Ship scattering characteristics database building method and system based on space-borne GNSS-S radar and AIS

Abstract

The present invention relates to a ship scattering characteristic library building method based on satellite-borne GNSS-S radar and AIS, the method comprising: S100, GNSS-S radar receives the scattering signal of the ship target on the sea surface, and obtains the position information of the ship target; S200, AIS receives the broadcast signal of the ship target at the corresponding position, and obtains the ship information of the ship target; S300, according to the position information, determines the multi-dimensional RCS information of the ship target; S400, according to the ship information, extracts the type, optical picture and physical form of the ship target; S500, according to the multi-dimensional RCS information, type, optical picture and physical form of the ship target, constructs a ship scattering characteristic library. The present invention combines GNSS-S radar and AIS to detect the position information and ship information of the ship target, and establishes a ship scattering characteristic library. The whole library building process is a passive, low-power consumption mode, which has the advantages of low power consumption, low cost, high efficiency and high library building accuracy.

Description

Technical Field

[0001] The present invention relates to the field of radar technology, and in particular to a method for building a ship scattering characteristic database based on a satellite-borne GNSS-S radar and an AIS (Automatic Identification System). Background Art

[0002] For a long time, all-day and all-weather ship detection and surveillance have been related to major issues such as my country's maritime security. At present, surface ship detection mainly relies on synthetic aperture radar (SAR) satellites, optical satellites, etc. Optical satellites are affected by weather such as clouds, fog and rain at sea, and it is difficult to give full play to their advantages of high-resolution detection and high-performance interpretation. SAR satellites have the advantage of all-day and all-weather detection, but the SAR payload consumes a lot of power, and each orbit can only work for about 10 minutes. In addition, the dimension of obtaining ship target scattering information is relatively single, and the information interpretation is difficult. In order to achieve higher performance and lower power consumption of surface ship target detection, new radar detection technology based on external radiation sources is developing rapidly.

[0003] With the full opening of my country's BeiDou-3 satellite navigation system, together with the GPS satellite navigation system and the Galileo satellite navigation system, a global navigation and positioning system (GNSS) consisting of more than 140 satellites has been formed. GNSS signals have the advantage of global full-time coverage, and the orbital altitude is above 20,000 km. They can be used as a "natural" radiation source for multi-station radar RCS (Radar Cross Section) measurement of surface ship targets, which will greatly reduce the complexity of the multi-station radar RCS measurement system of surface ships. However, the bandwidth of GNSS signals is relatively narrow, generally 1MHz to 20MHz, and the spatial resolution is low. It is difficult to classify surface ship targets by indicators such as spatial resolution, and it is urgent to find new information dimensions to improve the classification ability of surface ship targets. Summary of the invention

[0004] In view of this, an embodiment of the present invention proposes a ship scattering characteristics database building method based on space-borne GNSS-S radar and AIS, which has the advantages of low power consumption, low cost, high efficiency and high database building accuracy.

[0005] The embodiment of the present invention proposes a method for building a ship scattering characteristic database based on space-borne GNSS-S radar and AIS, the method comprising:

[0006] S100, GNSS-S radar receives the scattered signal of the ship target on the sea surface and obtains the position information of the ship target;

[0007] S200, the AIS receives a broadcast signal of a ship target at a corresponding position, and obtains ship information of the ship target;

[0008] S300, determining a multi-dimensional RCS value of the ship target;

[0009] S400, extracting the type, optical image and physical form of the ship target according to the ship information;

[0010] S500 builds a ship scattering characteristics library based on the multi-dimensional RCS value, type, optical image and physical form of the ship target.

[0011] Preferably, in step S100, there are multiple GNSS-S radars, each GNSS-S radar corresponds to one navigation satellite, the GNSS-S radar simultaneously receives 1.17 GHz and 1.57 GHz sub-band signals of multiple navigation satellites, and the GNSS-S radar simultaneously receives horizontal polarization echoes and vertical polarization echoes of ship targets.

[0012] Preferably, in step S200, the ship information includes the reported position, speed and ship number of the ship target.

[0013] Preferably, in step S300,

[0014] The multidimensional RCS value of the kth ship target is σ k,l,m,n ,l=1,2; m=1,2; n=1,2,...,N;

[0015] Where, l is the polarization scattering number; m is the frequency band scattering number; and N is the number of GNSS-S radars.

[0016] Preferably, the multidimensional RCS value σ of the kth ship target k,l,m,n The calculation formula is:

[0017]

[0018] Among them, SNR k,l,m,n R is the signal-to-noise ratio of different polarizations and frequency bands observed by the nth GNSS-S radar for the kth ship target, n is the distance between the nth navigation satellite and the ship target, R r is the distance between the radar receiver and the ship target, k is the Boltzmann constant, B n is the navigation satellite signal bandwidth, T0 is the GNSS-S radar receiver temperature, F n is the noise coefficient of the GNSS-S radar receiver, L s is the environmental attenuation, P tx,n With G tx,n are the transmission peak power and antenna gain of the nth navigation satellite, S a is the GNSS-S radar receiving antenna area, G s,nis the nth GNSS-S radar signal processing gain.

[0019] Preferably, the multidimensional RCS information includes multidimensional RCS values ​​of the ship target at different observation angles of GNSS-S radars; the multidimensional RCS value of the k-th ship target at different observation angles of GNSS-S radars is:

[0020]

[0021] Where n is the scattering sequence number of the GNSS-S radar formed by the nth navigation satellite; the observation angle of the nth GNSS-S radar is θ n , is the incident angle and azimuth of the nth navigation satellite signal, α q , β q are the incident angle and azimuth received by the GNSS-S radar, and q is the number of times the kth ship target is observed.

[0022] Preferably, in step S400, the AIS extracts the type, optical image and physical form of the ship target according to the ship number information of the ship target, and the physical form includes the physical length and physical width.

[0023] Preferably, in step S500, constructing a ship scattering characteristic library includes:

[0024] Taking the type of ship target as the index, the multi-dimensional RCS value under different observation angles of GNSS-S radar, the gray value of the optical image, the physical length and the physical width are taken as the characteristic values ​​to form a ship scattering characteristic library.

[0025] Preferably, constructing a ship scattering characteristic library further comprises:

[0026] When the GNSS-S radar and AIS observe the same type of ship target within multiple orbital periods of the satellite, the multi-dimensional RCS information of the corresponding type of ship target is expanded and the ship scattering characteristic library is updated.

[0027] Preferably, the number of GNSS-S radars is any number between 8 and 16.

[0028] According to at least one aspect of an embodiment of the present invention, an embodiment of the present invention utilizes the position of a ship target detected by a GNSS-S radar to estimate the multi-dimensional RCS value of the ship target, extracts information such as the ship target type, optical picture, physical form, etc. at the corresponding position through an AIS payload, and uses the ship target type as an index value and the multi-dimensional RCS value, optical picture, physical form, etc. of the ship target as characteristic values ​​to establish a ship target scattering characteristic library. The entire library building process is in a passive, low-power consumption mode, and the satellite has the advantage of continuous operation over a full orbit period.

[0029] According to at least one aspect of the embodiments of the present invention, only multiple GNSS satellites are used as transmission sources for detection and measurement, and there is no need to actively transmit any electromagnetic waves. The AIS payload passively receives ship information broadcast by the ship itself. The entire satellite works in a passive state, which has the advantages of low system complexity, low power consumption, low cost, and high efficiency.

[0030] According to at least one aspect of the embodiments of the present invention, a ship scattering characteristic library constructed by synchronously utilizing the multi-dimensional RCS information of the GNSS-S radar payload and the ship type, physical form and other information of the AIS payload has the advantages of high library construction accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a flow chart of a method for building a database of ship scattering characteristics based on space-borne GNSS-S radar and AIS according to an embodiment of the present invention;

[0033] Figure 2 A schematic diagram of a working scenario of a satellite for building a database using the method of an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the structure of a ship scattering characteristic library according to an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the structure of a ship scattering characteristics database building system based on space-borne GNSS-S radar and AIS. DETAILED DESCRIPTION

[0036] The description of the embodiments of this specification should be combined with the corresponding drawings, which should be considered as part of the complete specification. In the drawings, the shape or thickness of the embodiments may be enlarged and indicated for simplification or convenience. Furthermore, the parts of each structure in the drawings will be described separately. It is worth noting that the elements not shown in the drawings or not described in words are in a form known to ordinary technicians in the relevant technical field.

[0037] The description of the embodiments herein and any reference to directions and orientations are only for the convenience of description and are not to be construed as any limitation on the scope of protection of the present invention. The following description of the preferred embodiments may involve combinations of features, which may exist independently or in combination, and the present invention is not particularly limited to the preferred embodiments. The scope of the present invention is defined by the claims.

[0038] like Figure 1 FIG. 1 is a flow chart of a method for building a ship scattering characteristic database based on a satellite-borne GNSS-S radar and an AIS according to an embodiment of the present invention. The method includes:

[0039] S100, GNSS-S radar receives scattered signals from surface ship targets and obtains the position information of the ship targets.

[0040] In this embodiment, if Figure 2 As shown in Figure 1, the database building process includes multiple navigation satellites and low-orbit satellites. Multiple navigation satellites serve as signal transmitters to cover a large area of ​​the sea surface. Low-orbit satellites are equipped with GNSS-S radars (corresponding to Figure 2 GNSS-S antenna) and AIS (corresponding Figure 2 The GNSS-S radar payload receives the scattered signals of the surface ship targets to multiple navigation satellite signals. After signal processing, it can detect the distribution of surface ship targets and give the position of each ship target.

[0041] The GNSS-S radar payload can simultaneously receive the 1.17GHz and 1.57GHz sub-band signals of multiple navigation satellites, and can simultaneously receive the horizontal polarization echo (H) and vertical polarization echo (V) of ship targets. In each database building process, N navigation satellites are used as signal transmission sources for detection to form N dual-station GNSS-S radars, and the 4N-dimensional RCS values ​​of the ship target are obtained at the same time. N is generally 8 to 16, and the 4N dimensions consider the 1.17GHz frequency band echo signal, 1.57GHz frequency band echo signal, horizontal polarization echo signal, and vertical polarization echo signal of the ship target. Due to the large number of GNSS satellites, dozens of navigation satellite signals can be received in most sea areas. By carrying radar receivers on low-orbit satellites, dozens of GNSS-S dual-station radars can be formed with dozens of navigation satellites, and dozens of dual-station angle RCS values ​​of the same ship target can be obtained simultaneously. By using multiple consecutive observations of ship targets, a multi-dimensional scattering characteristic library of ship targets can be obtained.

[0042] S200, the AIS receives a broadcast signal of a ship target at a corresponding position, and obtains ship information of the ship target.

[0043] like Figure 2 As shown, in this embodiment, AIS is the AIS payload on the low-orbit satellite. Since the GNSS-S radar detects the target position by receiving scattered signals, there is a certain error. Therefore, after the GNSS-S radar detects the position of the target, the AIS payload detects the broadcast signal (which is an AIS signal) of the ship target closest to the position to obtain the exact position of the target. The information contained in the broadcast signal includes the position, speed and ship number of the ship target. The position information in the broadcast signal of the ship target is accurate position information. In this way, the accurate position information, speed and ship number information of the ship target can be obtained.

[0044] S300: Determine multi-dimensional RCS information of the ship target according to the position information.

[0045] In this embodiment, the multidimensional RCS information includes the multidimensional RCS values ​​of the ship target under the observation angles of different GNSS-S radars. The multidimensional RCS value of the kth ship target measured by the nth GNSS-S radar is σ k,l,m,n ,l=1,2;m=1,2;n=1,2,...,N. Among them, l is the polarization scattering number, l=1 represents the multi-dimensional RCS value of the ship target under the condition of vertical polarization reception, l=2 represents the multi-dimensional RCS value of the ship target under the condition of horizontal polarization reception; m is the frequency band scattering number, m=1 represents the multi-dimensional RCS value of the ship target under the condition of 1.17GHz frequency band reception, m=2 represents the multi-dimensional RCS value of the ship target under the condition of 1.57GHz frequency band reception; N is the number of GNSS-S radars, and the position information of the kth ship target is (x k ,y k ), where x k is the longitude coordinate value, y k is the latitude coordinate value.

[0046] The multi-dimensional RCS value σ of the kth ship target measured by the nth GNSS-S radar k,l,m,n The calculation formula is:

[0047]

[0048] Among them, SNR k,l,m,n is the signal-to-noise ratio (SNR) of different polarizations and frequency bands observed by the nth GNSS-S radar for the kth ship target, R n is the distance between the nth navigation satellite and the ship target, R r is the distance between the radar receiver and the ship target, k is the Boltzmann constant, B n is the navigation satellite signal bandwidth, T0 is the GNSS-S radar receiver temperature, F nis the noise coefficient of the GNSS-S radar receiver, L s is the environmental attenuation, P tx,n With G tx,n are the transmission peak power and antenna gain of the nth navigation satellite, S a is the GNSS-S radar receiving antenna area, G s,n is the nth GNSS-S radar signal processing gain.

[0049] The multi-dimensional RCS value of the kth ship target under different GNSS-S radar observation angles is:

[0050]

[0051] Where n is the scattering sequence number of the GNSS-S radar formed by the nth navigation satellite; the observation angle of the nth GNSS-S radar is θ n , is the incident angle and azimuth of the nth navigation satellite signal, α q , β q are the incident angle and azimuth received by the GNSS-S radar, and q is the number of times the kth ship target is observed.

[0052] S400: extracting the type, optical image and physical form of the ship target according to the ship information.

[0053] like Figure 2 As shown, in this embodiment, the AIS extracts the type, optical image and physical form of the ship target according to the ship number information of the ship target, and the physical form includes the physical length and physical width. The AIS can search the type, optical image and physical form information of the ship with the corresponding number in the public dedicated database according to the ship number information. Among them, the type of the kth ship target is x k , the gray value of the optical image is I k , the physical length is L k , the physical width is W k .

[0054] S500 builds a ship scattering characteristics library based on the multi-dimensional RCS value, type, optical image and physical form of the ship target.

[0055] like Figure 3 As shown, in this embodiment, constructing a ship scattering characteristic library includes:

[0056] Type of ship target x k As an index, the multi-dimensional RCS values ​​under different GNSS-S radar observation angles are Optical image gray value I k , physical length Lk With physical width W k As the characteristic value, the ship scattering characteristic library Ω(χ k ),k=1,2,...,K, where K is the total number of ship target types.

[0057] The ship scattering characteristics library is based on the ship target type x k The multidimensional scattering characteristic library of K-type ship targets is constructed as an index. The ship scattering characteristic library takes the physical form of the ship target as the true value basis, provides intermediate confirmation information for the establishment of the multidimensional scattering characteristic library of the ship target, and is mainly composed of information such as the length, width and optical picture of the ship. The ship scattering characteristic library is guided by the observation conditions as the mode, and provides mode information for the establishment of the multidimensional scattering characteristic library of the ship target. It is mainly composed of three parameters: observation angle, polarization mode, and signal frequency band. The ship scattering characteristic library takes the RCS value of the ship target as the characteristic, and assigns values ​​to the ship target under the guidance of different observation modes.

[0058] Furthermore, in this embodiment, the characteristic library is expanded by the following method:

[0059] When the GNSS-S radar and AIS both observe the type of ship target as x within P orbital periods of the satellite, k When , the expanded ship target type is x k Multidimensional RCS value And update the ship scattering characteristic library, where the maximum value of n is Pn and the maximum value of q is P. As the number of orbital periods P increases, the multi-dimensional RCS value of the ship target The more the ship scattering characteristics library Ω(χ k )The richer.

[0060] like Figure 4As shown, the present invention also provides a system for a ship scattering characteristic library building method based on satellite-borne GNSS-S radar and AIS, which is used to implement the above method, and the system includes: a GNSS-S radar module 401, which is used to detect sea surface ship targets and determine the preliminary position information of the ship targets according to the scattering signals of the ship targets; a ship multi-dimensional RCS calculation module 402, which is used to calculate the multi-dimensional RCS value of the ship target; a ship target position module 403, which is used to determine the accurate position information of the ship target; an AIS module 404, which is used to receive the broadcast signal sent by the ship target; a ship target type extraction module 405, which is used to extract the type of the ship target according to the position information of the ship target; a ship target physical form extraction module 406, which is used to extract the physical form of the ship target according to the position information and ship information of the ship target; a ship target heading extraction module 407, which is used to extract the heading information of the ship target according to the position information and attribute information of the ship target; a ship scattering characteristic library formation module 408, which is used to build a ship scattering characteristic library according to the ship target type.

[0061] The embodiment of the present invention utilizes the ship target position detected by the GNSS-S radar to estimate the multi-dimensional RCS value of the ship target, extracts the ship target type, optical picture, physical form and other information at the corresponding position through the AIS payload, takes the ship target type as the index value, and takes the ship target multi-dimensional RCS value, optical picture, physical form and the like as the characteristic values ​​to establish a ship target scattering characteristic library. The entire library building process is in a passive, low-power consumption mode, and the satellite has the advantage of continuous operation over a full orbit period.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for building a database of ship scattering characteristics based on space-borne GNSS-S radar and AIS, characterized in that: The method comprises: S100, GNSS-S radar receives the scattered signal of the ship target on the sea surface and obtains the position information of the ship target; S200, the AIS receives a broadcast signal of a ship target at a corresponding position, and obtains ship information of the ship target; S300, determining multi-dimensional RCS information of the ship target; S400, extracting the type, optical image and physical form of the ship target according to the ship information; S500 builds a ship scattering characteristics library based on the multi-dimensional RCS information, type, optical image and physical form of the ship target; In step S300, the multi-dimensional RCS value of the kth ship target measured by the nth GNSS-S radar is expressed as σ k,l,m,n ,l=1,2; m=1,2; n=1,2,...,N; Where l is the polarization scattering number, m is the frequency band scattering number, and N is the number of GNSS-S radars; The multi-dimensional RCS value σ of the kth ship target measured by the nth GNSS-S radar k,l,m,n The calculation formula is: Among them, SNR k,l,m,n R is the signal-to-noise ratio of different polarizations and frequency bands observed by the nth GNSS-S radar for the kth ship target, n is the distance between the nth navigation satellite and the ship target, R r is the distance between the radar receiver and the ship target, k is the Boltzmann constant, B n is the navigation satellite signal bandwidth, T0 is the GNSS-S radar receiver temperature, F n is the noise coefficient of the GNSS-S radar receiver, L s is the environmental attenuation, P tx,n With G tx,n are the peak transmission power and antenna gain of the nth navigation satellite, S a is the GNSS-S radar receiving antenna area, G s,n is the nth GNSS-S radar signal processing gain; The multi-dimensional RCS information includes multi-dimensional RCS values ​​of the ship target under different observation angles of GNSS-S radars; The multi-dimensional RCS value of the kth ship target under different GNSS-S radar observation angles is: Where n is the scattering number of the GNSS-S radar corresponding to the nth navigation satellite; the observation angle of the nth GNSS-S radar is θ n , is the incident angle and azimuth of the nth navigation satellite signal, α q , β q are the incident angle and azimuth received by the GNSS-S radar, and q is the number of times the kth ship target is observed.

2. The method for building a database of ship scattering characteristics based on space-borne GNSS-S radar and AIS according to claim 1 is characterized in that: In step S100, there are multiple GNSS-S radars, and each GNSS-S radar corresponds to one navigation satellite; The scattered signal received by the GNSS-S radar is formed by the signal emitted by its corresponding navigation satellite and scattered by the ship target.

3. The method for building a database of ship scattering characteristics based on space-borne GNSS-S radar and AIS according to claim 2 is characterized in that: In step S200, the ship information includes the reported position, speed and ship number of the ship target.

4. The method for building a database of ship scattering characteristics based on space-borne GNSS-S radar and AIS according to claim 1 is characterized in that: In step S400, The AIS extracts the type, optical image and physical form of the ship target according to the ship number information of the ship target, wherein the physical form includes the physical length and the physical width.

5. The method for building a database of ship scattering characteristics based on space-borne GNSS-S radar and AIS according to claim 4 is characterized in that: In step S500, constructing a ship scattering characteristic library includes: With the type of ship target as an index, the multi-dimensional RCS information of the ship target, the grayscale value of the optical image, the physical length and the physical width are used as characteristic values ​​to form a ship scattering characteristic library, wherein the ship scattering characteristic library includes one or more types of ship targets.

6. The method for building a database of ship scattering characteristics based on space-borne GNSS-S radar and AIS according to claim 5 is characterized in that: Building a ship scattering characteristics library further includes: When the GNSS-S radar and AIS observe the same type of ship target within multiple orbital periods of the satellite, the multi-dimensional RCS information of the corresponding type of ship target is expanded and the ship scattering characteristic library is updated.

7. The method for building a ship scattering characteristic database based on space-borne GNSS-S radar and AIS according to any one of claims 1 to 6, characterized in that: The number of GNSS-S radars is 8 to 16.

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