Ship monitoring method, ship monitoring device, electronic equipment and storage medium

Abstract

The invention discloses a ship monitoring method, a ship monitoring device, electronic equipment and a storage medium. The method comprises the following steps: determining an image Doppler offset of a ship according to a synthetic aperture radar image of the ship; constructing a theoretical Doppler offset generated by the radial speed and the squint angle of the ship; according to the image Doppler offset and the theoretical Doppler offset, calculating to estimate the radial speed of the ship; and determining the actual orientation of the ship according to the radial speed of the ship and the image orientation of the ship in the synthetic aperture radar image. According to the method, the Doppler offset generated by the radial speed and the squint angle is comprehensively considered, and the accuracy of estimating the radial speed of the ship in the sliding bunching mode can be improved. And resolving is performed based on the image Doppler offset and the theoretical Doppler offset, so that the complexity of the resolving process is greatly reduced, and the efficiency of estimating the radial speed of the ship in the sliding bunching mode can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of image processing, and particularly to a ship monitoring method, a ship monitoring device, an electronic device, and a storage medium. Background Art

[0002] Compared with other remote sensing means such as optical remote sensing, synthetic aperture radar (SAR) satellite remote sensing has the advantages of all-weather, all-day, and high resolution, and has become an indispensable observation means in the fields of reconnaissance, environmental monitoring, and marine monitoring. With the improvement of the requirements for remote sensing applications, in order to obtain high-resolution SAR images, the sliding spotlight SAR mode controls the azimuth beam pointing and irradiates the same area for a long time to increase the integration time of the irradiated target and achieve the purpose of high-resolution imaging. Currently, many on-orbit satellites, including China's GF-3 high-resolution satellite No. 3, have the sliding spotlight imaging mode in their system designs.

[0003] Currently, researchers have proposed many methods to estimate the radial velocity of ships at sea (such as ships, etc.). The radial velocity of ships at sea can be estimated based on the Automatic Identification System (AIS) method and the wake monitoring method. However, the auxiliary information of AIS must be matched with the SAR image. Therefore, in the case where the auxiliary information of AIS is missing or the auxiliary information of AIS cannot be matched with the SAR image, this AIS-based auxiliary method cannot be applied to the sliding spotlight SAR system. In addition, affected by the polarization mode and the radar viewing angle, there is no obvious wake of the ship in many imaging cases. Therefore, the wake monitoring-based method also has great limitations.

[0004] The single look complex (SLC) data of the sliding spotlight SAR system includes the phase information of the ship. Generally, two common methods can be used to estimate the radial velocity of the ship: the multi-channel method and the Doppler centroid anomaly (DCA) method. The multi-channel method uses the interference phase between the data of multiple channels to achieve a highly accurate estimate of the radial velocity, and it is one of the mainstream methods for measuring the ship speed currently. However, this system requires multiple sub-antennas to receive the target echo, so it cannot be applied to this single-channel SAR system in the sliding spotlight mode. The Doppler centroid anomaly DCA method estimates the radial velocity of ships at sea by estimating the Doppler offset related to the velocity. However, both the velocity of the ship and the true azimuth position are unknown terms. Therefore, the radial velocity of the ship cannot be effectively estimated based on the DCA method.

[0005] On the one hand, when estimating the radial velocity of a marine vessel in the existing sliding spotlight mode, only the Doppler shift caused by the radial velocity is considered, while the Doppler shift caused by other factors is not considered, resulting in a reduction in the accuracy of the radial velocity estimation of the vessel in the sliding spotlight mode. On the other hand, when estimating the radial velocity of a marine vessel in the existing sliding spotlight mode, a large number of calculation processes are required, seriously reducing the efficiency of estimating the radial velocity of the vessel in the sliding spotlight mode. Summary of the Invention

[0006] The present invention provides a vessel monitoring method, a vessel monitoring device, an electronic device, and a storage medium to solve the technical problems of poor accuracy and low efficiency when estimating the radial velocity of a marine vessel in the existing sliding spotlight mode.

[0007] The present invention provides a vessel monitoring method, including:

[0008] Determine the image Doppler shift amount of the vessel according to the synthetic aperture radar image of the vessel; the synthetic aperture radar image is obtained by a synthetic aperture radar system in the sliding spotlight mode;

[0009] Construct the theoretical Doppler shift amount of the vessel; the theoretical Doppler shift amount includes the Doppler shift amount generated by the radial velocity of the vessel and the Doppler shift amount generated by the squint angle respectively; the theoretical Doppler shift amount reflects the relationship between the Doppler shift amount and the radial velocity;

[0010] Solve according to the image Doppler shift amount and the theoretical Doppler shift amount to estimate the radial velocity of the vessel;

[0011] Determine the actual azimuth of the vessel according to the radial velocity of the vessel and the image azimuth of the vessel in the synthetic aperture radar image.

[0012] The present invention determines the image Doppler shift amount of the vessel through the synthetic aperture radar image obtained in the sliding spotlight mode; at the same time, comprehensively considering the Doppler shift amount generated by at least two aspects of the radial velocity and the squint angle, constructs the theoretical Doppler shift amount of the vessel, which can improve the accuracy of the radial velocity estimation of the vessel in the sliding spotlight mode. On the other hand, the present invention performs calculations based on the image Doppler shift amount and the theoretical Doppler shift amount, greatly reducing the complexity of the calculation process, and can improve the efficiency of the radial velocity estimation of the vessel in the sliding spotlight mode.

[0013] Furthermore, the present invention also provides a vessel monitoring device, including:

[0014] An image Doppler shift determination module is configured to determine the image Doppler shift of the ship based on the synthetic aperture radar image of the ship; the synthetic aperture radar image is acquired by the synthetic aperture radar system in the sliding spotlight mode;

[0015] A theoretical Doppler shift construction module is configured to construct the theoretical Doppler shift of the ship; the theoretical Doppler shift includes the Doppler shift generated by the radial velocity and the Doppler shift generated by the squint angle respectively; the theoretical Doppler shift reflects the relationship between the Doppler shift and the radial velocity;

[0016] A radial velocity estimation module is configured to solve and estimate the radial velocity of the ship according to the image Doppler shift and the theoretical Doppler shift;

[0017] A positioning module is configured to determine the actual azimuth of the ship according to the radial velocity of the ship and the image azimuth of the ship in the synthetic aperture radar image.

[0018] The image Doppler shift determination module of the present invention determines the image Doppler shift of the ship through the synthetic aperture radar image acquired in the sliding spotlight mode; at the same time, comprehensively considering the Doppler shift generated by at least two aspects of the radial velocity and the squint angle, constructs the theoretical Doppler shift of the ship, which can improve the accuracy of the radial velocity estimation of the ship in the sliding spotlight mode. On the other hand, the present invention performs calculations based on the image Doppler shift and the theoretical Doppler shift, greatly reducing the complexity of the calculation process and improving the efficiency of the radial velocity estimation of the ship in the sliding spotlight mode.

[0019] Furthermore, the present invention also provides an electronic device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, the ship monitoring method as described above is implemented.

[0020] Furthermore, the present invention also provides a computer-readable storage medium, which includes a stored computer program. When the computer program runs, it controls the device where the computer-readable storage medium is located to execute the ship monitoring method as described above.

[0021] Furthermore, the present invention also provides a computer program product, including a computer program / instructions. When the computer program / instructions are executed by a processor, the ship monitoring method as described above is implemented.

[0022] A ship monitoring method, a ship monitoring device, an electronic device, and a storage medium according to an embodiment of the present invention have the following beneficial effects compared with the prior art:

[0023] The present invention determines the image Doppler shift of a ship based on the synthetic aperture radar image obtained in the sliding spotlight mode; meanwhile, comprehensively considering the Doppler shift generated by at least two aspects of the radial velocity and the squint angle, a theoretical Doppler shift of the ship is constructed, which can improve the accuracy of the radial velocity estimation of the ship in the sliding spotlight mode. On the other hand, the present invention performs calculation based on the image Doppler shift and the theoretical Doppler shift, greatly reducing the complexity of the calculation process and improving the efficiency of the radial velocity estimation of the ship in the sliding spotlight mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 FIG. is a schematic flowchart of an embodiment of a ship monitoring method provided by the present invention;

[0025] Figure 2 FIG. is a schematic structural diagram of an embodiment of a ship monitoring device provided by the present invention;

[0026] Figure 3 FIG. is a schematic diagram of an embodiment of the echo data amplitude of a ship simulation experiment provided by the present invention;

[0027] Figure 4 FIG. is a schematic diagram of an embodiment of a focused SLC format image of a ship simulation experiment provided by the present invention;

[0028] Figure 5 FIG. is a schematic diagram of an embodiment of the Doppler spectrum signal of a ship simulation experiment provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Refer to Figure 1 , Figure 1 FIG. is a schematic flowchart of an embodiment of a ship monitoring method provided by the present invention. As shown in Figure 1 , the method includes S101-S103, which are specifically as follows:

[0031] S101: Determine the image Doppler shift of the ship according to the synthetic aperture radar image of the ship; the synthetic aperture radar image is obtained by the synthetic aperture radar system in the sliding spotlight mode;

[0032] S102: Construct the theoretical Doppler shift of the ship; the theoretical Doppler shift includes the Doppler shift generated by the radial velocity of the ship and the Doppler shift generated by the oblique viewing angle respectively; the theoretical Doppler shift reflects the relationship between the Doppler shift and the radial velocity;

[0033] S103: Solve based on the image Doppler shift and the theoretical Doppler shift to estimate the radial velocity of the ship;

[0034] S104: Determine the actual azimuth of the ship according to the radial velocity of the ship and the image azimuth of the ship in the synthetic aperture radar image.

[0035] A synthetic aperture radar system is a high-resolution imaging radar that can obtain high-resolution radar images similar to optical photography under extremely low visibility meteorological conditions. A radar that uses the relative motion between the radar and the target to synthesize a larger equivalent antenna aperture from a smaller real antenna aperture by means of data processing is an active earth observation system that can be installed on flight platforms such as airplanes, satellites, and spacecraft, and can observe the earth all day and all weather, and has a certain surface penetration ability.

[0036] The sliding spotlight mode is a working mode of the sliding spotlight SAR system, which means that by controlling the azimuth beam pointing, the target is irradiated for a long time (progressive scanning) to achieve high-resolution and more detailed imaging. Among them, the synthetic aperture radar image is data in the Single Look Complex (SLC) format. SLC data is the original data obtained by the synthetic aperture radar (SAR) system. These data are only focused once during imaging and are formed by the coherent superposition of the radar echo signals scattered by a single pixel. This processing method retains the highest spatial resolution.

[0037] In the embodiment of the present invention, the synthetic aperture radar image is obtained by the synthetic aperture radar system in the sliding spotlight mode. The synthetic aperture radar system obtains the synthetic aperture radar image in the SLC format by progressively scanning the scene containing the ship, and then the image Doppler shift of the ship can be determined based on the synthetic aperture radar image. The image Doppler shift is the Doppler shift obtained through the synthetic aperture radar image.

[0038] Since the Doppler shift of a ship is mainly generated by the radial velocity and the squint angle of the ship, and the squint angle refers to the squint relationship between the ship and the beam direction at different azimuth times in the sliding spotlight mode. Therefore, in the embodiments of the present invention, the Doppler shift generated by the radial velocity of the ship and the Doppler shift amount generated by the squint angle are fully considered, and the theoretical Doppler shift amount of the ship is constructed by combining the two aspects, which can improve the accuracy of the radial velocity estimation of the ship in the sliding spotlight mode. Among them, the theoretical Doppler shift amount of the ship reflects the relationship between the Doppler shift amount and the radial velocity.

[0039] After obtaining the image Doppler shift amount and the theoretical Doppler shift amount, the unknown quantity of the ship, that is, the radial velocity, can be estimated by solving based on the image Doppler shift amount and the theoretical Doppler shift amount. In the embodiments of the present invention, the complexity of the solving process is greatly reduced by solving based on the image Doppler shift amount and the theoretical Doppler shift amount, and the efficiency of the radial velocity estimation of the ship in the sliding spotlight mode can be improved.

[0040] After solving to obtain the radial velocity of the ship, based on the linear relationship between the radial velocity of the ship and the ship azimuth offset, the actual azimuth of the ship can be obtained through the following relationship between the actual azimuth of the ship and the image azimuth in the synthetic aperture radar image of the ship.

[0041]

[0042] Among them, represents the radial velocity of the ship estimated by solving, represents the actual azimuth of the ship, x 0 represents the image azimuth cross-range coordinate of the ship in the synthetic aperture radar image, y 0 represents the image azimuth along-track coordinate of the ship in the synthetic aperture radar image, v s represents the satellite velocity.

[0043] On the basis of accurately estimating the radial velocity of the ship, the embodiments of the present invention can improve the accuracy of determining the actual azimuth (relocation) of the ship.

[0044] The present invention determines the image Doppler shift amount of the ship through the synthetic aperture radar image obtained in the sliding spotlight mode; at the same time, the Doppler shift amount generated by at least two aspects of the radial velocity and the squint angle is comprehensively considered, and the theoretical Doppler shift amount of the ship is constructed, which can improve the accuracy of the radial velocity estimation of the ship in the sliding spotlight mode. On the other hand, the present invention solves based on the image Doppler shift amount and the theoretical Doppler shift amount, greatly reducing the complexity of the solving process and improving the efficiency of the radial velocity estimation of the ship in the sliding spotlight mode.

[0045] In a further embodiment, step S101, determining the image Doppler offset of the ship according to the synthetic aperture radar image of the ship includes:

[0046] Obtaining the synthetic aperture radar image of the target scene in the sliding spotlight mode through the synthetic aperture radar system; the target scene includes the ship;

[0047] Performing a fast Fourier transform on the ship in the synthetic aperture radar image to determine the Doppler spectrum signal of the ship;

[0048] Estimating the Doppler spectrum signal of the ship by using the frequency offset method to determine the image Doppler offset of the ship.

[0049] When determining the image Doppler offset of the ship, adjust the working mode of the synthetic aperture radar system to the sliding spotlight mode, and then the synthetic aperture radar system performs a progressive scan on the target scene including the ship in the sliding spotlight mode to obtain the synthetic aperture radar image of the ship. Here, the synthetic aperture radar image is an SLC format image.

[0050] Furthermore, by using the fast Fourier transform technology, the slice of the ship in the SLC format image of the synthetic aperture radar image is processed to obtain the Doppler spectrum signal. The fast Fourier transform (FFT) is one of the most basic methods in time-domain to frequency-domain transformation analysis. It is mainly used to transform the time-domain signal to the frequency domain for analysis. Specifically:

[0051] Assume that the signal of the ship slice in the SLC format image is s ship (t), the process of the fast Fourier transform FFT can be described as:

[0052]

[0053] where S ship (t) is the Doppler spectrum signal of the ship, f is the Doppler frequency, and t is the time.

[0054] Perform FFT on the SLC signal of the ship slice in the azimuth direction to transform the time-domain signal to the range-Doppler domain, thereby obtaining the Doppler spectrum signal of the ship SLC signal.

[0055] After obtaining the Doppler spectrum signal of the ship, the frequency offset method can be used to estimate the Doppler spectrum signal of the ship, and then the image Doppler offset of the ship can be determined.

[0056] In an embodiment of the present invention, the Doppler spectrum signal of the ship is determined by fast Fourier transform, and then the image Doppler shift of the ship is determined by the frequency offset method, which can improve the accuracy of the image Doppler shift obtained from the synthetic aperture radar image.

[0057] In a further embodiment, the obtaining of the synthetic aperture radar image of the target scene by the synthetic aperture radar system in the sliding spotlight mode includes:

[0058] Obtaining the synthetic aperture radar image by the synthetic aperture radar system of the satellite in the sliding spotlight mode.

[0059] In view that the synthetic aperture radar system can be configured on an aircraft, a spaceship or a satellite, in order to improve the high resolution of the synthetic aperture radar image in an embodiment of the present invention, the synthetic aperture radar system can be configured on the satellite, and the synthetic aperture radar image is obtained by the spaceborne synthetic aperture radar system in the sliding spotlight mode.

[0060] In a further embodiment, the estimating of the Doppler spectrum signal of the ship by the frequency offset method to determine the image Doppler shift of the ship includes:

[0061] Estimating the Doppler center of the Doppler spectrum signal by the frequency offset method;

[0062] Determining the image Doppler shift of the ship according to the Doppler center.

[0063] Specifically, the modulus square of the Doppler spectrum signal of the ship is obtained and averaged along the range direction to obtain the Doppler power spectrum of the ship. By the following function B(f), the frequency axis of the Doppler power spectrum of the ship is traversed. When the energies of the two parts divided by the function B(f) of the Doppler power spectrum are equal, the frequency value at this time is taken as the Doppler center frequency of this region. The expression of B(f) is as follows:

[0064]

[0065] where B a represents the Doppler bandwidth. Among them, the ship Doppler shift obtained by the frequency offset method can be expressed as f ship .

[0066] In a further embodiment, in step S102, the constructing of the theoretical Doppler shift of the ship includes:

[0067] Constructing a first Doppler shift of the ship according to the radial velocity of the ship; the first Doppler shift characterizes the Doppler shift generated by the radial velocity;

[0068] Construct a second Doppler shift of the ship according to the radial velocity of the ship; the second Doppler shift characterizes the Doppler shift generated by the squint angle.

[0069] Construct a theoretical Doppler shift of the ship according to the first Doppler shift and the second Doppler shift.

[0070] Given that the Doppler shift of the ship is mainly the Doppler shift generated by the radial velocity and the Doppler shift generated by the squint angle, comprehensively consider the Doppler shifts generated by the above two aspects of the radial velocity and the squint angle here, and construct the theoretical Doppler shift of the ship.

[0071] First, construct a first Doppler shift of the ship according to the radial velocity of the ship. Among them, the first Doppler shift characterizes the Doppler shift generated by the radial velocity.

[0072] Specifically, the Doppler shift generated by the radial velocity can be expressed as:

[0073]

[0074] Among them, v r represents the radial velocity of the ship, and f d (v r ) represents the first Doppler shift generated by the radial velocity, and λ represents the wavelength of the radar signal.

[0075] Second, construct a second Doppler shift of the ship according to the radial velocity of the ship. Among them, the second Doppler shift characterizes the Doppler shift generated by the squint angle.

[0076] Specifically, since the sliding spotlight SAR system operates in the (sliding spotlight) mode of azimuth beam progressive scanning, the squint relationship between the ship and the beam pointing at different azimuth times is different. Therefore, assuming that the ship at (x 0 , y 0 ) has a radial velocity expressed as v r , the azimuth position offset of the ship caused by it can be expressed as:

[0077]

[0078] Among them, Δx(v r ) represents the azimuth position offset of the ship caused by the radial velocity, K a is the Doppler modulation frequency of the signal, and v f represents the running speed of the radar beam footprint relative to the ground.

[0079] Furthermore, based on the image orientation of the ship in the image and the azimuth position offset related to the radial velocity, the actual azimuth of the ship can be obtained, which can be expressed as:

[0080]

[0081] where x′(v r ) is the actual azimuth of the ship, and x 0 is the image azimuth of the ship in the image.

[0082] Then, the relationship between the ship and the oblique viewing angle of the beam at the azimuth moment x′(v r ) can be expressed as:

[0083]

[0084] where θ′ look (v r ) represents the oblique viewing angle between the ship and the beam, ω represents the rotational angular velocity of the beam in the azimuth direction, x c represents the imaging center position, and the second Doppler shift generated by the oblique viewing angle can be expressed as:

[0085]

[0086] where v s represents the satellite velocity, and f′ look (v r ) is the second Doppler shift.

[0087] In a further embodiment, constructing the theoretical Doppler shift of the ship according to the first Doppler shift and the second Doppler shift includes:

[0088] Adding the first Doppler shift and the second Doppler shift to obtain the constructed theoretical Doppler shift of the ship.

[0089] After constructing the first Doppler shift generated by the radial velocity and the second Doppler shift generated by the oblique viewing angle, the theoretical Doppler shift of the ship can be constructed based on the first Doppler shift and the second Doppler shift. Specifically, adding the first Doppler shift and the second Doppler shift can obtain the theoretical Doppler shift of the ship.

[0090] Among them, based on the foregoing, the relationship between the radial velocity of the ship and the theoretical Doppler shift of the ship can be expressed as:

[0091]

[0092] where f shift (vr ) represents the theoretical Doppler shift of the ship, f d (v r ) represents the first Doppler shift of the ship caused by the radial velocity, f′ look (v r ) represents the second Doppler shift caused by the oblique viewing angle.

[0093] The embodiments of the present invention comprehensively consider the Doppler shifts generated by at least two aspects of the radial velocity and the oblique viewing angle, and construct the theoretical Doppler shift of the ship by adding the two aspects, which can improve the accuracy of the radial velocity estimation of the ship in the sliding spotlight mode.

[0094] In a further embodiment, the resolving according to the image Doppler shift and the theoretical Doppler shift to estimate the radial velocity of the ship includes:

[0095] Construct an equivalence relationship between the image Doppler shift and the theoretical Doppler shift, and estimate the radial velocity of the ship by resolving the equivalence relationship.

[0096] The Doppler shift of the ship is mainly caused by the relationship between the radial velocity and the oblique viewing angle between the ship and the beam, and is finally reflected in the image Doppler shift in the SLC format image of the ship. Therefore, according to the image Doppler shift and the theoretical Doppler shift of the ship, an equivalence relationship between the image Doppler shift and the theoretical Doppler shift can be constructed, which is specifically expressed as:

[0097] f shift (v r ) - f ship = 0

[0098] Based on the foregoing, it can be seen that the above formula is a function of the unknown radial velocity v of the ship r . By resolving the above equivalence relationship, the radial velocity of the ship can be estimated, that is, the estimated value of the radial velocity of the ship.

[0099] See Figure 2 , Figure 2 is a schematic structural diagram of an embodiment of a ship monitoring device provided by the present invention. As Figure 2 shown, the device includes:

[0100] An image Doppler shift determination module 201, configured to determine the image Doppler shift of the ship according to the synthetic aperture radar image of the ship; the synthetic aperture radar image is obtained by the synthetic aperture radar system in the sliding spotlight mode.

[0101] The theoretical Doppler shift amount construction module 202 is configured to construct the theoretical Doppler shift amount of the ship; the theoretical Doppler shift amount includes the Doppler shift amount generated by the radial velocity and the Doppler shift amount generated by the oblique viewing angle respectively; the theoretical Doppler shift amount reflects the relationship between the Doppler shift amount and the radial velocity.

[0102] The radial velocity estimation module 203 is configured to solve and estimate the radial velocity of the ship according to the image Doppler shift amount and the theoretical Doppler shift amount.

[0103] The positioning module 204 is configured to determine the actual azimuth of the ship according to the radial velocity of the ship and the image azimuth of the ship in the synthetic aperture radar image.

[0104] The image Doppler shift amount determination module 201 of the present invention determines the image Doppler shift amount of the ship through the synthetic aperture radar image obtained in the sliding spotlight mode; at the same time, comprehensively considering the Doppler shift amount generated by at least two aspects of the radial velocity and the oblique viewing angle, the theoretical Doppler shift amount construction module 202 constructs the theoretical Doppler shift amount of the ship, which can improve the accuracy of the radial velocity estimation of the ship in the sliding spotlight mode. On the other hand, the radial velocity estimation module 203 of the present invention performs calculations based on the image Doppler shift amount and the theoretical Doppler shift amount, greatly reducing the complexity of the calculation process and improving the efficiency of the radial velocity estimation of the ship in the sliding spotlight mode.

[0105] In a further embodiment, the image Doppler shift amount determination module 201 includes:

[0106] An image acquisition unit is configured to acquire the synthetic aperture radar image of the target scene in the sliding spotlight mode through the synthetic aperture radar system; the target scene includes the ship.

[0107] A Fourier transform unit is configured to perform a fast Fourier transform on the ship in the synthetic aperture radar image to determine the Doppler frequency spectrum signal of the ship.

[0108] An image Doppler shift amount determination unit is configured to estimate the Doppler frequency spectrum signal of the ship by using the frequency offset method to determine the image Doppler shift amount of the ship.

[0109] In the embodiment of the present invention, the Fourier transform unit determines the Doppler frequency spectrum signal of the ship through the fast Fourier transform, and then the image Doppler shift amount determination unit determines the image Doppler shift amount of the ship by using the frequency offset method, which can improve the accuracy of the image Doppler shift amount obtained through the synthetic aperture radar image.

[0110] In a further embodiment, the image acquisition unit includes:

[0111] An image acquisition subunit, configured to acquire the synthetic aperture radar image in a sliding spotlight mode through a synthetic aperture radar system of a satellite.

[0112] In view that the synthetic aperture radar system can be configured on an aircraft, a spaceship or a satellite, in order to improve the high resolution of the synthetic aperture radar image in the embodiments of the present invention, the synthetic aperture radar system can be configured on the satellite, and the image acquisition subunit acquires the synthetic aperture radar image in a sliding spotlight mode through the spaceborne synthetic aperture radar system.

[0113] In a further embodiment, the image Doppler shift amount determination unit includes:

[0114] A Doppler center estimation subunit, configured to estimate the Doppler center of the Doppler spectrum signal by using a frequency offset method;

[0115] An image Doppler shift amount determination subunit, configured to determine the image Doppler shift amount of the ship according to the Doppler center.

[0116] In a further embodiment, the theoretical Doppler shift amount construction module 202 includes:

[0117] A first Doppler shift amount construction unit, configured to construct a first Doppler shift amount of the ship according to the radial velocity of the ship; the first Doppler shift amount represents the Doppler shift amount generated by the radial velocity;

[0118] A second Doppler shift amount construction unit, configured to construct a second Doppler shift amount of the ship according to the radial velocity of the ship; the second Doppler shift amount represents the Doppler shift amount generated by the squint angle;

[0119] A theoretical Doppler shift amount construction unit, configured to construct a theoretical Doppler shift amount of the ship according to the first Doppler shift amount and the second Doppler shift amount.

[0120] In a further embodiment, the theoretical Doppler shift amount construction unit includes:

[0121] A Doppler shift amount summation subunit, configured to sum the first Doppler shift amount and the second Doppler shift amount to obtain the constructed theoretical Doppler shift amount of the ship.

[0122] The embodiments of the present invention comprehensively consider the Doppler shift amounts generated by at least two aspects of the radial velocity and the squint angle. The theoretical Doppler shift amount construction unit constructs the theoretical Doppler shift amount of the ship by summing the two aspects, which can improve the accuracy of the radial velocity estimation of the ship in the sliding spotlight mode.

[0123] In a further embodiment, the radial velocity estimation module 203 includes:

[0124] A radial velocity estimation unit, configured to construct an equivalence relationship between the image Doppler offset and the theoretical Doppler offset, and estimate the radial velocity of the ship by solving the equivalence relationship.

[0125] The following further elaborates on the method for estimating the radial velocity of a ship according to the present invention in combination with specific simulation experiments: In the simulation experiment, it is set that an ideal point ship in the target scene is located at the position (-2000m, 0) and has a constant radial velocity of 5m / s. The simulation parameters are shown in Table 1.

[0126] Simulation parameters Value Unit <![CDATA[Carrier frequency f c > 9.65 GHz <![CDATA[Satellite velocity v s > 7200 m / s Antenna size D 4 m PRF 4000 Hz <![CDATA[Pulse width T r > 10 μs <![CDATA[Bandwidth B r > 80 MHz <![CDATA[Sampling rate F r > 100 MHz <![CDATA[Shortest slant range R 0 > 600 km Total beam scanning angle θ 2.2 ° Beam scanning angular velocity ω 0.48 ° / s

[0127] Table 1

[0128] Under the sliding spotlight mode, echo simulation and imaging processing are performed on it to obtain the focused SLC format image (i.e., synthetic aperture radar image) of the ship. The amplitude of its echo data and the focused SLC format image are as Figure 3 and Figure 4 shown. It can be seen that due to the influence of the radial velocity of the ship, the imaging result is located at (-2416.7m, 0), resulting in an azimuth position offset of 416.7m. According to the method proposed by the present invention, the FFT (Fast Fourier Transform) operation is performed on the slice data of the ship to obtain its Doppler spectrum signal, as Figure 5 shown. According to the frequency offset method, the Doppler center offset can be obtained as 3285Hz. According to the proposed method, the estimated radial velocity result of the ship is 5.03m / s, and the estimation error is only 0.03m / s. The ship repositioning position is (-1997.5m, 0), and the positioning error is only 2.47m. In addition, by setting different radial velocities for the ship simulation and estimation respectively, the results are shown in Table 2. The average estimation error is only 0.037m / s, indicating that the method of the present invention has high generality and robustness.

[0129]

[0130]

[0131] Table 2

[0132] The present invention determines the image Doppler shift of a ship through a synthetic aperture radar image obtained in a sliding spotlight mode; meanwhile, comprehensively considering the Doppler shift generated by at least two aspects of the radial velocity and the squint angle, a theoretical Doppler shift of the ship is constructed, which can improve the accuracy of the radial velocity estimation of the ship in the sliding spotlight mode. On the other hand, the present invention performs calculations based on the image Doppler shift and the theoretical Doppler shift, greatly reducing the complexity of the calculation process and improving the efficiency of the radial velocity estimation of the ship in the sliding spotlight mode.

[0133] Each module in the above ship monitoring device can be implemented in whole or in part by software, hardware, and their combination. Each of the above modules can be embedded in the processor of the computer device in hardware form or be independent of it, or can be stored in the memory of the computer device in software form for the processor to call and execute the operations corresponding to each of the above modules. For the steps executed by each of the above modules or units (sub-units), please refer to the steps of the corresponding method embodiments of each of the above modules, which will not be elaborated here in detail.

[0134] Furthermore, an embodiment of the present invention also provides an electronic device. Among them, the above electronic device includes a server and / or a terminal. The terminal and the server can each independently execute the ship monitoring method provided in the embodiment of the present invention, and the terminal and the server can also cooperate to execute the ship monitoring method provided in the embodiment of the present invention. The terminal communicates with the server through a network. The data storage system can store the data that the server needs to process. The data storage system can be set up separately, integrated on the server, or placed on the cloud or other servers.

[0135] The server can be an independent physical server, a server cluster or a distributed system composed of multiple physical servers, or a cloud server providing cloud computing services. The terminal can be, but is not limited to, various personal computers, laptop computers, smart phones, tablet computers, Internet of Things devices, and portable wearable devices. The Internet of Things devices can be smart speakers, smart TVs, smart air conditioners, smart in-vehicle devices, projection devices, etc. The portable wearable devices can be smart watches, smart bracelets, head-mounted devices, etc. The head-mounted devices can be virtual reality (VR) devices, augmented reality (AR) devices, smart glasses, etc.

[0136] Among them, the server may specifically include: at least one processor, at least one memory, a power supply, a communication interface, an input / output interface, and a communication bus. In this embodiment, the power supply is used to provide working voltage for each hardware device on the server; the communication interface can create a data transmission channel between the server and external devices, and the communication protocol it follows is any communication protocol applicable to the technical solution of the present invention, and specific limitations are not imposed on it here; the input / output interface is used to obtain external input data or output data to the outside, and its specific interface type can be selected according to specific application needs, and no specific limitations are made here. Generally, the terminal in this embodiment includes: a processor and a memory. In some embodiments, the terminal may further include a display screen, an input / output interface, a communication interface, sensors, a power supply, and a communication bus.

[0137] Among them, the processor may include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor can be implemented in at least one hardware form of DSP (Digital Signal Processing), FPGA (Field-Programmable Gate Array), or PLA (Programmable Logic Array). The processor may also include a main processor and a coprocessor. The main processor is a processor used to process data in the wake state, also known as the CPU (Central Processing Unit); the coprocessor is a low-power processor used to process data in the standby state. In some embodiments, the processor may be integrated with a GPU (Graphics Processing Unit), and the GPU is responsible for rendering and drawing the content to be displayed on the display screen. In some embodiments, the processor may further include an AI (Artificial Intelligence) processor, and the AI processor is used to process computational operations related to machine learning.

[0138] Among them, the memory is used to store a computer program, which is loaded and executed by the processor to implement the relevant steps in the request processing disclosed in any of the foregoing embodiments. As a carrier for storing resources, the memory can be a read-only memory, a random access memory, a magnetic disk, an optical disc, etc. The resources stored thereon include an operating system, a computer program, data, etc. The storage method can be temporary storage or permanent storage. Among them, the operating system is used to manage and control each hardware device and computer program on the server to enable the processor to perform operations and processing on the data in the memory. It can be Windows Server, Netware, Unix, Linux, etc. In addition to the computer program that can be used to complete the request processing method disclosed in any of the foregoing embodiments, the computer program can further include a computer program that can be used to complete other specific tasks. In addition to data such as update information of the application program, the data can also include data such as developer information of the application program.

[0139] Furthermore, an embodiment of the present invention also discloses a storage medium in which computer-executable instructions are stored. When the computer-executable instructions are loaded and executed by a processor, the ship monitoring method disclosed in any of the foregoing embodiments is implemented. For the specific steps of this method, reference can be made to the corresponding content disclosed in the foregoing embodiments and will not be elaborated here.

[0140] Furthermore, an embodiment of the present invention also discloses a computer program product, including a computer program / instructions, which, when executed by a processor, implement the ship monitoring method described in any of the foregoing embodiments. For the specific steps of this method, reference can be made to the corresponding content disclosed in the foregoing embodiments and will not be elaborated here.

[0141] In summary, a ship monitoring method, a ship monitoring device, an electronic device, and a storage medium provided by the present invention determine the image Doppler offset of a ship through a synthetic aperture radar image obtained in a sliding spotlight mode; at the same time, comprehensively considering the Doppler offset generated by at least two aspects of the radial velocity and the squint angle, a theoretical Doppler offset of the ship is constructed, which can improve the accuracy of the radial velocity estimation of the ship in the sliding spotlight mode. On the other hand, the present invention performs calculations based on the image Doppler offset and the theoretical Doppler offset, greatly reducing the complexity of the calculation process and improving the efficiency of the radial velocity estimation of the ship in the sliding spotlight mode.

[0142] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the present invention are all information and data that have been authorized by the user or fully authorized by all parties, and the collection, use, and processing of relevant data need to comply with the relevant laws, regulations, and standards of relevant countries and regions.

[0143] It can be understood that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0144] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A ship monitoring method, characterized in that: include: Determining an image Doppler shift of the ship based on a synthetic aperture radar image of the ship; The synthetic aperture radar image is acquired by the synthetic aperture radar system in a sliding beamforming mode; Constructing a theoretical Doppler shift of the ship; the theoretical Doppler shift includes a Doppler shift generated by the radial velocity of the ship and a Doppler shift generated by the oblique angle; the theoretical Doppler shift reflects the relationship between the Doppler shift and the radial velocity; According to the image Doppler shift and the theoretical Doppler shift, a solution is performed to estimate the radial velocity of the ship; The actual azimuth of the ship is determined according to the radial velocity of the ship and the image azimuth of the ship in the synthetic aperture radar image.

2. The ship monitoring method according to claim 1, characterized in that: Determining the image Doppler shift of the ship according to the synthetic aperture radar image of the ship includes: Acquiring the synthetic aperture radar image of a target scene by a synthetic aperture radar system in a sliding spotlight mode; the target scene includes the ship; Performing a fast Fourier transform on the ship in the synthetic aperture radar image to determine a Doppler spectrum signal of the ship; The Doppler spectrum signal of the ship is estimated by using a frequency deviation method to determine the image Doppler shift of the ship.

3. The ship monitoring method according to claim 2, characterized in that: The step of acquiring the synthetic aperture radar image of the target scene by using the synthetic aperture radar system in a sliding beamforming mode comprises: The synthetic aperture radar image is acquired by a synthetic aperture radar system of a satellite in a sliding beam mode.

4. The ship monitoring method according to claim 2, characterized in that: The method of estimating the Doppler spectrum signal of the ship by using a frequency deviation method to determine the image Doppler shift of the ship includes: estimating the Doppler center of the Doppler spectrum signal by using a frequency deviation method; The image Doppler shift of the ship is determined according to the Doppler center.

5. The ship monitoring method according to claim 1, characterized in that: The step of constructing the theoretical Doppler shift of the ship comprises: constructing a first Doppler shift of the ship according to the radial velocity of the ship; the first Doppler shift represents a Doppler shift generated by the radial velocity; constructing a second Doppler shift of the ship according to the radial velocity of the ship, wherein the second Doppler shift represents a Doppler shift caused by a squint angle; A theoretical Doppler shift of the ship is constructed according to the first Doppler shift and the second Doppler shift.

6. The ship monitoring method according to claim 5, characterized in that: The step of constructing a theoretical Doppler shift of the ship according to the first Doppler shift and the second Doppler shift comprises: The first Doppler shift and the second Doppler shift are added together to obtain the constructed theoretical Doppler shift of the ship.

7. The ship monitoring method according to claim 1, characterized in that: The step of calculating, based on the image Doppler shift and the theoretical Doppler shift, to estimate the radial velocity of the ship comprises: An equivalent relationship between the image Doppler shift and the theoretical Doppler shift is constructed, and the radial velocity of the ship is estimated by solving the equivalent relationship.

8. A ship monitoring device, characterized in that: include: An image Doppler shift determination module is used to determine the image Doppler shift of the ship based on the synthetic aperture radar image of the ship; The synthetic aperture radar image is acquired by the synthetic aperture radar system in a sliding beamforming mode; A theoretical Doppler shift construction module is used to construct a theoretical Doppler shift of the ship; the theoretical Doppler shift includes a Doppler shift generated by a radial velocity and a Doppler shift generated by a squint angle; the theoretical Doppler shift reflects the relationship between the Doppler shift and the radial velocity; A radial velocity estimation module, used for resolving the image Doppler shift and the theoretical Doppler shift to estimate the radial velocity of the ship; A positioning module is used to determine the actual position of the ship according to the radial velocity of the ship and the image position of the ship in the synthetic aperture radar image.

9. An electronic device, characterized in that: The method comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the ship monitoring method according to any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located is controlled to execute the ship monitoring method according to any one of claims 1 to 7.

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