SAR sea surface flow field inversion method and system based on Doppler frequency shift correction

Abstract

The present invention discloses a SAR sea surface flow field inversion method and system based on Doppler frequency shift correction, belonging to the field of synthetic aperture radar technology. The method comprises dividing a SAR single-view complex image into sub-image blocks; estimating the Doppler center frequency shift of each sub-image block; estimating the range deviation according to the polarization mode and the beam center viewing angle; calculating the DC offset according to the adjacent land area data; combining the range deviation and the DC offset to remove the non-geophysical Doppler frequency shift error; calculating and removing the Doppler frequency shift caused by sea surface wind and waves to obtain the sea surface flow field. The present invention improves the estimation accuracy of the non-geophysical Doppler frequency shift error and reduces the error of SAR sea surface flow field inversion. At the same time, it reduces the requirements for fitting the non-geophysical Doppler frequency shift error to the land area data, and expands the application scenarios of SAR sea surface flow field inversion.

Description

Technical Field

[0001] The present invention belongs to the field of synthetic aperture radar (SAR) signal processing and marine remote sensing application technology, and specifically relates to a SAR sea surface flow field inversion method and system based on Doppler frequency shift correction. Background Art

[0002] Ocean currents are large-scale and relatively stable flows of seawater. The near-surface flow field of the ocean is a key physical parameter for measuring ocean movement. It has an important influence and restrictive effect on human development activities such as the utilization and development of marine resources. Accurate observation of the sea surface flow field is the core of studying ocean dynamics and sea-air interactions.

[0003] Synthetic Aperture Radar (SAR) is an active microwave imaging radar. Compared with drifting buoy observations and near-shore high-frequency radar observations, which have very limited and unevenly distributed data, SAR has the advantages of obtaining sea surface motion information all day, all weather, over a large range, and with high resolution, making it one of the main means of inverting sea surface flow fields.

[0004] The prior art has disclosed a correction method and system for inverting sea surface velocity based on synthetic aperture radar data. After obtaining the Doppler centroid frequency shift and removing the Doppler frequency shift caused by the relative motion between the satellite and the ground, the electromagnetic pointing linear error with the distance pixel position as the independent variable is fitted and removed through the land imaging area data of the same period and the same orbit or the same period adjacent orbits. The sea surface velocity is obtained after removing the Doppler frequency shift caused by sea surface wind and waves.

[0005] The existing methods completely utilize land area data to fit the non-geophysical Doppler frequency shift error. Therefore, in order to estimate and fit the accurate non-geophysical Doppler frequency shift error, it is necessary to use the entire land area data or the data with a large proportion of land area. For the case where such land area data is not included in the same period and the same orbit or the same period adjacent orbits, the existing methods are no longer applicable.

[0006] The accuracy of SAR sea surface flow field inversion is affected by the Doppler shift error of non-geophysical items, and the Doppler shift error of non-geophysical items varies with time and space. The land area data closest to the SAR data to be inverted is the most intuitive manifestation of the non-geophysical Doppler shift error. In order to calculate the non-geophysical Doppler shift error, the existing methods need to use data that contains sufficient land areas in both range and azimuth. However, such land area data are generally far away from the SAR data area to be inverted. Therefore, the estimation accuracy of the existing methods is not ideal, which brings errors to the inversion of sea surface flow fields. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a SAR sea surface flow field inversion method and system based on Doppler frequency shift correction. According to the distribution characteristics of the non-geophysical Doppler frequency shift error, the polarization mode of SAR data and the beam center viewing angle are extracted, the range deviation is estimated in advance, and the DC offset is calculated according to the data of the adjacent land area in the same scene or the same track, and the non-geophysical Doppler frequency shift error is obtained by combining the range deviation and the DC offset. Because when estimating the non-geophysical Doppler frequency shift error, the range deviation can be estimated without land data, and the DC offset can be calculated with only a small piece of land area data, which greatly expands the application scope of the SAR sea surface flow field inversion method. At the same time, the nearest land area data is used to improve the accuracy of the estimation of the non-geophysical Doppler frequency shift error and reduce the inversion error.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] A SAR sea surface flow field inversion method based on Doppler frequency shift correction includes the following steps:

[0010] Step 1: Divide the SAR single-view complex image into sub-image blocks;

[0011] Step 2, estimating the Doppler center frequency shift of each sub-image block;

[0012] Step 3: Estimate the range deviation according to the polarization mode and the beam center viewing angle;

[0013] Step 4, calculating the DC offset based on the adjacent land area data;

[0014] Step 5: Combine the range deviation and DC offset to remove the non-geophysical Doppler frequency shift error;

[0015] Step 6: Calculate and remove the Doppler frequency shift caused by sea surface wind and waves to obtain the sea surface flow field.

[0016] On the other hand, the present invention provides a SAR sea surface flow field inversion system based on Doppler frequency shift correction, comprising:

[0017] SAR single-view complex image division module is used to divide the SAR single-view complex image into sub-image blocks;

[0018] A Doppler center frequency shift estimation module, used for estimating the Doppler center frequency shift from the sub-image block;

[0019] Range deviation estimation module, used to extract polarization mode and beam center viewing angle to estimate range deviation;

[0020] A DC offset calculation module is used to obtain data of adjacent land areas to calculate DC offsets;

[0021] A Doppler frequency shift error calculation module is used to determine the non-geophysical Doppler frequency shift error by combining the range deviation and the DC offset;

[0022] Sea surface wind and wave Doppler frequency shift calculation module, used to calculate the Doppler frequency shift caused by sea surface wind and waves;

[0023] The sea surface flow field inversion module is used to remove the Doppler frequency shift error of non-geophysical items and the Doppler frequency shift caused by sea surface wind and waves, and convert it into Doppler velocity to realize SAR inversion of sea surface flow field.

[0024] In a third aspect, the present invention provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned SAR sea surface flow field inversion method based on Doppler frequency shift correction.

[0025] In a fourth aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned SAR sea surface flow field inversion method based on Doppler frequency shift correction.

[0026] The beneficial effects of the present invention are:

[0027] The present invention starts from SAR sea surface flow field inversion, fully considers the distribution characteristics of non-geophysical Doppler frequency shift errors, uses polarization mode and beam center viewing angle to accurately estimate the range deviation in advance, and uses adjacent land area data to accurately estimate the DC offset, thereby improving the estimation accuracy of non-geophysical Doppler frequency shift errors and reducing the error of SAR sea surface flow field inversion.

[0028] The present invention estimates the range deviation in advance according to the polarization mode and the beam center viewing angle during the SAR sea surface flow field inversion process, calculates the DC offset using the data of a small adjacent land area under the same scene or orbit, and obtains the non-geophysical Doppler shift error by combining the range deviation and the DC offset, thereby reducing the requirements for fitting the non-geophysical Doppler shift error for land area data, enhancing the applicability of the method, and providing support for the engineering application of SAR sea surface flow field inversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart of the SAR sea surface flow field inversion method based on Doppler frequency shift correction of the present invention;

[0030] Figure 2The present invention is a logic flow chart of the SAR sea surface flow field inversion method based on Doppler frequency shift correction;

[0031] Figure 3 Schematic diagram of the amplitude of a single-view complex image according to an embodiment of the present invention;

[0032] Figure 4 This is a graph showing the variation of the non-geophysical Doppler frequency shift error with the incident angle for land area data;

[0033] Figure 5 This is a schematic diagram of the Doppler frequency shift error of non-geophysical items;

[0034] Figure 6 This is a schematic diagram of the sea surface flow field inverted by SAR;

[0035] Figure 7 Schematic diagram of the sea surface flow field after correction. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0037] The invention provides a SAR sea surface flow field inversion method based on Doppler frequency shift correction. Based on Doppler center frequency shift estimation, by dividing the Doppler center frequency shift components contained in SAR data, when the SAR data imaging area only contains land areas, non-geophysical Doppler frequency shift errors can be obtained; based on the variation characteristics of the range deviation in the non-geophysical Doppler frequency shift error, the variation of the non-geophysical Doppler frequency shift error with the incident angle of SAR data with the same polarization mode and beam center viewing angle in different orbits and at different times is plotted, and it is determined that the range deviation of SAR data can be estimated in advance by extracting the polarization mode and beam center viewing angle of SAR data; based on the variation characteristics of the direct current offset in the non-geophysical Doppler frequency shift error, only the data of small adjacent land areas in the same scene or the same orbit can be used to accurately calculate the direct current offset; based on the distribution characteristics of the non-geophysical Doppler frequency shift error, the range deviation and the direct current offset are combined to solve the problem that the non-geophysical Doppler frequency shift error cannot be effectively estimated when there is no land or less land in the imaging area of ​​the same orbit or adjacent orbits of SAR data.

[0038] Specific as Figure 1 As shown in FIG. 1 , a flow chart of a SAR sea surface flow field inversion method based on Doppler frequency shift correction of the present invention is shown, which includes the following steps:

[0039] Step 1: Divide the SAR single-view complex image into sub-image blocks;

[0040] Step 2, estimating the Doppler center frequency shift of each sub-image block;

[0041] Step 3: Estimate the range deviation according to the polarization mode and the beam center viewing angle;

[0042] Step 4, calculating the DC offset based on the adjacent land area data;

[0043] Step 5: Combine the range deviation and DC offset to remove the non-geophysical Doppler frequency shift error;

[0044] Step 6: Calculate and remove the Doppler frequency shift caused by sea surface wind and waves to obtain the sea surface flow field.

[0045] Furthermore, in step 1, the SAR single-view complex image contains the Doppler information of the sea surface motion in the imaging coverage area, and the Doppler Centroid Anomaly (DCA) technology is used to divide the SAR single-view complex image into The sub-image blocks are of the same size. The requirements for the block division are generally to achieve a kilometer-level spatial resolution and to have sufficient image pixels in the sub-image blocks for frequency estimation, so as to subsequently obtain high-resolution and high-accuracy Doppler center frequency shift.

[0046] Furthermore, in step 2, estimating the Doppler center frequency shift of each sub-image block includes using a time domain estimation method based on an average cross correlation coefficient (ACCC) method to estimate the Doppler center frequency shift of each sub-image block. , the formula used is as follows:

[0047] (1)

[0048] in, To find the angle, For relevance, is the radar pulse repetition frequency, is the sampling interval. In actual calculation, The value is generally 1, and the autocorrelation function of each sub-image block is as follows:

[0049] (2)

[0050] in, is the first The complex value of pixels, is the number of pixels in the sub-image block, is the number of pixels in the sub-image block distance direction, with the superscript Indicates conjugate. At this time, the Doppler center frequency shift of each sub-image block is estimated based on ACCC, as shown in the following formula:

[0051] (3)

[0052] Furthermore, in step 3, the Doppler center frequency shift included in the SAR sea surface echo includes the following items:

[0053] (4)

[0054] in, The Doppler center frequency shift is a non-geophysical term, which is the Doppler frequency change caused by the relative motion between the radar platform and the earth's surface. It is the non-geophysical Doppler frequency shift error, which is the Doppler frequency change caused by the electronic mispointing of the radar antenna, the satellite orbit and attitude deviation. is the Doppler center frequency shift caused by sea surface wind and waves, is the Doppler center frequency shift caused by the sea surface flow field, is the residual error in the data processing process.

[0055] Non-geophysical Doppler center frequency shift It is a predictable quantity, usually calculated directly based on the system design parameters and the trajectory attitude data recorded in the flight:

[0056] (5)

[0057] in is the radar electromagnetic wave number, The speed of the satellite along its orbit, is the beam pitch angle, is the angle between the range plane and the orbital plane, is the angular velocity of the Earth's rotation, is the angular velocity of the satellite, is the latitude argument, is the orbital inclination, an intermediate parameter when the radar beam is viewed to the right ,otherwise .

[0058] Non-geophysical Doppler shift error The land and ocean areas of SAR single-view complex images exist together. The Doppler center frequency shift contained in the SAR single-view complex image can be calculated and the non-geophysical Doppler center frequency shift can be removed. In the land area data, there is no Doppler center frequency shift caused by sea surface wind waves and sea surface flow fields. and Therefore, the Doppler center frequency shift estimated from the land area data is That is, the non-geophysical Doppler frequency shift error of the data in this area .

[0059] Analysis of land area data shows that the non-geophysical Doppler shift error It has the following distribution characteristics: on the one hand, it presents an approximately quadratic change in the distance direction, which is called the range deviation; on the other hand, in addition to the range deviation, there is an offset between the Doppler frequency shift in the land area and the expected average zero Doppler frequency shift, which is called the DC offset.

[0060] Doppler frequency shift error according to non-geophysical terms Distribution characteristics can be divided into:

[0061] (6)

[0062] in, is the distance deviation, It represents the incident angle of the pixel point in the range direction. By fitting the non-geophysical Doppler shift error of the land area data under different polarization modes and beam center viewing angles, it is found that the range deviation presents an approximately quadratic change in the range direction, and the change trend is determined by the polarization mode and beam center viewing angle. Therefore, the range deviation of the SAR data to be inverted can be estimated in advance by extracting the polarization mode and beam center viewing angle of the SAR data. The quadratic equation of the range deviation with the incident angle as the independent variable is as follows:

[0063] (7)

[0064] in, and They are the quadratic and linear coefficients of the equation, respectively, and are determined by the polarization mode of the SAR data and the beam center viewing angle.

[0065] Furthermore, in step 4, in formula (6) The DC offset is the non-geophysical Doppler shift error of the land area data under the same polarization mode and beam center perspective. It is found that the DC offset varies greatly between different orbits and changes slowly within the same orbit. Therefore, it is only necessary to obtain the adjacent small land area data under the same scene or orbit to obtain the DC offset closest to the data to be inverted. , thereby calculating the accurate non-geophysical Doppler frequency shift error . Calculate the DC offset for the pixels belonging to the land area in the Doppler center frequency shift:

[0066] (8)

[0067] in, For the The incident angle of the distance to the pixel point is For Next The Doppler center frequency shift of the pixel point in the azimuth direction.

[0068] Find the average DC offset for pixels belonging to land areas:

[0069] (9)

[0070] in, and are the starting and ending points of the pixels belonging to the land area in the Doppler center frequency shift in azimuth, and the range is , and They are the starting and ending points of the pixel points belonging to the land area in the Doppler center frequency shift in the distance upward, and the range is , is the total number of pixels belonging to the land area in the Doppler center frequency shift.

[0071] Furthermore, in step 5, the range deviation and the DC offset are combined to obtain and remove the non-geophysical Doppler frequency shift error.

[0072] Furthermore, in step 6, the Doppler frequency shift caused by sea surface wind and waves is estimated using the CDOP empirical geophysical model function, and the formula is as follows:

[0073] (10)

[0074] in, and are wind speed and relative wind direction, respectively. is the polarization mode of the radar.

[0075] The Doppler frequency shift caused by the sea surface flow field is calculated using the following formula:

[0076] (11)

[0077] The sea surface radial velocity is calculated as follows:

[0078] (12)

[0079] So far, the SAR sea surface flow field inversion is completed.

[0080] The SAR sea surface flow field inversion method based on Doppler frequency shift correction proposed by the present invention is further described in detail below through specific embodiments:

[0081] like Figure 2 As shown, first, the selected Agulhas flow region GF-3 FSII mode single-view complex image is divided into sub-image blocks, and a GF-3 single-view complex image is selected. The amplitude image is as follows Figure 3 As shown in the figure, the pixel block size and step size in the azimuth and range directions are set to achieve a kilometer-level Doppler center frequency shift resolution.

[0082] The Doppler center frequency shift of each sub-image block is estimated according to formulas (1)-(3).

[0083] Taking the SAR data with HH polarization and 30.62° beam center angle as an example, the variation of the non-geophysical Doppler frequency shift error of the land area data at different orbits and times with the incident angle is statistically shown as follows: Figure 4 As shown in the figure, it is proved that SAR data with the same polarization mode and beam center viewing angle have the same range deviation, and SAR data with the same polarization mode and beam center viewing angle have different DC offsets between different scene data. According to formula (7), the quadratic equation of the range deviation is determined using the land area data with the same polarization mode and beam center viewing angle, and the DC offset is calculated using the adjacent land area data with the same scene or the same track according to formula (8) and formula (9).

[0084] According to formula (6), the range deviation and DC offset are combined to determine the non-geophysical Doppler frequency shift error: Figure 5 shown.

[0085] According to formula (10), the radar incident angle, polarization, wind speed, and relative wind direction are input into the CDOP empirical geophysical model function to obtain the Doppler frequency shift caused by sea surface wind waves.

[0086] Finally, the Doppler frequency shift caused by the sea surface flow field is obtained by applying formula (11), which is substituted into formula (12) to convert it into Doppler velocity, and the SAR inverted sea surface flow field is obtained, as follows: Figure 6 shown.

[0087] The sea surface flow field after correction of the multi-view GF-3 data of the Agulhas Basin is statistically analyzed, and the scatter density map is drawn by comparing the flow field of the HYCOM model data, such as Figure 7 As shown in the figure, the deviation, mean absolute error (MAE) and root mean square error (RMSE) are calculated respectively. The deviation is 0.22m / s, MAE is 0.27m / s, and RMSE is 0.33m / s. Compared with the existing methods, the error of SAR inversion of sea surface flow field in this area is effectively reduced.

[0088] Furthermore, when estimating the Doppler center frequency shift from each sub-image block, in addition to using the average cross-correlation coefficient-based method, other methods such as energy balancing and optimal estimation can also be used.

[0089] Furthermore, the range deviation in the non-geophysical Doppler frequency shift error can be approximated not only as a quadratic equation but also as a linear equation or other higher-order equations.

[0090] Furthermore, when estimating the Doppler shift caused by sea surface wind and waves, in addition to using the CDOP empirical geophysical model function, functions such as CDOP3S and DopRIM can also be used.

[0091] On the other hand, the present invention provides a SAR sea surface flow field inversion system based on Doppler frequency shift correction, the system comprising:

[0092] SAR single-view complex image division module is used to divide the SAR single-view complex image into sub-image blocks;

[0093] A Doppler center frequency shift estimation module, used for estimating the Doppler center frequency shift from the sub-image block;

[0094] Range deviation estimation module, used to extract polarization mode and beam center viewing angle to estimate range deviation;

[0095] A DC offset calculation module is used to obtain data of adjacent land areas to calculate DC offsets;

[0096] A Doppler frequency shift error calculation module is used to determine the non-geophysical Doppler frequency shift error by combining the range deviation and the DC offset;

[0097] Sea surface wind and wave Doppler frequency shift calculation module, used to calculate the Doppler frequency shift caused by sea surface wind and waves;

[0098] The sea surface flow field inversion module is used to remove the Doppler frequency shift error of non-geophysical items and the Doppler frequency shift caused by sea surface wind and waves, and convert it into Doppler velocity to realize SAR inversion of sea surface flow field.

[0099] In a third aspect, the present invention provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned SAR sea surface flow field inversion method based on Doppler frequency shift correction.

[0100] In a fourth aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned SAR sea surface flow field inversion method based on Doppler frequency shift correction.

[0101] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A SAR sea surface flow field inversion method based on Doppler frequency shift correction, characterized in that: The steps include: Step 1: Divide the SAR single-view complex image into sub-image blocks; Step 2, estimating the Doppler center frequency shift of each sub-image block; Step 3: Estimate the range deviation according to the polarization mode and the beam center viewing angle, including: assuming that the quadratic equation of the range deviation with the incident angle as the independent variable is as follows: （6） （7） in, is the non-geophysical Doppler shift error, is the distance deviation, Represents the incident angle of the distance to the pixel point, is the DC offset; and They are the quadratic and linear coefficients of the equation, respectively, which are determined by the polarization mode of the SAR data and the beam center viewing angle; Step 4: Calculate the DC offset based on the data of the adjacent land area in the same scene or track; including calculating the DC offset of the pixel points belonging to the land area in the Doppler center frequency shift: （8） in, For the The incident angle of the distance to the pixel point is For Next The Doppler center frequency shift of the pixel point in each azimuth direction; Find the average DC offset for pixels belonging to land areas: （9） in, and are the starting and ending points of the pixels belonging to the land area in the Doppler center frequency shift in azimuth, and the range is , and They are the starting and ending points of the pixel points belonging to the land area in the Doppler center frequency shift in the distance upward, and the range is , is the total number of pixels belonging to the land area in the Doppler center frequency shift; Step 5: Combine the range deviation and DC offset to remove the non-geophysical Doppler frequency shift error; Step 6: Calculate and remove the Doppler frequency shift caused by sea surface wind and waves to obtain the sea surface flow field.

2. The SAR sea surface flow field inversion method based on Doppler shift correction according to claim 1 is characterized in that: In step 1, the SAR single-view complex image is divided into sub-image blocks, each sub-image block has the same size.

3. The SAR sea surface flow field inversion method based on Doppler shift correction according to claim 2 is characterized in that: In step 2, the Doppler center frequency shift is estimated for each sub-image block based on the average cross-correlation coefficient method: （1） in, To find the angle, For relevance, is the radar pulse repetition frequency, is the sampling interval, is a constant of 1, and the autocorrelation function of each sub-image block is as follows: （2） in, is the first The complex value of pixels, is the number of pixels in the sub-image block, is the number of pixels in the sub-image block distance direction, with the superscript denotes conjugation; The Doppler center frequency shift of each sub-image block is estimated based on the average cross-correlation coefficient method: （3）。 4. The SAR sea surface flow field inversion method based on Doppler shift correction according to claim 3 is characterized in that: In step 3, the Doppler center frequency shift contained in the SAR sea surface echo is composed of the following five parts: composition: （4） in, is the non-geophysical Doppler center frequency shift, is the non-geophysical Doppler shift error, is the Doppler center frequency shift caused by sea surface wind and waves, is the Doppler center frequency shift caused by the sea surface flow field, is the residual error in the data processing process, where （5） in, is the radar electromagnetic wave number, is the speed of the satellite along the orbit, is the beam pitch angle, is the angle between the range plane and the orbital plane, is the angular velocity of the Earth's rotation, is the angular velocity of the satellite, is the latitude argument, is the orbital inclination, an intermediate parameter when the radar beam is viewed to the right ,otherwise .

5. The SAR sea surface flow field inversion method based on Doppler frequency shift correction according to claim 4 is characterized in that: In step 5, the non-geophysical Doppler frequency shift error is calculated and removed by combining the range deviation and the DC offset.

6. The SAR sea surface flow field inversion method based on Doppler shift correction according to claim 5, characterized in that: In step 6, the Doppler frequency shift caused by sea surface wind and waves is estimated using the CDOP empirical geophysical model function, and the formula is as follows: （10） in, and are wind speed and relative wind direction, respectively. is the polarization mode of the radar; The Doppler frequency shift caused by the sea surface flow field is calculated using the following formula: （11） The sea surface radial velocity is calculated as follows: （12）。 7. A SAR sea surface flow field inversion system based on Doppler frequency shift correction, characterized in that: include: SAR single-view complex image division module is used to divide the SAR single-view complex image into sub-image blocks; A Doppler center frequency shift estimation module, used for estimating the Doppler center frequency shift from the sub-image block; Range deviation estimation module, used to extract polarization mode and beam center viewing angle to estimate range deviation; Including, assuming that the quadratic equation of range deviation with the independent variable as the incident angle is as follows: （6） （7） in, is the non-geophysical Doppler shift error, is the distance deviation, Represents the incident angle of the distance to the pixel point, is the DC offset; and They are the quadratic and linear coefficients of the equation, respectively, which are determined by the polarization mode of the SAR data and the beam center viewing angle; The DC offset calculation module is used to obtain the data of the adjacent land area under the same scene or the same track to calculate the DC offset; including calculating the DC offset of the pixel points belonging to the land area in the Doppler center frequency shift: （8） in, For the The incident angle of the distance to the pixel point is For Next The Doppler center frequency shift of the pixel point in each azimuth direction; Find the average DC offset for pixels belonging to land areas: （9） in, and are the starting and ending points of the pixels belonging to the land area in the Doppler center frequency shift in azimuth, and the range is , and They are the starting and ending points of the pixel points belonging to the land area in the Doppler center frequency shift in the distance upward, and the range is , is the total number of pixels belonging to the land area in the Doppler center frequency shift; A Doppler frequency shift error calculation module is used to determine the non-geophysical Doppler frequency shift error by combining the range deviation and the DC offset; Sea surface wind and wave Doppler frequency shift calculation module, used to calculate the Doppler frequency shift caused by sea surface wind and waves; The sea surface flow field inversion module is used to remove the Doppler frequency shift error of non-geophysical items and the Doppler frequency shift caused by sea surface wind and waves, and convert it into Doppler velocity to realize SAR inversion of sea surface flow field.

8. An electronic device, characterized in that: include: one or more processors; A memory for storing one or more programs; Wherein, when one or more programs are executed by the one or more processors, the one or more processors implement the SAR sea surface flow field inversion method based on Doppler frequency shift correction as described in any one of claims 1-6.

9. A computer-readable storage medium, characterized in that: Executable instructions are stored thereon, and when the instructions are executed by the processor, the processor can implement the SAR sea surface flow field inversion method based on Doppler frequency shift correction as described in any one of claims 1 to 6.

Images