Ship positioning method and device based on R-mode reverse passive positioning algorithm

Abstract

The invention relates to a ship positioning method and device based on an R-mode reverse passive positioning algorithm, and relates to the technical field of ship positioning. The method comprises the following steps: acquiring a first ASM digital signal sequence sent by a ship; acquiring a second ASM digital signal sequence stored by the base station end; performing cross-correlation calculation on the first ASM digital signal sequence and the second ASM digital signal sequence to obtain a cross-correlation sequence, and determining the time delay between the ship and the base station according to the cross-correlation sequence; obtaining the distance between the ship and the base station according to the time delay between the ship and the base station; the distances between the to-be-positioned ship and the three base stations with the known coordinates are obtained, and ship positioning is achieved according to the distances between the to-be-positioned ship and the three base stations. According to the invention, ship spontaneous ASM signals are utilized, and through three-shore-based passive distance measurement and circle intersection, low-cost and anti-cheating ship positioning which does not depend on shore-based base station sending signals is realized.

Description

Technical Field

[0001] This invention relates to ship positioning technology, and more specifically, to a ship positioning method and apparatus based on an R-mode reverse passive positioning algorithm. Background Technology

[0002] Ship positioning is crucial for ensuring maritime safety and maintaining maritime national defense. Currently, VHF Data Exchange System (VDES) base stations typically acquire ship positions using traditional message positioning. This relies on ships actively and voluntarily sending electronic messages containing their longitude, latitude, and other information to the VDES base station. The base station then receives and parses these messages to directly determine the ship's position. This method depends on the ship's active cooperation, has a simple system structure, and is widely used globally.

[0003] However, the fatal flaw of message-based positioning lies in its "trusted source" assumption. If a ship or a third party maliciously tampers with the location field in the message, the base station will be unable to verify it. With intentional interference and deception, by altering the ship's location information in the message, the base station can obtain a misaligned ship location, leading to misjudgments and thus deceiving management authorities. In severe cases, this could threaten national defense security. Therefore, the industry urgently needs a passive positioning method that requires no additional shipboard or base station equipment and is compatible with existing VDES infrastructure to achieve independent verification of the ship's true location. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, this application provides a ship positioning method and device based on the R-mode reverse passive positioning algorithm. This invention utilizes the ship's self-generated ASM signal, through passive ranging and three-circle positioning using three shore-based base stations, to achieve ship positioning that is independent of shore-based base station signal transmission, low-cost, and spoofing-resistant.

[0005] The technical means employed in this invention are as follows:

[0006] A ship positioning method based on the R-mode reverse passive positioning algorithm includes the following steps: S1. Acquire the first ASM signal sent by the ship, perform analog-to-digital conversion on the first ASM signal, and generate a first ASM digital signal sequence; S2. Obtain the second ASM digital signal sequence stored at the base station; S3. Perform cross-correlation calculation on the first ASM digital signal sequence and the second ASM digital signal sequence to obtain a cross-correlation sequence, and determine the time delay between the ship and the base station based on the cross-correlation sequence; S4. Obtain the distance between the ship and the base station based on the time delay between the ship and the base station; S5. Based on S1-S4 above, obtain the distance between the ship to be located and three base stations with known coordinates, and realize ship positioning based on the distance between the ship to be located and the three base stations.

[0007] Furthermore, the cross-correlation of the first ASM digital signal sequence and the second ASM digital signal sequence is calculated according to the following formula:

[0008] Where x[n] represents the first ASM digital signal sequence, This indicates the second ASM digital signal sequence The conjugate sequence after shifting the second ASM digital signal sequence to the right by m sampling points, where m represents the number of sampling points shifted relative to the first ASM digital signal sequence, and its value range covers all possible relative delays between the two sequences. This represents a cross-correlation sequence.

[0009] Furthermore, the first ASM digital signal sequence and the second ASM digital signal sequence are cross-correlatedly calculated according to the following method: Obtain the first ASM digital signal sequence and the second ASM digital signal sequence, and perform discrete Fourier transform on them respectively to obtain the frequency domain sequence of the first ASM digital signal and the frequency domain sequence of the second ASM digital signal; The cross-correlation between the first ASM digital signal frequency domain sequence and the second ASM digital signal frequency domain sequence is calculated according to the following formula:

[0010] in, This represents the frequency domain sequence of the first ASM digital signal. This represents the conjugate sequence of the second ASM digital signal frequency domain sequence. Represents a frequency domain cross-correlation sequence; The cross-correlation sequence in the frequency domain is subjected to a discrete inverse Fourier transform to obtain the cross-correlation sequence in the time domain.

[0011] Furthermore, the latency between the ship and the base station is determined in the following ways: turn up Make

[0012] in, Represents a cross-correlated sequence with a length of . , Indicates time delay.

[0013] Furthermore, the distance between the ship and the base station is calculated using the following formula:

[0014] in, Indicates the distance between the ship and the base station. This indicates the latency between the ship and the base station. This indicates the speed at which electromagnetic waves propagate.

[0015] Furthermore, ship positioning is achieved based on the distances between the ship to be located and the three base stations, including solving the following equations to obtain the ship's position:

[0016] Where (X, Y) represents the ship's position, Indicates the location of the first base station. Indicates the location of the second base station. Indicates the location of the third base station. This indicates the distance between the ship and the first base station. This indicates the distance between the ship and the second base station. This indicates the distance between the ship and the third base station.

[0017] This invention also discloses a ship positioning device based on the R-mode reverse passive positioning algorithm, used to implement the aforementioned ship positioning method based on the R-mode reverse passive positioning algorithm, comprising: The signal receiving module is used to acquire the first ASM signal sent by the ship, perform analog-to-digital conversion on the first ASM signal, and generate a first ASM digital signal sequence. The local signal extraction module is used to acquire the second ASM digital signal sequence stored at the base station. The delay calculation module is used to perform cross-correlation calculation on the first ASM digital signal sequence and the second ASM digital signal sequence to obtain a cross-correlation sequence, and to determine the delay between the ship and the base station based on the cross-correlation sequence. The distance calculation module is used to obtain the distance between the ship and the base station based on the time delay between the ship and the base station; The ship positioning module is used to obtain the distance between the ship to be positioned and three base stations with known coordinates, and to achieve ship positioning based on the distance between the ship to be positioned and the three base stations.

[0018] Compared with the prior art, the present invention has the following advantages: 1. This invention applies passive positioning technology, calculating the target location by receiving wireless signals emitted by the target vessel without the base station itself emitting signals. Specifically, it can calculate the location using communication signals without the base station actively emitting signals to the vessel or demodulating and analyzing the signals emitted by the vessel. Based on existing equipment, no additional equipment is needed. By analyzing and processing the signals emitted by the vessel, the time delay from the vessel's signal to the base station is obtained, and the true distance between the vessel and the base station is calculated. Multiple base stations upload their data to a data center, which uses a shore-based ranging mode (R-mode) reverse positioning algorithm to achieve accurate positioning of the vessel.

[0019] 2. This invention does not require the construction of additional VDES base stations or the addition of new base station equipment, resulting in low engineering implementation costs. The base station passively receives the raw signals transmitted by the ship without actively transmitting ASM signals, thus achieving high concealment.

[0020] In summary, the method of this invention effectively overcomes the security deficiencies of traditional message-based positioning methods. Furthermore, based on the low cost and high stealth of R-mode reverse passive positioning technology, it enhances the reliability of maritime target positioning data. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of a ship positioning method based on the R-mode reverse passive positioning algorithm of the present invention.

[0023] Figure 2 This is a system architecture diagram for ship positioning in an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the time delay extraction results in an embodiment of the present invention.

[0025] Figure 4 This is a schematic diagram illustrating the principle of ship positioning based on three base stations in an embodiment of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] Example 1 like Figure 1 As shown, this invention provides a ship positioning method based on the R-mode reverse passive positioning algorithm, which mainly includes the following steps: S1. Acquire the first ASM signal sent by the ship, perform analog-to-digital conversion on the first ASM signal, and generate a first ASM digital signal sequence.

[0029] Specifically, this step is used to generate a first ASM signal based on the VDES transmitted by the ship. In a preferred embodiment of this application, the generation of the first ASM signal strictly follows the International Telecommunication Union Recommendation ITU-R M.2092-1. Specifically, the ASM signal is generated by the VDES, which adopts the frame concept of ITU-R M.2092-1, where one frame is one minute, one minute is divided into 2250 time slots, and one time slot is approximately 26.667 ms. ASM signal data access defaults to starting from the first time slot, and the time is synchronized with Coordinated Universal Time (UTC).

[0030] The ASM signal training sequence consists of code elements containing specific information appended to the transmitted data. Its format and content are fixed and known to both the sender and receiver. Therefore, the base station can process the received ASM signal data to calculate the signal propagation delay. In this embodiment, the ASM signal training sequence used is the double-bark sequence "111111001101010000011001010" as specified in ITU-R Recommendation M.2092-1, with the following modulation scheme: Quadrature Phase Shift Keying (QPSK) modulation with a roll-off factor of 0.35.

[0031] S2. Obtain the second ASM digital signal sequence stored at the base station.

[0032] As mentioned above, the second ASM digital signal sequence is known at the base station and is used to perform cross-correlation calculations with the received first ASM digital signal sequence.

[0033] S3. Perform cross-correlation calculation on the first ASM digital signal sequence and the second ASM digital signal sequence to obtain a cross-correlation sequence, and determine the time delay between the ship and the base station based on the cross-correlation sequence.

[0034] This step is used to convert the received first ASM signal into a processable first ASM digital signal sequence through analog-to-digital conversion, and to perform cross-correlation calculation with the locally generated second ASM digital signal sequence to obtain the propagation delay of the transmitted signal.

[0035] In an optional embodiment of this application, the cross-correlation operation of the first ASM digital signal sequence and the second ASM digital signal sequence is performed according to the following formula:

[0036] Where x[n] represents the first ASM digital signal sequence, This indicates the second ASM digital signal sequence The conjugate sequence after shifting m sampling points to the right, Let x[n] and y[n] represent cross-correlation sequences. x[n] and y[n] are discrete signal sequences of length N, and the signal propagation delay calculated from them is... arrive Within range The sampling point corresponding to the maximum value The product of the sampling period and the product of the two. It should be noted here that for equation (1)... When the sequence lengths are different, zeros need to be padded to the end of the shorter sequence to make it the same length as the longer sequence. In this case, the length of the cross-correlation calculation result is... , for Sequence length, for Sequence length.

[0037] In another optional embodiment of this application, considering that directly using equation (1) to calculate the cross-correlation value between the received sequence and the local sequence requires point-by-point multiplication and addition of each lag value, the overall computational complexity is... N is the sequence length, and the computational complexity increases quadratically with the sequence length. Therefore, to reduce the overall complexity of cross-correlation calculations, this invention utilizes the convolution theorem of Fourier transform to convert time-domain calculations into frequency-domain calculations. The specific process is as follows: Assume X[k]=DFT(x[n]), Y[k]=DFT(y[n]), This is a Discrete Fourier Transform. Then the product is calculated. (in (representing the complex conjugate of Y[k]), then performing an inverse discrete Fourier transform (IFFT) on the product sequence yields the time-domain sequence. and The cross-correlation value is calculated, and the proof is as follows: according to Definition, cross-correlation function of for:

[0038] In the formula, For mutual correlation The DFT results, i.e., the cross-correlation in the th... Frequency domain representation of a frequency point Let be the time-domain cross-correlation function, representing the sequence and In time shift The correlation is shown below, where N is the number of variables involved in the DFT calculation. Sequence length, m is the time-domain sequence index (from...) arrive ), k is the frequency domain index (representing the first value of the DFT). (Number of frequency points).

[0039] Substituting equation (1) into equation (2), we get

[0040] Commuting the summation order of expression (3), we get:

[0041] make ,but Substituting into equation (5), we get:

[0042] Equation (5) can be rearranged to obtain:

[0043] The DFT transformation formula is:

[0044] Taking the conjugate of equation (7) yields:

[0045] Substituting the result (8) into equation (5), we get:

[0046] The DFT transformation formula is:

[0047] Substituting the result into equation (9), we get:

[0048] Again The result can be obtained by performing the inverse discrete Fourier transform. .

[0049] At this point, the cross-correlation function is calculated. Transform into the known and Under the condition of, calculate The Discrete Fourier Transform (DFT) can be simplified using the Fast Fourier Transform (FFT), with a computational complexity of O(n log n). N is the length of the sequence involved in the calculation.

[0050] get ,turn up Make

[0051] This refers to the propagation delay of the ASM signal from the ship to the base station.

[0052] S4. Obtain the distance between the ship and the base station based on the time delay between the ship and the base station.

[0053] S5. Based on S1-S4 above, obtain the distance between the ship to be located and three base stations with known coordinates, and realize ship positioning based on the distance between the ship to be located and the three base stations.

[0054] The propagation delay between the ship and the three base stations is obtained as follows: , , ,distance , , They are respectively:

[0055] , , The distances between the ship and the three base stations are in kilometers. The propagation speed of electromagnetic waves is 300,000 km / s.

[0056] A ship transmits the same ASM signal, which is received by three base stations. The propagation delay from the transmitted signal to each base station is calculated using the method shown in S3. Multiplying each propagation delay by the speed of light yields the distance between the ship and each base station. Position circles are drawn with each base station as the center and the distance between the base station and the ship as the radius. Three position circles are obtained for the three base stations, and the intersection of these three circles represents the ship's position. The specific method is as follows: Assuming the ship's position is (X, Y), and the precise positions of three base stations A, B, and C are known respectively... , and The distances between the ship and three base stations were measured. , , They are respectively:

[0057] Simplifying equation (14) yields:

[0058] make

[0059]

[0060] Substituting equations (16) and (17) into equation (15), we get:

[0061] Therefore, the ship's position (X, Y) is obtained as follows:

[0062] The following specific application examples will further illustrate the solution and effects of the present invention.

[0063] The ship positioning and detection system architecture disclosed in this embodiment is as follows: Figure 2 As shown, the positioning process mainly includes the following steps: Step 1: Construct the ASM signal from ship to base station in the VDES system to obtain a local reference signal for cross-correlation calculation with the received signal. Specifically, the ASM baseband signal is generated locally at the base station according to ITU-R M.2092-1 Recommendation. The generated ASM signal contains a training sequence with a fixed format, which is a double-bark sequence "111111001101010000011001010", known to both the transmitting and receiving ends. In one embodiment, the roll-off factor is 0.35; the ASM signal is transmitted in one time slot according to the frame structure of ITU-R M.2092-1 Recommendation, with a time slot length of approximately 26.667 ms. This reference signal is used as the local sequence in subsequent cross-correlation calculations.

[0064] Step 2: Convert the received ASM signal into a processable digital signal sequence using analog-to-digital conversion. Perform cross-correlation calculation with the locally generated sequence to obtain the propagation delay of the transmitted signal. The formula used for cross-correlation calculation is:

[0065] Where x[n] represents the first ASM digital signal sequence transmitted from the ship's end. This indicates the second ASM digital signal sequence stored in the base station. The conjugate sequence after shifting the second ASM digital signal sequence to the right by m sampling points, where m represents the number of sampling points shifted relative to the first ASM digital signal sequence, and its value range covers all possible relative delays between the two sequences. This represents a cross-correlation sequence. It should be noted that this application only allows positive delays, where m ranges from [0, M], and M is the maximum delay Tmax. fs sampling rate. The maximum delay error Tmax is derived from the upper limit of the service range of the shore-based base station, 30 nautical miles / electromagnetic wave propagation speed.

[0066] To reduce the overall complexity of cross-correlation calculations, this embodiment utilizes the convolution theorem of Fourier transform to convert time-domain calculations into frequency-domain calculations. The Discrete Fourier Transform (DFT) yields the cross-correlation value. The DFT can be simplified using the Fast Fourier Transform (FFT), reducing the computational complexity by [previous value]. Become N is the length of the sequence involved in the calculation. We obtain... ,turn up Make

[0067] like Figure 3 As shown, This is the propagation delay of the ASM signal from the ship to the base station. Therefore, the propagation delay between the ship and the three base stations can be calculated as follows: , , ,distance , , They are respectively:

[0068] , , The distances between the ship and the three base stations are in kilometers. The propagation speed of electromagnetic waves is 300,000 km / s.

[0069] Step 3: Synchronous reception and ranging calculation of ASM signals transmitted by the same ship using multiple shore-based VDES base stations. The same ASM signal transmitted by a ship is received by three base stations. Each base station performs cross-correlation calculations on the received signal and its local reference signal, following the method in Step 2, to obtain the corresponding propagation delay and the distance from the ship to each base station. For example... Figure 4 As shown, location circles are drawn with each base station as the center and the corresponding distance as the radius. The intersection of multiple location circles represents the possible location area of ​​the ship. Furthermore, assuming the geographical locations of each base station are accurately known and their time bases are precisely synchronized, the distance between the ship and each base station is calculated by measuring the propagation delay of the ASM signal transmitted by the ship to each base station. The ship's planar coordinates are then calculated using the R-mode reverse passive positioning algorithm.

[0070] Assuming the ship's position is (X, Y), and the precise positions of three base stations A, B, and C are known respectively... , and The distances between the ship and three base stations were measured. , , They are respectively:

[0071] By simplifying and solving the above system of equations, an analytical expression for the ship's position (X, Y) can be obtained, thus enabling accurate inversion of the ship's position.

[0072] exist Figure 3In the specific example shown, the actual distance of the ship is 45km, meaning the actual propagation delay is 0.15ms. After receiving the signal, the VDES base station calculates the propagation delay by performing cross-correlation with the local sequence and finding the maximum value. The propagation delay estimation results using the cross-correlation of the training sequence show a clear correlation peak at the 0.15ms delay, where the estimated delay is basically consistent with the theoretical value. The correlation values ​​at other delay positions are close to noise levels, indicating that this method can reliably detect propagation delay.

[0073] This invention proposes a ship positioning method based on the R-mode reverse passive positioning algorithm. Accurate time delay is derived by cross-correlating the received ship signal with the local signal. Furthermore, the R-mode reverse passive positioning method used in this invention is mature and reliable, does not require the ship to actively report its position, and does not require additional equipment. It achieves both high-speed computation and cost savings.

[0074] Example 2 In another aspect of the embodiments of the present invention, a ship positioning device based on the R-mode reverse passive positioning algorithm is also disclosed, for implementing the above method, comprising: The signal receiving module is used to acquire the first ASM signal sent by the ship, perform analog-to-digital conversion on the first ASM signal, and thereby generate a first ASM digital signal sequence.

[0075] The local signal extraction module is used to acquire the second ASM digital signal sequence stored at the base station.

[0076] The delay calculation module is used to perform cross-correlation calculation on the first ASM digital signal sequence and the second ASM digital signal sequence to obtain a cross-correlation sequence, and to determine the delay between the ship and the base station based on the cross-correlation sequence.

[0077] The distance calculation module is used to obtain the distance between the ship and the base station based on the time delay between the ship and the base station.

[0078] The ship positioning module is used to obtain the distance between the ship to be positioned and three base stations with known coordinates, and to achieve ship positioning based on the distance between the ship to be positioned and the three base stations.

[0079] Specific examples in this embodiment can be found in the examples described in the above embodiments and optional implementations, and will not be repeated here.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ship positioning method based on the R-mode reverse passive positioning algorithm, characterized in that, Includes the following steps: S1. Acquire the first ASM signal sent by the ship, perform analog-to-digital conversion on the first ASM signal, and generate a first ASM digital signal sequence; S2. Obtain the second ASM digital signal sequence stored at the base station; S3. Perform cross-correlation calculation on the first ASM digital signal sequence and the second ASM digital signal sequence to obtain a cross-correlation sequence, and determine the time delay between the ship and the base station based on the cross-correlation sequence; S4. Obtain the distance between the ship and the base station based on the time delay between the ship and the base station; S5. Based on S1-S4 above, obtain the distance between the ship to be located and three base stations with known coordinates, and realize ship positioning based on the distance between the ship to be located and the three base stations.

2. The ship positioning method based on the R-mode reverse passive positioning algorithm according to claim 1, characterized in that, The cross-correlation between the first ASM digital signal sequence and the second ASM digital signal sequence is calculated according to the following formula: Where x[n] represents the first ASM digital signal sequence, This indicates the second ASM digital signal sequence The conjugate sequence after shifting the second ASM digital signal sequence to the right by m sampling points, where m represents the number of sampling points shifted relative to the first ASM digital signal sequence, and its value range covers all possible relative delays between the two sequences. This represents a cross-correlation sequence.

3. The ship positioning method based on the R-mode reverse passive positioning algorithm according to claim 1, characterized in that, The cross-correlation between the first ASM digital signal sequence and the second ASM digital signal sequence is calculated according to the following method: Obtain the first ASM digital signal sequence and the second ASM digital signal sequence, and perform discrete Fourier transform on them respectively to obtain the frequency domain sequence of the first ASM digital signal and the frequency domain sequence of the second ASM digital signal; The cross-correlation between the first ASM digital signal frequency domain sequence and the second ASM digital signal frequency domain sequence is calculated according to the following formula: in, This represents the frequency domain sequence of the first ASM digital signal. This represents the conjugate sequence of the second ASM digital signal frequency domain sequence. Represents a frequency domain cross-correlation sequence; The cross-correlation sequence in the frequency domain is subjected to a discrete inverse Fourier transform to obtain the cross-correlation sequence in the time domain.

4. A ship positioning method based on the R-mode reverse passive positioning algorithm according to claim 1, characterized in that, The time delay between the ship and the base station is determined in the following ways: turn up Make in, Represents a cross-correlated sequence with a length of . , Indicates time delay.

5. A ship positioning method based on the R-mode reverse passive positioning algorithm according to claim 1, characterized in that, The distance between the ship and the base station can be calculated using the following formula: in, Indicates the distance between the ship and the base station. This indicates the latency between the ship and the base station. This indicates the speed at which electromagnetic waves propagate.

6. The ship positioning method based on the R-mode reverse passive positioning algorithm according to claim 1, characterized in that, Ship positioning is achieved by determining the distances between the ship to be located and three base stations, including solving the following equations to obtain the ship's position: Where (X, Y) represents the ship's position, Indicates the location of the first base station. Indicates the location of the second base station. Indicates the location of the third base station. This indicates the distance between the ship and the first base station. This indicates the distance between the ship and the second base station. This indicates the distance between the ship and the third base station.

7. A ship positioning device based on an R-mode reverse passive positioning algorithm, used to implement the ship positioning method based on an R-mode reverse passive positioning algorithm as described in claim 1, characterized in that, include: The signal receiving module is used to acquire the first ASM signal sent by the ship, perform analog-to-digital conversion on the first ASM signal, and generate a first ASM digital signal sequence. The local signal extraction module is used to acquire the second ASM digital signal sequence stored at the base station. The delay calculation module is used to perform cross-correlation calculation on the first ASM digital signal sequence and the second ASM digital signal sequence to obtain a cross-correlation sequence, and to determine the delay between the ship and the base station based on the cross-correlation sequence. The distance calculation module is used to obtain the distance between the ship and the base station based on the time delay between the ship and the base station; The ship positioning module is used to obtain the distance between the ship to be positioned and three base stations with known coordinates, and to achieve ship positioning based on the distance between the ship to be positioned and the three base stations.

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