding to the ground control point based on the azimuth time parameter and range time parameter of the main satellite in the delay calibration parameters; then, based on the correspondence between the time parameter and the position parameter in the fitted trajectory parameters, it determines the target trajectory position corresponding to the azimuth sampling time; based on the target position parameter, the position of the main satellite trajectory corresponding to the imaging time of the main satellite can be determined.

[0073] In one implementation, the electronic device can first establish a primary star delay calibration model based on the primary star delay calibration parameters (primary star azimuth time parameters and range time parameters). Specifically:

[0074] From the position of the main star towards the starting time tmas0 and distance to start time τ mas0 As a calibration parameter, establish the calibration parameter vector γ mas =[t mas0 ,τ mas0 ] T Then, based on the pixel coordinates of the ground control points (e.g., 8 ground control points) on the primary satellite image, the azimuth sampling time t corresponding to each control point is calculated. mas :

[0075] t mas =t mas0 +m mas t step

[0076] Where, m mas Let t be the azimuth coordinates of the control point on the primary star image. step The azimuth sampling time interval corresponds to the control point on the primary star image. Then, based on the established trajectory model, the primary star trajectory position corresponding to the ground control point is calculated. and velocity vector

[0077] Among them, a Mk b Mk and c Mk These are the polynomial parameters of the primary star's trajectory calculated based on the above trajectory model.

[0078] This electronic device can also calculate the slant distance R corresponding to the control point:

[0079]

[0080] Where c is the speed of light and c = 299,792,458 m / s, n mas Let x be the distance coordinate corresponding to the control point. step The distance sampling interval.

[0081] Then, a time-delay calibration model for the primary star is established based on the primary star's RD equation:

[0082]

[0083] Where λ is the wavelength of the electromagnetic wave, f dM The Doppler center frequency of the ground control point on the main star image.

[0084] In this application, if the azimuth time parameters and range time parameters of the primary star do not meet the calibration conditions according to the RD equation, the least squares method is used to solve the primary star delay calibration model to obtain the final azimuth time parameters and range time parameters of the primary star.

[0085] For example, the least squares method can be used to solve for the starting time t of the primary star's azimuth. mas0 and distance to start time τ mas0 .

[0086] Specifically, the calculation formula for step q+1 in the iteration is:

[0087]

[0088] in, This represents the rate of change of slant range error with respect to the initial time of the primary star's azimuth. This represents the rate of change of slant range error with respect to the distance from the primary star towards the start time. This represents the rate of change of the Doppler frequency error with respect to the starting time of the primary star's azimuth. This represents the rate of change of the Doppler frequency error with respect to the distance from the primary star towards the start time:

[0089]

[0090]

[0091] in, This represents the rate of change of the velocity vector in the azimuth direction at the start time, and:

[0092]

[0093]

[0094]

[0095] In this application, the electronic device can also acquire the time corresponding to the first row in the second data of the main satellite imaging. This serves as the initial value for the azimuth start time. The range start time is provided in the second data from the main satellite imaging. As the initial value of the distance direction starting time, Then the least squares method is used to apply γ mas =[t mas0 ,τ mas0 ] T Iterative calculations are performed to obtain the final azimuth time parameters and range time parameters.

[0096] Here, the termination condition for the iteration is |γ|. mas(q+1) -γ mas(q) |<10 -9 .

[0097] In this application, the electronic device can obtain the range start time and azimuth start time using second data from primary and secondary satellite imaging, and calculate the slant range error based on the range start time and azimuth start time. like Figure 2 As shown, the range-direction start time γ of the system is obtained after time delay error correction. mas =[t mas0 ,τ mas0 ] T System slant range residual error like Figure 3 As shown.

[0098] like Figure 2 As shown, the slant distance error of the control points before the delay error correction is distributed between 38.9 and 39.5 m.

[0099] like Figure 3 As shown, after the delay error correction, the slant distance error of the control points is distributed between -0.3 and +0.3 m.

[0100] In this application, when the electronic device determines the position of the auxiliary satellite trajectory corresponding to the imaging time of the auxiliary satellite based on the delay calibration parameters and the fitted trajectory parameters of the primary and auxiliary satellites, it can determine the reception time and transmission time of the auxiliary satellite receiving the echo from the ground control point based on the azimuth time parameter and range time parameter of the auxiliary satellite in the delay calibration parameters; then, based on the correspondence between the time parameter and the position parameter in the fitted trajectory parameters, it determines the target trajectory position corresponding to the reception time and the transmission time; and based on the target position parameter, it determines the position of the auxiliary satellite trajectory corresponding to the imaging time of the auxiliary satellite.

[0101] Here, because spaceborne distributed InSAR typically employs a dual-satellite fly-around, dual-receiver operating mode—one satellite transmitting electromagnetic waves (primary satellite) and two satellites receiving them—the RD (Range-Doppler) equations for SAR satellites that only receive electromagnetic waves (secondary satellites) differ from those of ordinary single-satellite SAR. Existing SAR delay correction models cannot be applied to delay correction for secondary satellites. Therefore, it is necessary to modify the RD equations based on the operating principle of secondary satellites and establish a delay correction model suitable for them.

[0102] In one implementation, the electronic device can first determine the auxiliary satellite delay calibration parameters as the auxiliary satellite azimuth time parameter and range time parameter, and then establish an auxiliary satellite delay calibration model based on the auxiliary satellite delay calibration parameters.

[0103] Specifically, the auxiliary satellite's azimuth can be used to indicate the starting time t. sla0 and distance to start time τ sla0 As a calibration parameter, establish the parameter vector γ sla =[t sla0 ,τ sla0 ] T .

[0104] Then, the reception time t3 and transmission time t2 of the auxiliary satellite receiving the echo from the ground control point are calculated as follows:

[0105] t3=t sla0 +m sla t step

[0106] t2 = t3 - 2n sla x step / c-τ sla0

[0107] Where, m sla Let t be the azimuth coordinates of the ground control point on the auxiliary satellite image. step n is the azimuth sampling time interval corresponding to the ground control points on the auxiliary satellite image. sla x represents the range coordinates of the ground control points on the secondary satellite image. step This represents the range sampling interval corresponding to the ground control points on the auxiliary satellite image.

[0108] In this application, the electronic device can also calculate the trajectory position corresponding to the auxiliary satellite receiving the echo of the target control point based on the trajectory model established in the fitted trajectory parameters. and velocity vector and the trajectory position of the main satellite when it emits electromagnetic waves. and velocity vector

[0109] Among them, a Sk b Sk and c Sk These are the polynomial parameters of the auxiliary satellite trajectory calculated based on the trajectory model established when fitting the trajectory parameters.

[0110] In this application, the electronic device can also calculate the transmission slant range R2 and the reception slant range R3 corresponding to the ground control point:

[0111] R2=(X M (t2)-X GCP ) 2 +(Y M (t2)-Y GCP ) 2 +(Z M (t2)-Z GCP ) 2

[0112] R3=(X S (t3)-X GCP ) 2 +(Y S (t3)-Y GCP )2 +(Z S (t3)-Z GCP ) 2

[0113] A primary satellite delay calibration model is established based on the auxiliary satellite's RD equations:

[0114]

[0115] Among them, f dS The Doppler center frequency of the ground control point on the auxiliary satellite image.

[0116] Then, the auxiliary star delay calibration model is solved. The Newton-Raphson iteration method is used to solve for the auxiliary star azimuth start time t. sla0 and distance to start time τ sla0 .

[0117] Specifically, the calculation formula for step q+1 in the iteration is:

[0118]

[0119] in, This represents the rate of change of slant range error with the initial time of the auxiliary star's azimuth. This represents the rate of change of the launch slant range error with respect to the distance from the auxiliary satellite towards the start time. This represents the rate of change of the Doppler frequency error with respect to the initial time of the auxiliary star's azimuth. This represents the rate of change of the Doppler frequency error with respect to the distance from the secondary star towards the start time:

[0120]

[0121]

[0122] in, This represents the rate of change of the primary star's velocity vector with respect to the azimuth at the start time. This represents the rate of change of the auxiliary star's velocity vector with respect to the azimuth starting time. This represents the rate of change of the primary star's velocity vector with respect to the distance in the initial time dimension, and:

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129] In this application, the electronic device uses the time corresponding to the first row of imaging provided in the second data of the secondary star imaging. As the initial value for the azimuth starting time, the range starting time provided in the second data of the auxiliary star imaging... As the initial value for the distance direction starting time, i.e. Then, when the range-initiated time and azimuth-initiated time do not meet the calibration conditions, the least squares method is used to calibrate γ. sla =[t sla0 ,τ sla0 ] T Iterative calculations are performed to correct the range-time and azimuth-time parameters of the auxiliary star. The termination condition for the iteration is |γ|. sla(q+1) -γ sla(q) |<10 -9 s. Slant range error calculated using the range start time and azimuth start time recorded in the second data of the secondary star imaging. like Figure 4 As shown, the range-direction start time γ of the system is obtained after time delay error correction. sla =[t sla0 ,τ sla0 ] T System slant range residual error like Figure 5 As shown.

[0130] Figure 4 In the meantime, the slant distance error of the control points before the delay error correction is distributed between 36.8 and 37.4 m;

[0131] Figure 5 In the meantime, the slope distance error of the control points after delay error correction is distributed between -0.3 and +0.3 m.

[0132] In this application, the electronic device can also acquire the geographic coordinate parameters of the ground control point; convert the geographic coordinate parameters into geographic coordinate parameters in the geocentric-geofixed coordinate system; when determining the slant range parameters of the primary and secondary satellites corresponding to the ground control point based on the azimuth time parameter and range time parameter in the delay calibration parameter, the slant range parameters of the primary and secondary satellites can be determined based on the azimuth time parameter, range time parameter and the geographic coordinate parameters in the geocentric-geofixed coordinate system in the delay calibration parameter.

[0133] Step 103: Determine the baseline vector parameters of the ground control point based on the positions of the primary and secondary satellite trajectories.

[0134] In this application, after obtaining the positions of the primary and secondary satellite trajectories, the electronic device can subtract the positions of the primary and secondary satellite trajectories to obtain the baseline vector parameters of the ground control point.

[0135] Then, the baseline vector parameters are rotated to the primary star APC (Antenna Phase Center) coordinate system.

[0136] In one implementation, the electronic device can utilize the corrected primary star azimuth to the starting time t mas0 Combined with the azimuth coordinates m of the control points on the primary star image mas and azimuth time sampling interval t step Obtain the sampling time of the primary star's true azimuth corresponding to the control point:

[0137] t AMmas =t mas0 +m mas t step ;

[0138] And using the corrected primary star azimuth to the starting time t sla0 Combined with the azimuth coordinates m of the control point on the auxiliary star image sla and azimuth time sampling interval t step Obtain the actual azimuth sampling time of the auxiliary star corresponding to the control point:

[0139] t AMsla =t sla0 +m sla t step ;

[0140] Then, t AMmas Substituting these values ​​into the primary star trajectory equation yields the primary star trajectory position corresponding to the primary star imaging time at the control point. t AMsla Substituting these values ​​into the auxiliary star trajectory equation yields the auxiliary star trajectory position corresponding to the auxiliary star imaging time at the control point.

[0141]

[0142] The baseline vector is obtained from the imaging time position of the primary star and the imaging time position of the secondary star.

[0143]

[0144] Project the baseline in the geocentric-fixed coordinate system onto the primary star APC coordinate system. The Y-axis of the primary star APC is the tangent to the primary star's track. The Z-axis is the line connecting the center O of the WGS84 (World Geodetic System 1984) ellipsoid to the primary star. The X-axis is a straight line orthogonal to the Y-axis and Z-axis, satisfying the right-hand screw relation.

[0145]

[0146] Therefore, the formula for rotating the baseline in the ECEF coordinate system to the primary star APC coordinate system is:

[0147]

[0148] If there are N control points on the ground, then the baseline vector corresponding to the i-th control point in the primary satellite APC coordinate system is:

[0149]

[0150] In this application, after determining the baseline vector parameters of the ground control points based on the trajectory positions of the primary and secondary satellites, since there are usually more than three ground control points, the electronic device can also determine the rate of change parameter of the baseline vector parameters over time; and fit the rate of change parameter based on the baseline vector parameters to obtain the baseline vector parameters of the whole scene image pixels of the primary and secondary satellites.

[0151] In one implementation, the electronic device can also utilize a linear baseline model to describe the baseline (B) of the entire scene image. X B Y B Z )for:

[0152] B X =B X0 +B X1 t

[0153] B Y =B Y0 +B Y1 t

[0154] B Z =B Z0 +B Z1 t

[0155] Among them, B X0 B X1 B Y0 B Y1 B Z0 and B Z1 Let Δ be the undetermined parameter of the linear model, and t be time. j = (B j0 Bj1 ) T The subscript j represents the coordinate axis X, Y, or Z. Substitute the azimuth sampling time t = (t_0, t_1, t_2, t_3) corresponding to the control point. AMmas1 ,t AMmas2 ,...,t AMmasN ) T and baseline coordinate parameter B j = (B j1 B j2 ,...,B jN ) T Calculate using the linear least squares method:

[0156] Δ j =(T T T) -1 T T B j

[0157] Where T = [t1], and 1 = (1,1,...,1) T Therefore, B can be calculated. X0 B X1 B Y0 B Y1 B Z0 and B Z1 The primary star's azimuth, modified in step 5, is adjusted to the initial time t. mas0 Combined with azimuth time sampling interval t step Calculate the azimuth sampling time for each pixel in the entire image:

[0158] t AM =t step +mt mas0

[0159] Where m represents the azimuth sampling coordinates of the pixel. Then, by substituting the azimuth sampling time corresponding to each pixel in the entire image into the baseline linear model, the baseline component B of each pixel can be obtained. Xam B Yam and B Zam :

[0160] B Xam =B X0 +B X1 t am

[0161] B Yam =B Y0 +B Y1 t am

[0162] B Zam =B Z0 +B Z1 tam

[0163] The final baseline is as follows Figure 6 As shown.

[0164] Figure 6 In this process, the X-axis baseline component of the azimuth acquisition time corresponding to the ground control point can be fitted, the Y-axis baseline component of the azimuth acquisition time corresponding to the ground control point can be fitted, the Z-axis baseline component of the azimuth acquisition time corresponding to the ground control point can be fitted, and the total length of the baseline vector of the azimuth sampling time corresponding to the ground control point can be fitted.

[0165] The baseline estimation method for spaceborne distributed interferometric synthetic aperture radar provided in this application has the following advantages compared with existing experimental methods:

[0166] (1) The spaceborne distributed InSAR primary and secondary satellite calculation system delay error in this application can complete the range-direction start time and azimuth-direction start time correction, thereby realizing the trajectory position and slant range correction of the InSAR primary and secondary satellites, which can improve the geometric positioning accuracy of the system and solve the coupling problem between the baseline and the system delay error.

[0167] (2) The method provided in this application improves the baseline estimation accuracy by correcting the system delay error. Ground control points are set up in the calibration field, the corresponding pixels of the SAR image have strong echoes, high signal-to-noise ratio, large coherence coefficient, and accurate reference information, without introducing additional estimation errors.

[0168] (3) Based on the working principle of the auxiliary star, the RD equation is modified to establish a delay correction model suitable for the auxiliary star. It can be applied to the delay correction of the auxiliary star.

[0169] Figure 7 This document illustrates the implementation flow of the baseline estimation method for spaceborne distributed interferometric synthetic aperture radar in this application. Figure 2 ,like Figure 7 As shown, the method includes:

[0170] Step 701: Obtain the time parameters, status parameters, and geographic coordinate parameters of the ground control points for the primary and secondary satellites;

[0171] Here, the time parameters of the primary and secondary satellites are obtained based on the first data from the primary and secondary satellites; the status parameters of the primary and secondary satellites are obtained based on the second data from the primary and secondary satellites; the first and second data come from different devices. For example, the first data comes from a POS recording device, and the second data comes from an image acquisition device.

[0172] The geographic coordinate parameters of the ground control points include, but are not limited to, the longitude, latitude, and altitude information of the ground control points; the status parameters include, but are not limited to, the three-dimensional position, velocity, and time information of the primary and secondary satellites. The time parameters include the azimuth start time, range start time, azimuth sampling time interval, and range sampling time interval of the primary and secondary satellites.

[0173] Step 702: Calculate the geocentric and geofixed coordinates of the ground control points based on their geographic coordinate parameters;

[0174] Assuming there are N control points on the ground, calculate their geocentric coordinates using their longitude (LON), latitude (LAT), and altitude (H).

[0175]

[0176] Where i represents the control point number; d is the radius of curvature; a is the semi-major axis defined by the WGS84 (World Geodetic System 1984) ellipsoid, which is equal to 6378137m; and e is the first eccentricity, which is equal to 0.081819790992.

[0177] Step 703, primary star trajectory fitting;

[0178] Here, we first establish a trajectory model. We then use polynomial equations to fit the trajectory of the primary star.

[0179] Step 704: Determine the primary star delay calibration parameters and establish the primary star delay calibration model;

[0180] Here, the orientation of the primary star is used to guide the starting time t. mas0 and distance to start time τ mas0 As calibration parameters, establish the calibration parameter vector Υ mas =[t mas0 ,τ mas0 ] T .

[0181] Calculate the azimuth sampling time t corresponding to the control point based on the pixel coordinates of the control point on the primary star image. mas :

[0182] t mas =t mas0 +m mas t step

[0183] Where, m mas Let t be the azimuth coordinates of the control point on the primary star image. stepThis represents the azimuth sampling time interval for the control points on the primary star image. The primary star trajectory position corresponding to the control points is calculated based on the trajectory model established in step 3. and velocity vector

[0184]

[0185] Among them, a Mk b Mk and c Mk These are the polynomial parameters of the primary star's trajectory calculated based on step 3.

[0186] Calculate the slope distance R corresponding to the control point:

[0187]

[0188] Where c is the speed of light and c = 299,792,458 m / s, n mas Let x be the distance coordinate corresponding to the control point. step The distance sampling interval.

[0189] A primary star delay calibration model is established based on the primary star's RD equation:

[0190]

[0191] Where λ is the wavelength of the electromagnetic wave, f dM The Doppler center frequency of the ground control point on the main star image.

[0192] Step 705: Solve the primary star delay calibration model.

[0193] Here, Newton's iterative method is used to solve for the initial time t of the primary star's azimuth orientation. mas0 and distance to start time τ mas0 .

[0194] Step 706: Determine the trajectory coordinates of the primary satellite at the time of imaging corresponding to the ground control point;

[0195] Step 707, auxiliary star trajectory fitting;

[0196] Here, we first establish a trajectory model. We then use polynomial equations to fit the trajectory of the secondary star.

[0197] Step 708: Determine the auxiliary satellite delay calibration parameters and establish the auxiliary satellite delay calibration model;

[0198] Here, the position of the auxiliary star is used to guide the starting time t. sla0 and distance to start time τ sla0 As calibration parameters, establish the parameter vector Υ sla =[t sla0 ,τ sla0] T .

[0199] The reception time t3 and transmission time t2 of the echo from the auxiliary satellite receiving control point are calculated as follows:

[0200] t3=t sla0 +m sla t step

[0201] t2 = t3 - 2n sla x step / c-τ sla0

[0202] Where, m sla Let t be the azimuth coordinates of the control point on the auxiliary star image. step n is the azimuth sampling time interval. sla Let x be the range coordinates of the control point on the secondary star image. step The distance sampling interval.

[0203] Calculate the trajectory position corresponding to the echo received by the auxiliary satellite control point based on the trajectory model established in step 703. and velocity vector and the trajectory position of the electromagnetic waves emitted by the primary star and velocity vector

[0204]

[0205] Among them, a Sk b Sk and c Sk These are the polynomial parameters of the auxiliary star trajectory calculated based on step 3.

[0206] Calculate the transmit slant range R2 and receive slant range R3 corresponding to the control point:

[0207] R2=(X M (t2)-X GCP ) 2 +(Y M (t2)-Y GCP ) 2 +(Z M (t2)-Z GCP ) 2

[0208] R3=(X S (t3)-X GCP ) 2 +(Y S (t3)-Y GCP ) 2 +(Z S (t3)-ZGCP ) 2

[0209] A primary star delay calibration model is established based on the auxiliary star's RD equation:

[0210]

[0211] Among them, f dS The Doppler center frequency of the ground control point on the auxiliary satellite image.

[0212] Step 709: Solve the auxiliary star delay calibration model.

[0213] Here, Newton's iterative method is used to solve for the initial time t of the auxiliary star's azimuth orientation. sla0 and distance to start time τ sla0 .

[0214] Step 710: Determine the coordinates of the auxiliary satellite imaging time trajectory corresponding to the ground control point;

[0215] Step 711: Calculate the baseline vector corresponding to the ground control point.

[0216] Here, the baseline vector corresponding to the ground control point is determined based on the trajectory coordinates of the primary star at the time of imaging and the trajectory coordinates of the secondary star at the time of imaging.

[0217] Specifically, the primary star's azimuth, corrected in step 705, is used at the starting time t. mas0 Combined with the azimuth coordinates m of the control points on the primary star image mas and azimuth time sampling interval t step Obtain the sampling time of the primary star's true azimuth corresponding to the control point:

[0218] t AMmas =t mas0 +m mas t step

[0219] Using the primary star's azimuth starting time t after correction in step 709 sla0 Combined with the azimuth coordinates m of the control point on the auxiliary star image sla and azimuth time sampling interval t step Obtain the actual azimuth sampling time of the auxiliary star corresponding to the control point:

[0220] t AMsla =t sla0 +m sla t step

[0221] t AMmas Substituting these values ​​into the primary star trajectory equation yields the primary star trajectory position corresponding to the primary star imaging time at the control point. tAMsla Substituting these values ​​into the auxiliary star trajectory equation yields the auxiliary star trajectory position corresponding to the auxiliary star imaging time at the control point.

[0222]

[0223]

[0224] The baseline vector is obtained from the imaging time position of the primary star and the imaging time position of the secondary star.

[0225]

[0226] Project the baseline in the geocentric-fixed coordinate system onto the primary star APC coordinate system. The Y-axis of the primary star APC is the tangent to the primary star's track, the Z-axis is the line connecting the center O of the WGS84 (World Geodetic System 1984) ellipsoid to the primary star, and the X-axis is a straight line orthogonal to the Y-axis and Z-axis.

[0227]

[0228] Therefore, the formula for rotating the baseline in the ECEF coordinate system to the primary star APC coordinate system is:

[0229]

[0230] If there are N control points on the ground, then the baseline vector corresponding to the i-th control point in the primary satellite APC coordinate system is:

[0231]

[0232] Step 712: Obtain the baseline vector of the entire scene image based on the baseline vector of the ground control points.

[0233] The baseline (B) of the entire scene image is described using a linear baseline model. X B Y B Z )for:

[0234] B X =B X0 +B X1 t

[0235] B Y =B Y0 +B Y1 t

[0236] B Z =B Z0 +B Z1 t

[0237] Among them, B X0B X1 B Y0 B Y1 B Z0 and B Z1 Let Δ be the undetermined parameter of the linear model, and t be time. j = (B j0 B j1 ) T The subscript j represents the coordinate axis X, Y, or Z. Substitute the azimuth sampling time t = (t_0, t_1, t_2, t_3) corresponding to the control point. AMmas1 ,t AMmas2 ,...,t AMmasN ) T and baseline coordinate parameter B j = (B j1 B j2 ,...,B jN ) T Calculate using the linear least squares method:

[0238] Δ j =(T T T) -1 T T B j

[0239] Where T = [t1], and 1 = (1,1,...,1) T Therefore, B can be calculated. X0 B X1 B Y0 B Y1 B Z0 and B Z1 The primary star's azimuth, modified in step 5, is adjusted to the initial time t. mas0 Combined with azimuth time sampling interval t step Calculate the azimuth sampling time for each pixel in the entire image:

[0240] t AM =t step +mt mas0

[0241] Where m represents the azimuth sampling coordinates of the pixel. Then, by substituting the azimuth sampling time corresponding to each pixel in the entire image into the baseline linear model, the baseline component B of each pixel can be obtained. Xam B Yam and B Zam :

[0242] B Xam =B X0 +B X1 t am

[0243] BYam =B Y0 +B Y1 t am

[0244] B Zam =B Z0 +B Z1 t am

[0245] The final baseline is as follows Figure 6 As shown.

[0246] It should be noted that the method provided in the above embodiments is similar to... Figure 1 The provided method embodiments belong to the same concept, and their specific implementation process is detailed in [link to implementation details]. Figure 1 The method implementation examples will not be described in detail here.

[0247] Figure 8 This is a schematic diagram of the baseline estimation device structure for the spaceborne distributed interferometric synthetic aperture radar in this application, as shown below. Figure 8 As shown, the device includes:

[0248] The determining unit 801 is used to determine the delay calibration parameters of the primary and secondary satellites; and to determine the trajectory positions of the primary and secondary satellites corresponding to the imaging time of the primary and secondary satellites based on the delay calibration parameters and the fitted trajectory parameters of the primary and secondary satellites if the delay calibration parameters meet the calibration conditions; and to determine the baseline vector parameters of the ground control point based on the trajectory positions of the primary and secondary satellites.

[0249] The judgment unit 802 is used to determine whether the delay calibration parameters meet the calibration conditions.

[0250] In a preferred embodiment, the device further includes a calculation unit 803 and a comparison unit 804;

[0251] The determining unit 801 is further configured to determine the slant range parameters of the primary and secondary satellites corresponding to the ground control point based on the azimuth time parameter and range time parameter in the delay calibration parameters.

[0252] The calculation unit 803 is used to calculate the slant range difference between the slant range parameters of the primary and secondary satellites and the slant range reference parameters; and to use the slant range difference to calculate the delay error update amount;

[0253] Comparison unit 804 is used to compare the delay error update amount with a threshold.

[0254] The determining unit 801 is further configured to determine that the delay calibration parameter satisfies the calibration condition if the comparison result indicates that the delay error update amount is less than the threshold.

[0255] In a preferred embodiment, the device further includes: a correction unit 805;

[0256] The calculation unit 803 is also used to iteratively calculate the azimuth time parameter and the range time parameter using the least squares method if the comparison result indicates that the delay error update amount is greater than or equal to the threshold.

[0257] The correction unit 805 corrects the azimuth time parameter and the range time parameter according to the iterative calculation results until the delay error update amount is less than the threshold.

[0258] In a preferred embodiment, the determining unit 801 is further configured to determine the azimuth sampling time corresponding to the ground control point based on the azimuth time parameter and range time parameter of the main satellite in the delay calibration parameters; and to determine the target trajectory position corresponding to the azimuth sampling time based on the correspondence between the time parameter and the position parameter in the fitted trajectory parameters; and to determine the main satellite trajectory position corresponding to the main satellite imaging time of the ground control point based on the target position parameter.

[0259] In a preferred embodiment, the determining unit 801 is further configured to determine the reception time and transmission time of the auxiliary satellite receiving the echo from the ground control point based on the azimuth time parameter and range time parameter of the auxiliary satellite in the delay calibration parameters; and to determine the target trajectory position corresponding to the reception time and the transmission time based on the correspondence between the time parameter and the position parameter in the fitted trajectory parameters; and to determine the auxiliary satellite trajectory position corresponding to the imaging time of the auxiliary satellite at the ground control point based on the target position parameter.

[0260] In a preferred embodiment, the device further includes: a fitting unit 806;

[0261] The determining unit 801 is further configured to determine the state vector parameters of the primary and secondary satellites based on the first data of the primary and secondary satellites.

[0262] The fitting unit 806 is used to fit the trajectory parameters of the primary and secondary satellites according to the state vector parameters to obtain the fitted trajectory parameters.

[0263] In a preferred embodiment, the determining unit 801 is further configured to obtain the azimuth time parameters and range time parameters of the primary and secondary satellites based on the second data of the primary and secondary satellites; and to determine the azimuth time parameters and range time parameters as the delay calibration parameters of the primary and secondary satellites.

[0264] In a preferred embodiment, the determining unit 801 is further configured to determine the rate of change parameter of the baseline vector parameter over time;

[0265] The fitting unit 806 is also used to fit the rate of change parameter based on the baseline vector parameter to obtain the baseline vector parameters of the whole scene image pixels of the main and auxiliary satellites.

[0266] In a preferred embodiment, the determining unit 801 is further configured to obtain the geographic coordinate parameters of the ground control point;

[0267] The calculation unit 803 is also used to convert the geographic coordinate parameters into coordinates in the geocentric coordinate system;

[0268] The determining unit 801 is also used to determine the slant range parameters of the primary and secondary satellites based on the azimuth time parameter, the range time parameter and the coordinates in the geocentric-geo-fixed coordinate system in the delay calibration parameters.

[0269] It should be noted that the baseline estimation device for spaceborne distributed interferometric synthetic aperture radar provided in the above embodiments is 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. In addition, the device provided in the above embodiments and the method embodiments provided above belong to the same concept, and the specific implementation process can be found in the method embodiments, which will not be repeated here.

[0270] 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.

[0271] When the processor runs the computer program, it executes any one of the method steps in the above processing method.

[0272] Figure 9 This is a schematic diagram of the structure of the electronic device in this application. The electronic device 900 can be a terminal such as a computer or an information transceiver. Figure 9 The illustrated electronic device 900 includes at least one processor 901, a memory 902, at least one network interface 904, and a user interface 903. The various components in the electronic device 900 are coupled together via a bus system 905. It is understood that the bus system 905 is used to implement communication between these components. In addition to a data bus, the bus system 905 also includes a power bus, a control bus, and a status signal bus. However, for clarity, ... Figure 9 The general labeled all buses as Bus System 905.

[0273] The user interface 903 may include a monitor, keyboard, mouse, trackball, click wheel, buttons, touchpad, or touch screen.

[0274] It is understood that memory 902 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 902 described in the embodiments of this application is intended to include, but is not limited to, these and any other suitable types of memory.

[0275] In this embodiment, the memory 902 is used to store various types of data to support the operation of the electronic device 900. Examples of such data include: any computer program used to operate on the electronic device 900, such as the operating system 9021 and application program 9022; contact data; phonebook data; messages; pictures; audio, etc. The operating system 9021 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 9022 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 9022.

[0276] The methods disclosed in the embodiments of this application can be applied to or implemented by the processor 901. The processor 901 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 the processor 901 or by instructions in the form of software. The processor 901 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. The processor 901 can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The 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 the memory 902. The processor 901 reads the information in the memory 902 and combines its hardware to complete the steps of the aforementioned method.

[0277] In an exemplary embodiment, the electronic device 900 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.

[0278] In an exemplary embodiment, this application also provides a computer-readable storage medium, such as a memory 902 including a computer program, which can be executed by a processor 901 of an electronic device 900 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.

[0279] 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.

[0280] 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.

[0281] 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.

[0282] The methods disclosed in the several method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments.

[0283] The features disclosed in the several product embodiments provided in this application can be arbitrarily combined without conflict to obtain new product embodiments.

[0284] 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.

[0285] 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 estimation method for a spaceborne distributed interferometric synthetic aperture radar, characterized in that, The method includes: Determine the delay calibration parameters for the primary and secondary satellites; If the delay calibration parameters meet the calibration conditions, based on the delay calibration parameters and the fitted trajectory parameters of the primary and secondary satellites, the trajectory positions of the primary and secondary satellites corresponding to the imaging time of the primary and secondary satellites at the ground control points are determined. The baseline vector parameters of the ground control points are determined based on the positions of the primary and secondary satellite trajectories. The delay calibration parameters satisfy the calibration conditions, including: Based on the azimuth time parameter and range time parameter in the delay calibration parameters, determine the slant range parameters of the primary and secondary satellites corresponding to the ground control point; Calculate the slant range difference between the slant range parameters of the primary and secondary satellites and the slant range reference parameters; The delay error update amount is calculated using the slant distance difference; The delay error update amount is compared with the threshold. If the comparison result indicates that the delay error update amount is less than the threshold, it is determined that the delay calibration parameter meets the calibration condition. The step of determining the primary and secondary satellite trajectory positions of the ground control points corresponding to the imaging time of the primary and secondary satellites based on the delay calibration parameters and the fitted trajectory parameters of the primary and secondary satellites includes: Based on the azimuth time parameter and range time parameter of the main satellite in the delay calibration parameters, the azimuth sampling time corresponding to the ground control point is determined; based on the correspondence between the time parameter and the position parameter in the fitted trajectory parameters, the target trajectory position corresponding to the azimuth sampling time is determined; based on the target position parameter, the main satellite trajectory position corresponding to the main satellite imaging time of the ground control point is determined. Based on the azimuth and range time parameters of the auxiliary satellite in the delay calibration parameters, the reception time and transmission time of the auxiliary satellite receiving the echo from the ground control point are determined; based on the correspondence between the time parameters and position parameters in the fitted trajectory parameters, the target trajectory position corresponding to the reception time and the transmission time is determined; based on the target position parameters, the auxiliary satellite trajectory position corresponding to the imaging time of the auxiliary satellite and the ground control point is determined.

2. The method according to claim 1, characterized in that, The method further includes: If the comparison result indicates that the delay error update amount is greater than or equal to the threshold, the azimuth time parameter and range time parameter are corrected using the least squares method until the delay error update amount is less than the threshold.

3. The method according to claim 1, characterized in that, Before determining the primary and secondary satellite trajectory positions of the ground control points corresponding to the imaging time of the primary and secondary satellites based on the delay calibration parameters and the fitted trajectory parameters of the primary and secondary satellites, the method further includes: Based on the first data from the primary and secondary satellites, determine the state vector parameters of the primary and secondary satellites; The trajectory parameters of the primary and secondary satellites are fitted based on the state vector parameters to obtain the fitted trajectory parameters.

4. The method according to claim 1, characterized in that, The determination of the delay calibration parameters for the primary and secondary satellites includes: Based on the second data from the primary and secondary satellites, the azimuth time parameters and range time parameters of the primary and secondary satellites are obtained. The azimuth time parameter and range time parameter are determined as the delay calibration parameters for the primary and secondary satellites.

5. The method according to claim 1, characterized in that, The method further includes: Determine the rate of change of the baseline vector parameters over time; The baseline vector parameters are fitted to the rate of change parameters to obtain the baseline vector parameters of the pixel points of the whole scene image of the main and auxiliary satellites.

6. The method according to claim 1, characterized in that, The method further includes: Obtain the geographic coordinate parameters of the ground control points; Convert the geographic coordinate parameters into coordinates in the geocentric and geofixed coordinate system; The determination of the slant range parameters of the primary and secondary satellites corresponding to the ground control point based on the azimuth time parameter and range time parameter in the delay calibration parameters includes: The slant range parameters of the primary and secondary satellites are determined based on the azimuth time parameter, the range time parameter, and the coordinates in the geocentric-geofixed coordinate system in the delay calibration parameters.

7. A baseline estimation device for a spaceborne distributed interferometric synthetic aperture radar, characterized in that, The device includes: The unit is configured to determine the delay calibration parameters of the primary and secondary satellites; and to determine the trajectory positions of the ground control points corresponding to the imaging time of the primary and secondary satellites based on the delay calibration parameters and the fitted trajectory parameters of the primary and secondary satellites, if the delay calibration parameters meet the calibration conditions; and to determine the baseline vector parameters of the ground control points based on the trajectory positions of the primary and secondary satellites. The judgment unit is used to determine whether the delay calibration parameters meet the calibration conditions; The determining unit is further configured to determine the slant range parameters of the primary and secondary satellites corresponding to the ground control point based on the azimuth time parameter and range time parameter in the delay calibration parameters; The calculation unit is used to calculate the slant range difference between the slant range parameters of the primary and secondary satellites and the slant range reference parameters; and to use the slant range difference to calculate the delay error update amount; The comparison unit is used to compare the delay error update amount with a threshold. The determining unit is further configured to: determine that the delay calibration parameters meet the calibration conditions if the comparison result indicates that the delay error update amount is less than the threshold; determine the azimuth sampling time corresponding to the ground control point based on the azimuth time parameter and range time parameter of the main satellite in the delay calibration parameters; determine the target trajectory position corresponding to the azimuth sampling time based on the correspondence between the time parameter and the position parameter in the fitted trajectory parameters; determine the main satellite trajectory position corresponding to the main satellite imaging time based on the target position parameter; determine the reception time and transmission time of the auxiliary satellite receiving the echo from the ground control point based on the azimuth time parameter and range time parameter of the auxiliary satellite in the delay calibration parameters; determine the target trajectory position corresponding to the reception time and the transmission time based on the correspondence between the time parameter and the position parameter in the fitted trajectory parameters; and determine the auxiliary satellite trajectory position corresponding to the auxiliary satellite imaging time based on the target position parameter.

Images