A Real-Time Evaluation Method for SAR Imaging Performance Based on Aircraft Attitude

Abstract

This invention belongs to the field of airborne radar technology and discloses a real-time evaluation method for SAR imaging effects based on aircraft attitude. It calculates the radius of curvature of the current position in an ellipsoidal radius-of-curvature model based on the aircraft's latitude information. Based on the aircraft's flight altitude, imaging distance, and radius of curvature, it calculates the beam swirl angle of the imaging area. It sets lower and upper thresholds for the swirl angle, and evaluates the real-time imaging effect based on the obtained swirl angle thresholds. This invention addresses the needs of practical radar use by calculating the swirl angle to evaluate SAR imaging effects in real time, providing a clear and intuitive assistance to operators in selecting appropriate flight attitudes for SAR imaging to obtain high-quality SAR images. It avoids the problem that after the operator selects a target area in radar RBM mode, the swirl angle changes due to factors such as flight altitude, ground altitude, slant angle, and imaging distance, making it impossible to guarantee high-resolution SAR imaging of that area.

Description

Technical Field

[0001] This invention belongs to the field of airborne radar technology, specifically relating to a real-time evaluation method for SAR imaging effects based on aircraft attitude. Background Technology

[0002] Airborne radar ground observation functions typically employ multiple ground imaging methods, such as large-area, low-resolution beamforming (RBM) mapping and small-area, high-resolution synthetic aperture imaging (SAR). Because SAR imaging is characterized by its small-area, high-resolution capabilities, in scenarios where target coordinates are unavailable for guidance, coordinate guidance must be obtained from large-area, low-resolution methods like RBM before entering the target area.

[0003] In practical applications, terrain is typically imaged over a large area using RBM (Radar Beam Imaging), followed by high-resolution SAR (Special Radar Imaging) imaging of a designated area. Factors such as aircraft altitude, ground altitude, look-off angle, and imaging distance can cause variations in the beam grazing angle, thus affecting the SAR imaging results. Without accurate guidance, radar operators cannot assess the imaging performance of an area before SAR imaging. Summary of the Invention

[0004] In view of this, the present invention provides a real-time evaluation method for SAR imaging effect based on aircraft attitude. In response to the needs of actual radar use, the method evaluates the SAR imaging effect in real time by calculating the ground grazing angle during RBM imaging, and divides and displays the region according to the imaging effect to assist the operator in obtaining high-quality SAR imaging.

[0005] A real-time evaluation method for SAR imaging performance based on aircraft attitude includes the following steps:

[0006] Step 1: Obtain the aircraft's flight altitude, oblique angle, imaging distance, and aircraft latitude information;

[0007] Step 2: Calculate the radius of curvature of the current position in the ellipsoidal radius of curvature model based on the latitude information of the aircraft.

[0008] Step 3: Calculate the beam grazing angle of the imaging area based on the aircraft's flight altitude, imaging distance information, and the calculated radius of curvature;

[0009] Step 4: Set the lower and upper thresholds of the ground rubbing angle threshold, and evaluate the real-time imaging effect based on the obtained ground rubbing angle threshold of the imaging area beam.

[0010] Furthermore, the evaluation criteria for real-time imaging performance are as follows: if the beam rubbing angle of the imaging area is less than or equal to the lower threshold, the imaging performance is judged as poor; if the beam rubbing angle of the imaging area is within the range of the lower and upper thresholds, the imaging performance is judged as good; if the beam rubbing angle of the imaging area is greater than the upper threshold, the imaging performance is judged as unavailable.

[0011] Furthermore, in the ellipsoidal radius of curvature model, the Earth's radius of curvature...

[0012]

[0013] in, Re The radius of curvature of the Earth at the aircraft's location. Lat This represents the latitude value of the aircraft's location. a The radius of the Earth's major axis, e 2 represents the first eccentricity.

[0014] Furthermore, in step 3, based on the aircraft's flight altitude, imaging distance information, and the calculated radius of curvature... Re Calculate the beam rubbing angle in the imaging region θ EL for:

[0015]

[0016] in, h For the flight altitude of the carrier aircraft, L This represents the imaging distance.

[0017] Furthermore, using the radar transceiver on the carrier aircraft as a reference point, an RBM image of the radar scanning area is established. Based on the lower and upper thresholds of the ground rubbing angle threshold and the obtained ground rubbing angle of the imaging area beam, the corresponding area of ​​the RBM image is divided and the imaging effect evaluation results are displayed in real time.

[0018] Furthermore, by calculating the lower threshold of the rubbing angle threshold... θ EL1 and upper limit threshold θ EL2 Corresponding imaging distance L 1 and L 2,

[0019]

[0020] According to distance L 1 and L 2. The region is divided according to the SAR imaging oblique angle limitation, and the corresponding region of the RBM image is divided and the imaging effect evaluation result is displayed in real time.

[0021] Compared with existing technologies, the beneficial effects of this invention include at least the following: Addressing the needs of practical radar use, this invention calculates the ground grazing angle to evaluate SAR imaging performance in real time, providing clear and intuitive assistance to operators in selecting appropriate flight attitudes for SAR imaging, thereby obtaining high-quality SAR imaging. This avoids the problem that after an operator selects a target area in radar RBM mode, changes in the ground grazing angle due to factors such as flight altitude, ground altitude, angle of view, and imaging distance can compromise high-resolution SAR imaging of that area. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The flowchart shows the real-time evaluation method for SAR imaging performance based on aircraft attitude in Example 1 or 2.

[0024] Figure 2 This is a schematic diagram of the area division corresponding to the RBM screen in Example 2;

[0025] Figure 3 This is a schematic diagram of the beam rubbing angle in Example 2. Detailed Implementation

[0026] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0027] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] Example 1

[0029] See Figure 1 A real-time evaluation method for SAR imaging performance based on aircraft attitude includes the following steps:

[0030] Step 1: Obtain the aircraft's flight altitude, oblique angle, imaging distance, and aircraft latitude information;

[0031] Step 2: Calculate the radius of curvature of the current position in the ellipsoidal radius of curvature model based on the latitude information of the aircraft.

[0032] Step 3: Calculate the beam grazing angle of the imaging area based on the aircraft's flight altitude, imaging distance information, and the calculated radius of curvature;

[0033] Step 4: Set the lower and upper thresholds of the ground rubbing angle threshold, and evaluate the real-time imaging effect based on the obtained ground rubbing angle threshold of the imaging area beam.

[0034] In this embodiment, to meet the needs of actual radar use, the SAR imaging effect is evaluated in real time by calculating the ground scramble angle. This provides a clear and intuitive assistance to the operator in selecting the appropriate flight attitude for SAR imaging, thereby obtaining high-quality SAR images. This avoids the problem that after the operator selects a target area in the radar RBM mode, the ground scramble angle changes due to factors such as flight altitude, ground altitude, slant angle, and imaging distance, which makes it impossible to guarantee high-resolution SAR imaging of that area.

[0035] In this embodiment, the radar transceiver on the aircraft can be used as a reference point to establish a radar scanning area RBM image. Based on the lower and upper thresholds of the ground rubbing angle threshold, and the obtained ground rubbing angle of the imaging area beam, the corresponding area of ​​the RBM image is divided, and the imaging effect evaluation result is displayed in real time. This allows the operator to observe the imaging evaluation effect and select an appropriate flight attitude for SAR imaging. The real-time imaging effect is evaluated as follows: if the ground rubbing angle of the imaging area beam is less than or equal to the lower threshold, the imaging effect is judged as poor; if the ground rubbing angle of the imaging area beam is within the range of the lower and upper thresholds, the imaging effect is judged as good; if the ground rubbing angle of the imaging area beam is greater than the upper threshold, imaging is judged as impossible.

[0036] Example 2

[0037] See Figures 1-3 A real-time evaluation method for SAR imaging performance based on aircraft attitude includes the following steps:

[0038] 1) Obtain the flight altitude of the carrier aircraft Imaging distance Aircraft latitude Lat information;

[0039] 2) Obtain the Earth's radius of curvature in the ellipsoidal radius of curvature model. Re ;

[0040]

[0041] in, Re The radius of curvature of the Earth is the position of the aircraft. Lat This represents the latitude value of the aircraft's location. a The radius of the Earth's major axis; e 2 represents the first eccentricity. In this embodiment, it is taken as... , .

[0042] 3) Schematic diagram of beam rubbing angle as shown below Figure 3 As shown, the rubbing angle is calculated based on relevant parameters. ;

[0043]

[0044] 4) Select the lower threshold of the rubbing angle threshold. and upper limit threshold , θ EL In 0~ θ EL1 If the image quality is within the specified range, it is considered poor. θ EL exist ~ If the image quality is between these ranges, it is considered to have good imaging quality. θ EL > θ EL2 Therefore, it is determined that imaging is impossible. In this embodiment, the following is selected: It is 5°. It is 40°.

[0045] 5) Calculate the rubbing angle according to the following formula. and Corresponding imaging distance L 1 and L 2;

[0046]

[0047] 6) Based on distance L 1 and L 2. Regions are divided based on the SAR imaging's oblique angle limitation, and the imaging effect evaluation results are displayed in real-time in the corresponding region of the RBM image. For example... Figure 2 As shown, the azimuth ± θ angle range is the limitation of the SAR imaging oblique viewing angle. L 1. L 2 represents the distance calculated based on the wiping angle threshold.

[0048] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for real-time evaluation of SAR imaging performance based on carrier attitude, characterized in that, Includes the following steps: Step 1: Obtain the aircraft's flight altitude, oblique angle, imaging distance, and aircraft latitude information; Step 2. Calculate the current position radius of curvature in the ellipsoidal meridian curvature radius model based on the latitude information of the carrier wherein, Re R is the carrier position Earth curvature radius, Lat φ is the latitude value of the carrier position, a a is the Earth major axis radius, e 2 is the first eccentricity; Step 3: Calculate the beam grazing angle of the imaging area based on the aircraft's flight altitude, imaging distance information, and the calculated radius of curvature. ,in, h For the flight altitude of the carrier aircraft, L For imaging distance; Step 4: Set the lower and upper thresholds of the ground rubbing angle threshold, and evaluate the real-time imaging effect based on the obtained ground rubbing angle threshold of the imaging area beam.

2. The real-time evaluation method for SAR imaging effect based on aircraft attitude according to claim 1, characterized in that, The evaluation criteria for real-time imaging performance are as follows: if the beam rubbing angle of the imaging area is less than or equal to the lower threshold, the imaging performance is judged as poor; if the beam rubbing angle of the imaging area is within the range of the lower and upper thresholds, the imaging performance is judged as good; if the beam rubbing angle of the imaging area is greater than the upper threshold, the imaging performance is judged as impossible.

3. The real-time evaluation method for SAR imaging effect based on aircraft attitude according to any one of claims 1-2, characterized in that, Using the radar transceiver on the aircraft as a reference point, a true beam map (RBM) of the radar scanning area is established. Based on the lower and upper thresholds of the ground rubbing angle threshold and the obtained ground rubbing angle of the imaging area beam, the corresponding area of ​​the RBM is divided and the imaging effect evaluation results are displayed in real time.

4. The real-time evaluation method for SAR imaging effect based on aircraft attitude according to claim 3, characterized in that, By calculating the lower threshold of the rubbing angle threshold θ EL1 and upper limit threshold θ EL2 Corresponding imaging distance L 1 and L 2, According to distance L 1 and L 2. The region is divided according to the SAR imaging oblique angle limitation, and the corresponding region of the RBM image is divided and the imaging effect evaluation result is displayed in real time.

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