Single-beam multi-aspect ATI-SAR vector flow measurement method and system

Abstract

The present application belongs to the technical field of ocean vector current remote sensing observation, and particularly relates to a single-beam multi-look ATI-SAR vector current measurement method and system, which comprises: dividing the global ocean into multiple sea area grids according to longitude and latitude, and initializing an observation configuration library; in the calibration stage, calibrating the optimal for multiple groups of candidate azimuth look angle combinations preset for each sea area grid; in the observation stage, adaptively reading the corresponding optimal azimuth look angle combination for observation, and obtaining multi-look observation data; after correcting the multi-look observation data, constructing a multi-look over-determined observation equation set, estimating the sea surface vector current and residual deviation parameters, and obtaining the joint corrected sea surface vector current field. The present application realizes the adaptive multi-look observation geometry and vector current inversion according to the sea area under the single-beam ATI-SAR system, and can significantly improve the precision and consistency of the sea surface vector current measurement in different sea areas, thereby providing an engineering-realizable technical scheme for the high-precision and global remote sensing measurement of the ocean vector current.

Description

Technical Field

[0001] This invention belongs to the field of ocean vector current remote sensing observation technology, specifically relating to a single-beam multi-look ATI-SAR vector current measurement method and system. Background Technology

[0002] Currently, ocean surface vector current fields have significant application value in numerical model constraints, mass transport assessment, and the study of small- and medium-scale processes. Traditional ocean current measurements mainly rely on buoys, ADCP aerial surveys, and other methods, which have limited spatial coverage and temporal continuity. With the development of spaceborne synthetic aperture radar (SAR) technology, using along-track interferometric SAR (ATI-SAR) to obtain the radial velocity along the line of sight of the sea surface and further inverting the sea surface vector current has gradually become a research hotspot.

[0003] Current ATI-SAR current measurements mostly employ a single-beam system, utilizing the time interval between two receiving channels to acquire the radial velocity along the line of sight. This method can only directly provide the radial velocity component, requiring the use of external model fields, empirical models, or multi-track stitching to infer the complete vector flow field. Under multi-scale unsteady flow field conditions, it often faces problems such as strong ill-posedness and heavy reliance on prior knowledge. To address these issues, some studies have proposed using a dual-beam ATI method to acquire radial velocities in two independent line-of-sight directions, and then obtaining the sea surface vector current through geometric inversion.

[0004] However, dual-beam ATI vector current measurement is not only highly complex in engineering implementation, but more importantly, the observation errors of the two beams often lack consistency. Since the radial velocity observations of the two beams are relatively independent in terms of hardware links and signal processing, non-common-mode system biases are easily introduced. These biases are amplified during geometric inversion, leading to a significant directional offset in the inverted vector flow field. Furthermore, the two beam observations are often asynchronous in time or space, and the evolution of the actual flow field within the observation interval will further contribute to equivalent errors. Accurate calibration between channels is also difficult; subtle mismatches in baseline length, phase center position, and platform attitude residuals can all reduce inversion accuracy, thus weakening the overall stability and reliability of the dual-beam scheme. Publicly available information shows that no dual-beam spaceborne ATI ocean current measurement system has yet been observed operating in orbit for an extended period; this type of system remains primarily in the conceptual research and ground verification stages.

[0005] In summary, existing sea surface vector current remote sensing methods still have shortcomings in terms of observation system and error control. In particular, under the premise of ensuring engineering feasibility, how to effectively acquire vector current information and improve the accuracy and robustness of inversion results under the single-beam ATI-SAR system still needs further improvement. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of existing single-beam ATI-SAR methods, which can only obtain radial velocity along the line of sight and rely on external fields to infer vector flow, as well as the complex engineering implementation of dual-beam ATI systems, inconsistent observation errors between the two beams, and easy directional bias in the inversion results. Under the premise of ensuring engineering feasibility, this invention provides a single-beam multi-view ATI-SAR vector flow measurement method and system to achieve high-precision and robust measurement of sea surface vector flow in different sea areas.

[0007] The technical solution adopted by the present invention to achieve the above objectives is: a single-beam multi-look ATI-SAR vector flow measurement method, comprising the following steps:

[0008] S1: Divide the global ocean into multiple sea area grids according to latitude and longitude, and initialize the observation configuration library;

[0009] S2: Generate multiple sets of candidate azimuth angle combinations for each sea area grid, with each set containing at least two different azimuth angles;

[0010] S3: In the early stage of satellite in orbit or in the predetermined calibration stage, the single-beam ATI-SAR is controlled to conduct multi-slant view observations of the target sea area according to the candidate azimuth angle combination in sequence. Based on the preset performance evaluation index, the optimal azimuth angle combination and corresponding observation parameters of each sea area are selected and written into the observation configuration library.

[0011] S4: During the observation phase, the grid of the sea area to be measured is determined according to the latitude and longitude of the target, and the corresponding optimal azimuth angle combination and observation parameters are adaptively read from the observation configuration library;

[0012] S5: Control the single-beam ATI-SAR to observe the same sea area with at least two different azimuth angles within the same orbital repetition period according to the optimal azimuth angle combination and acquire multi-angle observation data.

[0013] S6: Perform along-track interferometry processing and wind and wave correction on multi-slant-view observation data, and use a joint inversion algorithm to obtain sea surface vector current and residual deviation parameters.

[0014] Preferably, in step S1, the sea area grid is a regular latitude and longitude grid divided based on flow field characteristics or an irregular grid form related to the sea area boundary. The observation configuration library stores the optimal azimuth angle combination and corresponding observation parameters of each sea area grid using grid number or grid center latitude and longitude as index.

[0015] Preferably, in step S3, the single-beam ATI-SAR payload includes two receiving antennas deployed along the track and a digital beamforming unit. The payload operates in single-beam imaging mode, transmitting and receiving only one radar beam at any given time for the same sea area. By adjusting the direction of the digital beamforming unit within the same track, the receiving beam is sequentially pointed to the same sea area in multiple azimuth angle directions to obtain multi-oblique-view observation data from at least two different azimuth angles.

[0016] Preferably, in step S3, the performance evaluation index is:

[0017] ;

[0018] In the formula, The performance evaluation index for candidate oblique angles. These are non-negative weighting coefficients; The condition number of the candidate observation matrix G, which is constructed from multiple oblique view observations corresponding to the candidate azimuth oblique view combination, is achieved through singular value decomposition. The variance of the velocity difference between the observation inversion results of the candidate azimuth oblique angle combination and the externally calibrated vector flow field in the target sea area;

[0019] By minimizing the performance evaluation metric Select the optimal combination of azimuth and oblique angles for each sea area; in the multi-oblique angle observations corresponding to each candidate azimuth and oblique angle combination, the time interval between different oblique angle observations shall not exceed the preset ocean current field time scale.

[0020] Preferably, in step S6, the along-track interferometry process includes: dual-channel single-view complex image registration, interferometric phase calculation, phase unwrapping and phase deviation correction, and the corrected phase difference is used to calculate the radial velocity along the line of sight.

[0021] Preferably, in step S6, the wind and wave correction specifically includes:

[0022] A parameterized wind-wave offset model based on the Doppler centroid shift or scattering mechanism is used to correct the radial velocity, where the wind-wave induced velocity offset varies with the incident angle, azimuth angle, wind speed, wind direction, and sea state. The observed radial flow velocity along the line of sight from each oblique angle is denoted as the uncorrected observation value. The observed value after wind and wave correction is Both conditions are met:

[0023] ;

[0024] In the formula, Angle of incidence For the first A directional oblique angle Wind speed at a height of h meters For wind direction, Sea state rating The wind- and wave-induced velocity bias is obtained from the parameterized model using the following formula:

[0025] ;

[0026] in, ~ These are the parameters of the wind and wave offset model. Their values ​​can be estimated by fitting the results of the comparison between multi-view observations and the external vector flow field during the calibration stage, and can be updated in the marine observation configuration library according to the marine grid.

[0027] Preferably, in step S6, the joint inversion algorithm specifically includes:

[0028] For the same sea surface resolution unit, at the first Observed radial velocity of line of sight after wind and wave correction at various oblique angles. satisfy:

[0029] ;

[0030] in, , Let the components of the sea surface vector current in two directions be determined in a predetermined horizontal coordinate system. Vector Streams , Components in the The projection coefficient of the line of sight upwards from each azimuth oblique angle. This is the residual deviation term, which includes wind and wave correction residuals and system residual deviations.

[0031] Different oblique angles The corresponding equations above, when combined, form the observation equation system. Let the observation vector be:

[0032] ;

[0033] Observation matrix of optimal oblique angle combination:

[0034] ;

[0035] Vector to be determined:

[0036] ;

[0037] Residual vector:

[0038] Then, the observation equation in matrix form is:

[0039] ;

[0040] The weighted least squares algorithm was used to solve the observation equations to obtain the solution values ​​for the sea surface vector current components:

[0041] ;

[0042] The residual bias terms of oblique observations in each direction are expressed as follows:

[0043] ;

[0044] in, To assign different confidence levels to strabismus observations from different orientations, a diagonal weight matrix is ​​used. The solution value is for the vector flow.

[0045] Preferably, the diagonal weight matrix weights The system adaptively updates based on the observed residuals to achieve adaptive identification and suppression of gross errors. The update relationship is as follows:

[0046] ;

[0047] in, Based on the basic noise level, For adjustment coefficients, Based on the residuals obtained from the current estimate, the weights are updated by iteratively solving the observation equations using weighted least squares. Simultaneously, robust joint inversion of sea surface vector current and residual bias term is completed. During the operational observation phase, long-term statistical analysis is performed on the residual bias term obtained in the joint inversion. Based on the statistical results, the wind and wave offset model parameters and inversion parameters of the corresponding sea area grid in the observation configuration library are updated.

[0048] A single-beam adaptive multi-look ATI-SAR vector flow measurement system includes:

[0049] M1: Single-beam ATI-SAR payload module. The payload operates in the ATI-SAR system and includes two receiving antennas deployed along the track and a digital beamforming unit. It is configured to perform single-beam imaging of the same sea area at any given time, and within the same orbital repetition period, by adjusting the direction of the digital beamforming unit, the receiving beam is sequentially pointed to the same sea area in multiple azimuth angle directions to obtain multi-angle observation data.

[0050] M2: Orbit and attitude acquisition module, used to acquire platform orbit and attitude parameters, and calculate the ground latitude and longitude and radar line of sight corresponding to each observation time;

[0051] M3: Marine observation configuration library module, used to store the optimal azimuth angle combination and corresponding observation parameters of each marine grid according to the marine grid, and supports query and update based on latitude and longitude;

[0052] M4: Sea area identification and observation plan generation module, used to determine the sea area grid to which the sea area belongs based on the latitude and longitude of the sea area to be measured, adaptively read the corresponding optimal azimuth angle combination and observation parameters from the sea area observation configuration library module, and generate a multi-angle observation plan by combining the orbit and attitude parameters, and send it to the single beam ATI-SAR payload module to control it to observe the same sea area sequentially according to the optimal azimuth angle combination within the same orbit repetition period;

[0053] M5: Vector flow joint inversion module, used to perform single-view along-track interferometry processing, wind and wave correction, construction and solution of multi-view observation equations on the multi-view observation data acquired by the single-beam ATI-SAR payload module, output the sea surface vector flow field after joint error correction, and write back the statistical results of residual deviation parameters to the sea area observation configuration library module.

[0054] Preferably, the observation configuration library uses grid number or grid center latitude and longitude as index, and reserves storage fields for each sea area grid to save the optimal azimuth angle combination and observation parameters corresponding to the sea area grid. In the initial state, each grid only creates an entry and does not fill in the specific angle configuration.

[0055] Compared with the prior art, the beneficial effects of this application are as follows:

[0056] 1. Maintaining a single-beam system with good engineering feasibility: Based on the traditional single-beam ATI-SAR payload, this invention uses digital beamforming to control the receiving beam to point sequentially to the same sea area in multiple azimuth angle directions, achieving multi-angle observation. It eliminates the need to construct two completely independent transmit-receive links and dual-beam imaging structures, significantly reducing system complexity and on-orbit risks. The engineering implementation difficulty and cost are significantly lower than those of the dual-beam ATI scheme.

[0057] 2. Adaptive optimization of multi-angle observation geometry by sea area: This invention divides the global ocean into sea area grids according to latitude and longitude. During the calibration phase, the optimal azimuth angle combination and observation parameters are calibrated and stored for each sea area grid. During the operation phase, it only needs to adaptively read the corresponding optimal azimuth angle combination from the sea area observation configuration library according to the target latitude and longitude and generate an observation plan. Thus, it can adaptively select the observation geometry according to the differences in current direction, main system and wind and wave conditions in different sea areas, avoiding the incompatibility caused by fixed azimuth configuration.

[0058] 3. Utilizing multi-view redundancy to achieve joint inversion and long-term optimization of vector current and error terms: This invention observes the same sea area from at least two different azimuth angles within the same orbital repetition period, constructs a multi-view overdetermined observation equation set, and uses weighted least squares or robust estimation algorithms for the wind and wave corrected multi-view radial velocity to achieve joint inversion of sea surface vector current and residual bias terms. It can also introduce constraints such as spatial smoothing and dynamic priors to effectively suppress wind and wave model errors and system residual errors. At the same time, based on the long-term statistical results of residual bias terms, the wind and wave bias model parameters and joint inversion parameters of each sea area grid are updated to continuously optimize the observation configuration and error model, thereby significantly improving the accuracy, robustness, and operational applicability of vector current measurement. Attached Figure Description

[0059] Figure 1 This is a flowchart of the method of the present invention.

[0060] Figure 2 This is a schematic diagram of the single-beam multi-slant-look observation geometry and the observation based on the marine observation configuration library of the present invention. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] Example 1: A single-beam, multi-look ATI-SAR vector flow measurement method:

[0063] In this embodiment, the platform can be a near-circular sun-synchronous orbit satellite, the payload operates in ATI-SAR mode, it uses two receiving antennas deployed along the orbit and is equipped with a digital beamforming unit, and achieves multi-slant-look observation by adjusting the azimuth direction of the receiving beam.

[0064] S1. Establishment of Marine Area Delineation and Observation Configuration Database:

[0065] This embodiment divides the global ocean into multiple marine grids based on latitude and longitude. For complex nearshore areas, irregular grids can be used based on coastlines and basin boundaries. Each marine grid is assigned a unique grid number, and the latitude and longitude of the grid center are recorded.

[0066] Based on this, a marine observation configuration database is established. This database uses grid number or grid center latitude and longitude as indexes, reserving storage fields for each marine grid to store the optimal azimuth and oblique angle combination and observation parameters corresponding to that grid. Initially, only entries are created for each grid, without specifying the oblique angle configuration.

[0067] S2. Generation of candidate azimuth oblique angle combinations:

[0068] In the early stages of satellite operation or during the pre-calibration phase, multiple sets of candidate azimuth angle combinations are generated for each sea area grid by combining platform orbital parameters, attitude control capabilities, and pointing maneuver constraints.

[0069] For example, a set of candidate azimuth angles {−30°, −15°, 0°, +15°, +30°} can be preset under a certain incident angle condition, and various candidate combinations can be constructed based on this, such as {−30°, +30°}, {−20°, +20°}, {−15°, 0°, +15°}, etc. Each candidate combination contains at least two different azimuth angles, and preferably three or more, to improve the diversity of observation geometry. The specific values ​​of the candidate combinations can be flexibly set according to the platform capabilities and mission requirements.

[0070] S3. Calibration Phase: Multiple Squinting Observations and Optimal Combination Selection

[0071] After the satellite enters the on-orbit calibration phase, it sequentially controls the single-beam ATI-SAR to conduct multi-slant-view observations of the target sea area according to the above candidate azimuth angle combination.

[0072] The payload operates in single-beam imaging mode, transmitting and receiving only one radar beam at any given time for the same sea area. By adjusting the direction of the digital beamforming unit within the same orbital repetition period, the receiving beam is sequentially pointed to the same sea area in multiple azimuth angle directions, thereby acquiring multi-view observation data from at least two different azimuth angles.

[0073] In terms of performance evaluation, the following indicators can be selected in this embodiment:

[0074] ;

[0075] In the formula, The performance evaluation index for candidate oblique angles. Non-negative weighting coefficients are preferred. ; The condition number of the candidate observation matrix G, constructed from the multiple oblique view observations corresponding to the candidate azimuth oblique view combination, is achieved through singular value decomposition. The variance of the velocity difference between the observation inversion results of the candidate azimuth oblique angle combination and the external calibration vector flow field in the target sea area.

[0076] By minimizing the performance evaluation metric Select the optimal combination of azimuth and oblique angles for each sea area; under preferred conditions, the time interval between oblique observations of different azimuths does not exceed the preset ocean current time scale, so as to obtain sufficiently diverse multi-oblique observation geometry while ensuring that the changes in the current field can be modeled.

[0077] S4. Operational phase: Combined use of sea area identification and azimuth angle view.

[0078] Once the routine operational observation phase begins, this embodiment determines the sea area grid to which any sea surface resolution unit belongs based on its latitude and longitude coordinates. The optimal azimuth and oblique angle combination and corresponding observation parameters for that sea area grid are obtained by searching the sea area observation configuration database.

[0079] The current orbital position and attitude information are acquired through the orbit and attitude acquisition module. Combined with the optimal azimuth oblique angle combination, a multi-oblique-view observation plan is generated, including the observation time arrangement, pointing angle, and imaging mode for each oblique angle, and then sent to the single-beam ATI-SAR payload for execution. Therefore, during the operation phase, the user only needs to specify the target latitude and longitude to complete the adaptive configuration of the observation geometry, without needing to re-search and optimize the oblique angle.

[0080] S5. Acquisition of single-beam multi-slant-look observation data:

[0081] According to the above-mentioned multi-view observation plan, the single-beam ATI-SAR payload is controlled to observe the same sea area from at least two different azimuth angles within the same orbital repetition period, and the corresponding multi-view observation data is collected.

[0082] S6. Multi-view data processing and joint inversion of vector flow:

[0083] For the multi-view observation data collected above, the following interferometry processing is first performed at the single-view level, including but not limited to: dual-channel image registration to enable the two receiving channels to achieve co-view at the pixel level; interferometric phase calculation to obtain complex interferogram; interferometric phase unwrapping and phase deviation correction; and calculation of the radial velocity of the line of sight in the line of sight direction based on the corrected interferometric phase difference and channel time interval.

[0084] Then, based on the parameterized wind-wave offset model of the Doppler centroid shift or scattering mechanism, the above-mentioned radial velocity along the line of sight is corrected for wind-wave induced velocity offset, resulting in the wind-wave corrected radial velocity observations:

[0085] The wave-induced offset can be considered as a function of the incident angle, azimuth angle, wind speed, wind direction, and sea state level. The observed radial flow velocity along the line of sight from each oblique angle is denoted as the uncorrected observation value. The observed value after wind and wave correction is Both conditions are met:

[0086] ;

[0087] In the formula, Angle of incidence For the first A directional oblique angle Select a wind speed at a height of 10m and mark it as... , For wind direction, Sea state rating The wind- and wave-induced velocity bias is obtained from the parameterized model using the following formula:

[0088] ;

[0089] in, ~ These are the parameters of the wind and wave offset model. Their values ​​can be estimated by fitting the results of the comparison between multi-view observations and the external vector flow field during the calibration stage, and can be updated in the marine observation configuration library according to the marine grid.

[0090] For the same sea surface resolution unit, at the first Observed radial velocity of line of sight after wind and wave correction at various oblique angles. satisfy:

[0091] ;

[0092] in, , Let the components of the sea surface vector current in two directions be determined in a predetermined horizontal coordinate system. Vector Streams , Components in the The projection coefficient of the line of sight upwards from each azimuth oblique angle. This is the residual deviation term, which includes wind and wave correction residuals and system residual deviations.

[0093] Different oblique angles The corresponding equations above, when combined, form the observation equation system. Let the observation vector be:

[0094] ;

[0095] Observation matrix of optimal oblique angle combination:

[0096] ;

[0097] Vector to be determined:

[0098] ;

[0099] Residual vector:

[0100] ;

[0101] Then, the observation equation in matrix form is:

[0102] ;

[0103] The weighted least squares algorithm was used to solve the observation equations to obtain the solution values ​​for the sea surface vector current components:

[0104] ;

[0105] The residual bias terms of oblique observations in each direction are expressed as follows:

[0106] ;

[0107] in, To assign different confidence levels to strabismus observations from different orientations, a diagonal weight matrix is ​​used. The solution value is for the vector flow.

[0108] The diagonal weight matrix weights The system adaptively updates based on the observed residuals to achieve adaptive identification and suppression of gross errors. The update relationship is as follows:

[0109] ;

[0110] in, Based on the basic noise level, For adjustment coefficients, Based on the residuals obtained from the current estimate, the weights are updated by iteratively solving the observation equations using weighted least squares. Simultaneously, robust joint inversion of sea surface vector current and residual bias term is completed. During the operational observation phase, long-term statistical analysis is performed on the residual bias term obtained in the joint inversion. Based on the statistical results, the wind and wave offset model parameters and inversion parameters of the corresponding sea area grid in the observation configuration library are updated.

[0111] Through the above implementation process, this embodiment realizes high-precision sea surface vector current measurement of different sea areas under the single-beam ATI-SAR system by using the optimal multi-look observation geometry calibrated according to the sea area and the multi-look joint inversion method.

[0112] Example 2: Single-beam adaptive multi-look ATI-SAR vector flow measurement system:

[0113] This embodiment provides a single-beam adaptive multi-look ATI-SAR vector flow measurement system for implementing the above method. The system mainly includes the following functional modules:

[0114] M1. Single-beam ATI-SAR payload module:

[0115] This module includes two receiving antennas deployed along the track and a digital beamforming unit. The payload operates in ATI-SAR mode and is configured to perform single-beam imaging of the same sea area at any given time. Based on instructions from the observation plan generation module, the digital beamforming unit adjusts the azimuth direction of the receiving beam within the same orbital repetition period, causing the receiving beam to sequentially point towards the same sea area from multiple azimuth angles, thus acquiring multi-angle observation data.

[0116] M2. Orbit and Attitude Acquisition Module:

[0117] It is used to acquire the orbital and attitude parameters of the satellite platform in real time, and to calculate the ground latitude and longitude and radar line of sight corresponding to each observation time, providing input for observation geometry configuration, azimuth angle calculation and projection coefficient determination.

[0118] M3. Marine Observation Configuration Library Module:

[0119] This module stores the optimal azimuth and oblique angle combinations and corresponding observation parameters for each sea area grid, including observation time windows, preferred oblique angle sets, joint inversion weight parameters, and wind and wave offset model parameters. It supports querying corresponding sea area grid entries based on latitude and longitude and updates the database parameters based on residual deviation statistics.

[0120] M4. Marine Area Identification and Observation Plan Generation Module:

[0121] This tool is used to determine the sea area grid based on the latitude and longitude of the target sea area given by the user or mission plan. It adaptively reads the corresponding optimal azimuth oblique angle combination and observation parameters from the sea area observation configuration library module, and combines the orbit position and attitude information provided by the orbit and attitude acquisition module to generate a multi-oblique angle observation plan, including the observation time, pointing angle and imaging mode of each oblique angle, and sends the observation plan to the single-beam ATI-SAR payload module for execution.

[0122] M5. Vector Stream Joint Inversion Module:

[0123] This module receives multi-view observation data transmitted from the single-beam ATI-SAR payload module, performs single-view along-track interferometry processing, wind and wave offset correction, and constructs and solves the multi-view observation equations, outputting the sea surface vector flow field after joint error correction. This module is also responsible for long-term statistical analysis of the residual bias terms obtained during the inversion process and writes the statistical results back to the sea area observation configuration library module. This updates the wind and wave offset model parameters and joint inversion parameters for different sea area grids, enabling adaptive optimization of the system during long-term operation.

[0124] The system described in this embodiment can be carried by a spaceborne platform or extended to airborne or other platforms. As long as it meets the requirements of single-beam ATI-SAR system, multi-directional squint observation, and corresponding data processing and inversion capabilities, the single-beam adaptive multi-slant-look vector flow measurement method proposed in this invention can be realized.

[0125] In summary, this invention comprehensively utilizes the geometric redundancy of multi-slant-view observations and regional calibration results to effectively overcome the problems of single-beam ATI-SAR being able to acquire radial current velocity along a single line of sight, and the complexity of engineering and difficulty in consistent error in dual-beam ATI systems. It can significantly improve the accuracy, stability, and operational capability of sea surface vector current measurements in different sea areas, and has good engineering application prospects and promotional value.

[0126] In this specification, the present invention has been described with reference to specific embodiments. The above embodiments are preferred embodiments of this application and are not intended to limit the scope of the invention. It should be noted that the present invention is not limited to the specific embodiments described above. Improvements, variations, combinations, substitutions, etc., made by those skilled in the art without departing from the principles of the present invention are all within the scope of protection claimed in the claims of this invention.

[0127] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A single-beam multi-aspect ATI-SAR vector flow measurement method, characterized in that, The method comprises the following steps: S1: dividing the global ocean into a plurality of sea area grids according to latitude and longitude, and initializing an observation configuration library; S2: generating a plurality of groups of candidate azimuth squint angle combinations for each sea area grid, each group containing at least two different azimuth squint angles; S3: in the early stage of satellite on-orbit or in the scheduled calibration stage, sequentially controlling the single-beam ATI-SAR to perform multi-squint observation on the target sea area according to the candidate azimuth squint angle combinations, selecting the optimal azimuth squint angle combination and corresponding observation parameters of each sea area based on a preset performance evaluation index, and writing the optimal azimuth squint angle combination and the corresponding observation parameters into the observation configuration library; S4: in the running observation stage, determining the sea area grid to which the to-be-measured latitude and longitude belong, and adaptively reading the corresponding optimal azimuth squint angle combination and observation parameters from the observation configuration library; S5: controlling the single-beam ATI-SAR to perform observation on the same sea area at at least two different azimuth squint angles in the same orbit repeat cycle according to the optimal azimuth squint angle combination, and obtaining multi-squint observation data; S6: performing along-track interference processing and wind wave correction on the multi-squint observation data, and obtaining the sea surface vector flow and residual bias parameters by using a joint inversion algorithm; The wind wave correction is specifically as follows: For the The observed radial flow velocity along the line of sight from each oblique angle is denoted as the uncorrected observation value. The observed value after wind and wave correction is Both conditions are met: ； wherein is the incident angle, is the first is the azimuth angle, is the h is the wind speed at 10 m height, is the wind direction, is the sea state, is the wind wave induced speed bias, obtained from the parametric model: ； wherein, , is the wind wave bias model parameter, the value of which can be fitted and estimated based on the comparison results of multi-look observations and external vector flow field in the calibration stage, and can be updated in the sea area observation configuration library according to the sea area grid. The joint inversion algorithm is specifically as follows: The radial velocity observation value of the line-of-sight at the first azimuth angle of view under the wind and wave correction for the same sea surface resolution unit The radial velocity observation value of the line-of-sight at the first azimuth angle of view under the wind and wave correction for the same sea surface resolution unit Satisfies: ； wherein, , are the two components of the sea surface vector current to be determined in a predetermined horizontal coordinate system, , are the two components of the vector current , are the projection coefficients of the components of the vector current in the direction of the line of sight of the th azimuthal look angle, is a residual bias term, including a wind wave correction residual, a system residual bias; The above equations corresponding to different azimuthal angles of strabismus are combined to form an observation equation set, , let the observation vector be: ； The observation matrix of the optimal squint angle combination is as follows: ； The to-be-solved vector is as follows: ； Residual vector: ; The observation equation in the matrix form is as follows: ； The weighted least square algorithm is used to solve the observation equation set, and the solution value of the sea surface vector flow component is obtained: ； Each azimuth squint observation residual bias term is expressed as follows: ； wherein, is a diagonal weight matrix that assigns different reliability to observations of different azimuthal gaze directions, is the solution value of the vector flow.

2. The single-beam multi-bistatic ATI-SAR vector flow measurement method according to claim 1, characterized in that, In step S1, the sea area grid is a regular latitude and longitude grid based on flow field characteristics or an irregular grid related to the sea area boundary, and the observation configuration library stores the optimal azimuth squint angle combination and corresponding observation parameters of each sea area grid by taking the grid number or the central latitude and longitude of the grid as an index.

3. The single-beam multi-bistatic ATI-SAR vector flow measurement method according to claim 1, characterized in that, In step S3, the single-beam ATI-SAR load includes a receiving antenna arranged along the track and a digital beam forming unit, and the load works in a single-beam imaging mode, transmits and receives only one radar beam to the same sea area at any time, and adjusts the pointing direction of the digital beam forming unit to make the receiving beam point to the same sea area in multiple azimuth squint angle directions in sequence, so as to obtain multi-squint observation data at at least two different azimuth squint angles.

4. The single-beam multi-looking ATI-SAR vector flow measurement method according to claim 1, characterized in that, In step S3, the performance evaluation index is as follows: In the formula, is a performance evaluation index of the candidate strabismus angle, is a non-negative weight coefficient; is a condition number of a candidate observation matrix G constructed by a plurality of strabismus observations corresponding to the candidate azimuth-strabismus angle combination, realized by singular value decomposition; is a variance of the velocity difference between the observation inversion result of the candidate azimuth-strabismus angle combination and the external calibration vector flow field in the target sea area. by minimizing the performance evaluation index selecting the optimal azimuth and squint angle combination for each sea area; In the multi-squint observation corresponding to each candidate azimuth squint angle combination, the time interval between different squint observations is not more than a preset ocean flow field time scale.

5. The single-beam multi-look ATI-SAR vector flow measurement method according to claim 1, characterized in that, In step S6, the along-track interference processing includes: double-channel single-view complex image registration, interference phase calculation, phase unwrapping and phase bias correction, and the line-of-sight radial flow velocity is calculated based on the corrected phase difference.

6. The single-beam multi-look ATI-SAR vector flow measurement method according to claim 1, characterized in that, The diagonal weight matrix The weight value According to the observation residual adaptive update, the adaptive identification and suppression of the gross error observation are realized, and the update relationship is: ； wherein, is a base noise level, is a regulation coefficient, is a residual error based on the current estimation; by solving the observation equation set by iterative weighted least squares, the robust joint inversion of the sea surface vector flow and the residual error term is completed while updating the weight , and in the running observation stage, the residual error term obtained in the joint inversion is statistically analyzed for a long time, and the wind wave bias model parameters and inversion parameters of the corresponding sea area grid in the observation configuration library are updated according to the statistical results.

7. A single-beam squinted ATI-SAR vector flow measurement system for implementing the single-beam squinted ATI-SAR vector flow measurement method according to any one of claims 1 to 6, characterized in that It comprises: A single-beam ATI-SAR load module: the load works in an ATI-SAR system, includes a receiving antenna arranged along the track and a digital beam forming unit, is configured to perform single-beam imaging on the same sea area at any time, and adjusts the pointing direction of the digital beam forming unit to make the receiving beam point to the same sea area in multiple azimuth squint angle directions in sequence in the same orbit repeat cycle, so as to obtain multi-squint observation data; An orbit and attitude acquisition module is configured to acquire platform orbit parameters and attitude parameters, and to calculate ground longitude and latitude and radar line-of-sight direction corresponding to each observation time; A sea area observation configuration library module is configured to store optimal azimuth and oblique viewing angle combinations and corresponding observation parameters of each sea area grid according to sea area grids, and to support longitude and latitude-based query and update; A sea area identification and observation plan generation module is configured to determine a sea area grid to which a to-be-measured sea area belongs according to the longitude and latitude of the to-be-measured sea area, to adaptively read the corresponding optimal azimuth and oblique viewing angle combination and observation parameters from the sea area observation configuration library module, and to generate a multi-oblique viewing observation plan in combination with orbit and attitude parameters, and to issue the multi-oblique viewing observation plan to the single-beam ATI-SAR load module to control the single-beam ATI-SAR load module to sequentially observe the same sea area according to the optimal azimuth and oblique viewing angle combination in the same orbit repeat period; A vector flow joint inversion module is configured to perform single-viewing-angle along-track interference processing, wind and wave correction, multi-oblique viewing observation equation construction and solving on multi-oblique viewing observation data acquired by the single-beam ATI-SAR load module, to output a sea surface vector flow field after error joint correction, and to write statistical results of residual deviation parameters back to the sea area observation configuration library module.

8. The single-beam multi-look ATI-SAR vector flow measurement system of claim 7, wherein, The observation configuration library takes grid numbers or grid center longitude and latitude as indexes, reserves storage fields for each sea area grid, and is configured to save optimal azimuth and oblique viewing angle combinations and observation parameters corresponding to the sea area grid. In an initial state, each grid only establishes an entry and does not fill in specific oblique viewing angle configurations.

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