An equidistant chart making method for a vessel traffic management system

Abstract

The application discloses a method for making an equidistant chart for a ship traffic management system, comprising the following steps: 1, obtaining chart basic data; 2, drawing sea area markers; 3, obtaining radar polar coordinates of ship targets; 4, converting the radar polar coordinates into latitude and longitude coordinates; specifically comprising the following steps: 4-1, converting the radar polar coordinates into radar rectangular coordinates; 4-2, converting the radar rectangular coordinates into WGS84 rectangular coordinates; 4-3, calculating latitude and longitude coordinates; 5, drawing ship targets: latitude and longitude coordinates of each ship target in step 4 are converted into radar equidistant screen coordinates in the form of equidistant cylindrical projection, and are drawn on the basic chart formed in step 2 to form an equidistant chart. The application is based on the equidistance requirement of maritime affairs, and through processing and conversion of chart data, equidistant display of chart rendering targets is realized.

Description

Technical Field

[0001] This invention relates to the fields of ship traffic management systems and nautical chart production, and in particular to a method for producing isometric nautical charts for ship traffic management systems. Background Technology

[0002] In ship traffic management systems, radar scan target echoes are typically equidistant circles, therefore they also need to be displayed as equidistant circles on nautical charts. However, traditional chart production methods use the Mercator projection, resulting in unequal spacing on the charts, such as... Figure 2 As shown, the outline of the radar echo cannot be accurately displayed, nor can the radar echo and AIS target be aligned and overlapped on the nautical chart. Therefore, this presents the following problems for the ship traffic management system:

[0003] 1. Because radar echoes and AIS targets are misaligned on nautical charts, the accuracy and reliability of the chart information provided are reduced, making it difficult for navigators to understand the surrounding environment and ship traffic conditions, and making them prone to making wrong decisions.

[0004] 2. Unequal-distance nautical charts are not conducive to the maritime authorities' requirements for observing target vessels, predicting situations, and conducting watchkeeping command, and cannot provide effective support to the maritime authorities. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing an isometric chart production method for a ship traffic management system. This isometric chart production method for a ship traffic management system is based on the maritime requirement for isometrics and processes and transforms the chart data to make the target of the chart rendering appear isometric.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for creating isometric nautical charts for a ship traffic management system includes the following steps.

[0008] Step 1: Obtain basic nautical chart data: Download the basic nautical chart data for the sea area to be monitored; the basic nautical chart data includes the latitude and longitude coordinates of the sea area markers.

[0009] Step 2: Draw marine markers: Take the latitude and longitude coordinates of each marine marker in Step 1 and use equidistant cylindrical projection to form equidistant screen coordinates of the marker, and draw them on a blank nautical chart to form a basic nautical chart.

[0010] Step 3: Obtain ship targets: The radar scan obtains the ship targets and their radar polar coordinates; the radar polar coordinates of each ship target include range, azimuth and elevation.

[0011] Step 4: Convert radar polar coordinates to latitude and longitude coordinates, which includes the following steps:

[0012] Step 4-1: Convert radar polar coordinates to radar rectangular coordinates: Convert the radar polar coordinates of each ship target, including range r, azimuth a, and elevation e, to radar rectangular coordinates (x, y, z). The specific conversion formula is as follows:

[0013] x = r * cos(e) * sin(a)

[0014] y = r * cos(e) * cos(a)

[0015] z = r * sin(e)

[0016] Step 4-2: Convert radar rectangular coordinates to WGS84 rectangular coordinates: Convert the radar rectangular coordinates (x, y, z) of each ship target to WGS84 rectangular coordinates (X, Y, Z) in the WGS84 rectangular coordinate system.

[0017] Step 4-3: Calculate latitude and longitude coordinates: Based on the WGS84 rectangular coordinates converted in Step 4-2, calculate the latitude and longitude coordinates corresponding to each ship target.

[0018] Step 5: Draw ship targets: Take the latitude and longitude coordinates of each ship target in Step 4 and use equidistant cylindrical projection to form radar equidistant screen coordinates. Then, draw them on the basic nautical chart formed in Step 2 to form an equidistant nautical chart.

[0019] In steps 2 and 5, the specific formulas for converting equidistant cylindrical projections are as follows:

[0020]

[0021]

[0022]

[0023] Where x', y', z' are the converted coordinates of the marker or radar equidistant screen, and L represents the distance value of 1 degree of latitude, in meters; λ represents the latitude coordinates of the sea area markers or ship targets before the conversion; λ represents the longitude coordinates of the sea area markers or ship targets before the conversion; λ0 represents the longitude coordinates of the central meridian, which is a constant.

[0024] L = 111110.

[0025] In steps 2 and 5, the equidistant cylindrical projection uses a 4x4 affine transformation matrix; where the 4x4 affine transformation matrix is:

[0026]

[0027] In step 4-2, the conversion formula for converting radar rectangular coordinates (x, y, z) to WGS84 rectangular coordinates (X, Y, Z) is as follows:

[0028] (X,Y,Z)=R²×T²×(x,y,z)

[0029] in:

[0030]

[0031]

[0032] In the formula, R2 is the rotation matrix, T2 is the translation matrix; θ is the rotation angle of the WGS84 rectangular coordinate system relative to the radar rectangular coordinate system; (x0, y0, z0) is the translation value of the origin of the WGS84 rectangular coordinate system relative to the origin of the radar rectangular coordinate system. In step 4-3, the longitude coordinate λ and latitude coordinate of each ship target are... The calculation formulas are as follows:

[0033]

[0034]

[0035] in:

[0036]

[0037]

[0038]

[0039] In the formula, R a R is the semi-major axis of the WGS84 ellipsoid; b This is the semi-minor axis of the WGS84 ellipsoid;

[0040] E1 is the first eccentricity of the ellipsoid in WGS84; E2 is the second eccentricity of the ellipsoid in WGS84.

[0041] Both U and P are intermediate variables in the calculation.

[0042] In step 1, marine markers include water depth, topography, navigation marks, and channel information.

[0043] It also includes step 6, drawing the target marker A, which specifically includes the following steps:

[0044] Step 6-1: Obtain radar isometric screen coordinates: Based on the position of target marker A to be drawn on the isometric nautical chart, obtain the radar isometric screen coordinates of target marker A.

[0045] Step 6-2, Reverse calculation of latitude and longitude coordinates: Using the inverse operation of step 5, the radar equidistant screen coordinates of target marker A are converted into the latitude and longitude coordinates of target marker A.

[0046] Step 6-3, reverse calculation of WGS84 rectangular coordinates: using the inverse operation of step 4-3, the latitude and longitude coordinates of target marker A are converted into the WGS84 rectangular coordinates of target marker A.

[0047] Step 6-4: Calculate the straight-line distance: Based on the WGS84 rectangular coordinates of target marker A and the WGS84 rectangular coordinates of existing ship targets on the equidistant nautical chart, calculate the straight-line distance between target marker A and each existing ship target.

[0048] Step 6-5, Collision Risk Assessment: When all straight-line distances calculated in Step 6-4 are not less than the set distance threshold, target marker A is considered to have no collision risk; at this time, target marker A can be displayed at the location to be drawn on the equidistant nautical chart.

[0049] In step 6, target marker A is a new water depth, new topography, new navigation mark, new waterway, or new ship target.

[0050] It also includes step 7, which reversely calculates the radar polar coordinates, specifically including the following steps:

[0051] Step 7-1, Reverse calculation of radar rectangular coordinates: Using the inverse operation of step 4-2, the WGS84 rectangular coordinates of target marker A are converted into the radar rectangular coordinates of target marker A.

[0052] Step 7-2, Reverse calculation of radar polar coordinates: Using the inverse operation of step 4-1, the radar rectangular coordinates of target marker A are converted into the radar polar coordinates of target marker A.

[0053] Step 7-3: Store the radar polar coordinates of target marker A in the radar station corresponding to the sea area to be monitored.

[0054] The present invention has the following beneficial effects:

[0055] 1. This invention, by introducing the interchange between radar polar coordinates and screen coordinates, ensures that radar echoes are spatially equidistant on nautical charts, eliminating spatial stretching and distortion. Furthermore, during the radar polar coordinate conversion, the straight-line distance between two points is used, without calculating the Earth's curvature, thus ignoring the influence of the Earth's surface curvature, consistent with the principle that radar electromagnetic waves propagate in straight lines. This ensures consistency between the radar measurement position and the nautical chart display position, avoiding deviations and erroneous positional distortions. Consequently, it allows AIS targets and radar echoes to be aligned and coincident on the nautical chart, achieving the function of equidistant alignment between the nautical chart and the actual radar measurement target without deviation.

[0056] 2. This invention, by maintaining an equidistant distance between the nautical chart and the actual radar-measured target, meets the requirements of ship traffic management systems for equidistant nautical charts. The charts produced by this invention present equidistant circles in the radar echo display of scanned targets, improving the accuracy and reliability of ship traffic management systems. Furthermore, this allows navigators to better understand the surrounding environment and ship traffic conditions, enabling them to make correct decisions. Secondly, equidistant nautical charts meet the requirements of maritime authorities for observing target vessels, predicting situations, and conducting watchkeeping operations, providing them with effective tools and support. This invention fills the gap in equidistant nautical chart production within ship traffic management systems.

[0057] 3. The application of isometric charts can also improve the efficiency and safety of vessel traffic management systems. By aligning radar echoes and AIS targets on the chart, vessel traffic management systems can more accurately monitor and manage the position and movement of vessels, promptly detect potential dangers and conflicts, and take corresponding measures for scheduling and guidance to ensure navigational safety. In other words, this invention can provide effective decision support for navigators and maritime authorities, improving the efficiency and safety of vessel traffic management systems. Attached Figure Description

[0058] Figure 1 The flowchart shows a method for creating equidistant nautical charts for a ship traffic management system according to the present invention.

[0059] Figure 2 A schematic diagram of a traditional nautical chart is shown.

[0060] Figure 3 A schematic diagram of the equidistant nautical chart of the present invention is shown. Detailed Implementation

[0061] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0062] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention.

[0063] like Figure 1 As shown, a method for creating isometric nautical charts for a ship traffic management system includes the following steps.

[0064] Step 1: Obtain basic nautical chart data: Download the basic nautical chart data for the sea area to be monitored; the basic nautical chart data includes the latitude and longitude coordinates of marine landmarks. Preferably, marine landmarks include information such as water depth, topography, navigation marks, and waterways.

[0065] In the process of chart production, standard chart production specifications and formats, such as S57 and S52, can be used. These specifications and formats define the structure and content of chart data.

[0066] Step 2: Draw marine markers: Take the latitude and longitude coordinates of each marine marker in Step 1 and use equidistant cylindrical projection to form equidistant screen coordinates of the marker, and draw them on a blank nautical chart to form a basic nautical chart.

[0067] The aforementioned equidistant cylindrical projection preferably employs a 4x4 affine transformation matrix; wherein, the 4x4 affine transformation matrix is:

[0068]

[0069] The specific screen coordinates of the markers after transformation by the 4x4 affine transformation matrix are as follows:

[0070]

[0071]

[0072]

[0073] Where x', y', and z' are the converted screen coordinates of the marker;

[0074] L represents the distance value of 1 degree of latitude, in meters; in this embodiment, L = 111110;

[0075] The latitude coordinates of the marine landmarks before conversion;

[0076] λ represents the longitude coordinates of the marine landmark before the conversion;

[0077] λ0 is the longitude coordinate value of the central meridian, which is a constant.

[0078] Step 3: Obtain ship targets: The radar scan obtains the ship targets and their radar polar coordinates; the radar polar coordinates of each ship target include range, azimuth and elevation.

[0079] Step 4: Convert radar polar coordinates to latitude and longitude coordinates, which includes the following steps:

[0080] Step 4-1: Convert radar polar coordinates to radar rectangular coordinates: Convert the radar polar coordinates of each ship target, including range r, azimuth a, and elevation e, to radar rectangular coordinates (x, y, z). The specific conversion formula is as follows:

[0081] x = r * cos(e) * sin(a)

[0082] y = r * cos(e) * cos(a)

[0083] z = r * sin(e)

[0084] Step 4-2: Convert radar rectangular coordinates to WGS84 rectangular coordinates: Convert the radar rectangular coordinates (x, y, z) of each ship target to WGS84 rectangular coordinates (X, Y, Z) in the WGS84 rectangular coordinate system. The preferred conversion formula is as follows:

[0085] (X,Y,Z)=R²×T²×(x,y,z)

[0086] in:

[0087]

[0088]

[0089] In the formula, R2 is the rotation matrix, T2 is the translation matrix; θ is the rotation angle of the WGS84 rectangular coordinate system relative to the radar rectangular coordinate system; (x0,y0,z0) is the translation value of the origin of the WGS84 rectangular coordinate system relative to the origin of the radar rectangular coordinate system.

[0090] Step 4-3: Calculate latitude and longitude coordinates: Based on the WGS84 rectangular coordinates converted in Step 4-2, calculate the latitude and longitude coordinates corresponding to each ship target. Specifically, the longitude coordinate λ and latitude coordinates for each ship target are... The preferred calculation formulas are as follows:

[0091]

[0092]

[0093] in:

[0094]

[0095]

[0096]

[0097] In the formula, R a R is the semi-major axis of the WGS84 ellipsoid; bThis is the semi-minor axis of the WGS84 ellipsoid;

[0098] E1 is the first eccentricity of the ellipsoid in WGS84; E2 is the second eccentricity of the ellipsoid in WGS84.

[0099] Both U and P are intermediate variables in the calculation.

[0100] Additionally, based on the WGS84 rectangular coordinates converted in step 4-2, the height H corresponding to each ship target is calculated using the following formula:

[0101]

[0102] in:

[0103]

[0104] In the formula, N is an intermediate variable in the calculation.

[0105] Step 5: Draw ship targets: For each ship target from Step 4, use equidistant cylindrical projection to generate radar equidistant screen coordinates. Then, use QPainter high-speed rendering to draw these coordinates onto the base nautical chart generated in Step 2, creating a map as shown below. Figure 3 The chart shown is an equidistant, circular nautical chart.

[0106] The equidistant cylindrical projection here is based on the same principle as step 2, except that x', y', and z' are the converted radar equidistant screen coordinates, respectively. λ represents the latitude coordinates of the target ship before conversion; λ represents the longitude coordinates of the target ship before conversion; λ0 represents the longitude coordinates of the central meridian, which is a constant.

[0107] Step 6, draw the target marker A, which includes the following steps:

[0108] Step 6-1: Obtain radar equidistant screen coordinates: Based on the location of target marker A to be plotted on the equidistant nautical chart, obtain the radar equidistant screen coordinates of target marker A. Target marker A is preferably a new water depth, new terrain, new navigation mark, new channel, or new ship target, etc.

[0109] Step 6-2, Reverse calculation of latitude and longitude coordinates: Using the inverse operation of step 5, the radar equidistant screen coordinates of target marker A are converted into the latitude and longitude coordinates of target marker A.

[0110] Step 6-3, reverse calculation of WGS84 rectangular coordinates: using the inverse operation of step 4-3, the latitude and longitude coordinates of target marker A are converted into the WGS84 rectangular coordinates of target marker A.

[0111] Step 6-4: Calculate the straight-line distance: Based on the WGS84 rectangular coordinates of target marker A and the WGS84 rectangular coordinates of existing ship targets on the equidistant nautical chart, calculate the straight-line distance between target marker A and each existing ship target.

[0112] Step 6-5, Collision Risk Assessment: When all straight-line distances calculated in Step 6-4 are not less than the set distance threshold, target marker A is considered to have no collision risk; at this time, target marker A can be displayed at the location to be drawn on the equidistant nautical chart.

[0113] Step 7, reverse calculation of radar polar coordinates, specifically including the following steps:

[0114] Step 7-1, Reverse calculation of radar rectangular coordinates: Using the inverse operation of step 4-2, the WGS84 rectangular coordinates of target marker A are converted into the radar rectangular coordinates of target marker A.

[0115] Step 7-2, Reverse calculation of radar polar coordinates: Using the inverse operation of step 4-1, the radar rectangular coordinates of target marker A are converted into the radar polar coordinates of target marker A.

[0116] Step 7-3: Store the radar polar coordinates of target marker A in the radar station corresponding to the sea area to be monitored.

[0117] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A method for producing isometric nautical charts for a ship traffic management system, characterized in that: Includes the following steps: Step 1: Obtain basic nautical chart data: Download the basic nautical chart data for the sea area to be monitored; the basic nautical chart data includes the latitude and longitude coordinates of the sea area landmarks; Step 2: Draw marine markers: Take the latitude and longitude coordinates of each marine marker in Step 1 and use equidistant cylindrical projection to form equidistant screen coordinates of the marker, and draw them on a blank nautical chart to form a basic nautical chart. Step 3: Obtain ship targets: The radar scan obtains the ship targets and their radar polar coordinates; the radar polar coordinates of each ship target include range, azimuth, and elevation. Step 4: Convert radar polar coordinates to latitude and longitude coordinates, which includes the following steps: Step 4-1: Convert radar polar coordinates to radar rectangular coordinates: Convert the radar polar coordinates of each ship target, including range r, azimuth a, and elevation e, to radar rectangular coordinates (x, y, z). The specific conversion formula is as follows: x = r * cos(e) * sin(a) y = r * cos(e) * cos(a) z = r * sin(e) Step 4-2: Convert radar rectangular coordinates to WGS84 rectangular coordinates: Convert the radar rectangular coordinates (x, y, z) of each ship target to WGS84 rectangular coordinates (X, Y, Z) in the WGS84 rectangular coordinate system. Step 4-3: Calculate latitude and longitude coordinates: Based on the WGS84 rectangular coordinates converted in Step 4-2, calculate the latitude and longitude coordinates corresponding to each ship target; Step 5: Draw ship targets: Take the latitude and longitude coordinates of each ship target in Step 4 and use equidistant cylindrical projection to form radar equidistant screen coordinates. Then, draw them on the basic nautical chart formed in Step 2 to form an equidistant nautical chart.

2. The method for producing isometric nautical charts for a ship traffic management system according to claim 1, characterized in that: In steps 2 and 5, the specific formulas for converting equidistant cylindrical projections are as follows: Where x', y', z' are the converted coordinates of the marker or radar equidistant screen, and L represents the distance value of 1 degree of latitude, in meters; λ represents the latitude coordinates of the sea area markers or ship targets before the conversion; λ represents the longitude coordinates of the sea area markers or ship targets before the conversion; λ0 represents the longitude coordinates of the central meridian, which is a constant.

3. The method for producing isometric nautical charts for a ship traffic management system according to claim 2, characterized in that: L＝111110。 4. In the isometric chart production method for a ship traffic management system according to claim 2, in steps 2 and 5, the isometric cylindrical projection uses a 4x4 affine transformation matrix; wherein, The 4x4 affine transformation matrix is:

5. The method for producing isometric nautical charts for a ship traffic management system according to claim 1, characterized in that: In step 4-2, the conversion formula for converting radar rectangular coordinates (x, y, z) to WGS84 rectangular coordinates (X, Y, Z) is as follows: (X,Y,Z)=R²×T²×(x,y,z) in: In the formula, R2 is the rotation matrix, T2 is the translation matrix; θ is the rotation angle of the WGS84 rectangular coordinate system relative to the radar rectangular coordinate system; (x0,y0,z0) is the translation value of the origin of the WGS84 rectangular coordinate system relative to the origin of the radar rectangular coordinate system.

6. The method for producing isometric nautical charts for a ship traffic management system according to claim 1, characterized in that: In step 4-3, the longitude coordinate λ and latitude coordinates corresponding to each ship target are... The calculation formulas are as follows: in: In the formula, R a R is the semi-major axis of the WGS84 ellipsoid; b This is the semi-minor axis of the WGS84 ellipsoid; E1 is the first eccentricity of the ellipsoid in WGS84; E2 is the second eccentricity of the ellipsoid in WGS84. Both U and P are intermediate variables in the calculation.

7. The method for producing isometric nautical charts for a ship traffic management system according to claim 1, characterized in that: In step 1, marine markers include water depth, topography, navigation marks, and channel information.

8. The method for producing isometric nautical charts for a ship traffic management system according to claim 1, characterized in that: It also includes step 6, drawing the target marker A, which specifically includes the following steps: Step 6-1: Obtain radar equidistant screen coordinates: Based on the position of target marker A to be drawn on the equidistant nautical chart, obtain the radar equidistant screen coordinates of target marker A; Step 6-2, Reverse calculation of latitude and longitude coordinates: Using the inverse operation of step 5, the radar equidistant screen coordinates of target marker A are converted into the latitude and longitude coordinates of target marker A. Step 6-3, Reverse calculation of WGS84 rectangular coordinates: Using the inverse operation of step 4-3, the latitude and longitude coordinates of target marker A are converted into the WGS84 rectangular coordinates of target marker A. Step 6-4: Calculate the straight-line distance: Based on the WGS84 rectangular coordinates of target marker A and the WGS84 rectangular coordinates of existing ship targets on the equidistant nautical chart, calculate the straight-line distance between target marker A and each existing ship target. Step 6-5, Collision Risk Assessment: When all straight-line distances calculated in Step 6-4 are not less than the set distance threshold, target marker A is considered to have no collision risk; at this time, target marker A can be displayed at the location to be drawn on the equidistant nautical chart.

9. The method for producing isometric nautical charts for a ship traffic management system according to claim 8, characterized in that: In step 6, target marker A is a new water depth, new topography, new navigation mark, new waterway, or new ship target.

10. The method for producing isometric nautical charts for a ship traffic management system according to claim 8, characterized in that: It also includes step 7, which reversely calculates the radar polar coordinates, specifically including the following steps: Step 7-1, Reverse calculation of radar rectangular coordinates: Using the inverse operation of step 4-2, the WGS84 rectangular coordinates of target marker A are converted into the radar rectangular coordinates of target marker A. Step 7-2, Reverse calculation of radar polar coordinates: Using the inverse operation of step 4-1, the radar rectangular coordinates of target marker A are converted into the radar polar coordinates of target marker A. Step 7-3: Store the radar polar coordinates of target marker A in the radar station corresponding to the sea area to be monitored.

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