Marine ship association identification method based on AIS and satellite-borne SAR data

Abstract

The invention belongs to the field of remote sensing data ocean application processing, and particularly relates to an ocean ship association identification method based on AIS and satellite-borne SAR data. The method mainly comprises the following steps: step 1, acquiring AIS data based on SAR satellite imaging time; step 2, AIS data cleaning and processing; step 3, ship trajectory recovery in an AIS time interval; 4, deducing the state of the ship in the AIS time interval; the deduction comprises establishment of a time-distance direction or time-azimuth direction speed mapping relation; 5, revising the real position of the ship based on a satellite-borne SAR (Synthetic Aperture Radar) imaging principle; step 6, AIS and satellite-borne SAR data ocean ship target accurate association processing is carried out; and 7, calculating the geometric error of the satellite-borne SAR ocean image system. According to the method, state information such as the real position, the navigational speed and the course of a ship at the satellite imaging moment is deduced through modes such as data processing, mapping relation establishment and distance and speed decomposition, and the displacement degree of the SAR when the moving target is imaged can be effectively quantified.

Description

Technical Field

[0001] This patent belongs to the field of marine application processing of remote sensing data, specifically a method for marine vessel association identification based on AIS and satellite-borne SAR data. Background Art

[0002] Marine surveillance is of great significance for safeguarding national marine rights and interests and ensuring national marine security. Among them, marine ship target surveillance is of great value in application fields such as marine situation, maritime rights protection, maritime traffic, fishery management and combating maritime terrorist activities. The fusion processing of marine target information of satellite-borne synthetic aperture radar (SAR) and automatic identification system (AIS) solves the problem of accurate identification of ship targets in satellite-borne SAR images, and can fully realize the complementarity of SAR and AIS information, and improve the application ability of satellite-borne SAR images in automatic detection and identification of ship targets. AIS is a marine information communication platform provided by the International Lighthouse Association for marine ships. AIS equipment operates at 161.975MHZ and 162.025MHZ frequencies, and the platforms include shore-based, ship-borne, airborne and satellite-based platforms. At present, service platforms such as Ship Information Network can provide and publish data of various AIS in the world in real time, so the ground can collect AIS data in the area of ​​interest and fuse it with other multi-source data.

[0003] There are two main existing fusion technology methods. Among them, the space-based method, that is, the AIS receiving device and on-board processing equipment are installed on the satellite platform, which can realize information association and fusion in real time on orbit, and has extremely high application value. However, since AIS is a low-frequency signal, its receiving antenna size is large, which constrains the structural shape of the SAR satellite, increases the difficulty of on-board data flow design, and increases the weight of the satellite and the cost of launching and developing. Therefore, lightweight and miniaturized commercial SAR satellites usually use ground processing methods to perform information fusion to obtain information on marine ship targets. The method currently used is mainly an association method based on position feature information. The ship targets and AIS report targets within the scope of the satellite-borne SAR image scene are matched with each other, and the association is performed based on the position features to complete the fusion of the two data. However, due to the discontinuity of AIS data, the multi-source and complexity of AIS data obtained on the ground, the geometric system deviation of SAR images, and the imaging position offset of moving ship targets in SAR images, these errors reduce the accuracy of association based on position features, which is easy to lead to erroneous association results. Summary of the invention

[0004] The invention purpose of this patent is to propose a method for rapid association and identification of marine vessel targets by fusion processing of AIS and satellite-borne SAR data, aiming to make full use of AIS data to deduce the status information of different ships at the time of SAR imaging, compensate for the offset of satellite-borne SAR moving targets to the imaging position, and calculate the system offset, so as to provide supporting data for improving the rapid matching and identification accuracy of AIS and satellite-borne SAR ship targets, as well as the evaluation and improvement of the positioning accuracy of satellite-borne SAR image products.

[0005] To achieve this goal, the implementation of the present invention comprises the following steps: Step 1: Obtain AIS data based on SAR satellite imaging time; Step 2: AIS data cleaning and processing; Step 3: Restoration of the ship's trajectory within the AIS time interval; Step 4: Ship status deduction within the AIS time interval (establishment of time-distance (azimuth) speed mapping relationship); Step 5: Revise the real position of the ship based on the principle of spaceborne SAR imaging; Step 6: Accurate correlation processing of ocean vessel targets using AIS and satellite-borne SAR data; Step 7: Calculation of geometric errors of spaceborne SAR ocean image system.

[0006] As a further technical solution of the present invention, in step one: based on the imaging longitude and latitude range of the SAR satellite, the imaging time and the azimuth angle of the satellite corresponding to the imaging time, the ship AIS data within the longitude and latitude range is screened and downloaded.

[0007] As a further technical solution of the present invention, in step 2: based on the time-longitude (latitude) data, the data is pre-processed using the Vondrak data smoothing method, and the correct AIS sequence is obtained after deleting the erroneous AIS data; the cleaned data is vectorized, and the existing data is classified and processed according to the relative position information and the existing attributes of the ship type, and the discontinuous trajectories under different ships are extracted.

[0008] In the Vondrak data smoothing method, for a certain data sequence ,in It's time. is the longitude or latitude; the basic assumption of the Vondrak data smoothing method is: ; in: , where: is the smoothed value; express The third derivative of ; It is power; is the coefficient to be determined; It is called the degree of approximation; It is called smoothness; It is called the smoothing coefficient, and the value of the smoothing coefficient determines the smoothness of the data curve.

[0009] As a further technical solution of the present invention, in step three: based on the cubic spline interpolation method, the AIS data is sorted according to time, the longitude and latitude of the time starting point are selected as the coordinate origin, and the time difference of the AIS data before and after the calculation is used as the interpolation sequence, and the cubic spline interpolation of the time-longitude trajectory and the time-latitude trajectory are obtained respectively, and the navigation trajectory of the ship is obtained by merging the above two cubic spline curves.

[0010] As a further technical solution of the present invention, in step four: a tangent equation of any point is established based on the navigation trajectory to obtain the corresponding heading at any time; based on the time-speed information and heading information of different ships, combined with satellite imaging parameters, velocity component decomposition and linear interpolation are used to establish time-distance speed and speed-azimuth speed mapping relationships; and by merging the speed values ​​in the above directions, the ship speed values ​​corresponding to different times are obtained.

[0011] As a further technical solution of the present invention, in step 5: combining the satellite azimuth at the time of satellite imaging, and the calculated actual ship position and heading, obtaining the ship on the SAR image closest along the distance direction as the target associated ship, and performing offset compensation on the ship azimuth; The azimuth position offset of the ship target is expressed as: ; in, Indicates the azimuth position offset of the ship target. Indicates the minimum slant range between the radar and the target. It represents the distance speed of the ship target. represents the incident angle of the radar, Indicates radar speed.

[0012] As a further technical solution of the present invention, in step 6: the ship in the SAR scene at the imaging time is subjected to azimuth offset processing, and then the corrected SAR target position and the AIS deduced position are associated, and the SAR target position and the AIS deduced position with the smallest distance along the distance are the same ship; Based on the SAR satellite imaging plan, SAR imaging at time t is obtained; based on the established time-longitude and latitude, the imaging time t value is substituted to deduce the theoretical position of the ship at the imaging time, and the tangent angle formed based on the position, and the ship heading at the time is further obtained through the front and rear relative positions; the time-speed mapping relationship is used to obtain the ship speed at the imaging time.

[0013] As a further technical solution of the present invention, in step seven: the satellite azimuth at the time of satellite imaging, and the calculated actual ship position and heading, are combined to calculate the distance difference with the corresponding ship position on the compensated SAR image, and the offset distance of the ship in the range direction at the time of SAR imaging is decomposed to obtain the offset distance, which is used as the quantified value of the system error in the range direction when SAR images a moving target.

[0014] The position of a ship based on AIS deduction is assumed to be , the corresponding position of the same ship on the SAR image formed under the SAR satellite imaging plan is ; The two sets of coordinate values ​​are transformed into , calculate the distance ; ; Combined heading angle And the satellite azimuth corresponding to the imaging time , calculate the degree of displacement in distance ; ; Finally, the degree of system displacement in the range and azimuth directions when SAR images a moving target is quantified. .

[0015] The present invention has the following beneficial effects: This algorithm uses a cubic spline interpolation algorithm to form a complete ship trajectory within the AIS time interval; the speed is interpolated from the range and azimuth dimensions according to the satellite orbit to form two sets of mapping relationships, which are combined to form the speed at any specified time; the heading information at any specified time can be effectively obtained by performing tangent calculations on the position at any time on the trajectory; by processing the AIS data, the ship information of the SAR data at the imaging time can be extracted, such as the latitude and longitude information, heading, speed information of the ship at that time, and the speed information in the SAR range and azimuth directions; the real ship position on the SAR image is revised based on the satellite-borne SAR imaging parameters, and the range and azimuth system errors of the satellite-borne SAR ocean scene are calculated by comparing the AIS data extrapolation results and the actual imaging results of the ship in the SAR image after compensating for motion deviations, and can provide support for the subsequent geometric precision correction of satellite-borne SAR image products.

[0016] In summary, the method of the present invention combines the AIS multi-dimensional attribute mapping method and the compensation processing method for the position offset caused by the movement of the spaceborne SAR, realizes the rapid and accurate association and recognition of the ship target data in the spaceborne SAR ocean image, obtains the more accurate position and attribute information of the ship target, and improves the ocean application capability of the spaceborne SAR. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a method step diagram of the present invention; Figure 2 It is a schematic diagram of the relationship between the heading and the satellite azimuth in the present invention; Figure 3 It is the imaging result of the SAR mission plan in the present invention; Figure 4 This is a schematic diagram of the performance of the two ships to be simulated on the SAR image; Figure 5 is a schematic diagram of the ship trajectory after repair by the cubic spline interpolation method within the AIS time interval; Figure (a) shows the complete trajectory of INTERASIA HORIZON; Figure (b) shows the complete trajectory of HUGE; FIG6 is a schematic diagram of the time-longitude (speed) mapping relationship of each ship; ... Figure 7 is a schematic diagram of the ship status deduction results on the SAR image at the imaging time based on the AIS data. Figure (e) shows the deduced position of INTERASIA HORIZON at the SAR imaging time; Figure (f) shows the deduced position of HUGE at the SAR imaging time. DETAILED DESCRIPTION

[0018] The present invention is described in detail below with reference to the accompanying drawings and embodiments. The present invention provides a method for rapid association and recognition of marine ship targets by fusion application of AIS data and satellite-borne SAR image data, which integrates the AIS multi-dimensional attribute mapping method and the compensation processing method for position offset caused by satellite-borne SAR motion, realizes rapid and accurate association and recognition of ship target data in satellite-borne SAR marine images, obtains relatively accurate position and attribute information of ship targets, and improves the marine application capability of satellite-borne SAR.

[0019] See also Figure 1 The method for rapid association and identification of marine vessel targets by fusion processing of AIS and satellite-borne SAR data of the present invention mainly comprises the following steps: Step 1: Obtain AIS data based on SAR satellite imaging time: Based on the SAR satellite imaging plan, it mainly includes the imaging longitude and latitude range, imaging time, and the satellite azimuth angle at the imaging time. Filter and download the ship AIS data collected by the US Coast Guard within the longitude and latitude range; Step 2: AIS data cleaning and processing: AIS data often has errors. Common errors can be summarized as repeated AIS data during travel, speed exceeding the normal range, track position deviation, and acceleration exceeding the normal range. Based on time-longitude (latitude) data, the Vondrak data smoothing method is used to pre-process the data, and the correct AIS sequence is obtained after deleting the erroneous AIS data; In the Vondrak data smoothing method, for a certain data series ,in It's time. is the longitude or latitude. The basic assumption of the Vondrak data smoothing method is: ; in: , where: is the smoothed value; express The third derivative of ; It is power; is the coefficient to be determined; It is called the degree of approximation; It's called smoothness. It is called the smoothing coefficient, and the value of the smoothing coefficient determines the smoothness of the data curve.

[0020] The cleaned data is vectorized, and the existing data is classified according to existing attributes such as relative position information and ship type, and discontinuous trajectories under different ships are extracted.

[0021] Step 3: Restoration of ship trajectory within the AIS time interval: After data cleaning, a relatively accurate AIS data sequence is obtained. Based on the cubic spline interpolation method, the AIS data is sorted by time, the longitude and latitude of the starting time are selected as the coordinate origin, and the time difference of the AIS data before and after calculation is used as the interpolation sequence. The cubic spline interpolation of the time-longitude trajectory and the time-latitude trajectory are obtained respectively. The navigation trajectory of the ship is obtained by merging the above two cubic spline curves.

[0022] The specific principle of cubic spline interpolation is as follows. Taking the longitude of a ship as an example, assume that the longitude of the ship is is a function of time, and in the time period The inner cubic spline function ,but According to the boundary conditions, and The time should meet: ; According to the boundary value of the sequence segment to be interpolated The spline function coefficients can be obtained to determine the longitude About time The function expression of is then used to obtain the longitude value of the corresponding trajectory point according to the interpolation time interval. The interpolation method of the latitude value of the trajectory sequence is similar to this and will not be repeated here.

[0023] Step 4: Ship state deduction within the AIS time interval: Based on the above trajectory, establish the tangent equation of any point to obtain the corresponding heading at any time. Based on the time-speed information and heading information of different ships, combined with satellite imaging parameters, velocity component decomposition and linear interpolation are used to establish the time-distance speed and speed-azimuth speed mapping relationship. And by combining the speed values ​​in the above directions, the ship speed values ​​corresponding to different times are obtained.

[0024] like Figure 2 and Table 1, assuming that the time is , the speed is , the heading angle is , the satellite azimuth corresponding to the imaging time is The speed in the distance direction is calculated as shown in formula (1), and the speed in the azimuth direction is calculated as shown in formula (2). and the speed in the north-south latitude direction Perform linear interpolation on t to obtain the linear function of velocity in each direction with respect to time. The speed in the distance direction at any time t , the calculation formula is shown in formula (3); for The velocity in the azimuth direction at any time t Finally, by combining the velocity components in the two directions, we can get the speed of the ship at any time t: , the calculation formula is shown in formula (4).

[0025] Table 1 ; Step 5: Revision of the true position of the ship based on the principle of spaceborne SAR imaging: Since the range motion of the ship target will cause its Doppler center frequency to shift, the ship target will shift in azimuth in the SAR image. The azimuth position shift of the ship target can be expressed as: ; in, Indicates the azimuth position offset of the ship target. Indicates the minimum slant range between the radar and the target. It represents the distance speed of the ship target. represents the incident angle of the radar, Indicates radar speed.

[0026] Combined with the satellite azimuth at the moment of satellite imaging, and the calculated actual ship position and heading, the ship on the nearest SAR image along the distance direction is obtained as the target associated ship, and the azimuth of the ship is offset compensated.

[0027] Step 6: Accurately associate AIS and satellite-borne SAR data with ocean vessel targets: Perform azimuth offset processing on the vessels in the SAR scene at the time of imaging, and then associate the corrected SAR target position with the AIS deduced position. The SAR target position and AIS deduced position with the smallest distance along the distance are the same ship.

[0028] Based on the SAR satellite imaging plan, SAR imaging is performed at time t. Based on the time-longitude and latitude established in the previous steps, the value of imaging time t is substituted to deduce the theoretical position of the ship at the imaging time, and the tangent angle formed based on the position, and the ship's heading at the time is further obtained through the front and rear relative positions. The ship's speed at the imaging time is obtained using the time-speed mapping relationship.

[0029] Step 7. Calculation of geometric error of satellite-borne SAR ocean image system: Combine the satellite azimuth at the time of satellite imaging, as well as the calculated actual ship position and heading, and perform distance difference with the corresponding ship position on the compensated SAR image, and decompose to obtain the offset distance of the ship in the range direction at the time of SAR imaging. This offset distance is used as the quantified value of the system error in the range direction when SAR images moving targets.

[0030] Assume that the position of a ship based on AIS is , the corresponding position of the same ship on the SAR image formed under the SAR satellite imaging plan is The two sets of coordinate values ​​are converted into , calculate the distance . ; Combined heading angle And the satellite azimuth corresponding to the imaging time , calculate the degree of displacement in distance . ; Finally, the degree of system displacement in the range and azimuth directions when SAR images a moving target is quantified. .

[0031] Based on the imaging time and regional position of each target on the satellite-borne SAR image, this method obtains the AIS data within the imaging range through the service platform, and obtains effective AIS attribute information by cleaning the AIS data and eliminating gross errors. The ship trajectory established based on the AIS data is a discrete spatiotemporal sequence. The mapping relationship under different dimensions is constructed by combining longitude and latitude, time, and speed, so as to form a continuous ship trajectory corresponding to the AIS time period within the longitude and latitude range. At the same time, the longitude and latitude, speed, and heading of different ships at the SAR imaging time are deduced using the mapping relationship under each dimension that has been constructed. In addition, since the range movement of the ship moving target will cause its Doppler center frequency to shift, it is manifested in the azimuth shift of the ship target in the SAR image. This method combines the satellite parameters at the satellite imaging time and the position and heading information of the deduced ship to relocate the position of the ship in the SAR image, making full use of multi-dimensional feature information to improve the association and recognition accuracy.

[0032] Example See also Figure 3 , This embodiment selects AS01 SAR data as the test, the data uses TOPS mode, the range resolution is 4.6m, the azimuth resolution is 10.0m, and the polarization mode is HH. The satellite is scheduled to start imaging a certain area at 02:52:37.698 (UTC) on February 27, 2024. The longitude range of the area is: 113.951°~115.166°, the latitude range is: 20.973°~22.459°, the satellite azimuth corresponding to the imaging time is 192.65°, and the central incidence angle of the radar is The angle is 28.75°, the short-range distance is 581675m, and the radar speed is 7171.6m / s. The final image is as follows Figure 3 shown.

[0033] See also Figure 4, based on the latitude and longitude range, the corresponding AIS data is downloaded, and the AIS data is cleaned and processed, and finally the ships within the latitude and longitude range are screened out. This time, the imaging moments corresponding to two ships (ship names: INTERASIA HORIZON, HUGE) are selected to implement the verification experiment of this algorithm.

[0034] The specific implementation and process results are as follows: After data cleaning, a relatively accurate AIS data sequence is obtained, and detailed information is shown in Table 2.

[0035] Please refer to FIG5 , based on the cubic spline interpolation method, cubic spline interpolation is performed in combination with the cleaned AIS data information to obtain the navigation track of the ship.

[0036] According to the AIS information corresponding to the ship, a function expression of longitude with respect to time is established, and then the longitude value of the corresponding trajectory point is obtained according to the interpolation time interval. Based on the above trajectory, a tangent equation of any point is established to obtain the corresponding heading at any time. Then, based on the time-speed information of different ships, combined with the heading information and the satellite azimuth corresponding to the imaging time, velocity component decomposition and linear interpolation are used to establish the time-distance speed and time-azimuth speed mapping relationships. By combining the speed values ​​in the above directions, the ship speed values ​​corresponding to different times are obtained. The relationship between time and longitude and the relationship between time and speed are shown in Figure 6 below; Each ship in the AIS data is arranged in ascending order according to the longitude, and the time difference of the ship at the time of SAR satellite planned imaging is calculated based on the first signal time corresponding to the minimum longitude in the time range, as shown in Table 2. Combined with the established mapping model between time and various attribute information, the status of each ship at the time of SAR imaging can be deduced, as shown in Figure 7 below, where the red dot is the location of the SAR imaging time; Based on the time-longitude and latitude established in the previous steps, the time difference of each ship is brought in to deduce the theoretical position of the ship at the imaging moment, and the tangent angle formed based on the position, and the ship's heading at the moment is further obtained through the front and rear relative positions. The time-range (azimuth) speed mapping relationship is used to obtain the speed of the ship in the SAR range and azimuth directions at the imaging moment, as well as the actual speed.

[0037] Through calculation and deduction, the ship status at the time of SAR imaging is shown in Table 3, where positive values ​​represent imaging along the range (azimuth) direction, and negative values ​​represent the opposite direction (the same below): Table 3 Results of ship status deduction on SAR images at the imaging time based on AIS data ; The radial velocity will cause the ship target to have a position offset in the azimuth direction of the SAR image. Combined with the satellite azimuth of 192.65° at the time of satellite imaging, the closest slant distance between the radar and the target is 581675m, the central incident angle of the radar is 28.75°, the radar speed is 7171.6m / s, and the range speed of each ship target. According to the relationship between the radial velocity and the range speed, the azimuth position offset of each ship is obtained as shown in the following table: Table 4 Estimated azimuth offset of each ship ; Combined with the satellite azimuth at the time of satellite imaging, and the calculated actual ship position and heading, the ship on the SAR image closest to the distance is obtained as the target associated ship, and the azimuth offset compensation is performed on the ship azimuth. The position transformation before and after compensation is shown in the following table: Table 5 Changes in longitude and latitude before and after offset compensation ; By comparing the compensation of azimuth offset before and after, it can be seen that in addition to the position offset of the ship target in the azimuth direction of the SAR image caused by the radial velocity of the radar itself, there is also a range offset in the imaging process. The range difference between the position of the ship target in the compensated SAR image and the ship position in the AIS is calculated to obtain the range and azimuth offsets, which are the system errors introduced in the SAR imaging process. Table 6 Estimation of the system offset of each ship's distance

Claims

1. A method for associating and identifying ocean vessels based on AIS and spaceborne SAR data, characterized in that: The following steps are involved: Step 1: Obtain AIS data based on SAR satellite imaging time; Step 2: AIS data cleaning and processing; Step 3: Ship track recovery within the AIS time interval; Step 4: Ship status deduction within the AIS time interval; deduction includes the establishment of time-distance or time-azimuth velocity mapping relationships; Step 5: Revise the real position of the ship based on the principle of spaceborne SAR imaging; Step 6: Accurate correlation processing of ocean vessel targets with AIS and satellite-borne SAR data; Step 7: Calculation of geometric errors of spaceborne SAR ocean image system.

2. The method for associating and identifying ocean vessels based on AIS and spaceborne SAR data according to claim 1, characterized in that: Step one specifically includes the following steps: based on the imaging longitude and latitude range of the SAR satellite, the imaging time, and the azimuth angle of the satellite corresponding to the imaging time, screening and downloading the AIS data of ships within the longitude and latitude range.

3. The method for associating and identifying ocean vessels based on AIS and spaceborne SAR data according to claim 1, characterized in that: Step 2 specifically includes the following steps: Based on the time-longitude (latitude) data, the Vondrak data smoothing method is used to pre-process the data, and the correct AIS sequence is obtained after deleting the erroneous AIS data; The cleaned data is vectorized, the existing data is classified according to the relative position information and existing attributes of the ship type, and the discontinuous trajectories of different ships are extracted.

4. The method for associating and identifying ocean vessels based on AIS and spaceborne SAR data according to claim 3, characterized in that: In the Vondrak data smoothing method, for a certain data series ,in It's time. is the longitude or latitude; the basic assumption of the Vondrak data smoothing method is: ； in: , where: is the smoothed value; express The third derivative of ; It is power; is the coefficient to be determined; It is called the degree of approximation; It is called smoothness; It is called the smoothing coefficient, and the value of the smoothing coefficient determines the smoothness of the data curve.

5. The method for associating and identifying ocean vessels based on AIS and spaceborne SAR data according to claim 1, characterized in that: Step three specifically includes the following steps: based on the cubic spline interpolation method, the AIS data is sorted according to time, the longitude and latitude of the starting time are selected as the coordinate origin, and the time difference of the AIS data before and after calculation is used as the interpolation sequence to obtain the cubic spline interpolation of the time-longitude trajectory and the time-latitude trajectory respectively, and the navigation trajectory of the ship is obtained by merging the above two cubic spline curves.

6. The method for associating and identifying ocean vessels based on AIS and spaceborne SAR data according to claim 1, characterized in that: Step 4 specifically includes the following steps: establishing a tangent equation at any point based on the navigation trajectory to obtain the corresponding heading at any time; based on the time-speed information and heading information of different ships, combined with satellite imaging parameters, using velocity component decomposition and linear interpolation to establish time-distance speed and speed-azimuth speed mapping relationships; and by merging the speed values ​​in the above directions, obtaining the ship speed values ​​corresponding to different times.

7. The method for associating and identifying ocean vessels based on AIS and spaceborne SAR data according to claim 1, characterized in that: Step 5 specifically includes the following steps: combining the satellite azimuth at the time of satellite imaging, and the calculated actual ship position and heading, obtaining the ship on the SAR image closest along the distance direction as the target associated ship, and performing offset compensation on the ship azimuth; The azimuth position offset of the ship target is expressed as: ； in, Indicates the azimuth position offset of the ship target. Indicates the minimum slant range between the radar and the target. It represents the distance speed of the ship target. represents the incident angle of the radar, Indicates radar speed.

8. The method for associating and identifying ocean vessels based on AIS and spaceborne SAR data according to claim 1, characterized in that: Step six specifically includes the following steps: The ships in the SAR scene at the time of imaging are processed in azimuth offset, and then the corrected SAR target position and AIS deduced position are associated. The SAR target position and AIS deduced position with the smallest distance along the range are the same ship. Based on the SAR satellite imaging plan, SAR imaging at time t is obtained; based on the established time-longitude and latitude, the imaging time t value is substituted to deduce the theoretical position of the ship at the imaging time, and the tangent angle formed based on the position, and the ship heading at the time is further obtained through the front and rear relative positions; the time-speed mapping relationship is used to obtain the ship speed at the imaging time.

9. The method for associating and identifying ocean vessels based on AIS and spaceborne SAR data according to claim 1, characterized in that: Step seven specifically includes the following steps: combining the satellite azimuth at the time of satellite imaging, and the calculated actual ship position and heading, and performing distance difference with the corresponding ship position on the compensated SAR image, and decomposing the offset distance of the ship in the range direction at the time of SAR imaging, and the offset distance is used as the quantified value of the system error in the range direction when SAR images a moving target.

10. The method for associating and identifying ocean vessels based on AIS and spaceborne SAR data according to claim 9, characterized in that: Specifically: Assume that the position of a ship based on AIS is , the corresponding position of the same ship on the SAR image formed under the SAR satellite imaging plan is ; The two sets of coordinate values ​​are transformed into , calculate the distance ; ; Combined heading angle And the satellite azimuth corresponding to the imaging time , calculate the degree of displacement in distance ; ; Finally, the degree of system displacement in the range and azimuth directions when SAR images a moving target is quantified. .

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