A method for calculating the equivalent model of radar cross section of large ship targets

Abstract

This invention discloses a method for calculating the equivalent model of the radar cross-section of a large ship target, comprising the following steps: establishing a three-dimensional geometric model of the large ship target; establishing a virtual electromagnetic wave incident aperture surface approaching infinity based on the target geometry, and discretizing the aperture surface to obtain individual ray tubes; tracking the reflection direction of each ray tube on the target surface until the ray leaves the target surface; calculating the scattering field of each ray tube in the receiving direction, and superimposing the scattering fields of all ray tubes to obtain the total scattering field of the target; plotting the horizontal cross-section and vertical gain diagram of the ship target based on the calculated target radar scattering gain at typical horizontal azimuth and vertical elevation angles; and calculating the radar cross-section of the ship target when detected by radar equipment in different directions based on the target radar scattering gain diagram using interpolation formulas. This invention improves the calculation accuracy and speed of scattering of large ship targets, and is helpful for the stealth assessment of large ship targets.

Description

Technical Field

[0001] This invention relates to the field of radar and electronic countermeasures, specifically to a method for calculating the equivalent model of radar cross section of a large ship target. Background Technology

[0002] The radar cross section (RCS) of a target is a physical quantity characterizing its ability to scatter electromagnetic waves. It is closely related to the target's structure, azimuth, the position and attitude of the transmitter and receiver, polarization, and the frequency of the incident electromagnetic waves. Large surface ships are mostly 100m-300m in length, with extremely large electrical dimensions. The numerous weapons, electronic equipment, and structures on the upper deck are compactly arranged and vary in style, making large surface ships densely packed with geometric shapes. Their radar wave scattering mechanisms are diverse and complex. Traditional geometric optics, physical optics, geometric diffraction theory, and physical diffraction theory analyze and calculate the RCS from only a single angle, making them unsuitable for calculating the RCS of large ship targets. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for calculating the equivalent model of the radar cross section of a large ship target. By establishing a radar scattering characteristic model of the target, it provides target characteristic parameters for radar reconnaissance and detection.

[0004] The objective of this invention is achieved through the following technical solution: a method for calculating the equivalent model of the radar cross-section of a large ship target, comprising the following steps:

[0005] Step 1: Establish a three-dimensional geometric model of the large ship target;

[0006] Step 2: Based on the target geometry, establish a virtual electromagnetic wave incident aperture surface at a distance approaching infinity, and discretize the aperture surface to obtain a single ray tube;

[0007] Step 3: Track the reflection direction of each ray tube on the target surface until the ray leaves the target surface;

[0008] Step 4: Calculate the scattered field of each ray tube in the receiving direction, and superimpose the scattered fields of all ray tubes to obtain the total scattered field of the target.

[0009] Step 5: Based on the calculated target radar scattering gain at typical horizontal azimuth and vertical elevation angles, plot the horizontal cross-section and vertical gain diagram of the ship target.

[0010] Step 6: Based on the target radar scattering gain map, use interpolation formulas to calculate the radar cross section of the ship target when the radar equipment detects from different directions.

[0011] Preferably, step 2 includes at least the following steps:

[0012] Step 2.1: Project the 3D point information (X, Y, Z) on the target onto a virtual aperture surface at a certain distance from the target and perpendicular to the plane wave incident direction through coordinate transformation. The transformed coordinates are: Where θ is X r The angle between the Z-axis and the Z-axis It is X r The angle between the projection of the xoy plane and the positive x-axis;

[0013] The transformation relationship is as follows:

[0014]

[0015] Step 2.2: Traverse all two-dimensional points to obtain the maximum and minimum values ​​y in two directions on the virtual aperture surface. θmax y θmin , The size of the rectangular aperture surface is obtained; when the ray tube is generated, its division step size is 1 / 10 of the electromagnetic wave wavelength λ.

[0016] Preferably, step 3 includes at least the following steps:

[0017] Step 3.1: Discretize the target into triangular facets;

[0018] Step 3.2: For different triangular facets, calculate the intersection points of the rays and the triangular facets;

[0019] Step 3.3: Calculate the reflection direction and reflection field strength of the multiple reflections of the ray on the surface of the surface element.

[0020] Preferably, step 3.2 includes at least the following steps:

[0021] Step 3.2.1: Based on the coordinates of the three points of the triangular element, they are as follows: The normal unit vector of the triangular element is Establish the equation of the plane containing the triangle:

[0022]

[0023] Step 3.2.2: Based on the ray exit point and the vector of ray propagation direction Establish the ray equation:

[0024]

[0025] Step 3.2.3: Solve for the intersection of the ray and the triangular surface element and the t value.

[0026] Preferably, step 3.3 includes at least the following steps:

[0027] Step 3.3.1: Based on Snell's law, the unit vector of the incident ray direction... Unit normal vector at the reflection point Calculate the direction vector of the reflected ray

[0028]

[0029] Step 3.3.2: Calculate the incident field strength: E i (r′) represents the incident field strength and H under parallel polarization. i (r′) represents the incident field strength under vertical polarization; calculate the reflected field strength: E r (r′) represents the reflected field strength under parallel polarization, H r (r′) represents the reflected field strength under vertical polarization, as shown in the following equation:

[0030]

[0031] in:

[0032]

[0033] In the formula, R ∥ R is the reflection coefficient of the target surface under parallel polarization. ⊥ E represents the reflection coefficient of the target surface under vertical polarization. e∥ and E e⊥ These represent the amplitudes of the electric field vector in the two polarization directions;

[0034] Step 3.3.3: Update the reflection based on the ray reflection direction and field strength, and continuously iterate the calculation using steps 3.3.1 and 3.3.2 until the ray detaches from the target.

[0035] Preferably, step 4 includes at least the following steps:

[0036] Step 4.1: Calculate the scattered field of a single ray tube in the receiving direction:

[0037]

[0038] in, Let A be the receiving direction of the scattered field in polar coordinates. θ , It is a function of the electric field strength at each point on the exiting ray tube and the quadrilateral enclosed by the ray tube;

[0039] Step 4.2: Traverse all ray tubes and superimpose the scattered fields of all ray tubes to obtain the scattering cross-section gain value of the target at typical azimuth angle and typical elevation angle;

[0040]

[0041] In the formula, σ Vv σ represents the scattering cross-section gain value at a typical azimuth angle of the target. HH This represents the gain value of the scattering cross section at typical high and low angles.

[0042] Preferably, step 5 includes at least the following steps:

[0043] Step 5.1: Set the calculated target radar cross section gain value for typical azimuth angles, connect the radar cross section gain values ​​corresponding to each typical azimuth angle, and draw the horizontal cross section gain diagram of the ship target.

[0044] Step 5.2: For typical elevation angles, set the calculated target radar cross section gain value, connect the radar cross section gain values ​​corresponding to each typical elevation angle, and draw the vertical cross section gain diagram of the ship target.

[0045] Preferably, step 6 includes at least the following steps:

[0046] Step 6.1: Calculate the azimuth and elevation angles of the radar equipment relative to the large ship target;

[0047] Step 6.2, Calculation of target radar cross section interpolation.

[0048] Preferably, step 6.1 includes at least the following steps:

[0049] Step 6.1.1: Calculate the horizontal distance Δx and the height difference Δy between the radar equipment and the large ship target:

[0050]

[0051] Δy=(lat m -lat s )·60·1852

[0052] Among them, lon m Longitude and latitude of the location of the radar equipment m latitude, h m For height; lon s For the longitude and latitude of the ship target s Latitude;

[0053] Step 6.1.2: Calculate the azimuth angle α and elevation angle β of the radar equipment relative to the large ship target:

[0054] α = atan2(Δx, Δy)

[0055]

[0056] Preferably, step 6.2 includes at least the following steps:

[0057] Step 6.2.1: Interpolate and calculate the horizontal gain of the target's radar cross-section:

[0058]

[0059] In the formula, α1 and α2 are typical azimuth angles;

[0060] Step 6.2.2: Interpolate the vertical gain of the target's radar cross-section:

[0061]

[0062] In the formula, β1 and β2 are typical elevation angles.

[0063] Step 6.2.3: Calculate the target radar cross section (rcs) of the ship relative to the radar equipment:

[0064] rcs=rcs ref ·krcs α ·krcs β

[0065] In the formula, rcs ref The reference cross-sectional value is the typical value for the target.

[0066] Compared with the prior art, the present invention has the following advantages:

[0067] This invention provides a method for calculating the equivalent model of radar cross section of large ship targets. Based on the physical optics method, it combines optical ray tracing to make the scattered field reflect on the surface of complex targets. Then, the total field is obtained by superimposing all the reflected ray fields, which greatly improves the calculation accuracy and speed of the scattering of large ship targets. It helps to evaluate the stealth of large ship targets and is beneficial to the design and optimization of radar systems for enemy large ship targets.

[0068] This invention establishes a geometric model of a large ship target, divides the scattering source structure of the large ship, and adopts the emitted ray method (bouncing ray method). It integrates geometric optics, physical optics, geometric diffraction theory, physical diffraction theory, and equivalent electromagnetic flow method. It can discretize complex structures into several surface elements for physical optics calculation, ensuring the accuracy of the image direction, and can also handle ray tracing and various diffraction problems. It is suitable for the calculation and analysis of the RCS of large ships. Attached Figure Description

[0069] Figure 1 This is a flowchart of a method for calculating the equivalent model of radar cross section of a large ship target in this invention;

[0070] Figure 2 This is a schematic diagram illustrating the transformation relationship between target coordinates and virtual aperture surface coordinates in an embodiment of the present invention;

[0071] Figure 3 This is a schematic diagram of the generation of the X-ray tube in an embodiment of the present invention;

[0072] Figure 4 This is a schematic diagram of the reflection relationship of the reflection points in an embodiment of the present invention;

[0073] Figure 5 This is a gain diagram of the horizontal cross-section of the ship target in an embodiment of the present invention;

[0074] Figure 6 This is a gain diagram of the vertical cross-section of the ship target in an embodiment of the present invention. Detailed Implementation

[0075] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0076] like Figure 1 As shown, the technical solution of the present invention provides a method for calculating the equivalent model of the radar cross-section of a large ship target, including the following steps:

[0077] Step 1: Establish a three-dimensional geometric model of the large ship target;

[0078] Step 2: Based on the target geometry, establish a virtual electromagnetic wave incident aperture surface at a distance approaching infinity, and discretize the aperture surface to obtain a single ray tube;

[0079] Step 3: Track the reflection direction of each ray tube on the target surface until the ray leaves the target surface;

[0080] Step 4: Calculate the scattered field of each ray tube in the receiving direction, and superimpose the scattered fields of all ray tubes to obtain the total scattered field of the target.

[0081] Step 5: Based on the calculated target radar scattering gain at typical horizontal azimuth and vertical elevation angles, plot the horizontal cross-section and vertical gain diagram of the ship target.

[0082] Step 6: Based on the target radar scattering gain map, use interpolation formulas to calculate the radar cross section of the ship target when the radar equipment detects from different directions.

[0083] In one embodiment of the present invention, step 1 involves creating a 3D model of a large ship using the 3D modeling software 3ds Max, specifically including:

[0084] Step 1.1 Obtain the specific physical parameters of the ship target from reliable sources, such as: ship length, beam, hull structure parameters, structural parameters of the main scattering sources on the ship, structural parameters of the superstructure, size parameters of the mast and antennas arranged on the mast, deployment position and size parameters of weapons and equipment on the deck, etc.

[0085] Step 1.2: Launch 3ds Max, create a basic model block based on the acquired physical parameters of the ship target, select "Convert to Editable Poly," and launch the "NURMS" tool. Set an appropriate number of iterations and smoothness to achieve 3D modeling of the ship target. In this embodiment, a combination of NURBS (Non-Uniform Rational B-Spline) surface and planar element approximation is used to construct the geometric model of the ship target. This method can flexibly and arbitrarily approximate the target shape, eliminate redundant information that does not participate in the calculation, consider the multiple scattering mechanism, and is suitable for handling occlusion problems.

[0086] In one embodiment of the present invention, a method for obtaining a single ray tube in step 2 is provided. Based on the target geometry, a virtual electromagnetic wave incident aperture surface is established at an infinity-like distance. The aperture surface is discretized according to certain rules to obtain a single ray tube. The method includes at least the following steps:

[0087] Step 2.1, as follows Figure 2 As shown, the three-dimensional point information (X, Y, Z) on the target is projected onto a virtual aperture surface at a certain distance from the target and perpendicular to the plane wave incident direction through coordinate transformation. The transformed coordinates are... Where θ is X r The angle between the Z-axis and the Z-axis It is X r The angle between the projection of the xoy plane and the positive x-axis;

[0088] The transformation relationship is as follows:

[0089]

[0090] Assume the coordinates of the two-dimensional point are Then there is

[0091]

[0092] Step 2.2: Traverse all two-dimensional points to obtain the maximum and minimum values ​​y in two directions on the virtual aperture surface. θmax y θmin , Obtain the size of the rectangular aperture surface; such as Figure 3As shown, to ensure calculation accuracy when generating the ray tube, the division step size of the ray tube is at least 1 / 10 of the electromagnetic wave wavelength λ. Let M and N be y and N respectively. θ , If the number of ray tubes in each direction (each ray tube includes one central ray and four corner rays) is:

[0093]

[0094] In one embodiment of the present invention, in step 3, when each ray tube irradiates the target surface, it is necessary to determine whether the incident ray illuminates the surface element of the target surface. If it does, the reflection direction of the ray needs to be determined according to Snell's theorem until the ray leaves the target surface. Specifically, this includes the following steps:

[0095] Step 3.1: Discretize the target into triangular facets. Specifically:

[0096] The target is discretized into triangular facets. Based on the modeling and meshing information, the coordinates of three points of each triangular facet can be calculated.

[0097] Step 3.2: For different triangular facets, calculate the intersection points of the ray and the triangular facet:

[0098] Step 3.2.1: Based on the coordinates of the three points of the triangular element, they are as follows: The normal unit vector of the triangular element is Establish the equation of the plane containing the triangle:

[0099]

[0100] Step 3.2.2: Based on the ray exit point and the vector of ray propagation direction Establish the ray equation:

[0101]

[0102] Step 3.2.3: Solve for the intersection of the ray and the triangular surface element and the t value.

[0103] The intersection point between the ray and the target surface element has been determined. If the reflection direction of the ray on the surface element can be determined, the equation of the reflected ray can be calculated. Snell's law can be used to calculate the reflection direction of the ray after it intersects the surface element at the target surface.

[0104] Step 3.3: Calculate the reflection direction and reflection field strength of the multiple reflections of the ray on the surface of the surface element.

[0105] Step 3.3.1, as follows Figure 4As shown, based on Snell's law, the unit vector of the incident ray direction... Unit normal vector at the reflection point Calculate the direction vector of the reflected ray

[0106]

[0107] Step 3.3.2, as follows Figure 4 As shown, when rays are incident on and reflected from the target surface, their field strengths also satisfy certain corresponding relationships. Depending on the radar antenna polarization, the incident field strength E under horizontal polarization conditions is calculated. i (r′), Field strength of the reflected field E r (r′) and the incident field strength H under vertical polarization conditions i (r′), field strength of the reflected field H r (r′):

[0108]

[0109] in:

[0110]

[0111] In the formula, R ∥ R is the reflection coefficient of the target surface under parallel polarization. ⊥ E represents the reflection coefficient of the target surface under vertical polarization. e∥ and E e⊥ These represent the amplitudes of the electric field vector in the two polarization directions;

[0112] Step 3.3.3: Update the reflected ray and field strength according to the ray reflection direction and field strength. Update the reflected ray to the incident ray and the reflected field strength to the new incident field strength. Iterate the calculation continuously using steps 3.3.1 and 3.3.2 until the ray leaves the target.

[0113] In one embodiment of the present invention, step 4 involves calculating the scattered field of each ray tube in the receiving direction, traversing all ray tubes, and superimposing the scattered fields of all ray tubes to obtain the total scattered field of the target. This includes at least the following steps:

[0114] Step 4.1: Calculate the scattered field of a single ray tube in the receiving direction:

[0115]

[0116] in, Let A be the receiving direction of the scattered field in polar coordinates. θ , It is a function of the electric field strength at each point on the exiting ray tube and the quadrilateral enclosed by the ray tube;

[0117] Step 4.2: Traverse all ray tubes and superimpose the scattered fields of all ray tubes to obtain the scattering cross-section gain value of the target at typical azimuth angle and typical elevation angle;

[0118]

[0119] In the formula, σ VV σ represents the scattering cross-section gain value at a typical azimuth angle of the target. HH This represents the gain value of the scattering cross section at typical high and low angles.

[0120] In one embodiment of the present invention, step 5, based on the calculated target radar scattering gain at a typical horizontal azimuth angle, plots the horizontal cross-section gain map and the vertical cross-section gain map of the ship target, respectively, including at least the following steps:

[0121] Step 5.1, as follows Figure 5 As shown, the target radar cross section gain value is calculated for typical azimuth angles. Connect the radar cross section gain values ​​corresponding to each typical azimuth angle. The typical azimuth angles are: 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, and 300°. Plot the horizontal cross section gain diagram of the ship target.

[0122] Step 5.2, as follows Figure 6 As shown, the target radar cross section gain value is calculated for typical elevation angles. Connect the radar cross section gain values ​​corresponding to each typical elevation angle. The typical elevation angles are -22.5°, 0°, 22.5°, 45°, 67.5°, and 90°. Plot the vertical cross section gain diagram of the ship target.

[0123] In one embodiment of the present invention, a method for calculating the radar cross-section of a ship target during radar detection from different directions in step 6 is provided. The method uses an interpolation formula and specifically includes the following steps:

[0124] Step 6.1: The azimuth and elevation angles of the computer-borne radar relative to large ship targets, specifically including:

[0125] Step 6.1.1: Calculate the horizontal distance Δx and the height difference Δy (in meters) between the radar equipment and the large ship target:

[0126]

[0127] Δy=(lat m -lat s )·60·1852

[0128] Among them, lon mLongitude and latitude of the location of the radar equipment m latitude, h m For height; lon s For the longitude and latitude of the ship target s Latitude is expressed in radians, and altitude in meters.

[0129] Step 6.1.2: Calculate the azimuth angle α and elevation angle β of the radar equipment relative to the large ship target:

[0130] α = atan2(Δx, Δy)

[0131]

[0132] Step 6.2, Interpolation calculation of the target radar cross-section relative to the airborne radar, specifically includes:

[0133] Step 6.2.1: Interpolate and calculate the horizontal gain of the radar cross-section of the ship target:

[0134]

[0135] In the formula, α1 and α2 are typical azimuth angles, and the azimuth angle α of the radar equipment relative to the ship target falls within the interval [α1, α2].

[0136] Step 6.2.2: Interpolate and calculate the vertical gain of the radar cross-section of the ship target:

[0137]

[0138] In the formula, β1 and β2 are typical elevation angles, and the elevation angle β of the airborne radar equipment relative to the ship target falls within the interval [β1, β2]. Step 6.2.3: Calculate the target radar cross-section rcs of the ship target relative to the airborne radar:

[0139] rcs=rcs ref ·krcs α ·krcs βγ

[0140] In the formula, rcs ref The reference cross-sectional value is the typical value for the target.

[0141] This invention overcomes the limitations of using a single method to calculate the radar cross section (RCS) of ship targets based on their characteristics. It provides a bouncing ray method that combines geometric optics principles with physical optics. Based on a constructed three-dimensional model of the ship target, the RCS gain values ​​in the typical horizontal and vertical directions of the ship target are calculated through processes such as ray tube generation, ray tube tracking and updating, and far-field integration. The horizontal and vertical RCS gain maps of the ship target are then plotted. When different radar devices detect the target, the RCS of the ship target can be calculated quickly and easily using interpolation formulas based on the horizontal and vertical RCS gain maps.

[0142] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for calculating the equivalent model of radar cross-section of a large ship target, characterized in that: The method includes the following steps: Step 1: Establish a three-dimensional geometric model of the large ship target; Step 2: Based on the target geometry, establish a virtual electromagnetic wave incident aperture surface at a distance approaching infinity, and discretize the aperture surface to obtain a single ray tube; Step 2 includes at least the following steps: Step 2.1: Project the 3D point information (X, Y, Z) on the target onto a virtual aperture surface at a certain distance from the target and perpendicular to the plane wave incident direction through coordinate transformation. The transformed coordinates are... Where θ is X r The angle between the Z-axis and the Z-axis It is X r The angle between the projection of the xoy plane and the positive x-axis; The transformation relationship is as follows: Step 2.2: Traverse all two-dimensional points to obtain the maximum and minimum values ​​y in two directions on the virtual aperture surface. θmax y θmin , The size of the rectangular aperture surface is obtained; when the ray tube is generated, its division step size is 1 / 10 of the electromagnetic wave wavelength λ; Step 3: Track the reflection direction of each ray tube on the target surface until the ray leaves the target surface; Step 3 includes at least the following steps: Step 3.1: Discretize the target into triangular facets; Step 3.2: For different triangular facets, calculate the intersection points of the rays and the triangular facets; Step 3.2 includes at least the following steps: Step 3.2.1: Based on the coordinates of the three points of the triangular element, they are as follows: The normal unit vector of the triangular element is Establish the equation of the plane containing the triangle: Step 3.2.2: Based on the ray exit point and the vector of ray propagation direction Establish the ray equation: Step 3.2.3: Solve for the intersection points of the ray and the triangular surface element, and the value of t; Step 3.3: Calculate the reflection direction and reflection field intensity of the multiple reflections of the ray on the surface of the surface element; Step 3.3 includes at least the following steps: Step 3.3.1: Based on Snell's law, the unit vector of the incident ray direction... Unit normal vector at the reflection point Calculate the direction vector of the reflected ray Step 3.3.2: Calculate the incident field strength: E i (r ′ ) represents the incident field strength under parallel polarization, H i (r ′ (E) represents the incident field strength under vertical polarization; calculate the reflected field strength: E r (r ′ ) represents the reflected field strength under parallel polarization, H r (r ′ The reflected field strength under vertical polarization is given by the following formula: in: In the formula, R || R is the reflection coefficient of the target surface under parallel polarization. ⊥ E represents the reflection coefficient of the target surface under vertical polarization. e|| and E e⊥ These represent the amplitudes of the electric field vector in the two polarization directions; Step 3.3.3: Update the reflection based on the ray reflection direction and field strength, and iterate continuously using steps 3.3.1 and 3.3.2 until the ray detaches from the target; Step 4: Calculate the scattered field of each ray tube in the receiving direction, and superimpose the scattered fields of all ray tubes to obtain the total scattered field of the target; Step 4 includes at least the following steps: Step 4.1: Calculate the scattered field of a single ray tube in the receiving direction: in, Let A be the receiving direction of the scattered field in polar coordinates. θ , It is a function of the electric field strength at each point on the exiting ray tube and the quadrilateral enclosed by the ray tube; Step 4.2: Traverse all ray tubes and superimpose the scattered fields of all ray tubes to obtain the scattering cross-section gain value of the target at typical azimuth angle and typical elevation angle; In the formula, σ VV σ represents the scattering cross-section gain value at a typical azimuth angle of the target. HH This represents the typical high and low angle scattering cross-section gain values; Step 5: Based on the calculated target radar scattering gain at typical horizontal azimuth and vertical elevation angles, draw the horizontal cross-section and vertical gain diagram of the ship target. Step 6: Based on the target radar scattering gain map, use interpolation formulas to calculate the radar cross section of the ship target when the radar equipment detects from different directions.

2. The method for calculating the equivalent model of radar cross-section of a large ship target as described in claim 1, characterized in that: Step 5 includes at least the following steps: Step 5.1: Set the calculated target radar cross section gain value for typical azimuth angles, connect the radar cross section gain values ​​corresponding to each typical azimuth angle, and draw the horizontal cross section gain diagram of the ship target. Step 5.2: For typical elevation angles, set the calculated target radar cross section gain value, connect the radar cross section gain values ​​corresponding to each typical elevation angle, and draw the vertical cross section gain diagram of the ship target.

3. The method for calculating the equivalent model of radar cross-section of a large ship target as described in claim 1, characterized in that: Step 6 includes at least the following steps: Step 6.1: Calculate the azimuth and elevation angles of the radar equipment relative to the large ship target; Step 6.2, Calculation of target radar cross section interpolation.

4. The method for calculating the equivalent model of radar cross-section of a large ship target as described in claim 3, characterized in that: Step 6.1 includes at least the following steps: Step 6.1.1: Calculate the horizontal distance Δx and the height difference Δy between the radar equipment and the large ship target: Δy=(lat m -years s )·60·1852 Among them, lon m Longitude and latitude of the location of the radar equipment m latitude, h m For height; lon s For the longitude and latitude of the ship target s Latitude; Step 6.1.2: Calculate the azimuth angle α and elevation angle β of the radar equipment relative to the large ship target: α = atan2(Δx, Δy) 5. The method for calculating the equivalent model of radar cross-section of a large ship target as described in claim 4, characterized in that: Step 6.2 includes at least the following steps: Step 6.2.1: Interpolate and calculate the horizontal gain of the target's radar cross-section: In the formula, α1 and α2 are typical azimuth angles; Step 6.2.2: Interpolate the vertical gain of the target's radar cross-section: In the formula, β1 and β2 are typical elevation angles; Step 6.2.3: Calculate the target radar cross section (rcs) of the ship relative to the radar equipment: rcs=rcs ref ·krcs α ·krcs β In the formula, rcs ref The reference cross-sectional value is the typical value for the target.

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