A method for evaluating the moving target shadow detection capability of a video SAR system

Abstract

The application discloses a kind of video SAR system's moving target shadow detection capability evaluation method, comprising: S1, for the moving target in the observation area of video SAR system under certain parameters, judge whether to satisfy the condition of formula, if satisfy then determine that the moving target shadow in video SAR image can be effectively detected, continue to execute step S2, otherwise determine that moving target shadow is difficult to be detected;S2, define effective shadow pixel number index to quantitatively evaluate the shadow detection capability of video SAR system, and the greater the effective shadow pixel number index value, the stronger the ability of video SAR system to detect moving target shadow.The present application can be used for the detectability decision of video SAR system moving target shadow, and the quantitative evaluation of moving target shadow detection capability, the present application can provide theoretical and technical support for video SAR system optimization design and performance evaluation.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of radar detection and microwave remote sensing, and more specifically, to a method for evaluating the moving target shadow detection capability of a video SAR system. Background Technology

[0002] With the increasing development of microwave detection technology, SAR systems are playing an increasingly important role as a crucial means of Earth observation. Video SAR is a special imaging mode of SAR systems that generates continuous image frames by staring at a target area. Compared to traditional SAR operating modes, video SAR can acquire dynamic information about targets within the observation area, breaking through the limitation of the minimum detectable speed for moving target detection. It can perceive the target's state information by detecting the shadows cast by the actual location of the moving target. However, it also faces many new technical challenges. For example, the ability of video SAR systems to detect shadows of moving targets within the monitoring area is limited by target parameters (target size, target velocity, etc.) and radar system parameters (platform speed, imaging resolution, synthetic aperture time, viewing angle, etc.). Therefore, it is necessary to develop a method for evaluating the moving target shadow detection capability of video SAR systems. Summary of the Invention

[0003] The purpose of this invention is to provide a method for evaluating the moving target shadow detection capability of a video SAR system, so as to overcome the defects of the existing technology.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for evaluating the moving target shadow detection capability of a video SAR system includes the following steps:

[0006] S1. For moving targets within the observation area of ​​the video SAR system under certain parameters, determine whether the following formula is satisfied. If satisfied, it is determined that the shadow of the moving target in the video SAR image can be effectively detected, and step S2 is continued; otherwise, it is determined that the shadow of the moving target is difficult to detect.

[0007]

[0008] In the formula, L T V is the target length. T Let ρ be the target's velocity, ρ be the system's imaging resolution, λ be the wavelength, and σ be the velocity. b σ is the background backscattering coefficient. N R0 is the total noise of the radar system, V is the slant range, and V is the velocity of the video SAR platform.

[0009] S2. Define the effective shadow pixel count index to quantitatively evaluate the shadow detection capability of a video SAR system. The larger the effective shadow pixel count index value, the stronger the video SAR system's ability to detect shadows of moving targets. The calculation formula for the effective shadow pixel count index is as follows:

[0010]

[0011] In the formula, W T Where L is the target width, H is the antenna azimuth dimension, and L is the antenna azimuth dimension. T Let θ be the target height, θ be the angle between the direction of motion and the distance direction, and α be the downward angle.

[0012] Furthermore, the derivation steps of the formula in step S1 are as follows:

[0013] Equivalent backscattering intensity σ in the shadow region of a moving target S and the equivalent backscattering intensity σ in the background clutter region C They are represented as follows:

[0014]

[0015]

[0016] In the formula, σn represents the additive noise equivalent backscattering, expressed as the multiplicative noise ratio MNR and the scene-averaged backscattering. The product represents multiplicative noise;

[0017] The ratio of the scattering intensity of the shadow center region of a moving target to that of the surrounding scene region, ShCR, is calculated using the following formula:

[0018]

[0019] In the formula, β is the shadow coefficient, which represents the proportion of the time that the shadow area of ​​the moving target is blocked during the synthetic aperture time to the synthetic aperture time. 0≤β≤1. The larger β is, the weaker the scattering in the region and the more significant the shadow feature. Similarly, the larger the ShCR value, the closer the shadow is to the background and the less likely the shadow is to be effectively detected.

[0020] When the target length meets the condition When the shadow center region has β, it is:

[0021]

[0022] When the ratio of the scattering intensity of the target shadow center region to that of the surrounding scene region is less than -3dB, the shadow intensity is low enough that the target shadow can be effectively detected under this condition.

[0023]

[0024] The above equation can be simplified to:

[0025]

[0026] Compared with the prior art, the advantages of the present invention are: the present invention can be used for the detectionability determination of moving target shadows in video SAR systems, as well as the quantitative evaluation of moving target shadow detection capability. The present invention can provide theoretical and technical support for the optimized design and performance evaluation of video SAR systems. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of the method for evaluating the moving target shadow detection capability of the video SAR system of the present invention.

[0029] Figure 2 This is a flowchart of the evaluation process for the moving target shadow detection capability of the video SAR system in this invention. Detailed Implementation

[0030] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0031] See Figure 1 As shown in the figure, this embodiment discloses a method for evaluating the moving target shadow detection capability of a video SAR system, including the following steps:

[0032] Step S1: For moving targets within the observation area of ​​the video SAR system under certain parameters, determine whether the following formula is satisfied. If satisfied, it is determined that the moving target shadow in the video SAR image can be effectively detected, and proceed to step S2; otherwise, it is determined that the moving target shadow is difficult to detect.

[0033]

[0034] In the formula, L T V is the target length. T Let ρ be the target's velocity, ρ be the system's imaging resolution, λ be the wavelength, and σ be the velocity. b σ is the background backscattering coefficient. N R0 represents the total noise of the radar system, V represents the slant range, and V represents the speed of the video SAR platform.

[0035] In this embodiment, the formula The derivation steps are as follows:

[0036] Equivalent backscattering intensity σ in the shadow region of a moving target S and the equivalent backscattering intensity σ in the background clutter region C They are represented as follows:

[0037]

[0038]

[0039] In the formula, σ n The equivalent backscattering of additive noise is represented by the multiplicative noise ratio (MNR) and the scene-averaged backscattering. The product represents multiplicative noise (Radar Imaging Technology [M], edited by Bao Zheng, Xing Mengdao, and Wang Tong, Electronic Industry Press, 2005, p. 116).

[0040] The ratio of the scattering intensity of the shadow center region of a moving target to that of the surrounding scene region, ShCR, is calculated using the following formula.

[0041]

[0042] In the formula, β is the shadow coefficient, which represents the proportion of the time that the shadow area of ​​the moving target is blocked during the synthetic aperture time to the synthetic aperture time. 0≤β≤1. The larger β is, the weaker the scattering in the region and the more significant the shadow feature. Similarly, the larger the ShCR value, the closer the shadow is to the background and the less likely the shadow is to be effectively detected.

[0043] When the target length meets the condition When the shadow center region has β, it is:

[0044]

[0045] When the ratio of the scattering intensity of the target shadow center region to that of the surrounding scene region is less than -3dB, the shadow intensity is low enough that the target shadow can be effectively detected under this condition.

[0046]

[0047] The above equation can be simplified to:

[0048]

[0049] Step S2: Define the effective shadow pixel count index to quantitatively evaluate the shadow detection capability of the video SAR system. The larger the effective shadow pixel count index value, the stronger the video SAR system's ability to detect shadows of moving targets. The calculation formula for the effective shadow pixel count index is as follows:

[0050]

[0051] In the formula, W T Where L is the target width, H is the antenna azimuth dimension, and L is the antenna azimuth dimension. T Let θ be the target height, θ be the angle between the direction of motion and the distance direction, and α be the downward angle.

[0052] Specifically, Figure 2 This invention provides a flowchart for evaluating the shadow detection capability of a video SAR system. Figure 1 Based on this, for a moving target that meets the detectability decision criteria, the number N of effective pixels within its shadow area that meet the detectability decision criteria is calculated. SE Points meeting the judgment criteria are set to 1, and those not meeting them are set to 0. Research shows that the target shadow exhibits a "light-dark-light" gradient along the direction of movement. Using ShCR = -3dB, the length of the shadow gradient interval meeting the criteria is... This leads to N. SE It is the ratio of the product of the gradient interval length and the shadow area width to the resolution in the range and azimuth directions.

[0053] By iterating through each point in the shaded area, we can obtain:

[0054]

[0055] Therefore, by defining the effective shadow pixel count index N SE This allows for a quantitative assessment of the moving target shadow detection capability of video SAR systems, and the derivation is complete.

[0056] This invention can be used to determine the detectability of moving target shadows in video SAR systems and to quantitatively evaluate the ability to detect moving target shadows. This invention can provide theoretical and technical support for the optimized design and performance evaluation of video SAR systems.

[0057] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, the patent owner may make various modifications or alterations within the scope of the appended claims, as long as they do not exceed the protection scope described in the claims of the present invention, they shall be within the protection scope of the present invention.

Claims

1. A method for evaluating the moving target shadow detection capability of a video SAR system, characterized in that, Includes the following steps: Equivalent backscattering intensity in the shadow region of a moving target and the equivalent backscattering intensity of the background clutter region They are represented as follows: In the formula, The equivalent backscattering of additive noise is represented by the multiplicative noise ratio. and scene average backscatter The product represents multiplicative noise. The background backscattering coefficient is... This represents the total noise of the radar system. The ratio of the scattering intensity of the shadow center region of a moving target to that of the surrounding scene region can be calculated using the following formula. : In the formula, The shadow coefficient represents the proportion of the time a moving target's shadow area is obscured within the total synthesized aperture time. , The larger the value, the weaker the scattering in that region, and the more pronounced the shadow features. Similarly, A higher value indicates that the shadow is closer to the background, and the shadow is less likely to be detected effectively. When the target length meets the condition At that time, the central area of ​​the shadow for: When the ratio of the scattering intensity of the target's shadow center region to that of the surrounding scene region is less than At this point, the shadow intensity is low enough that the target shadow can be effectively detected under these conditions, thus yielding: The above equation can be simplified to: ； S1. For moving targets within the observation area of ​​the video SAR system under certain parameters, determine whether the following formula is satisfied. If satisfied, it is determined that the shadow of the moving target in the video SAR image can be effectively detected, and step S2 is continued; otherwise, it is determined that the shadow of the moving target is difficult to detect. In the formula, For the target length, For the target speed of motion, For the system imaging resolution, For wavelength, The background backscattering coefficient is... The total noise of the radar system, Slope distance The speed of motion of the video SAR platform; S2. Define the effective shadow pixel count index to quantitatively evaluate the shadow detection capability of a video SAR system. The larger the effective shadow pixel count index value, the stronger the video SAR system's ability to detect shadows of moving targets. The calculation formula for the effective shadow pixel count index is as follows: In the formula, For target width, This refers to the antenna azimuth dimension. For the target height, The angle between the direction of motion and the distance direction. This is a bottom-view perspective.

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