Method, device and equipment for detecting and positioning sea surface moving ship of high-orbit SAR (Synthetic Aperture Radar) satellite and medium

Abstract

The invention provides a high-orbit SAR satellite sea surface moving ship detection and positioning method, device and equipment and a medium, and is applied to the technical field of synthetic aperture radars, and the method comprises the steps: determining a high-orbit SAR extended imaging region through dynamically calculating a union set region of satellite beam coverage and ship motion offset; dividing all synthetic aperture time into a plurality of sub-aperture time periods, and performing space division on the extended imaging region in each sub-aperture time period to obtain N sub-block imaging regions corresponding to the current sub-aperture time period; respectively carrying out imaging processing and ship detection positioning on each sub-block imaging area to obtain ship position and speed information in each sub-block; synthesizing the information of the N sub-block imaging regions in each sub-aperture time period to obtain a comprehensive result of the extended imaging region in the sub-aperture time period; and based on the sequential relationship of ship positioning results at the center moments of the sub-apertures, carrying out ship target association across the sub-apertures, and forming a space-time continuous ship navigation trajectory.

Description

[0001] This disclosure claims priority to patent application number 202511753701.7, the contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to the field of synthetic aperture radar technology, and more specifically to a method, apparatus, equipment and medium for detecting and locating ships moving on the sea surface using high-orbit SAR satellites. Background Technology

[0003] Existing methods for detecting and locating ships on the sea surface using Synthetic Aperture Radar (SAR) satellites are primarily designed for ship observation data acquired by low-Earth orbit (LEO) SAR satellites. In contrast, high-Earth orbit (HEO) SAR satellites operate in geosynchronous orbits at an altitude of approximately 36,000 km, with an orbital period equal to the Earth's rotation period. Their radar beam ground projection velocity is approximately 15 m / s to 200 m / s, and their L-band synthetic aperture time is approximately several minutes to tens of minutes. Therefore, existing ship detection and location methods for LEO SAR satellites are no longer applicable to HEO satellites.

[0004] In a fixed Earth coordinate system, high-orbit SAR operates at a very slow speed within a fixed latitude and longitude range, repeating its course daily. It can simultaneously observe the Earth and transmit data within an imaging timeframe of tens of minutes. However, due to the extremely wide swath of high-orbit SAR, sea clutter accumulates a significant amount of energy. Range compression can only achieve one-dimensional accumulation of ship energy, which is often lower than the sea clutter energy, making effective detection difficult. Furthermore, because the relative velocity between the satellite and the ground is slow in high-orbit SAR, the contribution of ship motion cannot be ignored. The azimuth and phase modulation caused by this motion is very significant over long synthetic aperture times, resulting in severe defocusing of moving ships in high-orbit SAR images. In addition, the positioning deviation caused by ship motion is proportional to the slant range and inversely proportional to the relative velocity between the satellite and the ground. In high-orbit SAR, this positioning deviation can reach hundreds of kilometers, easily exceeding the set imaging area and causing positional ambiguity. In such cases, the distance migration of moving ships cannot be corrected along with the stationary scene, easily leading to low accuracy and lag in the detection and positioning of moving ships on the sea surface using high-orbit SAR. Summary of the Invention

[0005] This disclosure provides a method, device, equipment, and medium for detecting and locating ships moving on the sea surface using high-orbit SAR satellites.

[0006] According to the first aspect of this disclosure, a method for detecting and locating ships moving on the sea surface using a high-orbit SAR satellite is provided, comprising: determining the extended imaging region of the high-orbit SAR imaging by dynamically calculating the union region of satellite beam coverage and ship motion offset; dividing the high-orbit SAR fully synthetic aperture time into multiple sub-aperture time periods, and spatially dividing the extended imaging region within each sub-aperture time period to obtain N sub-block imaging regions corresponding to the current sub-aperture time period; wherein, the sub-aperture time period is determined based on the quadratic phase error caused by ship motion, and N is a positive integer greater than 1; performing imaging processing and ship detection and location on each sub-block imaging region to obtain ship information in each sub-block imaging region, the ship information including actual position information and velocity information; synthesizing the ship information of the N sub-block imaging regions within each sub-aperture time period to obtain a complete sub-aperture image within that sub-aperture time period, the complete sub-aperture image being the ship detection and location result within the current sub-aperture length; and performing cross-sub-aperture ship target association and matching based on the temporal relationship between the center time of each sub-aperture and the corresponding ship detection and location result to construct a spatiotemporally continuous ship navigation trajectory.

[0007] According to embodiments of this disclosure, high-orbit SAR imaging includes imaging data from multiple consecutive time points. The extended imaging region of the high-orbit SAR imaging is determined by dynamically calculating the union region of satellite beam coverage and ship motion offset. This includes: calculating the latitude and longitude grid of the beam center's projection point on the ground based on the satellite position and attitude, antenna pointing, and radiation pattern at each time point to determine the satellite beam coverage area; calculating the latitude and longitude grid of the moving ship after position offset at a specific cruising speed and in different cruising directions based on the position offset decomposition results at each time point, obtaining a first set containing multiple latitude and longitude grids, where the first set represents the ship motion offset region at each time point; wherein the position offset decomposition results are obtained based on the moving ship influence modeling process; merging the satellite beam coverage area and the ship motion offset region at the same time point to obtain the extended region at each time point; merging the extended regions at each time point in the high-orbit SAR imaging time to obtain the extended imaging region of the high-orbit SAR imaging, wherein the extended imaging region is a second set containing multiple latitude and longitude grids.

[0008] According to embodiments of this disclosure, the high-orbit SAR fully synthetic aperture time is divided into multiple sub-aperture time periods. Within each sub-aperture time period, the extended imaging region is spatially divided to obtain N sub-block imaging regions corresponding to the current sub-aperture time period. This includes: determining the target sub-aperture length based on the secondary phase error caused by the moving ship; responding to the received SAR echo signal reaching the target duration corresponding to the target sub-aperture length in time, dividing multiple latitude and longitude grids of the extended region within the target sub-aperture length according to the proximity principle, and uniformly dividing the multiple latitude and longitude grids into N sub-blocks to obtain N sub-block imaging regions.

[0009] According to embodiments of this disclosure, the ship information includes actual position information and velocity information. Imaging processing and ship detection and positioning are performed on each sub-block imaging region to obtain ship information in each sub-block imaging region. This includes performing the following operations on each sub-block imaging region: discretizing the sub-block imaging region into a two-dimensional pixel matrix, and obtaining a sub-block image of the sub-block imaging region based on the imaging results of each pixel point in the sub-block imaging region; performing ship detection on the sub-block image to obtain the ship's position information; calculating the ship's range Doppler parameters based on a preset stationary target point, the satellite position vector at the sub-aperture center time, and the velocity vector, the range Doppler parameters being used to establish a position mapping relationship between the moving ship before and after repositioning; and determining the ship's actual position information and velocity information based on the ship's position information and range Doppler information.

[0010] According to embodiments of this disclosure, imaging processing and ship detection and positioning are performed in parallel by calling multiple computing units, including: in response to obtaining N sub-block imaging regions, the N sub-block imaging regions are sequentially pushed to idle computing units among the multiple computing units according to a preset time interval, so that the computing units perform imaging processing and ship detection and positioning on the received sub-block imaging regions.

[0011] According to embodiments of this disclosure, based on the temporal relationship between the center time of each sub-aperture and the corresponding ship detection and positioning results, cross-sub-aperture ship target association and matching are performed to form a spatiotemporally continuous ship navigation trajectory. This includes: establishing the temporal relationship between the center time of each sub-aperture and the ship information of the sub-aperture; associating and matching discrete points belonging to the same trajectory on multiple sub-aperture images to obtain a ship navigation trajectory composed of discrete points belonging to the same trajectory, where the discrete points are signal points representing ships in the sub-aperture images.

[0012] According to embodiments of this disclosure, the method further includes: establishing a geodetic coordinate system with the instantaneous position of the moving vessel in the SAR imaging data as the origin, and converting the satellite position vector, velocity vector, moving target position vector, and velocity vector in the SAR imaging data to the geodetic coordinate system; decomposing the position offset of the moving vessel into directions parallel to the slant range ground projection direction and perpendicular to the slant range ground projection direction to obtain the position offset decomposition result of the moving vessel; and calculating the secondary phase error based on the velocity of the moving vessel and the SAR velocity.

[0013] According to a second aspect of this disclosure, a device for detecting and locating ships moving on the sea surface using a high-orbit SAR satellite is provided, comprising: a determination module, used to determine the extended imaging region of the high-orbit SAR imaging by dynamically calculating the union region of satellite beam coverage and ship motion offset; a division module, used to divide the high-orbit SAR fully synthetic aperture time into multiple sub-aperture time periods, and spatially divide the extended imaging region within each sub-aperture time period to obtain N sub-block imaging regions corresponding to the current sub-aperture time period; wherein, the sub-aperture time period is determined based on the quadratic phase error caused by ship motion, and N is a positive integer greater than 1; and a processing detection module. The system is used to perform imaging processing and ship detection and positioning on each sub-block imaging region to obtain ship information in each sub-block imaging region. The ship information includes actual position information and speed information. The synthesis module is used to synthesize the ship information of N sub-block imaging regions within each sub-aperture time to obtain a complete sub-aperture image within that sub-aperture time. The complete sub-aperture image is a continuous ship detection result in geospatial space within the current sub-aperture length. The association module is used to perform cross-sub-aperture ship target association and matching based on the temporal relationship between the center time of each sub-aperture and the corresponding ship detection and positioning result to form a spatiotemporally continuous ship navigation trajectory.

[0014] According to a third aspect of this disclosure, an electronic device is provided, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the methods described above.

[0015] According to a fourth aspect of this disclosure, a computer-readable storage medium is provided that stores a computer program or instructions thereon, characterized in that the computer program or instructions, when executed by a processor, implement the steps of the method described above.

[0016] The high-orbit SAR satellite method for detecting and locating ships moving on the sea surface provided in this disclosure has at least the following beneficial effects:

[0017] By expanding the imaging area and using sub-aperture imaging, the defocusing effect caused by positional ambiguity and long synthetic aperture time is reduced, improving the signal-to-clutter ratio of moving ships and solving the problem of difficult detection of moving ships in high-orbit SAR, thus improving the accuracy of ship detection. By using the ship's range Doppler information, the ship's position in the sub-aperture sub-block image is transformed into a combination of the ship's actual position and velocity at the center time of the selected sub-aperture, improving the accuracy of ship detection and positioning. Attached Figure Description

[0018] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0019] Figure 1 A flowchart illustrating a method for detecting and locating moving ships on the sea surface using a high-orbit SAR satellite according to an embodiment of the present disclosure is shown.

[0020] Figure 2 The schematic diagram illustrates the principle of a high-orbit SAR satellite method for detecting and locating moving ships on the sea surface according to an embodiment of the present disclosure;

[0021] Figure 3 This schematic diagram illustrates the concept of the relative positioning relationship between moving and stationary targets under non-flat imaging geometry of high-orbit SAR;

[0022] Figure 4 This schematically illustrates a flowchart of determining the extended imaging region of high-orbit SAR imaging by dynamically calculating the union region of satellite beam coverage and ship motion offset according to an embodiment of the present disclosure.

[0023] Figure 5 This schematically illustrates a flowchart of dividing the extended imaging region into N sub-block imaging regions corresponding to the current sub-aperture time period according to an embodiment of the present disclosure, based on the target sub-aperture length.

[0024] Figure 6 This schematically illustrates a flowchart of imaging processing and ship detection and localization performed on each sub-block imaging region according to an embodiment of the present disclosure to obtain ship information in each sub-block imaging region;

[0025] Figure 7 The flowchart illustrates the temporal relationship between the center time of each sub-aperture based on its length and the ship detection results, according to an embodiment of the present disclosure, and the process of correlating and matching discrete points on the sub-aperture images of different sub-block imaging regions.

[0026] Figure 8 This schematic diagram illustrates the structural block diagram of a high-orbit SAR satellite-based device for detecting and locating ships moving on the sea surface according to an embodiment of the present disclosure.

[0027] Figure 9 A block diagram of an electronic device according to an embodiment of the present disclosure is shown schematically. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of a feature, step, operation, and / or component, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0030] In this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0031] In the description of this disclosure, it should be understood that the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the subsystem or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0032] Throughout the accompanying drawings, identical elements are represented by the same or similar reference numerals. Conventional structures or configurations have been omitted where they may cause confusion in understanding this disclosure. Furthermore, the shapes, dimensions, and positional relationships of the components in the drawings do not reflect actual size, scale, or actual positional relationships. Additionally, any reference symbols enclosed in parentheses should not be construed as limiting.

[0033] Similarly, to simplify this disclosure and aid in understanding one or more of the various aspects of the disclosure, in the above description of exemplary embodiments of the present disclosure, various features of the present disclosure are sometimes grouped together in a single embodiment, figure, or description thereof. The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refers to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present disclosure. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0035] This disclosure provides a method for detecting and locating ships moving on the sea surface using a high-orbit SAR satellite. The method includes: determining the extended imaging region of the high-orbit SAR imaging by dynamically calculating the union region of satellite beam coverage and ship motion offset; dividing the high-orbit SAR fully synthetic aperture time into multiple sub-aperture time periods, and spatially dividing the extended imaging region within each sub-aperture time period to obtain N sub-block imaging regions corresponding to the current sub-aperture time period; performing imaging processing and ship detection and location on each sub-block imaging region to obtain ship information in each sub-block imaging region, wherein the ship information includes actual position information and velocity information; synthesizing the ship information of the N sub-block imaging regions within each sub-aperture time period to obtain the ship detection and location result of the complete imaging region within that sub-aperture time period; and performing cross-sub-aperture ship target association and matching based on the temporal relationship between the center time of each sub-aperture and the corresponding ship detection and location result to construct a spatiotemporally continuous ship navigation trajectory.

[0036] This embodiment of the disclosure reduces positional ambiguity and defocusing effects caused by long synthetic aperture times by extending the imaging region and using sub-aperture imaging, thereby improving the signal-to-clutter ratio of moving ships and solving the problem of difficult detection of moving ships using high-orbit SAR, thus improving the accuracy of ship detection. A "ping-pong" operation of sub-aperture data storage and sub-aperture imaging processing is achieved through the alternating operation of the storage unit and the computing unit. The extended imaging region is divided into blocks for parallel processing through physical / logical allocation of the computing unit, achieving accurate data flow control and real-time processing. By establishing a high-orbit SAR moving ship positioning model, the ship position in the sub-aperture sub-block image is transformed into a combination of the ship's actual position and velocity at the center time of the candidate sub-aperture. All sub-aperture images are then combined for filtering and refinement. A numerical calculation scheme is used to solve the problem of the difficulty in analytically solving the relocation model, improving the accuracy of ship position and velocity information.

[0037] Figure 1 A flowchart illustrating a method for detecting and locating moving ships on the sea surface using a high-orbit SAR satellite according to an embodiment of the present disclosure is shown. Figure 2 The schematic diagram illustrates the principle of a high-orbit SAR satellite method for detecting and locating ships moving on the sea surface according to an embodiment of the present disclosure.

[0038] like Figure 1As shown, the high-orbit SAR satellite sea surface motion vessel detection and positioning method of this embodiment includes operations S110 to S150.

[0039] In operation S110, the extended imaging area of ​​high-orbit SAR imaging is determined by dynamically calculating the union area of ​​satellite beam coverage and ship motion offset.

[0040] In some embodiments, the satellite's coverage area over the ground at a given moment can be calculated in real time based on satellite orbit parameters, antenna pointing, and beamwidth. Combining the ship's real-time position, speed, heading, and acceleration, the ship's trajectory during SAR imaging (i.e., the period during which the satellite beam sweeps across the ship) is predicted, and the potential deviation of the ship from its initial predicted position is calculated. The satellite beam coverage area and the ship's motion offset area are then combined to obtain an extended imaging area that includes both the satellite beam and the ship's potential motion range. This extended imaging area ensures that even if the ship deviates from the original imaging area due to motion, it can still be detected, avoiding missed detections.

[0041] In operation S120, the high-orbit SAR fully synthetic aperture time is divided into multiple sub-aperture time periods. Within each sub-aperture time period, the extended imaging area is spatially divided to obtain N sub-block imaging areas corresponding to the current sub-aperture time period. The sub-aperture time period is determined based on the secondary phase error caused by ship motion, and N is a positive integer greater than 1.

[0042] In some embodiments, ship motion (especially acceleration) causes changes in Doppler frequency, resulting in a secondary phase error. This error affects the resolution and phase consistency of SAR images. By analyzing the impact of the secondary phase error on image quality, an optimal sub-aperture length can be determined, thereby controlling the phase error within each sub-block and improving image quality and the accuracy of ship detection.

[0043] In some embodiments, the received data can be divided into time and space dimensions in sequence to reduce the amount of data processed in a single operation and improve processing efficiency and timeliness.

[0044] In the time dimension, large datasets can be segmented into smaller sub-aperture data through sub-aperture partitioning to reduce the data size processed in a single run. For example, once the collected data reaches the set sub-aperture length (i.e., the amount of data within the time period corresponding to the sub-aperture length), the processing flow can be initiated without waiting for all data to be collected for an extended period. Data processing for different sub-apertures can be performed in parallel, effectively improving processing efficiency and flexibility. For sub-aperture data within each target sub-aperture length (i.e., sub-aperture time period), further spatial partitioning can be performed, dividing the expanded area into N sub-block imaging regions. Sub-aperture data at each moment may contain a large scene on Earth, with rich and complex information. By spatially partitioning this large scene at each moment into N sub-block imaging regions, parallel processing of different sub-block imaging regions can be achieved, improving the timeliness and accuracy of data processing.

[0045] In operation S130, imaging processing and ship detection and positioning are performed on each sub-block imaging area to obtain ship information in each sub-block imaging area, including actual position information and speed information.

[0046] In some embodiments, SAR imaging algorithms (such as the BP algorithm) can be used to focus on each sub-block imaging region to obtain sub-aperture images of each sub-block imaging region. Traditional CFAR methods or neural network correlation methods can be used to detect ships in the sub-block regions. Based on the SAR imaging principle of equal-distance equal-Doppler and the influence model of moving ships, the actual position and speed information of the detected ships are determined.

[0047] In operation S140, the ship information of N sub-imaging regions within each sub-aperture time period is synthesized to obtain a complete sub-aperture image within that sub-aperture time period. The sub-aperture image is a continuous ship detection and positioning result in geospatial space within the current sub-aperture length.

[0048] In some embodiments, vessel information may include the vessel's actual position and speed. By arranging the vessel detection results of sub-block areas according to latitude and longitude (i.e., actual position information), continuous vessel detection and positioning results in geospatial space can be formed, facilitating subsequent vessel tracking, positioning, and track generation.

[0049] In operation S150, based on the temporal relationship between the center time of each sub-aperture and the corresponding ship detection and positioning results, ship targets across sub-apertures are associated and matched to form a spatiotemporally continuous ship navigation trajectory.

[0050] In some embodiments, for each sub-block imaging region within each sub-aperture time period, the ship detection results are arranged according to latitude and longitude to form a continuous ship detection effect in geospatial space within the current sub-aperture time period, resulting in a sub-aperture image for that sub-aperture time period. Corresponding to the ship detection results for different sub-aperture time periods, the discrete points detected on different sub-aperture images are associated and matched through the temporal relationship between the sub-aperture center time and the sub-aperture ship information (i.e., the ship detection results at each sub-aperture length), thereby achieving temporal continuity between the sub-aperture images.

[0051] The center time of a sub-aperture can be the midpoint of the time range corresponding to that sub-aperture, representing a typical time point within the time period covered by that sub-aperture, used to identify and distinguish different sub-apertures. A temporal relationship between multiple sub-aperture images can be established based on the center times of each sub-aperture, associating and matching discrete points detected on different sub-aperture images. For example, based on the detection results of ships in different sub-aperture images and their corresponding center times, trajectory association algorithms (such as nearest neighbor association, Kalman filtering, etc.) can be used to connect discrete ship detection points in chronological order, obtaining a spatiotemporally continuous ship navigation trajectory. The ship navigation trajectory may include, for example, a trajectory start point, end point, intermediate point, and corresponding timestamp.

[0052] The method disclosed herein ensures that ships can still be detected by SAR even if they deviate from their initial predicted position due to motion by dynamically calculating the union region of satellite beam coverage and ship motion offset, thus avoiding missed detections and effectively improving the accuracy and reliability of ship detection. By associating and matching discrete points on different sub-block imaging regions through temporal relationships, a spatiotemporally continuous ship navigation trajectory is generated, effectively enhancing the continuity and real-time nature of the ship trajectory. Dividing the complete data into multiple sub-aperture data points along the time dimension and further spatially subdividing each sub-aperture data point to divide the extended area into multiple sub-block imaging regions effectively reduces the amount of data processed each time, improving the timeliness of data processing. By performing imaging processing and ship detection in parallel on multiple sub-block imaging regions, the processing efficiency of SAR images is significantly improved.

[0053] In some embodiments, a preprocessing operation may be performed before executing operation S110. The preprocessing operation may include two parts: global mesh generation and moving ship impact modeling.

[0054] The global surface can be divided into regular latitude and longitude grids through global grid partitioning, providing a spatial positioning framework and data management foundation for subsequent expansion of imaging areas and sub-block imaging areas. The number of global grid partitions can be calculated by setting the latitude and longitude grid cell size, and each grid can be assigned a corresponding index number and latitude and longitude range, allowing for quick retrieval and access to the target grid using the index number. For example, setting the latitude and longitude grid cell size to 0.01 degrees × 0.01 degrees results in a global partition of 36000 × 18100 grids, with the (i,j)th grid having a latitude and longitude range of... value range , .

[0055] In some embodiments, modeling the impact of moving vessels may include: establishing a geodetic coordinate system with the instantaneous position of the moving vessel in the SAR imaging data as the origin, and transforming the satellite position vector, velocity vector, moving target position vector, and velocity vector in the SAR imaging data to the geodetic coordinate system; decomposing the position offset of the moving vessel into directions parallel to the slant range ground projection direction and perpendicular to the slant range ground projection direction to obtain the position offset decomposition result of the moving vessel; and calculating the secondary phase error based on the velocity of the moving vessel and the velocity of the SAR satellite.

[0056] Figure 3 A conceptual diagram illustrating the relative positioning relationship of moving / stationary targets under non-flat imaging geometry of high-orbit SAR is shown.

[0057] See Figure 3 The coordinate system is a geodetic coordinate system, with the position of the instantaneously moving target P as the origin. Due to motion, the imaging position shifts and coincides with the stationary target Q. Based on the assumption that the instantaneous slant range and Doppler center frequency are equal, the instantaneous slant range and Doppler center frequency of P and Q are equal in the image acquired by the time-domain BP algorithm. Therefore, by establishing expressions for the positional offset of the moving target P and the quadratic phase error, a model can be provided for the analysis of images of moving ships.

[0058] For example, based on the latitude and longitude of the moving target P, a transformation matrix is ​​established from the WGS84 coordinate system to the geodetic coordinate system (with P as the origin). ; convert the satellite position vector in the WGS84 coordinate system and velocity vector Convert to position vector in geodetic coordinate system and velocity vector ; The position vector of the moving target P in the WGS848 coordinate system and velocity vector Convert to position vector in geodetic coordinate system and velocity vector ; Calculate the relative position vector between the satellite and the moving target This leads to the relative position vector after projection onto the XY plane. and velocity vector For ease of expression, the position offset of the moving target can be decomposed into... direction and In the vertical direction, the position offset decomposition result is obtained, where the decomposition is to The result of the direction can be expressed as Decomposed into The result in the vertical direction can be expressed as . The expression is:

[0059]

[0060] The expression is:

[0061]

[0062] The expression for the quadratic phase error QPE caused by motion is:

[0063]

[0064] Among them, T a λ is the synthetic aperture time, and λ is the wavelength of the radar signal.

[0065] Figure 4 The flowchart illustrates a process for determining the extended imaging region of high-orbit SAR imaging by dynamically calculating the union region of satellite beam coverage and ship motion offset according to an embodiment of the present disclosure.

[0066] like Figure 4 As shown, this embodiment determines the extended imaging area of ​​high-orbit SAR imaging by dynamically calculating the union area of ​​satellite beam coverage and ship motion offset, including operations S210 to S240.

[0067] In operation S210, based on the satellite position and attitude, antenna pointing and radiation pattern at each time, the latitude and longitude grid of the beam center projected on the ground is calculated to determine the satellite beam coverage area.

[0068] In operation S220, the latitude and longitude grids where the moving ship is located after its position offset at a specific cruising speed and in different cruising directions are calculated based on the decomposition results of the position offset of the moving ship at each time. This results in a first set containing multiple latitude and longitude grids, which represents the ship's motion offset region at each time. The position offset decomposition results are obtained based on the moving ship's influence modeling process.

[0069] In operation S230, the satellite beam coverage area and the ship motion offset area at the same time are merged to obtain the extended area at each time.

[0070] In operation S240, the extended regions at each time point in the high-orbit SAR imaging time are merged to obtain the extended imaging region of the high-orbit SAR imaging, wherein the extended imaging region is a second set containing multiple latitude and longitude grids.

[0071] In some embodiments, high-orbit SAR imaging comprises imaging data at multiple consecutive time points. For the imaging data at each time point, the extended region at that time point can be determined by calculating the satellite beam coverage area and the ship motion offset area at that time point. After the extended region at each time point is determined, the extended imaging region of the SAR imaging is obtained by merging the extended regions at each time point in the high-orbit SAR imaging time.

[0072] The following uses high-orbit SAR imaging, including t 0 Time and t 1 Taking a specific time point as an example, this paper further introduces the process of determining the extended region in high-orbit SAR extended imaging.

[0073] In t 0 At time, according to t 0 Based on the satellite's position and attitude, antenna pointing and radiation pattern, calculate the latitude and longitude grid index number of the beam center's projection point on the ground. Calculate the latitude and longitude grid set of the entire beam's projection onto the ground. The satellite beam coverage area is obtained;

[0074] Set the moving target (i.e., the ship) to latitude and longitude. Based on the ship's maximum cruising speed of 16 m / s and a cruising direction due east, calculate the latitude and longitude grid index number of the moving target after the position shift. This yields the latitude and longitude grid set of the imaging area to be expanded under the current settings. .

[0075] Iterate through all cruise directions (e.g., due north / due west / due south / northeast / northwest / southwest / southeast) and calculate the latitude and longitude grid set of the imaging area to be expanded in each direction. (like ), which is the area of ​​the ship's motion offset at the current moment.

[0076] For t 0 The satellite beam coverage area and the ship motion offset area are merged at a given time to obtain t. 0 The extended imaging region at time, the extended imaging region It can be represented by a set of latitude and longitude grids: , ;

[0077] In t 1 At time, according to t 1 Based on the satellite's position and attitude, antenna pointing and radiation pattern, calculate the latitude and longitude grid index number of the beam center's projection point on the ground. Calculate the latitude and longitude grid set of the entire beam's projection onto the ground. The satellite beam coverage area was obtained.

[0078] Set the motion target to latitude and longitude. Based on the ship's maximum cruising speed of 16 m / s and a cruising direction due east, calculate the latitude and longitude grid index number of the moving target after the position shift. This yields the latitude and longitude grid set of the imaging area to be expanded under the current settings. .

[0079] Iterate through all cruise directions (e.g., due north / due west / due south / northeast / northwest / southwest / southeast) and calculate the latitude and longitude grid set of the imaging area to be expanded in each direction. (like This gives the area of ​​the ship's motion offset at the current moment.

[0080] For t 1 The satellite beam coverage area and the ship motion offset area are merged at a given time to obtain t. 1 Extended imaging region latitude and longitude grid set at time t. , , i.e. t 1 The extended region of time.

[0081] Throughout the imaging time, the final determined extended imaging region, taking into account the positional offset of the moving target, can be represented as a set of latitude and longitude grids. .

[0082] Figure 5 The flowchart illustrates a process of spatially dividing an extended imaging region within each sub-aperture time period according to an embodiment of the present disclosure to obtain N sub-block imaging regions corresponding to the current sub-aperture time period.

[0083] like Figure 5 As shown, in this embodiment, the extended imaging region is spatially divided within each sub-aperture time period to obtain N sub-block imaging regions corresponding to the current sub-aperture time period, including operations S310 to S320.

[0084] In operation S310, the target sub-aperture length is determined based on the secondary phase error caused during the movement of the vessel.

[0085] In some embodiments, sub-aperture length is a measure of data partitioning in the time dimension. It specifies how continuously received signal data is divided into segments of a certain time length during data processing. For example, continuously received signals can be divided into sub-aperture lengths of 30 seconds, 2 minutes, or longer. The selection of sub-aperture length needs to consider the contradiction between the energy coherence accumulation caused by increasing the sub-aperture and the energy dissipation of moving ships. By selecting an appropriate sub-aperture length for sub-aperture imaging processing, the detectability of moving ships in the sub-aperture image can be guaranteed.

[0086] In practice, the selection of the sub-aperture length is related to factors such as the ship's RCS and the sea surface backscattering coefficient. This disclosure assumes that, given the uncertainty of these factors, the secondary phase error caused by the ship's motion is used as the basis for selecting the sub-aperture length. It should be noted that this disclosure does not limit the method for determining the sub-aperture length; those skilled in the art can choose the appropriate method based on the actual situation.

[0087] In some embodiments, determining the sub-aperture length may include setting a series of sub-aperture times, such as T. a =[3,6,9,12,15,18,21,24,27,30]. Starting from the shortest sub-aperture time, calculate the secondary phase error caused by the target motion according to the ship's maximum cruising speed of 16 m / s and a due east cruising direction. Iterate through all cruising directions sequentially (e.g., calculate every 15 degrees counterclockwise), calculating the secondary phase error in each direction. If the maximum value of the secondary phase error among all cruising directions at the current sub-aperture time does not exceed 10π, then that sub-aperture time is retained as a candidate. Iterate through all sub-aperture times sequentially, selecting the largest available sub-aperture time from the multiple candidate options as the target sub-aperture length.

[0088] When operating S320, in response to the received SAR echo signal reaching the target sub-aperture length in time, the extended imaging area within the target sub-aperture length is divided into multiple latitude and longitude grids according to the principle of proximity, and the multiple latitude and longitude grids are evenly divided into N sub-blocks to obtain N sub-block imaging areas.

[0089] In some embodiments, the sub-aperture data reception duration (i.e., target duration) refers to the time required to actually receive the corresponding amount of data according to the set sub-aperture length. There is a direct positive correlation between sub-aperture length and sub-aperture data reception duration, and the sub-aperture data reception duration is affected by the data transmission rate (i.e., the amount of data that can be transmitted per unit time). After the sub-aperture length is confirmed, the data reception duration for each sub-aperture can be calculated according to the data transmission rate. Once this reception duration is reached, it is considered that the amount of data meeting the sub-aperture length requirement has been collected. Based on the imaging efficiency of the time-domain BP algorithm, ship detection, and related parameter calculation efficiency, the time required for a single computing server to complete the processing of the entire extended area can be estimated. , This determines the delay between the completion time of sub-aperture data processing and the completion time of sub-aperture data reception.

[0090] In order to reduce This requires dividing the entire extended region into multiple sub-regions and using multiple computing servers for parallel processing. As expected... Where M is a multiplier coefficient, used to limit the upper limit of data processing time relative to data reception time. Then the number of sub-blocks N is:

[0091]

[0092] That is, N computing servers are needed to process the sub-aperture data of the sub-block region in parallel.

[0093] In some embodiments, the collection can be The latitude and longitude grid is evenly divided into each sub-block area according to the principle of proximity, ensuring that the computational load of each sub-block area is basically the same and the amount of echo data it occupies is relatively small.

[0094] Figure 6 The flowchart illustrates a process of performing imaging processing and ship detection and positioning on each sub-block imaging region according to an embodiment of the present disclosure to obtain ship information in each sub-block imaging region.

[0095] like Figure 6 As shown, this embodiment performs imaging processing and ship detection on each sub-block imaging region to obtain ship information in each sub-block imaging region, including operations S510 to S540. Operations S510 to S540 can be performed on each sub-block imaging region.

[0096] In operation S510, the sub-block imaging region is discretized into a two-dimensional pixel matrix, and the sub-block image of the sub-block imaging region is obtained based on the imaging results of each pixel in the sub-block imaging region.

[0097] In some embodiments, the latitude and longitude of the beam center projected onto the ground point are calculated based on the satellite position and velocity, satellite platform attitude, and antenna beam pointing. The geometric relationship of high-orbit SAR satellite-ground imaging is established. The equidistant direction and the equal-Doppler direction are obtained using the range gradient method and the Doppler gradient method. The nominal resolution of the equidistant direction and the nominal resolution of the equal-Doppler direction are calculated. 0.8 times the smaller value of the two directional resolutions is taken as the pixel interval size. The sub-block region is discretized to obtain a two-dimensional pixel matrix.

[0098] For each pixel in the sub-block region, the distance history within the sub-aperture time is calculated. The complex signal of that pixel in each frame is interpolated, and after azimuth and phase compensation, it is coherently accumulated to obtain the imaging result of that pixel. The imaging results of each pixel are obtained sequentially, and the sub-block image of the sub-block imaging region is obtained based on the imaging results of each pixel.

[0099] During the operation of S520, ship detection is performed on the sub-block image to obtain the ship's position information.

[0100] In some embodiments, traditional CFAR detection methods or neural network correlation detection methods can be used for ship detection. In one embodiment of this disclosure, considering that the moving ship to be detected still has some defocus and appears as a bright line in the image, a neural network correlation method is used for ship detection. For example, the ability to extract and recognize linear features can be trained in the network to achieve moving ship detection and obtain the ship detection result. The ship detection result for the sub-block region image is the longitude-latitude value and the index number of the longitude and latitude grid cell. The detected ship positions are then reordered according to the longitude and latitude grid cells, i.e. , representing the longitude of the nth ship within the latitude and longitude grid cell with index (i,j). and latitude .

[0101] When operating S530, the range Doppler parameters of the ship are calculated based on the preset stationary target point, the satellite position vector and velocity vector at the sub-aperture center time. The range Doppler parameters are used to establish the position mapping relationship of the moving ship before and after repositioning.

[0102] In some embodiments, a stationary target point is set at... Establish the position vector of the stationary point in the WGS84 coordinate system. Based on the satellite position vector r at the sub-aperture center time. s and velocity vector V s Calculate the slant distance R of the stationary point at the center of the sub-aperture using the vector analysis method. c and Doppler center frequency f dc .

[0103] Among them, the slant distance R c The expression is:

[0104]

[0105] Doppler center frequency f dc The expression is:

[0106]

[0107] Based on the assumption that the instantaneous slant range and the Doppler center frequency are equal, the slant range Doppler center frequency of the ship at the moment of the sub-aperture center can be expressed as: Distance Doppler parameters are key information for establishing the position mapping relationship between a moving vessel before and after repositioning.

[0108] When operating S540, the ship's actual position and speed are determined based on the ship's position information and distance Doppler information.

[0109] In some embodiments, according to the SAR imaging principle, the actual position of the ship at the sub-aperture center time should be distributed in a circle centered on the satellite position at the sub-aperture center time. On a sphere with radius r, constrained by its intersection with the ground surface and the beam coverage area. The latitude and longitude grid cells where the intersection with the ground surface is located within the beam coverage area are traversed one by one, and the latitude and longitude grid cell that best fits the motion ship influence model is found as the candidate value for the actual position of the ship at the current sub-aperture center time, and the candidate value for the ship's motion speed is calculated based on this.

[0110] Obtain the latitude and longitude of the center of the latitude and longitude grid cell Assuming this point is the actual location of the ship, the position vector of this point in the WGS84 coordinate system is established as follows: Similar to the modeling process of the impact of moving ships described above, the following calculations were performed sequentially: , , , , .

[0111] Calculate the position offset of the moving ship in Projection size in the direction for:

[0112]

[0113] Based on the modeling results of the moving vessel's influence mentioned above, the positional offset of the moving vessel is calculated in... Projection size in the vertical direction for:

[0114]

[0115] according to and The position deviation of the moving vessel is recalculated and compared with the current candidate vessel position to obtain the calculated deviation. .

[0116] Traversing the latitude and longitude grid cells where the surface intersection line is located within the beam coverage area, in order to Using the minimum absolute value as the criterion, and These are the candidate values ​​for the ship's actual latitude, longitude, and position vector at the current sub-aperture center moment.

[0117] Based on the modeling results of the influence of moving ships described above, the ship's velocity vector is calculated in... The projection size in the direction is:

[0118]

[0119] After simple organization, the velocity vector of the ship can be obtained. The projection size in the direction is:

[0120]

[0121] At this point, the candidate result of the combination of the ship's actual position and velocity at the sub-aperture center time can be expressed as: .

[0122] According to one embodiment of this disclosure, the processing of each sub-aperture data can be performed in parallel by calling multiple computing units, that is, operations S510 to S540 can be performed by multiple computing units.

[0123] In some embodiments, in response to obtaining N sub-block imaging regions, the N sub-block imaging regions are sequentially pushed to idle computing units among multiple computing units at preset time intervals, so that the computing units perform imaging processing and ship detection on the received sub-block imaging regions.

[0124] Seamless data processing and transmission can be achieved by having sub-aperture data reception, sub-block region sub-aperture imaging processing, sub-block region image ship detection, ship distance Doppler parameter calculation, and ship candidate position velocity combination calculation functions alternately buffered between the storage unit and the computing unit, avoiding delays caused by waiting for data preparation. For example, one storage unit and X sets of computing units can be configured, with each set of computing units including Y physical or virtual computing servers.

[0125] The following example uses X=3 and N=4 to illustrate... Figure 5 The imaging processing and ship inspection process shown will be further explained.

[0126] Before pushing the sub-aperture data to the computing unit, the high-orbit SAR data transmission data is received, decoded, deformatted, range compressed and stored. The received sub-aperture time is calculated. Once the selected sub-aperture length is reached, the sub-aperture data is pushed to the computing unit, and the next sub-aperture data is prepared. This process can be processed in real time frame by frame. The data transmission rate and computational load are relatively small, and there is no data backlog in the storage unit.

[0127] Each computing unit is equipped with 4 computing servers to process data in parallel. Each computing server is responsible for imaging processing, ship detection, Doppler parameter calculation, and velocity calculation of the candidate position for one sub-block area. This results in the latitude and longitude, slant distance and Doppler center frequency of each ship before and after repositioning, as well as the candidate position and velocity after repositioning of the sub-aperture center time.

[0128] The process start time is set to zero, and the first sub-aperture data is... The data is pushed out continuously, and simultaneously, the first set of computing units begins processing the first sub-aperture data; the second sub-aperture data is... The data is pushed out continuously, and simultaneously, the second set of computing units begins processing the second sub-aperture data; the third sub-aperture data is... The data is pushed out continuously, and simultaneously, the third set of computing units begins processing the third sub-aperture data. The fourth sub-aperture data is... The data is being pushed out continuously. At this point, the first set of computing units has completed processing the first sub-aperture data and begins processing the fourth sub-aperture data; the fifth sub-aperture data is... The data is being pushed out continuously. At this point, the second set of computing units has completed the processing of the second sub-aperture data and begins processing the fifth sub-aperture data; the sixth sub-aperture data is... The data is pushed out continuously. At this time, the third set of computing units has completed the processing of the third sub-aperture data and begins the processing of the sixth sub-aperture data.

[0129] Similarly, the first set of computing units is responsible for processing the 3n+1 (n=0,1,...)th sub-aperture data, the second set of computing units is responsible for processing the 3n+2 (n=0,1,...)th sub-aperture data, and the third set of computing units is responsible for processing the 3n+3 (n=0,1,...)th sub-aperture data. The three sets of computing units work together in accordance with the prescribed timing, and there is no backlog of data between computing units.

[0130] After the last sub-aperture data is pushed, after The delay is that the processing time of the last sub-aperture data is completed, and the delay between the completion time of processing all aperture data and the completion time of receiving all sub-aperture data does not exceed [a certain value]. This disclosure utilizes the time-sequential collaboration of multiple sets of computing units to perform parallel processing on sub-block regions, achieving accurate data flow control and real-time processing, thereby improving the timeliness of ship detection and positioning.

[0131] Figure 7 The flowchart illustrates the temporal relationship between the center time of each sub-aperture based on its length and the ship detection results, according to an embodiment of the present disclosure, and the process of correlating and matching discrete points on the sub-aperture images of different sub-block imaging regions.

[0132] like Figure 7As shown, this embodiment describes the temporal relationship between the center time of each sub-aperture and the ship detection results, based on the sub-aperture length, and the correlation and matching of discrete points on the sub-aperture images of different sub-block imaging regions, including operations S610 to S620.

[0133] In operation S610, establish the time sequence relationship between the sub-aperture center time and the sub-aperture ship information.

[0134] In operation S620, discrete points belonging to the same track on multiple sub-aperture images are associated and matched to obtain a ship navigation trajectory composed of discrete points belonging to the same track, wherein the discrete points are signal points representing the ship in the sub-aperture images.

[0135] In some embodiments, sub-aperture joint trajectory tracking establishes a temporal relationship between the sub-aperture center time and sub-aperture vessel information, and associates and matches discrete points detected on different sub-aperture images. Sub-aperture joint vessel tracking can be based on Processing can also be based on Alternatively, a weighted judgment can be made based on the separate processing of the two.

[0136] First, determine the starting point of the track. Then, establish a correlation between discrete points and the track based on the starting point. Using classic methods such as logical analysis and sliding window analysis, analyze the consistency of the ship's motion track at multiple sub-aperture moments. If the consistency constraint condition is met, it is determined to be the starting point of the track.

[0137] Based on the initial track, classic methods such as Nearest Neighbor (NN), Probabilistic Association (PDA), and Joint Probabilistic Association (JPDA) can be used to calculate the competition probability of multiple tracks for the same discrete point. The track to which the discrete point belongs is determined according to the magnitude of the probability value. For example, if track A has the highest competition probability for discrete point 1, then discrete point 1 is determined to belong to track A, thus realizing dynamic track updates.

[0138] After sub-aperture joint ship tracking, for any given ship, a time-varying sequence of its position and velocity vector combination can be established, i.e. .

[0139] In this embodiment, the sub-aperture joint ship positioning and track generation process targets a single ship. Kalman filtering is applied to the acquired position and velocity vectors, which contain measurement errors, to suppress these errors. By establishing a ship motion model and continuously predicting and updating position and velocity information, optimal estimation of the ship motion model parameters is achieved, resulting in a spatiotemporally continuous ship trajectory. This effectively improves the accuracy of ship positioning and track generation.

[0140] Since the ship's velocity vector is not directly obtained, but rather its radial projection, the state vector in this embodiment is set as follows: , and This improves the accuracy of describing the ship's motion state. It is described using a state transition matrix. Changes in [the data] allow for the prediction of the ship's future state. Utilizing [this data] Length and Changes in direction (angle) are used as constraints for state prediction and updating, thereby suppressing measurement errors and improving ship positioning accuracy and track accuracy.

[0141] Figure 8 A schematic block diagram of a high-orbit SAR satellite sea surface motion vessel detection and positioning device according to an embodiment of the present disclosure is shown.

[0142] like Figure 8 As shown, the high-orbit SAR satellite sea surface motion vessel detection and positioning device 800 of this embodiment includes a determination module 810, a division module 820, a processing and detection module 830, a synthesis module 840, and an association module 850.

[0143] The determination module 810 is used to determine the extended area of ​​SAR imaging by dynamically calculating the union area of ​​satellite beam coverage and ship motion offset. In one embodiment, the determination module 810 can be used to perform the operation S110 described above, which will not be repeated here.

[0144] The partitioning module 820 is used to divide the high-orbit SAR fully synthetic aperture time into multiple sub-aperture time periods. Within each sub-aperture time period, the extended imaging region is spatially divided to obtain N sub-block imaging regions corresponding to the current sub-aperture time period. The sub-aperture time period is determined based on the secondary phase error caused by ship motion, and N is a positive integer greater than 1. In one embodiment, the partitioning module 820 can be used to perform the operation S120 described above, which will not be repeated here.

[0145] The processing and detection module 830 is used to perform imaging processing and ship detection and positioning on each sub-block imaging region, and to obtain ship information in each sub-block imaging region, wherein the ship information includes actual position information and speed information. In one embodiment, the processing and detection module 830 can be used to perform the operation S130 described above, which will not be repeated here.

[0146] The synthesis module 840 is used to synthesize the ship information of N sub-block imaging areas within each sub-aperture time period to obtain a complete sub-aperture image within that sub-aperture time period. The sub-aperture image is a continuous ship detection result in geospatial space within the current sub-aperture length. In one embodiment, the synthesis module 840 can be used to perform the operation S140 described above, which will not be repeated here.

[0147] The association module 850 is used to perform cross-sub-aperture ship target association and matching based on the temporal relationship between the center time of each sub-aperture and the corresponding ship detection and positioning results, thereby forming a spatiotemporally continuous ship navigation trajectory. In one embodiment, the association module 850 can be used to perform the operation S150 described above, which will not be repeated here.

[0148] According to embodiments of this disclosure, any multiple modules among the determining module 810, partitioning module 820, processing and detection module 830, synthesis module 840, and association module 850 can be combined into one module, or any one of these modules can be split into multiple modules. Alternatively, at least some of the functions of one or more of these modules can be combined with at least some of the functions of other modules and implemented in one module. According to embodiments of this disclosure, at least one of the determining module 810, partitioning module 820, processing and detection module 830, synthesis module 840, and association module 850 can be at least partially implemented as hardware circuitry, such as a field-programmable gate array (FPGA), a programmable logic array (PLA), a system-on-a-chip, a system-on-a-substrate, a system-on-package, an application-specific integrated circuit (ASIC), or implemented in hardware or firmware by any other reasonable means of integrating or packaging circuitry, or implemented in software, hardware, or firmware, or in any suitable combination of any of these three implementation methods. Alternatively, at least one of the determining module 810, the dividing module 820, the processing and detection module 830, the synthesizing module 840, and the associating module 850 may be at least partially implemented as a computer program module, which can perform corresponding functions when the computer program module is run.

[0149] Figure 9 A block diagram of an electronic device according to an embodiment of the present disclosure is shown schematically.

[0150] like Figure 9As shown, an electronic device 900 according to an embodiment of the present disclosure includes a processor 901, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 902 or a program loaded from a storage portion 908 into a random access memory (RAM) 903. The processor 901 may include, for example, a general-purpose microprocessor (e.g., a CPU), an instruction set processor and / or an associated chipset and / or a special-purpose microprocessor (e.g., an application-specific integrated circuit (ASIC)), etc. The processor 901 may also include onboard memory for caching purposes. The processor 901 may include a single processing unit or multiple processing units for performing different actions of the method flow according to an embodiment of the present disclosure.

[0151] RAM 903 stores various programs and data required for the operation of electronic device 900. Processor 901, ROM 902, and RAM 903 are interconnected via bus 904. Processor 901 performs various operations of the method flow according to embodiments of the present disclosure by executing programs in ROM 902 and / or RAM 903. It should be noted that the program may also be stored in one or more memories other than ROM 902 and RAM 903. Processor 901 may also perform various operations of the method flow according to embodiments of the present disclosure by executing programs stored in one or more memories.

[0152] According to embodiments of this disclosure, the electronic device 900 may further include an input / output (I / O) interface 905, which is also connected to a bus 904. The electronic device 900 may also include one or more of the following components connected to the input / output (I / O) interface 905: an input section 906 including a keyboard, mouse, etc.; an output section 907 including a cathode ray tube (CRT), liquid crystal display (LCD), etc., and a speaker, etc.; a storage section 908 including a hard disk, etc.; and a communication section 909 including a network interface card such as a LAN card, modem, etc. The communication section 909 performs communication processing via a network such as the Internet. A drive 910 is also connected to the input / output (I / O) interface 905 as needed. A removable medium 911, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., is installed on the drive 910 as needed so that computer programs read from it can be installed into the storage section 908 as needed.

[0153] This disclosure also provides a computer-readable storage medium, which may be included in the device / apparatus / system described in the above embodiments; or it may exist independently and not assembled into the device / apparatus / system. The computer-readable storage medium carries one or more programs that, when executed, implement the method according to the embodiments of this disclosure.

[0154] According to embodiments of this disclosure, the computer-readable storage medium can be a non-volatile computer-readable storage medium. Examples include, but are not limited to: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this disclosure, the computer-readable storage medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0155] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Without departing from the scope of this disclosure, those skilled in the art can make various substitutions and modifications, all of which should be included within the protection scope of this disclosure.

Claims

1. A method for detecting and locating moving ships on the sea surface using high-orbit SAR satellites, characterized in that, The method includes: The extended imaging area of ​​high-orbit SAR imaging is determined by dynamically calculating the union region of satellite beam coverage and ship motion offset. The high-orbit SAR fully synthetic aperture time is divided into multiple sub-aperture time periods. Within each sub-aperture time period, the extended imaging region is spatially divided to obtain N sub-block imaging regions corresponding to the current sub-aperture time period. The sub-aperture time period is determined based on the secondary phase error caused by ship motion, and N is a positive integer greater than 1. Imaging processing and ship detection and positioning are performed on each sub-block imaging region to obtain ship information in each sub-block imaging region; the ship information includes actual position information and speed information. Ship information from N sub-block imaging regions within each sub-aperture time period is synthesized to obtain a complete sub-aperture image within that sub-aperture time period. The complete sub-aperture image represents the continuous ship detection and positioning results in geospatial space within the current sub-aperture time period. Based on the temporal relationship between the center time of each sub-aperture and the corresponding ship detection and positioning results, ship targets across sub-apertures are associated and matched to form a spatiotemporally continuous ship navigation trajectory.

2. The method according to claim 1, characterized in that, The high-orbit SAR imaging includes imaging data from multiple consecutive time points. The process of determining the extended imaging area of ​​the high-orbit SAR imaging by dynamically calculating the union region of satellite beam coverage and ship motion offset includes: Based on the satellite position and attitude, antenna pointing and radiation pattern at each time, calculate the latitude and longitude grid of the beam center projection point on the ground to determine the satellite beam coverage area; Based on the decomposition results of the position offset of the moving vessel at each moment, the latitude and longitude grids where the moving vessel is located after its position offset at a specific cruising speed and in different cruising directions are calculated, resulting in a first set containing multiple latitude and longitude grids. The first set represents the vessel's motion offset region at each moment. The position offset decomposition results are obtained based on the moving vessel's influence modeling process. The satellite beam coverage area and the ship motion offset area at the same time are merged to obtain the extended area at each time. By merging the extended regions at each time point in the high-orbit SAR imaging time, an extended imaging region of the high-orbit SAR imaging is obtained, wherein the extended imaging region is a second set containing multiple latitude and longitude grids.

3. The method according to claim 1, characterized in that, The process involves dividing the high-orbit SAR fully synthetic aperture time into multiple sub-aperture time periods, and spatially dividing the extended imaging region within each sub-aperture time period to obtain N sub-block imaging regions corresponding to the current sub-aperture time period, including: The target sub-aperture length is determined based on the secondary phase error caused during the movement of the vessel. In response to the received SAR echo signal reaching the target sub-aperture length in time, the extended imaging region within the target sub-aperture length is divided into multiple latitude and longitude grids according to the principle of proximity, and the multiple latitude and longitude grids are evenly divided into N sub-blocks to obtain N sub-block imaging regions.

4. The method according to claim 1, characterized in that, The process of performing imaging processing and ship detection and positioning on each sub-block imaging region to obtain ship information in each sub-block imaging region includes: Perform the following operations on each sub-block imaging region: The sub-block imaging region is discretized into a two-dimensional pixel matrix, and the sub-block image of the sub-block imaging region is obtained based on the imaging results of each pixel in the sub-block imaging region. The ship is detected and located in the sub-block image to obtain the ship's position information; The range Doppler parameters of the ship are calculated based on the preset stationary target point, the satellite position vector and velocity vector at the center of the sub-aperture. The range Doppler parameters are used to establish the position mapping relationship of the moving ship before and after repositioning. The actual position and speed of the ship are determined based on the ship's position information and the distance Doppler information.

5. The method according to claim 4, characterized in that, The method includes executing the imaging processing and ship detection and positioning in parallel by calling multiple computing units: In response to obtaining N sub-block imaging regions, the N sub-block imaging regions are sequentially pushed to idle computing units among the plurality of computing units according to a preset time interval, so that the computing units perform imaging processing and ship detection and positioning on the received sub-block imaging regions.

6. The method according to claim 1, characterized in that, The process of associating and matching ship targets across sub-apertures based on the temporal relationship between the center time of each sub-aperture and the corresponding ship detection and positioning results, thereby constructing a spatiotemporally continuous ship navigation trajectory, includes: Establish the temporal relationship between the center time of each sub-aperture and the ship information of each sub-aperture; By associating and matching discrete points belonging to the same track on multiple sub-aperture images, a ship's navigation trajectory composed of discrete points belonging to the same track is obtained. The discrete points are signal points representing ships in the sub-aperture images.

7. The method according to claim 1, further comprising: A geodetic coordinate system is established with the instantaneous position of the moving vessel in the SAR imaging data as the origin, and the satellite position vector, velocity vector, moving target position vector, and velocity vector in the SAR imaging data are transformed into the geodetic coordinate system. The position offset of the moving vessel is decomposed into directions parallel to the slant distance from the ground projection direction and directions perpendicular to the slant distance from the ground projection direction, thus obtaining the decomposition result of the position offset of the moving vessel. The secondary phase error is calculated based on the speed of the moving vessel and the speed of the SAR satellite.

8. A high-orbit SAR satellite device for detecting and locating ships moving on the sea surface, characterized in that, The device includes: The determination module is used to determine the extended imaging area of ​​high-orbit SAR imaging by dynamically calculating the union area of ​​satellite beam coverage and ship motion offset. The partitioning module is used to divide the high-orbit SAR fully synthetic aperture time into multiple sub-aperture time periods, and to spatially partition the extended imaging region within each sub-aperture time period to obtain N sub-block imaging regions corresponding to the current sub-aperture time period. The sub-aperture time period is determined based on the secondary phase error caused by ship motion, and N is a positive integer greater than 1. The processing and detection module is used to perform imaging processing and ship detection and positioning on each sub-block imaging area to obtain ship information in each sub-block imaging area; the ship information includes actual position information and speed information. The synthesis module synthesizes the ship information of N sub-block imaging regions within each sub-aperture time period to obtain a complete sub-aperture image within that sub-aperture time period. The complete sub-aperture image is the ship detection and positioning result within the current sub-aperture time period. The association module is used to associate and match ship targets across sub-apertures based on the temporal relationship between the center time of each sub-aperture and the corresponding ship detection and positioning results, thereby forming a spatiotemporally continuous ship navigation trajectory.

9. An electronic device, comprising: One or more processors; Memory, used to store one or more computer programs. The characteristic feature is that the one or more processors execute the one or more computer programs to implement the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program or instructions stored thereon, characterized in that, When the computer program or instructions are executed by a processor, they implement the steps of the method according to any one of claims 1 to 7.

Images