Beidou short message AIS information compression transmission method based on grid coding

Abstract

The invention discloses a Beidou short message AIS information compression transmission method based on grid coding. The problem of character capacity limitation of AIS information in Beidou short message transmission at present is mainly solved. The method is characterized in that a sea area of a current position of a ship is divided into a plurality of grids, traditional longitude and latitude representation is replaced by grid numbers, and compression of position information is achieved. The invention provides an effective AIS information compression scheme, simple and convenient coding and efficient transmission of ship information are realized, and an innovative solution is provided for application of Beidou short messages in marine multi-ship information transmission.

Description

Technical Field

[0001] The present invention relates to the field of marine communications, and in particular to a Beidou short message AIS information compression transmission method based on grid coding. Background Art

[0002] Satellite AIS is a ship positioning technology that receives AIS message information sent by ships through low-orbit satellites. The satellites will receive and decode the AIS message information and forward it to the corresponding earth station, so that land management agencies can grasp the relevant dynamic information of the ship and monitor ships sailing in the distant seas.

[0003] However, the use of Beidou short messages for long-distance transmission of AIS information is limited by the following issues:

[0004] 1) Limited information capacity

[0005] Beidou short message transmission has data capacity limitations and can usually only carry a limited number of characters. When it is necessary to transmit the AIS information of multiple ships in distant sea areas, the limited character capacity makes it impossible to cover all the necessary information in one transmission. In the traditional method, the latitude, longitude and direction information of each ship requires more characters to be fully represented. This problem limits the transmission efficiency of AIS information and the number of ships transmitted.

[0006] 2) Trade-off between data accuracy and transmission efficiency

[0007] Existing AIS information transmission usually relies on detailed latitude, longitude and direction data, requiring a large amount of data, which limits the application of short messages in the transmission of multi-ship information in distant sea areas. When the character capacity is insufficient, the information may be split and transmitted multiple times, which not only increases the transmission cost but also reduces the real-time requirements of the system.

[0008] 3) Lack of standardized scheme for character compression

[0009] The current transmission method of AIS information in Beidou short messages is relatively scattered, and there is a lack of a standardized character compression method to increase the effective information volume of a single transmission, especially to achieve the transmission of information across multiple ships. Therefore, the information utilization and compressibility of AIS data of multiple ships in long-distance transmission are insufficient. Summary of the invention

[0010] In order to overcome the shortcomings of the background technology, the present invention provides a Beidou short message AIS information compression transmission method based on grid coding, which mainly solves the problem of character capacity limitation of AIS information in Beidou short message transmission.

[0011] The technical solution of the present invention is:

[0012] A Beidou short message AIS information compression transmission method based on grid coding comprises the following steps:

[0013] Step 1: Grid division and position coding,

[0014] Receive AIS data, set the radius R of the target transmission area with the current position as the center, divide it into N×N network areas, and assign a unique number to each network; given the latitude and longitude position (x, y) of a ship, calculate the network number as follows:

[0015] Step length calculation: Assume the side length of each grid is

[0016] Position conversion: Convert the position (x, y) to the grid number k, and calculate the position of the horizontal and vertical coordinates in the grid according to the formula:

[0017]

[0018] Network Number:

[0019] k=i×N+j+1

[0020] Step 2: Direction encoding,

[0021] The heading angle θ of the ship is discretized into D intervals (e.g. 8 directions, each interval is 45 degrees), and a number is assigned to each direction. The direction coding formula is:

[0022]

[0023] Step 3: Compressed encoding representation,

[0024] The position network code k obtained in step 1 and the direction code d obtained in step 2 are combined into a short single code C, which represents the latitude and longitude position and direction of the ship:

[0025]

[0026] Also includes step 4, decoding

[0027] After receiving the code C, the receiver decodes it as follows:

[0028] Grid number restoration:

[0029]

[0030] Direction number restoration:

[0031]

[0032] In step 1, R is 3 to 5 nautical miles.

[0033] In step 1, the network is divided into N×N network areas, where N is 100 to 300.

[0034] The beneficial effects of the present invention are as follows: the present invention provides a Beidou short message AIS information compression transmission method based on grid coding, and the present invention has the following advantages and effects: 1) Significant reduction in the number of characters. By converting the longitude and latitude and direction into short numbers, the present invention reduces the number of characters transmitted by Beidou short messages, occupies fewer characters, and can contain more ship information in a single transmission; 2) Improvement of transmission efficiency. Compared with traditional methods, the present invention can transmit more information within a limited number of characters, improve data transmission efficiency, and is particularly suitable for remote transmission of multiple ship information, reducing the need for multiple transmissions. 3) Simple decoding. The receiver only needs to perform simple decoding according to the coding table to restore the location information and direction information of the ship. The decoding process is efficient and fast, and no complex calculations are required. 4) Adapting to the safety monitoring of distant sea areas. The present invention realizes efficient information compression and decoding in Beidou short messages, so that AIS information can be transmitted in remote areas such as distant sea areas, ensuring the real-time and information coverage of maritime safety monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Attached Figure 1 It is a logic block diagram of the present invention. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with the accompanying drawings: As shown in the figure, a Beidou short message AIS information compression transmission method based on grid coding includes the following steps:

[0037] Step 1: Grid division and position coding,

[0038] Receive AIS data, set the radius R of the target transmission area with the current position as the center, divide it into N×N network areas, and assign a unique number to each network; given the latitude and longitude position (x, y) of a ship, calculate the network number as follows:

[0039] Step length calculation: Assume the side length of each grid is

[0040] Position conversion: Convert the position (x, y) to the grid number k, and calculate the position of the horizontal and vertical coordinates in the grid according to the formula:

[0041]

[0042] Network Number:

[0043] k=i×N+j+1

[0044] Step 2: Direction encoding,

[0045] The heading angle θ of the ship is discretized into D intervals (e.g. 8 directions, each interval is 45 degrees), and a number is assigned to each direction. The direction coding formula is:

[0046]

[0047] Step 3: Compressed encoding representation,

[0048] The position network code k obtained in step 1 and the direction code d obtained in step 2 are combined into a short single code C, which represents the latitude and longitude position and direction of the ship:

[0049]

[0050] This code indicates that it contains the ship's position and direction information and is transmitted with a smaller number of characters.

[0051] Also includes step 4, decoding

[0052] After receiving the code C, the receiver decodes it as follows:

[0053] Grid number restoration:

[0054]

[0055] Direction number restoration:

[0056]

[0057] In step 1, R is 3 to 5 nautical miles.

[0058] In step 1, the network is divided into N×N network areas, where N is 100 to 300.

[0059] Example: AIS information compression and transmission based on grid coding

[0060] System structure and composition

[0061] The AIS compression transmission system mainly consists of the following parts:

[0062] 1) AIS receiving module

[0063] Receive the ship's AIS information, including the latitude and longitude position (x, y) and heading angle (θ). The received data will enter the next step of encoding processing.

[0064] 2) Position encoding module

[0065] The module is centered on the current location and divided into N×N=10×10 grid areas with a radius of R=3 nautical miles, and each grid is assigned a unique number. For example, the upper left corner of the grid is numbered 1, and the lower right corner is numbered 100.

[0066] 3) Direction encoding module

[0067] The heading angle θ of the ship is discretized into 8 direction intervals (each interval is 45 degrees), and each interval is assigned a number from 1 to 8. For example, the direction between 0° and 45° is coded as 1, the direction between 45° and 90° is coded as 2, and so on.

[0068] 4) Coding combination module

[0069] The grid number k generated by the position encoding module and the direction number d generated by the direction encoding module are combined into a compression code C in the following way:

[0070] C=k×10+d

[0071] This encoding means compressing the latitude and longitude position and direction information into a short number, so that AIS information can be transmitted in a concise form in the Beidou short message.

[0072] 5) Beidou short message transmission module

[0073] This module is responsible for transmitting the compressed code C to the shore-based receiving center through the Beidou short message. The compressed AIS information can be transmitted remotely with a smaller character capacity, which improves the transmission efficiency.

[0074] 6) Decoding module (receiver)

[0075] The receiver restores the ship's position and direction through a decoding algorithm based on the transmitted code C. The decoding process involves extracting the grid number k and direction number d from C and restoring them to approximate longitude and latitude position and direction information.

[0076] Specific implementation steps:

[0077] Data reception and data initialization

[0078] The system receives the actual latitude and longitude position (x, y) and heading θ of the ship and initializes the encoding parameters, including the network side length d = 0.6 nautical miles (calculated as ), and 8 direction intervals.

[0079] Positional encoding calculation

[0080] Calculate the grid number of the ship according to the position (x, y). Assuming the ship's position is (0.5, -0.8) nautical miles, the corresponding grid number k is calculated as follows:

[0081]

[0082] Network Number:

[0083] k=i×N+j+1=54

[0084] 3. Direction encoding calculation

[0085] Discretize the heading θ = 70° into the direction number d, calculated as follows:

[0086]

[0087] 4. Compression encoding generation

[0088] Combining the position and direction numbers produces a compressed encoding:

[0089]

[0090] Data Transfer

[0091] The generated code C=542 is transmitted to the shore-based information center via Beidou short message.

[0092] Data decoding and restoration

[0093] After receiving the code C, the shore-based receiver decodes it into a network number k=54 and a direction number d=2, and resolves it into the approximate latitude and longitude position and heading of the ship based on the predetermined network position and direction mark.

[0094] This application achieves compression of location information by dividing the sea area where the ship is currently located into multiple grids and replacing the traditional longitude and latitude representation with grid numbers. It innovatively proposes the setting of the radius and side length of grid division, as well as a method for calculating the corresponding grid number based on the actual position of the ship.

[0095] The ship's heading angle is discretized into fixed intervals and assigned numbers to reduce the number of characters. This direction encoding method ensures that the character capacity is greatly reduced without significantly reducing the accuracy, thus improving the efficiency of information transmission.

[0096] The grid number and direction number are combined into a single compressed code, so that the latitude, longitude and heading of the AIS information can be represented with fewer characters. The combined coding algorithm includes a combination of the position number and the direction number to ensure that the generated code occupies the minimum number of characters in the Beidou short message transmission.

[0097] The receiver parses and restores the latitude and longitude position and direction of the ship based on the grid number and direction number in the transmission code to achieve effective decoding of the data. This decoding method ensures that the compressed coded data can be accurately restored to approximate AIS information.

[0098] The embodiments described are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention. The embodiments should not be regarded as limiting the present invention, but any improvements made based on the spirit of the present invention should be within the scope of protection of the present invention.

Claims

1. A Beidou short message AIS information compression transmission method based on grid coding, characterized in that: The following steps are included: Step 1: Grid division and position coding, Receive AIS data, set the radius R of the target transmission area with the current position as the center, divide it into N×N network areas, and assign a unique number to each network; given the latitude and longitude position (x, y) of a ship, calculate the network number as follows: Step length calculation: Assume the side length of each grid is Position conversion: Convert the position (x, y) to the grid number k, and calculate the position of the horizontal and vertical coordinates in the grid according to the formula: Network Number: k=i×N+j+1 Step 2: Direction encoding, The heading angle θ of the ship is discretized into D intervals (e.g. 8 directions, each interval is 45 degrees), and a number is assigned to each direction. The direction coding formula is: Step 3: Compressed encoding representation, The position network code k obtained in step 1 and the direction code d obtained in step 2 are combined into a short single code C, which represents the latitude and longitude position and direction of the ship:

2. A Beidou short message AIS information compression transmission method based on grid coding according to claim 1, characterized in that: Also includes step 4, decoding After receiving the code C, the receiver decodes it as follows: Grid number restoration: Direction number restoration:

3. A Beidou short message AIS information compression transmission method based on grid coding according to claim 1, characterized in that: In step 1, R is 3 to 5 nautical miles.

4. The Beidou short message AIS information compression transmission method based on grid coding according to claim 1 is characterized in that: In step 1, the network is divided into N×N network areas, where N is 100 to 300.

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