CN117392311A - SAR image simulation method and device for damage scene - Google Patents
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Abstract
The invention discloses a method and a device for simulating SAR images of a damage scene, wherein the method comprises the following steps: establishing three-dimensional models of explosion pits under different soil medium types, explosive amounts and explosive depths based on explosion mechanics; performing explosion pit and backscattering characteristic of scene where the explosion pit is located based on calculation electromagnetism; and simulating and imaging echo data of the explosion pit according to the three-dimensional model of the explosion pit and the backscattering characteristics of the explosion pit and the scene where the explosion pit is located. The method can indirectly acquire the post-explosion damage scene information, and has important significance for post-disaster quick evaluation, post-disaster reconstruction, engineering construction, fire-extinguishing rescue and other works.
Description
Technical Field
The invention relates to the technical field of synthetic aperture radar image simulation, in particular to a method and a device for simulating a SAR image of a damage scene.
Background
Explosion is a process in which a substance rapidly releases a great amount of energy and produces a severe reaction in a very short time. Sudden explosion disasters occur. Explosion plays an important role in engineering construction, fire-extinguishing rescue and other works, for example, the rapid excavation of underground space can be realized by utilizing the blasting technology. Whether it is a sudden explosion hazard or a planned blasting application, the occurrence of an explosion often causes significant changes to the site, such as building collapse, explosion pit formation, surface deformation, even cracking, etc. The method for acquiring the post-explosion damage scene information has important significance for post-disaster quick evaluation, post-disaster reconstruction, engineering construction, fire-extinguishing rescue and other works.
The method for acquiring the information of the damage scene after explosion can be divided into a direct acquisition method and an indirect acquisition method. The direct method is to obtain the information of the damaged scene after explosion in the modes of on-site investigation, photographing, shooting, remote sensing and the like; the indirect method is to predict the information of the post-explosion damage scene in a simulation mode. Compared with a direct method, the indirect method has the advantages of safety, low cost, repeatability, controllability and the like, not only can save a great deal of manpower and financial resources and reduce test workload, but also can control and adjust conditions such as an explosion device, an explosion scale and the like, thereby comprehensively and completely acquiring damage scene information under different explosion conditions and providing important references for post-disaster rescue force deployment, pre-explosion effect evaluation, engineering blasting dosage design, fire-extinguishing rescue ammunition delivery and the like.
The existing method for establishing the three-dimensional model of the damage scene based on explosion mechanics has the following two technical defects: 1) The accurate modeling of the explosion pit is the basis of the accuracy and the authenticity of the modeling of the damage scene, but the existing modeling method of the explosion pit is simplified, and the factors such as the influence on the form of the explosion pit, the throwing speed of the soil medium after the explosion, the actual throwing distance and the like under different explosion conditions are difficult to reveal, so that the modeling result is inaccurate; 2) Most of the existing three-dimensional modeling methods of the damaged scene are limited to realizing the visualization of the scene under different surface types based on a simple texture mapping technology, are difficult to reflect the influences of different surface coverings, surface roughness and the like, and have insufficient accuracy.
Disclosure of Invention
In order to solve the technical problems, the invention provides a damage scene SAR image simulation method. In the method and the device, the information of the damage scene after explosion is indirectly acquired, and the method and the device have important significance for post-disaster rapid evaluation, post-disaster reconstruction, engineering construction, fire-extinguishing rescue and other works.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
the SAR image simulation method for the damage scene comprises the following steps:
s1: establishing three-dimensional models of explosion pits under different soil medium types, explosive amounts and explosive depths based on explosion mechanics;
s2: performing explosion pit and backscattering characteristic of scene where the explosion pit is located based on calculation electromagnetism;
s3: and simulating and imaging echo data of the explosion pit according to the three-dimensional model of the explosion pit and the backscattering characteristics of the explosion pit and the scene where the explosion pit is located.
Preferably, the step S1 specifically includes the following steps:
s11: acquiring parameter settings in an explosion scene, wherein the parameters in the explosion scene comprise soil medium types, explosive quantity and explosive burial depth data, and calculating critical proportion burial depths corresponding to the soil medium types based on the explosive quantity; judging whether the depth of the explosive exceeds the critical proportion depth, if so, ending simulation; if not, entering the next step;
s12: selecting an explosion pit calculation model according to parameters in an explosion scene, determining a fitting coefficient corresponding to the explosion pit calculation model, and acquiring point cloud data of the explosion pit based on the explosion pit calculation model;
s13: and preprocessing the point cloud data of the explosion pit, and reconstructing the processed point cloud data into a three-dimensional model by adopting a Delaunay triangulation algorithm.
Preferably, the preprocessing includes denoising and resampling.
Preferably, in said S12, the step of generating a signal,
1) Under the above-ground explosion scene, the explosion pit calculation model is a touchdown explosion pit model, and mainly comprises a parabolic explosion pit, wherein the radius and depth calculation of the parabolic explosion pit are shown in the formula (1) and the formula (2):
d in a To strike the ground the radius of the explosion pit, H a The depth of the ground-touching explosion pit is m is the explosive quantity, d is the depth of the explosion, A a Fitting coefficients 1, B for diameter a Fitting coefficients 2, E to diameter a Fitting coefficients 1, F for depth a Fitting coefficients 2, A for depth a 、B a 、E a 、F a Is determined by the physical properties of the soil medium;
2) Under the underground explosion scene, the explosion pit calculation model selects a standard throwing funnel type explosion pit calculation model, the explosion pit calculation model consists of a parabolic explosion pit and a throwing accumulation area, and the radius and depth calculation of the parabolic explosion pit are shown as the formula (3) and the formula (4);
d in u Is the radius of a standard throwing funnel type explosion pit, H u The depth of the explosion pit is m is the explosive quantity, d is the depth of the explosion pit, A u Fitting coefficients 1, B for diameter u Fitting coefficient 2, A for diameter u 、B u Are determined by the physical properties of the soil medium;
calculating the maximum throwing speed of explosion according to a formula (5), and determining throwing speed distribution by a throwing speed model of a formula (6); determining the throwing distance of the rock and soil through the influence of the ballistic motion of the rock and soil and the resistance in the throwing process; fitting a histogram of the throw distance distribution with the Weibull distribution to obtain a shape of the throw stack zone, wherein:
v in max For maximum slinging speed of explosion occurrence, v i Is the throwing speed; m is the explosive quantity, d is the depth of burial of the explosive, A v 、B v Fitting coefficients for maximum casting speed, C v 、E v The fitting coefficient of the throwing speed is determined by the physical property of the soil medium.
Preferably, the step S2 specifically includes the following steps:
s21: adjusting triangular surface element subdivision of the explosion pit three-dimensional model obtained in the step S1 according to the proper size of the resolution unit; performing visibility analysis on each split surface element and calculating primary backscattering characteristics of the visible surface element by using a PO method; calculating the reflected wave of the visible bin by bin, judging the bin irradiated by the reflected wave, and continuously calculating the secondary scattering of the explosion pit for the bin irradiated by the reflected wave; integrating the calculation results of primary scattering and secondary scattering, and outputting the backscattering characteristic of the explosion pit;
s22: and calculating the backscattering characteristic of the scene where the explosion pit is located based on the existing SAR image serving as the backscattering characteristic of the scene where the explosion pit is located or by analyzing and judging the type of the ground object of the scene where the explosion pit is located.
Preferably, the step S3 specifically includes the following steps:
s31: obtaining simulation parameters of a simulation scene, wherein the simulation parameters comprise satellite orbit parameters, emission signal parameters and target position parameters;
s32: according to the simulation parameters input in the S31 and the backscattering characteristics of the target and the scene output in the S2 scene backscattering characteristic calculation part, calculating to obtain simulated scene echo data;
s33: simulating speckle noise based on a speckle statistical model, and introducing the speckle noise into scene echo data obtained in the step S32;
s34: and (3) performing imaging processing on the scene echo data obtained in the step (S33) and introducing the speckle noise.
Preferably, the step S32 specifically includes the following steps:
the fast time domain simulation algorithm based on FFT calculates the frequency spectrums of the azimuth direction signal and the distance direction signal respectively, and the SAR echo signal is obtained by calculating the inverse Fourier transform of the product of the azimuth direction signal and the distance direction signal, and the calculation formula is as follows:
wherein τ is distance-wise time; t is azimuth time, k r For the frequency modulation rate of the transmitted chirp signal, σ is the backscattering characteristic value, λ is the carrier wavelength, T a For synthetic aperture time, c is the speed of light and r is the target point slant distance.
Preferably, the speckle statistical model comprises a Rayleigh distribution model, a K distribution model, a W distribution model and a heavy tail generalized Rayleigh distribution model.
Preferably, in S34, an imaging process is performed by using a chirp scaling algorithm, a range doppler algorithm, and a range migration algorithm.
Based on the above, the invention also discloses a device for simulating the SAR image of the damage scene, which comprises: a model building unit, a scattering calculation unit and an echo imaging unit, wherein,
the model building unit is used for building three-dimensional models of different soil medium types, explosive quantity and explosion pits under the explosion depth of the explosive based on explosion mechanics;
the scattering calculation unit is used for carrying out explosion pit and backscattering characteristics of the scene where the explosion pit is located based on calculation electromagnetism;
the echo imaging unit is used for simulating and imaging echo data of the explosion pit according to the three-dimensional model of the explosion pit and the backscattering characteristics of the explosion pit and the scene where the explosion pit is located.
Based on the technical scheme, the invention has the beneficial effects that: the invention firstly establishes three-dimensional models of different soil medium types, explosive amount and explosion pits under the burial depth of explosive based on explosion mechanics, and solves the problems of oversimplification and low accuracy of the explosion pit model; then, based on calculation electromagnetism, the backscattering characteristics of the explosion pit and the scene where the explosion pit is located are calculated, so that the problem that the influence of different ground coverings, ground roughness and the like is not considered is solved; and finally, simulating and imaging SAR echo data of the damage scene, and realizing SAR image output of the simulated damage scene. SAR images have the advantage of revealing information such as the geometry of the target, the earth's surface coverage, the earth's surface roughness, etc., compared to optical images. SAR image simulation results of the damaged scene not only reveal the influences of different soil medium types, different explosive amounts and different explosive burial depths on the shape of an explosion pit, but also accurately establish an explosion pit model according to the throwing speed and the actual throwing distance of the soil medium after explosion occurs, and can reflect the influences of different earth surface coverings, earth surface roughness and the like.
Drawings
FIG. 1 is a schematic diagram of a method for simulating SAR images of a destructive scene in one embodiment;
FIG. 2 is a schematic illustration of a standard slinger funnel type blast pit;
FIG. 3 is a schematic representation of a three-dimensional model of a standard slinger funnel type blast pit;
FIG. 4 is a flow chart of the calculation of the scattering coefficient of an explosion pit in a method for simulating SAR images of a damaged scene in one embodiment;
FIG. 5 is a diagram of simulation results of a destructive scene in a method for simulating SAR images of a destructive scene in one embodiment;
fig. 6 is a schematic structural diagram of a device for simulating a SAR image of a damaged scene in one embodiment.
In the drawings, each reference numeral is:
1-casting a pile-up area; 2-parabolic detonation pits.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
As shown in fig. 1, the embodiment provides a method for simulating a damage scene SAR image, which is based on computational electromagnetics, considers the influence of different ground coverings, ground roughness and the like, introduces a scattering calculation model on the basis of the existing method for modeling the damage scene, improves the accuracy of the damage scene model, realizes the simulation of the damage scene SAR image, and specifically comprises the following steps:
s1: based on explosion mechanics, three-dimensional models of different soil medium types, explosive amount and explosion pits under the explosion depth are established, and the technical defects that the explosion pit model is too simplified and the accuracy is not high are overcome.
The computer equipment establishes a proper explosion pit calculation model based on explosion mechanics, and calculates to obtain point cloud data of the explosion pit; the method comprises the steps of carrying out preprocessing such as denoising and resampling on point cloud data of an explosion pit, and converting the preprocessed point cloud data into a three-dimensional model of the explosion pit, and specifically:
s11: setting parameters in an explosion scene, including setting the type and parameters of a soil medium in the explosion scene, such as the density, the shearing strength and the like of the soil medium, setting the explosive quantity and the explosive burial depth, wherein if the set explosive burial depth is greater than 0, the set explosive burial depth is the explosion below the ground, and if the set explosive burial depth is less than 0, the set explosive burial depth is the explosion above the ground. When the explosion under the ground occurs, the critical proportion burial depth under the corresponding soil medium is calculated through the set explosive quantity, when the explosive burial depth exceeds the critical proportion burial depth, the energy generated by the explosion is almost absorbed by the soil body, namely the closed explosion or the hidden explosion can be considered to occur, no obvious explosion pit is formed at the moment, and the simulation is terminated;
s12: and selecting a corresponding explosion pit calculation model according to the parameters set in the step S11. Under the explosion scene above the ground, the explosion pit calculation model selects a touchdown explosion pit model, the explosion pit calculation model mainly comprises a parabolic explosion pit, and the radius and depth calculation of the parabolic explosion pit can be calculated according to the following formula;
d in a To strike the ground the radius of the explosion pit, H a The depth of the ground-touching explosion pit is m is the explosive quantity, d is the depth of the explosion, A a Fitting coefficients 1, B for diameter a Fitting coefficients 2, E to diameter a Fitting coefficients 1, F for depth a Fitting coefficients 2, A for depth a 、B a 、E a 、F a As determined by the physical properties of the earth medium, A in an explosion above the dry silt clay floor a ＝0.152，B a ＝1.241，E a ＝5.05，F a ＝5.78。
Under the underground explosion scene, the explosion pit calculation model selects a standard casting funnel type explosion pit calculation model, the model consists of a parabolic explosion pit and a casting accumulation area, and the radius and depth calculation of the parabolic explosion pit are shown in the formulas (3) and (4);
d in u Is the radius of a standard throwing funnel type explosion pit, H u The depth of the explosion pit is m is the explosive quantity, d is the depth of the explosion pit, A u Fitting coefficients 1, B for diameter u Fitting coefficient 2, A for diameter u 、B u Is determined by physical properties of soil medium, A in explosion under the sandy soil ground with low water content u ＝1.22，B u = -0.4, a in a sub-saturated sand explosion u ＝1.33，B u ＝-0.31。
The method comprises the steps of firstly, calculating the maximum throwing speed of explosion according to a formula (5), then determining throwing speed distribution by a throwing speed model of a formula (6), determining the throwing distance of rock and soil by taking the influence of resistance in the throwing process into consideration through the ballistic movement of the rock and soil, and finally, fitting a histogram of the throwing distance distribution by utilizing Weibull distribution to obtain the shape of the throwing stacking region.
V in max The maximum throwing speed of explosion is the explosive quantity m, d is the depth of burial of the explosive, A v 、B v 、C v 、E v Is constant and is determined by physical properties of soil medium, A in concrete v ＝5.18，B v ＝1.93，C v ＝-0.099，E v ＝-0.16。
S13: the method comprises the steps of firstly preprocessing point cloud data of an explosion pit, including denoising, resampling and the like, then converting the preprocessed point cloud data into the three-dimensional model of the explosion pit, and taking the three-dimensional model as an output result of the step S1, wherein a point cloud reconstruction algorithm adopted in the method is Delaunay triangulation.
S2: based on the backscattering characteristics of the explosion pit and the scene where the explosion pit is located by calculation electromagnetics, the technical defect that the influences of different ground surface coverings, ground surface roughness and the like are difficult to reflect in the prior art scheme is overcome, and specifically:
s21: and performing backward scattering property calculation of the target, namely calculating the backward scattering property of the explosion pit, wherein the scattering property calculation of the target adopts a bouncing ray method-a physical optical method (SBR-PO) method. The calculation flow of the SBR-PO method is shown in FIG. 5. Firstly, adjusting triangular surface element subdivision of the explosion pit three-dimensional model obtained in the step S1 according to a proper resolution unit size, then carrying out visibility analysis on each subdivision surface element, calculating primary scattering characteristics of the visible surface element by using a physical optical method (PO), as shown in a formula (7), then continuously calculating reflection waves of the visible surface element by surface element, judging irradiation surface elements of the reflection waves, so as to calculate secondary scattering of the explosion pit, wherein the secondary scattering calculation is shown in a formula (8), and finally outputting scattering characteristics of a target;
in the method, in the process of the invention,is the normal vector of the target triangle element, +.>Is the unit vector of the incident magnetic field,/>For the position vector of the target triangle element, +.>And->The midpoint position vector and the direction vector of the mth side of the triangular surface element are respectively, T is +.>Projection length on plane, and +.>
In the method, in the process of the invention,is the direction vector of the primary reflection magnetic field, T 1 Is->Projection length on bin 1, and
s22: and determining the backscattering characteristic of the scene, wherein an existing SAR image can be selected and input, or an empirical formula of ground feature scattering calculation can be adopted to calculate the backscattering characteristic of the scene, as shown in the following formula, and then the scattering characteristic of the scene is output.
Wherein A is σ 、B σ 、C σ 、D σ Is constant and is determined by the type of ground object, such as A in sand σ ＝0.05、B σ ＝0.83、C σ ＝0.0013、D σ ＝2.3，σ h The standard deviation of height fluctuation of the facet unit is represented by θ, the incident angle of the facet unit is represented by λ, and the wavelength of the reflected radar electromagnetic wave is represented by λ.
S3: and simulating and imaging SAR echo data of the damage scene.
The computer equipment carries out SAR echo data simulation of the explosion pit and the scene where the explosion pit is located under the preset parameters, and then carries out imaging processing on the obtained echo data to realize simulated SAR image output of the damaged scene.
S31: setting simulation parameters of a simulated scene, including satellite orbit parameters (or aircraft track parameters), emission signal parameters, target position parameters and the like;
s32: according to the simulation parameters input in the step S31, simulated scene echo data are obtained, a fast time domain simulation algorithm based on Fourier transform (FFT) is adopted for echo data simulation, frequency spectrums of azimuth signals and distance signals are calculated respectively, SAR echo signals are obtained through calculating inverse Fourier transform of products of the azimuth signals and the distance signals, and the formula (10) is an echo simulation formula of the fast time domain simulation method based on FFT; the echo simulation processing step in the invention can also adopt a distance time domain pulse phase method;
wherein τ is distance time; t is azimuth time, k r For the frequency modulation rate of the transmitted chirp signal, σ is the scattering characteristic value, λ is the carrier wavelength, T a The synthetic aperture time is c is the light speed, and r is the target point slant distance;
s33: and simulating the speckle noise under the system parameters, and selecting different models such as Rayleigh distribution, K distribution, W distribution, heavy tail generalized Rayleigh distribution and the like according to specific conditions. For example, rayleigh distribution is adopted in low-resolution SAR simulation of a uniform region, K distribution is adopted in high-resolution SAR simulation of a non-uniform region, and heavy-tail generalized Rayleigh distribution is adopted when simulating long-tail amplitude of a city region. Introducing speckle noise into the scene echo data obtained in the step S32;
s34: and (3) performing imaging processing on the scene echo data obtained in the step (S33) and introducing the speckle noise by using a linear frequency modulation scaling algorithm (CS) to realize the output of the SAR simulation image of the damaged scene. CS imaging firstly carries out azimuth FFT on echo data, and then carries out product operation on the converted data and CS factors; then, after the signal with the new frequency is subjected to distance FFT, the transformation result is multiplied by a distance compensation factor, and then the distance FFT (IFFT) is performed; and finally, multiplying the obtained distance-oriented time domain data with an orientation compensation factor, and then carrying out orientation IFFT to carry out orientation processing. The imaging processing step in the present invention may also be replaced by imaging algorithms such as range-doppler (RD) algorithm, range-migration (RMA) algorithm, etc.
It should be understood that, although the steps in the above-described flowcharts are shown in order as indicated by the arrows, these steps are not necessarily performed in order as indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in the flowcharts described above may include a plurality of sub-steps or stages that are not necessarily performed at the same time, but may be performed at different times, and the order of execution of the sub-steps or stages is not necessarily sequential, but may be performed alternately or alternately with at least a part of the sub-steps or stages of other steps or other steps.
The specific implementation steps and input parameters are as follows:
s1: the explosion pit three-dimensional model creation section S1 creates a three-dimensional model of the explosion pit.
S11: setting the type of soil medium in the explosion scene as sandy soil, wherein the density of the soil medium is 1440kg/m -3 Shear strength of 3.4kPa, etc.;
s12: setting the explosive quantity and the explosive burial depth, wherein the explosive quantity is 100kg, and the explosive burial depth is 6m;
s13: the depth of the buried explosive is less than 0 and is positioned below the ground, and the critical proportion of the buried explosive under the sand is 2m/kg through the arranged explosive quantity and the related parameters of the soil medium 1/3 Comparing the explosive depth with the critical proportion depth, and continuing simulation when the explosive depth does not exceed the critical proportion depth and closed explosion or hidden explosion does not occur;
s14: according to the input parameters in the steps S11 and S12, as the set explosive burial depth is greater than 0, an explosion pit calculation model below the ground is selected first, and the explosion pit below the ground is a standard throwing funnel type, and mainly comprises a throwing pile and a parabolic explosion pit (visible bullet pit) as shown in fig. 2. Then determining a diameter fitting coefficient A of the explosion pit calculation model according to the soil medium parameters u ＝1.33，B u In the calculation process of the explosion pit below the ground, the fitting coefficient A of the throwing speed is also required to be determined, wherein the fitting coefficient A of the throwing speed is = -0.31 v ＝20，B v ＝1.5，C v ＝-0.099，E v After determining a proper fitting coefficient, calculating point cloud data of the explosion pit and outputting the point cloud data;
s15: reconstructing the point cloud of the explosion pit obtained in the step S14 into a three-dimensional model, firstly preprocessing the point cloud data of the explosion pit, including denoising, resampling and the like, and then converting the preprocessed point cloud data into the three-dimensional model of the explosion pit through a point cloud reconstruction technology, wherein the three-dimensional model is shown in the figure 3 and is used as an output result of the step S1.
S2: and a scene scattering characteristic calculation unit for performing a scene backscattering characteristic calculation, that is, a backscattering characteristic calculation of the object and the scene.
S21: the backscattering characteristic of the target was calculated by SBR-PO method, and the calculation flow is shown in fig. 4. Firstly, triangular surface element subdivision of the explosion pit three-dimensional model obtained in the step S1 is adjusted according to the proper size of a resolution unit, then, visibility analysis is carried out on each surface element after subdivision, which surface elements are visible is determined by judging the size of an included angle between an incident vector and a normal vector of the surface element mainly in a ray tracing mode, primary scattering characteristics of the visible surface elements are calculated by using a PO method, reflected waves of the visible surface elements are continuously calculated from surface element to surface element, the surface elements irradiated by the reflected waves are judged, secondary scattering of the explosion pit is continuously calculated on the surface elements irradiated by the reflected waves, and finally, the calculation results of the primary scattering and the secondary scattering are integrated, and the scattering characteristics of a target are output;
s22: the backscattering characteristics of the scene where the explosion pit is located are determined, an existing SAR image can be selected to be input as the backscattering characteristics of the scene where the explosion pit is located, the backscattering characteristics of the scene where the explosion pit is located can be calculated by analyzing and judging the ground object type of the scene where the explosion pit is located, and then the scattering characteristics of the scene where the explosion pit is located are output.
S3: and the SAR echo simulation imaging part is used for simulating and imaging echo data of the explosion pit.
S31: setting simulation parameters of a simulated scene, including satellite orbit parameters (aircraft track parameters), emission signal parameters, target position parameters and the like;
s32: according to the simulation parameters input in the S31 and the scattering characteristics of the targets and the scenes output in the S2 scene scattering characteristic calculation part, calculating to obtain simulated scene echo data, wherein the echo data simulation adopts a fast time domain simulation algorithm based on FFT;
s33: the method comprises the steps of simulating speckle noise under system parameters, selecting a Rayleigh distribution model in the embodiment of the invention, and introducing the speckle noise into scene echo data obtained in S32 by using the selected speckle statistical model;
s34: and (3) imaging the scene echo data obtained in the step (S33) and introducing the speckle noise to realize the output of SAR simulation images of the explosion pits, as shown in fig. 5.
In one embodiment, a structural schematic diagram of a device for simulating a SAR image of a damaged scene is shown in fig. 6, and the device may be built in an electronic device, and the device mainly includes:
the model building unit is used for building three-dimensional models of different soil medium types, explosive quantity and explosion pits under the depth of the explosive burial based on explosion mechanics;
the scattering calculation unit is used for carrying out the backscattering characteristic of the explosion pit and the scene where the explosion pit is located based on calculation electromagnetism;
and the echo imaging unit is used for simulating and imaging echo data of the explosion pit according to the three-dimensional model of the explosion pit and the backscattering characteristics of the explosion pit and the scene where the explosion pit is located.
In one embodiment, a model building unit of the damage scene SAR image simulation device comprises: the parameter setting module is used for setting the type and the parameter of the soil medium, the explosive quantity, the explosive burial depth and the like in the explosion scene; the explosion pit calculation model is used for selecting a corresponding explosion pit calculation model according to the input of the parameter setting module, and calculating to obtain point cloud data of the explosion pit; the point cloud reconstruction module is used for preprocessing the point cloud data of the explosion pit and reconstructing the point cloud data into a three-dimensional model;
in one embodiment, a scatter calculating unit of the SAR image simulation device for the damage scene comprises: the explosion pit scattering calculation module calculates the scattering coefficient of the explosion pit by using an SBR-PO method; the scene scattering calculation module is used for acquiring scattering characteristics of the scene where the explosion pit is located based on the existing SAR image or the empirical model;
in one embodiment, an echo imaging unit of a device for simulating SAR images of a damaged scene comprises: the simulation parameter setting module is used for setting parameters of a radar and a target required by simulation imaging; the echo simulation module simulates echo data of a damaged scene according to the input simulation parameters; the noise simulation module simulates the speckle noise under the system parameters and introduces the speckle noise into echo data of a scene; and the imaging module is used for carrying out imaging processing on the scene echo data introduced with the speckle noise and outputting a simulated destructive scene SAR image.
The foregoing is only a preferred implementation manner of the method and apparatus for simulating a SAR image of a damaged scene disclosed in the present invention, and is not intended to limit the scope of the embodiments of the present disclosure. Any modification, equivalent replacement, improvement, or the like made within the spirit and principles of the embodiments of the present specification should be included in the protection scope of the embodiments of the present specification.
Claims (10)
1. The SAR image simulation method for the damage scene is characterized by comprising the following steps of:
s1: establishing three-dimensional models of explosion pits under different soil medium types, explosive amounts and explosive depths based on explosion mechanics;
s2: performing explosion pit and backscattering characteristic of scene where the explosion pit is located based on calculation electromagnetism;
s3: and simulating and imaging echo data of the explosion pit according to the three-dimensional model of the explosion pit and the backscattering characteristics of the explosion pit and the scene where the explosion pit is located.
2. The method for simulating the SAR image of the destructive scene according to claim 1, wherein said S1 comprises the following steps:
s11: acquiring parameter settings in an explosion scene, wherein the parameters in the explosion scene comprise soil medium types, explosive quantity and explosive burial depth data, and calculating critical proportion burial depths corresponding to the soil medium types based on the explosive quantity; judging whether the depth of the explosive exceeds the critical proportion depth, if so, ending simulation; if not, entering the next step;
s12: selecting an explosion pit calculation model according to parameters in an explosion scene, determining a fitting coefficient corresponding to the explosion pit calculation model, and acquiring point cloud data of the explosion pit based on the explosion pit calculation model;
s13: and preprocessing the point cloud data of the explosion pit, and reconstructing the processed point cloud data into a three-dimensional model by adopting a Delaunay triangulation algorithm.
3. The method for simulating a SAR image of a destructive scene according to claim 2, wherein said preprocessing comprises denoising, resampling.
4. The method for simulating a SAR image of a destructive scene according to claim 2, wherein, in S12,
1) Under the above-ground explosion scene, the explosion pit calculation model is a touchdown explosion pit model, the explosion pit calculation model consists of parabolic explosion pits, and the radius and depth calculation of the parabolic explosion pits are shown in the formulas (1) and (2):
d in a To strike the ground the radius of the explosion pit, H a The depth of the ground-touching explosion pit is m is the explosive quantity, d is the depth of the explosion, A a Fitting coefficients 1, B for diameter a Fitting coefficients 2, E to diameter a Fitting coefficients 1, F for depth a Fitting coefficients 2, A for depth a 、B a 、E a 、F a Is determined by the physical properties of the soil medium;
2) Under the underground explosion scene, the explosion pit calculation model selects a standard throwing funnel type explosion pit calculation model, the explosion pit calculation model consists of a parabolic explosion pit and a throwing accumulation area, and the radius and depth calculation of the parabolic explosion pit are shown as the formula (3) and the formula (4);
d in u Is the radius of a standard throwing funnel type explosion pit, H u The depth of the explosion pit is m is the explosive quantity, d is the depth of the explosion pit, A u Fitting coefficients 1, B for diameter u Fitting coefficient 2, A for diameter u 、B u Are determined by the physical properties of the soil medium;
calculating the maximum throwing speed of explosion according to a formula (5), and determining throwing speed distribution by a throwing speed model of a formula (6); determining the throwing distance of the rock and soil through the influence of the ballistic motion of the rock and soil and the resistance in the throwing process; fitting a histogram of the throw distance distribution with the Weibull distribution to obtain a shape of the throw stack zone, wherein:
v in max For maximum slinging speed of explosion occurrence, v i Is the throwing speed; m is the explosive quantity, d is the depth of burial of the explosive, A v 、B v Fitting coefficients for maximum casting speed, C v 、E v The fitting coefficient of the throwing speed is determined by the physical property of the soil medium.
5. The method for simulating the SAR image of the destructive scene according to claim 1, wherein said step S2 comprises the following steps:
s21: adjusting triangular surface element subdivision of the explosion pit three-dimensional model obtained in the step S1 according to the proper size of the resolution unit; performing visibility analysis on each split surface element and calculating primary backscattering characteristics of the visible surface element by using a PO method; calculating the reflected wave of the visible bin by bin, judging the bin irradiated by the reflected wave, and continuously calculating the secondary scattering of the explosion pit for the bin irradiated by the reflected wave; integrating the calculation results of primary scattering and secondary scattering, and outputting the backscattering characteristic of the explosion pit;
s22: and calculating the backscattering characteristic of the scene where the explosion pit is located based on the existing SAR image serving as the backscattering characteristic of the scene where the explosion pit is located or by analyzing and judging the type of the ground object of the scene where the explosion pit is located.
6. The method for simulating the SAR image of the destructive scene according to claim 1, wherein said step S3 comprises the following steps:
s31: obtaining simulation parameters of a simulation scene, wherein the simulation parameters comprise satellite orbit parameters, emission signal parameters and target position parameters;
s32: according to the simulation parameters input in the S31 and the backscattering characteristics of the target and the scene output in the S2 scene backscattering characteristic calculation part, calculating to obtain simulated scene echo data;
s33: simulating speckle noise based on a speckle statistical model, and introducing the speckle noise into scene echo data obtained in the step S32;
s34: and (3) performing imaging processing on the scene echo data obtained in the step (S33) and introducing the speckle noise.
7. The method for simulating the SAR image of a damaged scene according to claim 6, wherein said S32 comprises the steps of:
the fast time domain simulation algorithm based on FFT calculates the frequency spectrums of the azimuth direction signal and the distance direction signal respectively, and the SAR echo signal is obtained by calculating the inverse Fourier transform of the product of the azimuth direction signal and the distance direction signal, and the calculation formula is as follows:
wherein τ is distance-wise time; t is azimuth time, k r For the frequency modulation rate of the transmitted chirp signal, σ is the backscattering characteristic value, λ is the carrier wavelength, T a For synthetic aperture time, c is the speed of light and r is the target point slant distance.
8. The method for simulating a SAR image of a destructive scene according to claim 6, wherein said speckle statistical model comprises a rayleigh distribution model, a K distribution model, a W distribution model, and a heavy tail generalized rayleigh distribution model.
9. The method for simulating a SAR image of a damaged scene according to claim 6, wherein in S34, the imaging process is performed using a chirp scaling algorithm, a range-doppler algorithm, or a range-migration algorithm.
10. The SAR image simulation device for the damage scene is characterized by comprising: a model building unit, a scattering calculation unit and an echo imaging unit, wherein,
the model building unit is used for building three-dimensional models of different soil medium types, explosive quantity and explosion pits under the explosion depth of the explosive based on explosion mechanics;
the scattering calculation unit is used for carrying out explosion pit and backscattering characteristics of the scene where the explosion pit is located based on calculation electromagnetism;
the echo imaging unit is used for simulating and imaging echo data of the explosion pit according to the three-dimensional model of the explosion pit and the backscattering characteristics of the explosion pit and the scene where the explosion pit is located.
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