Method and device for lightning location correction under complex propagation path

Abstract

The application provides a lightning positioning correction method and device under a complex propagation path, which comprises the following steps: grid processing of a research area, determining candidate positioning grid points of lightning according to a grid point where an initial positioning position of lightning is located; extracting time delay factors of each measuring station to each candidate positioning grid point, the time delay factor being a difference between lightning signal arrival time of lightning at each candidate positioning grid point under a complex path and ideal ground surface transmission to each measuring station; subtracting the time when a peak value of an electromagnetic wave waveform of lightning detected by each measuring station corresponds from the time delay factor of each measuring station to each candidate positioning grid point, to obtain a corrected lightning signal arrival time; substituting the corrected lightning signal arrival time into a lightning positioning equation to obtain a lightning position, and selecting an optimal lightning position from the lightning position. The application corrects the actual lightning arrival time of each measuring station, realizes the correction of lightning positioning based on the corrected lightning arrival time, and improves the positioning accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lightning location, in particular to a lightning location correction method and device under complex propagation path. BACKGROUND

[0002] Currently, the time difference of arrival method is usually used for lightning location, that is, first, a lightning electromagnetic wave waveform signal in a detection frequency band is received by a time-synchronized observation instrument through a GPS (Global Positioning System), then the time of signal arrival at the station is determined, and finally a lightning location algorithm is used to solve the result. Accurate lightning location requires accurate acquisition of the propagation speed of lightning signals and the time of signal arrival at the station, and the uncertainty of these two factors restricts the improvement of lightning location accuracy. In actual application, environmental noise, electromagnetic interference and propagation path, etc. can cause waveform distortion and cause deviation in the identification of signal arrival time, ultimately leading to lightning location error.

[0003] Due to the inability to accurately measure the propagation speed, environmental noise and electromagnetic interference, etc. can be avoided as much as possible through reasonable site selection, but the complex situation of the propagation path, especially the mixed sea-land path propagation of lightning electromagnetic waves in coastal areas, and even the undulating mountain bodies in mountainous areas, also cannot be ignored. Considering the arrival time deviation caused by the complex propagation path, the common methods include redefining the arrival time, terrain envelope equivalence and time compensation method, etc., but these methods are difficult to solve the time delay correction problem of lightning electromagnetic waves on the specific propagation path. By simulating the propagation process of lightning electromagnetic waves under complex path, the time delay caused by the propagation path is obtained and corrected, which is beneficial to improve and enhance the lightning location error.

[0004] However, the use of the finite difference time domain algorithm to simulate the propagation of lightning electromagnetic waves under complex propagation path often requires a large amount of computing resources, and usually presents individual results, which is difficult to apply on a large scale in the regional level. In addition, the ground conductivity of the real terrain is not continuously changing, especially the sudden change of the conductivity at the sea-land junction, which affects the time delay of the arrival of lightning electromagnetic waves, and is related to the accuracy of the time delay factor correction. SUMMARY

[0005] The present application provides a lightning location correction method and device under complex propagation path, which solves the defect that the time delay of lightning electromagnetic waves under complex propagation path is difficult to accurately obtain in the prior art, resulting in poor lightning location accuracy, realizes fast and accurate simulation of the propagation process of lightning electromagnetic waves under complex paths such as sea-land mixing, corrects the arrival time delay, realizes the correction of lightning location, and improves the location accuracy.

[0006] The application provides a lightning positioning correction method under a complex propagation path, comprising:

[0007] Grid processing is performed on a research area, and candidate positioning grid points of lightning are determined according to a grid point where an initial positioning position of lightning is located;

[0008] Time delay factors of each measuring station to each candidate positioning grid point are extracted, the time delay factor being a difference between lightning signal arrival times of lightning at each candidate positioning grid point under a complex path and an ideal ground surface;

[0009] The time corresponding to a peak value of an electromagnetic wave waveform of lightning detected by each measuring station is subtracted from the time delay factor of each measuring station to each candidate positioning grid point, so as to obtain a corrected lightning signal arrival time of each measuring station;

[0010] The corrected lightning signal arrival time is substituted into a lightning positioning equation, so as to obtain a lightning position corresponding to the corrected lightning signal arrival time of each measuring station, and an optimal lightning position is selected from the lightning position.

[0011] According to the lightning positioning correction method under the complex propagation path, the time delay factors of each measuring station to each candidate positioning grid point are extracted, comprising:

[0012] A lightning electromagnetic wave propagation model under a complex path is established based on a two-dimensional finite difference time domain algorithm;

[0013] In a case where lightning is located at the center of each grid, a lightning electromagnetic wave waveform received by each measuring station is simulated through the lightning electromagnetic wave propagation model, and a time corresponding to a peak value of the simulated lightning electromagnetic wave waveform is taken as a lightning signal arrival time under the complex path;

[0014] In the case where lightning is located at the center of each grid, a time of lightning propagation to each measuring station at the speed of light is calculated as a lightning signal arrival time under an ideal ground surface according to distances between the lightning and each measuring station;

[0015] A difference between the lightning signal arrival times of lightning at each grid to each measuring station under the complex path and the ideal ground surface is taken as a time delay factor;

[0016] A time delay factor database is constructed according to the time delay factors of all grids corresponding to each measuring station;

[0017] The time delay factors of each measuring station to each candidate positioning grid point are extracted from the time delay factor database.

[0018] According to the lightning positioning correction method under the complex propagation path, the lightning electromagnetic wave propagation model is used to simulate the lightning electromagnetic wave waveform received by each measuring station, comprising:

[0019] The electromagnetic parameters between different media distributed in the cell space in the lightning electromagnetic wave propagation model are simulated by using the equivalent coefficient with the conformal grid technology.

[0020] According to the lightning positioning correction method under the complex propagation path provided by the application, the lightning electromagnetic wave waveform received by each measuring station is simulated by the lightning electromagnetic wave propagation model, and the method comprises the following steps:

[0021] The simulation speed of the lightning electromagnetic wave propagation is accelerated by using the mobile computing domain technology.

[0022] According to the lightning positioning correction method under the complex propagation path provided by the application, the lightning signal arrival time after correction is substituted into the lightning positioning equation, and the lightning position corresponding to the lightning signal arrival time after correction of each measuring station is obtained by solving. The optimal solution of the equation is obtained by multiple iteration fitting of the Levenberg-Marquardt nonlinear least square method. For the solution obtained in the iteration process, the goodness of fit χ 2 is measured, when χ 2 is the minimum, the iteration is ended, and the corresponding solution is the optimal solution of the equation, that is, the lightning position obtained by solving.

[0023] The goodness of fit χ 2 is determined by the following formula:

[0024]

[0025] Wherein, N is the total number of measuring stations, is the lightning signal arrival time after correction of the i-th measuring station, is the arrival time of the lightning position obtained by solving and propagating to the i-th measuring station at the speed of light, and σ 2 is the time measurement error of the lightning detection system.

[0026] According to the lightning positioning correction method under the complex propagation path provided by the application, the optimal lightning position is selected from the lightning position, and the method comprises the following steps:

[0027] The difference between the lightning signal arrival time after correction of each measuring station and the lightning signal arrival time of each lightning position propagating to the measuring station at the speed of light is calculated.

[0028] The difference is compared with the lightning signal arrival time of each lightning position propagating to the measuring station at the speed of light.

[0029] The lightning position corresponding to the minimum of the ratio is the optimal lightning position.

[0030] According to the lightning positioning correction method under the complex propagation path provided by the application, the calculation formula of the ratio is as follows:

[0031]

[0032] wherein, t mi is the time corresponding to the peak value of the electromagnetic wave waveform of the lightning measured by the i th measuring station, Δt i is the time delay factor of the i th measuring station to any lightning position, t ci is the time of any lightning position propagating to the i th measuring station at the speed of light, and N is the number of measuring stations.

[0033] The application also provides a lightning positioning correction device under a complex propagation path, comprising:

[0034] a screening module, configured to grid the research area, and determine candidate positioning grid points of lightning according to the grid points where the initial positioning positions of lightning are located;

[0035] an extraction module, configured to extract time delay factors of each measuring station to each candidate positioning grid point, the time delay factor being the difference between the lightning signal arrival time of each candidate positioning grid point under a complex path and the lightning signal arrival time of each measuring station under an ideal ground surface;

[0036] a correction module, configured to subtract the time corresponding to the peak value of the electromagnetic wave waveform of lightning detected by each measuring station from the time delay factor of each measuring station to each candidate positioning grid point, to obtain the corrected lightning signal arrival time of each measuring station;

[0037] a positioning module, configured to substitute the corrected lightning signal arrival time into a lightning positioning equation, and solve to obtain the lightning position corresponding to the corrected lightning signal arrival time of each measuring station, and select an optimal lightning position from the lightning positions.

[0038] The application also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the lightning positioning correction method under a complex propagation path according to any of the above.

[0039] The application also provides a non-transitory computer readable storage medium, which stores a computer program, wherein the computer program is executable on a processor to implement the lightning positioning correction method under a complex propagation path according to any of the above.

[0040] The application also provides a computer program product, comprising a computer program, wherein the computer program is executable on a processor to implement the lightning positioning correction method under a complex propagation path according to any of the above.

[0041] The lightning location correction method and apparatus provided by this invention, under complex propagation paths, considers the influence of complex propagation paths, especially the changes in land and sea topography and ground conductivity, on the propagation of lightning electromagnetic waves. It quickly and accurately simulates the propagation process of lightning electromagnetic waves under complex paths such as mixed land and sea. The difference between the arrival time of lightning signals at each candidate location grid point under complex paths and under ideal ground surfaces is used as a time delay factor to correct the measured arrival time of lightning at each station. Based on the corrected arrival time of lightning, the lightning location is corrected, thereby improving the positioning accuracy. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in this 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0043] Figure 1 This is one of the flowcharts of the lightning location correction method under complex propagation paths provided by the present invention;

[0044] Figure 2 This is a schematic diagram of a specific time delay correction in the lightning location correction method under complex propagation paths provided by the present invention;

[0045] Figure 3 This is a schematic diagram of the configuration of the lightning electromagnetic wave propagation model in the lightning location correction method under complex propagation paths provided by the present invention;

[0046] Figure 4 (a) is a schematic diagram of the Yee cell structure; (b) is an equivalent schematic diagram of the electromagnetic parameters of the medium in the conformal mesh under the mixed land-sea path.

[0047] Figure 5 This is the second flowchart of the lightning location correction method under complex propagation paths provided by the present invention;

[0048] Figure 6 This is a schematic diagram of the structural modules of the lightning location correction device under complex propagation paths provided by the present invention;

[0049] Figure 7 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0050] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below in conjunction with the drawings in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection scope of the present application.

[0051] The present application will be described below in conjunction with Figure 1 A lightning location correction method under a complex propagation path of the present application is described, comprising:

[0052] Step 101, grid processing of a research area, determining candidate location grid points of lightning according to the grid point where the initial location position of lightning is located;

[0053] Step 102, extracting the time delay factor of each candidate location grid point of each station, the time delay factor being the difference between the lightning signal arrival time of the lightning at each candidate location grid point under a complex path and an ideal ground surface to each station;

[0054] Step 103, subtracting the time corresponding to the peak value of the electromagnetic wave waveform of lightning detected by each station from the time delay factor of each candidate location grid point of each station, to obtain the corrected lightning signal arrival time of each station;

[0055] Step 104, substituting the corrected lightning signal arrival time into the lightning location equation to obtain the lightning position corresponding to the corrected lightning signal arrival time of each station, and selecting the optimal lightning position from the lightning position.

[0056] The research area is divided into 0.1°×0.1° (about 10 km×10 km) grid, and the grid number is recorded as (i,j), wherein i=1,2,……,I; j=1,2,……,J. I and J are the grid numbers of the research area in the latitude direction and the longitude direction, respectively. The stations are recorded as S1, S2,……SN, and N is the number of stations in the research area. N

[0057] For all grids in the research area, the time delay factor corresponding to each station can be obtained, and a time delay factor database is established with the station name and grid number as the search.

[0058] The peak point time of the measured waveform or the waveform recorded in the location file can be taken as the arrival time of the lightning signal, recorded as (t m1 , t m2 ,……,t mn ​Let n be the number of stations that received the lightning signal. Substitute this set of arrival times into the lightning location equation to solve for the initial lightning location. Alternatively, the initial lightning location can be directly read from the location file and denoted as P0(x,y,z).

[0059] The grid point where the initial lightning location is located can be used as the center. All grid points within a 20 km radius can be selected as candidate location grid points. Using each candidate location grid point and each station that received the lightning signal as an index, the corresponding time delay factor can be extracted from the time delay factor database.

[0060] For example, the initial location of lightning within the study area is determined by the grid point (i0, j0). Twenty-five grid points with grid numbers (i0-2:i0+2, j0-2:j0+2) are selected, and the time delay factors from these 25 grid points to the receiving lightning signal station are extracted from the time delay factor database, forming 25 sets of time delay factors. Table 1 shows the 25 sets of time delay factors extracted from the time delay factor database based on grid number and station name.

[0061] Table 1

[0062]

[0063] The arrival time of the lightning signal is subtracted from the extracted time delay factor to obtain the corrected arrival time of the lightning signal. This corrected time is then substituted into the lightning location equation to solve for the corresponding lightning location.

[0064] For example, the arrival time of the obtained lightning signal (t) m1 , t m2 , ..., t mn Subtracting the 25 sets of time delay factors from the original time delay factors yields the 25 corrected arrival times of the lightning signal. For example... Figure 2 The diagram shown illustrates a time delay correction for a single instance. There are 10 stations (S1, S2, ... S...). 10 Upon receiving the lightning signal, the peak times of each station were read from the measured waveform and denoted as t1, t2, ..., t3. 10 The time delay factors are extracted from the initial lightning position P0, encompassing 25 grid points, resulting in a total of 25 sets of time delay factors. The figure illustrates one set of time delay factors, denoted as Δt1, Δt2, ..., Δt 10 Subtracting the delay factor from the peak time yields the corrected arrival time of the lightning signal, denoted as t1', t2', ..., t 10 Substituting the arrival times of the 25 corrected lightning signals into the lightning location equation, and based on the principle of minimizing the goodness of fit, the corresponding 25 lightning locations are solved, denoted as P1, P2, ..., P... 25 .

[0065] The optimal lightning position can be selected from the lightning positions by means of root mean square minimum and elimination of stations with large delay factor values, and the optimized lightning position is obtained.

[0066] The embodiment considers the influence of complex propagation paths, especially sea-land topography and ground conductivity variation on lightning electromagnetic wave propagation, quickly and accurately simulates the lightning electromagnetic wave propagation process under complex paths such as sea-land mixed paths, takes the difference between the lightning signals arriving time of each candidate positioning grid under complex paths and ideal ground as the delay factor, corrects the measured lightning arriving time of each station, and realizes the correction of lightning positioning based on the corrected lightning arriving time, thereby improving the positioning accuracy.

[0067] On the basis of the above embodiment, the delay factor of each station to each candidate positioning grid is extracted in the embodiment, including:

[0068] A lightning electromagnetic wave propagation model under complex paths is established based on a two-dimensional finite difference time domain algorithm (2D-FDTD).

[0069] In the case that the lightning is located at the center of each grid, the lightning electromagnetic wave waveform received by each station is simulated by the lightning electromagnetic wave propagation model, and the time corresponding to the peak value of the simulated lightning electromagnetic wave waveform is taken as the lightning signal arriving time under complex paths.

[0070] In the case that the lightning is located at the center of each grid, the time of the lightning propagating to each station at the speed of light is calculated as the lightning signal arriving time under ideal ground according to the distance between the lightning and each station.

[0071] The difference between the lightning signal arriving time of each grid under complex paths and ideal ground is taken as the delay factor.

[0072] According to the delay factor of all grids corresponding to each station, a delay factor database is constructed with the station name and grid serial number as the retrieval.

[0073] The delay factor of each station to each candidate positioning grid is extracted from the delay factor database.

[0074] The lightning source is placed at the center of each grid as the model input, and the model output is the simulated waveform of the lightning electromagnetic wave propagating to each station along the profile ground path of the grid center and the station connection line, and the peak point time of the waveform is read as the lightning signal arriving time.

[0075] Figure 3Fig. 1 is a schematic diagram of the lightning electromagnetic wave propagation model based on the 2D-FDTD algorithm under complex paths. The spatial step is Δr = Δz = 10 m, and the time step is Δt = 16.6 ns. The size of the simulation domain is L x 11 km. L depends on the distance between the lightning source and the measuring station. The lightning channel is vertically placed on the left symmetry axis, and the lightning current is injected from the bottom end of the channel. The lightning current waveform is a double Heidler function, and the lightning current transmission model is the MTLE model with an exponential decay of the return stroke current with height. The height of the lightning channel is H = 7.5 km, the current decay factor is λ = 2 km, and the return stroke velocity is set to v = 1.5 x 10 8 m / s. The upper and right boundaries of the model use the convolutional perfectly matched layer (CPML) as absorbing boundaries to simulate open-region electromagnetic processes in a finite region. The lower boundary of the model is set to a flat ground with a thickness of 500 m, which can effectively avoid the influence of boundary reflected waves. The real terrain is located above the flat ground, and the conductivity and relative permittivity of the two are the same, represented as σ g and ε r , respectively. The elevation data of the real terrain uses SRTM data, and the ground conductivity and relative permittivity are processed according to land and sea. The conductivity of the land uses the soil conductivity in the HWSD data, and the conductivity of the sea is set to 4 S / m. The relative permittivity of the land is set to 10, and that of the sea is set to 81.5. The conductivity and permittivity of air are σ0 = 0 and ε0 = 8.854 x 10 -12 F / m, respectively.

[0076] The lightning source is placed at the center of each grid, and the profile of the ground surface path and the corresponding electromagnetic parameters of the lightning source and N measuring stations can be replaced by equivalent coefficients using the conformal grid technique and input into the established lightning electromagnetic wave propagation model. The model output is the lightning electromagnetic wave from the lightning source to N measuring stations at the (i, j) grid, and then the output waveform is filtered to be consistent with the instrument detection frequency band. The time of the waveform peak point from the filtered simulation waveform is directly read as the lightning signal arrival time under complex paths, denoted as t1, t2, …, t N .

[0077] The distance between the lightning source at the grid (i, j) and N measuring stations is calculated using the distance function in matlab, denoted as d1, d2, …, d N . According to the lightning electromagnetic wave propagating to the measuring station at the speed of light c, the arrival time of the lightning signal under the ideal ground surface is calculated as d1 / c, d2 / c, …, d N / c, denoted as t c1 , t c2 , …, t cN .

[0078] The arrival time of lightning signals along a complex path is compared with that of an ideal surface, and the difference between the two is used as a time delay factor. The arrival time delay at grid (i, j) is calculated as t1-t. c1 ,t2-t c2 ,……, t N -t cN Labeled as Δt1, Δt2, ..., Δt N For each station and all corresponding grids, a time delay factor database is established, which is searchable by station name and grid number.

[0079] Based on the above embodiments, this embodiment simulates the waveform of lightning electromagnetic waves received by each station using the lightning electromagnetic wave propagation model, including:

[0080] The conformal mesh technique is used to simulate the electromagnetic parameters between different media distributed in the cell space of the lightning electromagnetic wave propagation model using equivalent coefficients.

[0081] Yee cells (such as) Figure 4 (a) shows a structure for the spatial distribution of electromagnetic field components in the FDTD algorithm. Through continuous iteration and development in time and space, lightning electromagnetic waves propagate from the lightning channel to the station in space. The electromagnetic field E and H components are discretely sampled alternately in space and time. Each E (or H) field component is surrounded by 4 H (or E) field components (i.e., Yee cells), which transforms the Maxwell differential equation with time variables into a difference equation and gradually advances the solution of the spatial electromagnetic field along the time axis. In the two-dimensional coordinate system, the r direction is the direction of propagation of lightning electromagnetic waves, the φ direction is perpendicular to the roz plane and pointing inwards, and the z direction is vertically upwards, which can represent the horizontal electric field Er, the transverse magnetic field Hφ, and the vertical electric field Ez, respectively. The blue and green arrows represent the electric field component E. r and E z The red cross indicates the magnetic field component H. φ The red cross in the upper right square represents the magnetic field component. The green arrow to the left of the top right square indicates the electric field component. The blue arrow below the top right square indicates the electric field components. The red cross in the bottom left square represents the magnetic field component. The green arrow to the upper left of the bottom left square indicates the electric field component. The blue arrow below the bottom left square indicates the electric field component. The blue arrow below the bottom right square indicates the electric field component. .

[0082] Since the lower boundary of the model is the real terrain, the terrain undulation and the change of ground conductivity will affect the propagation of lightning electromagnetic wave. In the FDTD calculation, the medium in Yee cell is not uniform (as shown in (b) of FIG. 1), which will cause rough simulation accuracy. The conformal mesh technique is a method of using equivalent coefficients to accurately simulate the electromagnetic parameters between different media distributed in the cell space, especially the electromagnetic parameters of the sea and the land in the sea-land mixed path. Figure 4

[0083] The formula of the equivalent coefficient is as follows:

[0084] (1)

[0085] (2)

[0086] wherein, , , , and , , , respectively represent the equivalent dielectric coefficient and the equivalent conductivity at the four electric field nodes A, B, C and D. and respectively represent the equivalent permeability and the equivalent magnetic conductivity at the magnetic field node F.

[0087] , , , and , , , respectively represent the dielectric coefficient, the conductivity, the permeability and the magnetic conductivity of the medium 1 and the medium 2.

[0088] and respectively represent the length of the medium 1 and the medium 2 on the edge where the electric field node A is located, and respectively represent the length of the medium 1 and the medium 2 on the edge where the electric field node C is located. and respectively represent the area of the medium 1 and the medium 2 on the side where the magnetic field node F is located.

[0089] and respectively represent the length of the grid in the r direction and the z direction.

[0090] ​The embodiment uses a conformal mesh technique, can accurately simulate the complex propagation path of lightning electromagnetic wave from the lightning strike point to the station, is more in line with the actual propagation situation, and the time delay factor obtained is more realistic and valuable.

[0091] Further, the lightning current waveform at the bottom of the lightning channel adopts a double Heidler function expression as follows:

[0092] (3)

[0093] (4)

[0094] (5)

[0095] The lightning current adopted is a typical subsequent return stroke, i 01 = 10.7 kA and i 02 = 6.5 kA are the peak values of the breakdown current and the corona current, respectively, and η1 and η2 are correction factors of the corresponding current peak values; τ 11 = 0.25 μs and τ 12 = 2 μs are the rise time and the fall time of the breakdown current waveform, respectively, and τ 21 = 2.5 μs and τ 22 = 230 μs are the rise time and the fall time of the corona current waveform, respectively.

[0096] On the basis of the above embodiment, the lightning electromagnetic wave waveform received by each station is simulated by the lightning electromagnetic wave propagation model in the embodiment, including:

[0097] The moving calculation domain technique is adopted to speed up the simulation speed of the lightning electromagnetic wave propagation.

[0098] The moving calculation domain technique is adopted to speed up the simulation speed of the lightning electromagnetic wave propagation, Figure 3 The gray area in the formula (6) is the calculation domain range. The calculation domain changes according to the electromagnetic wave travel in the actual simulation process, the left boundary is set as max(0, c(t-tw)), the right boundary is set as min(ct, L), and the window width tw can be flexibly set according to the width of the waveform concerned. Considering that the arrival time of the lightning electromagnetic wave signal in the embodiment is taken as the peak point time, the general lightning waveform width is in the range of tens of microseconds to several tens of microseconds, therefore, the window width is set to 25 microseconds, which fully contains the peak time of the waveform concerned, can also reflect the basic shape of the lightning waveform, and saves the calculation resources and speeds up the simulation process.

[0099] The moving calculation domain technique is adopted in the embodiment, calculation resources are saved, and the lightning electromagnetic wave fast simulation under the complex propagation path can be applied.

[0100] On the basis of the above embodiments, the nonlinear equations about lightning discharge propagation to the measuring station established according to the time difference of arrival method in this embodiment are as follows:

[0101] (6)

[0102] Where (x, y, z, t) is the lightning occurrence position and time, (x i , y i , z i ) is the geographic position of the i-th measuring station, t i is the time of lightning signal arriving at the i-th measuring station, i = 1, 2, …, n, where n is the number of measuring stations, and c is the speed of light.

[0103] The time difference (t i -t1) between different measuring stations is used to eliminate t in the nonlinear equations composed of formula (6) and rewritten in the form of hyperbolic intersection positioning as follows:

[0104] (7)

[0105] The optimal solution of the equation is obtained by multiple iterations fitting through the Levenberg-Marquardt nonlinear least squares method. For the solution obtained in the iteration process, the goodness of fit χ 2 is used to measure its goodness, when χ 2 is the smallest, the iteration ends, and the corresponding solution is the optimal solution of the equation, that is, the lightning position solved.

[0106] The goodness of fit χ 2 is determined by the following formula:

[0107] (8)

[0108] Where N is the total number of measuring stations, is the corrected lightning signal arrival time at the i-th measuring station, is the lightning position solved and the arrival time of the lightning signal propagating to the i-th measuring station at the speed of light, σ 2 is the time measurement error of the lightning detection system, also known as the system error, generally taken as 100 ns, and N-4 is the degree of freedom.

[0109] On the basis of the above embodiments, in this embodiment, the optimal lightning position is selected from the lightning positions, comprising:

[0110] Calculating the difference between the corrected lightning signal arrival time at each measuring station and the lightning signal arrival time at the measuring station at the speed of light from each lightning position;

[0111] Taking the ratio of the difference and the lightning signal arrival time at the measuring station at the speed of light from each lightning position.

[0112] The lightning position corresponding to the minimum ratio is the optimal lightning position.

[0113] In order to avoid that the optimal lightning position is affected by a single measuring station, a negative optimization may occur, and the mean absolute percentage error (MAPE) is used to measure the optimization effect, and the optimal positioning result in 25 lightning positions is determined. By normalizing the error of each measuring station, the influence of the absolute error of the outlier can be significantly reduced, and the point with better overall optimization effect is selected.

[0114] On the basis of the above embodiments, the calculation formula of the ratio in the embodiment is as follows:

[0115] (9)

[0116] Wherein, t mi is the time corresponding to the peak value of the electromagnetic wave waveform of the lightning measured by the i th measuring station, Δt i is the time delay factor of the i th measuring station to any lightning position, t ci is the time of any lightning position propagating to the i th measuring station at the speed of light, and N is the number of measuring stations.

[0117] By comparing the numerical values of the 25 mean absolute percentage errors, the lightning position corresponding to the minimum is the optimal lightning position. The complete flow chart is shown in Figure 5 .

[0118] In order to consider whether the time delay factor of an individual measuring station will affect the final positioning optimization result, the outliers with larger deviation are selected from the time delay factors of the measuring stations, the corresponding arrival time is not considered in the arrival time correction step, and the corresponding measuring station is not considered in the lightning positioning optimization algorithm based on the time delay factor correction. In the positioning process, the positioning result of the measuring station corresponding to the time delay factor outlier is compared with the previous optimization result, and the smaller result is selected as the final positioning optimization result.

[0119] The complex propagation path lightning positioning correction device provided by the present application is described below. The complex propagation path lightning positioning correction device described below can be referred to each other with the complex propagation path lightning positioning correction method described above.

[0120] As shown in Figure 6 , the device comprises a screening module 601, an extraction module 602, a correction module 603 and a positioning module 604, wherein:

[0121] The screening module 601 is used for grid processing of the research area, and determining the candidate positioning grid point of lightning according to the grid point where the initial positioning position of lightning is located.

[0122] The extraction module 602 is configured to extract a time delay factor of each candidate positioning grid point of each station, the time delay factor being a difference between a lightning signal arrival time of lightning at each candidate positioning grid point propagating to each station under a complex path and an ideal earth surface;

[0123] The correction module 603 is configured to subtract the time delay factor of each candidate positioning grid point of each station from a time corresponding to a peak value of an electromagnetic wave waveform of lightning detected by each station, to obtain a corrected lightning signal arrival time of each station;

[0124] The positioning module 604 is configured to substitute the corrected lightning signal arrival time into a lightning positioning equation, to obtain a lightning position corresponding to the corrected lightning signal arrival time of each station, and to select an optimal lightning position from the lightning position.

[0125] The embodiment considers the influence of a complex propagation path, in particular, a sea-land topography and a ground conductivity change on lightning electromagnetic wave propagation, quickly and accurately simulates a lightning electromagnetic wave propagation process under a complex path such as a sea-land mixed path, takes a difference between a lightning signal arrival time of lightning at each candidate positioning grid point propagating to each station under a complex path and an ideal earth surface as a time delay factor, corrects a measured lightning arrival time of each station, and realizes correction of lightning positioning based on the corrected lightning arrival time, thereby improving positioning accuracy.

[0126] Figure 7 An example of an entity structure diagram of an electronic device is shown in Figure 7 As shown in the figure, the electronic device can include a processor 710, a communications interface 720, a memory 730, and a communications bus 740, wherein the processor 710, the communications interface 720, and the memory 730 complete mutual communication through the communications bus 740. The processor 710 can invoke a logical instruction in the memory 730 to execute a lightning positioning correction method under a complex propagation path, the method including: grid processing of a research area, determining candidate positioning grid points of lightning according to a grid point where an initial positioning position of lightning is located; extracting a time delay factor of each candidate positioning grid point of each station, the time delay factor being a difference between a lightning signal arrival time of lightning at each candidate positioning grid point propagating to each station under a complex path and an ideal earth surface; subtracting a time corresponding to a peak value of an electromagnetic wave waveform of lightning detected by each station from the time delay factor of each candidate positioning grid point of each station, to obtain a corrected lightning signal arrival time; substituting the corrected lightning signal arrival time into a lightning positioning equation, to obtain a lightning position, and selecting an optimal lightning position from the lightning position.

[0127] In addition, the logic instructions in the memory 730 described above can be implemented in the form of a software function unit and sold or used as an independent product, which can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the parts that contribute to the prior art or parts of the technical solutions can be embodied in the form of a software product, which is stored in a storage medium, including a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the methods described in various embodiments of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0128] In another aspect, the present application also provides a computer program product, which comprises a computer program, the computer program can be stored on a non-transitory computer readable storage medium, and the computer program can be executed by a processor to enable a computer to execute the lightning location correction method under a complex propagation path provided by the above-mentioned methods, the method comprising: grid processing a research area, determining candidate location grid points of lightning according to the grid point where the initial location position of lightning is located; extracting time delay factors of each candidate location grid point from each station, the time delay factor being the difference between the lightning signal arrival time of the lightning at each candidate location grid point under a complex path and an ideal ground surface to each station; subtracting the time corresponding to the peak value of the electromagnetic wave waveform of the lightning detected by each station from the time delay factor of each candidate location grid point from each station respectively to obtain the corrected lightning signal arrival time; substituting the corrected lightning signal arrival time into the lightning location equation to obtain the lightning position, and selecting the optimal lightning position from the lightning position.

[0129] In another aspect, the present application also provides a non-transitory computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the lightning location correction method under a complex propagation path provided by the above-mentioned methods, the method comprising: grid processing a research area, determining candidate location grid points of lightning according to the grid point where the initial location position of lightning is located; extracting time delay factors of each candidate location grid point from each station, the time delay factor being the difference between the lightning signal arrival time of the lightning at each candidate location grid point under a complex path and an ideal ground surface to each station; subtracting the time corresponding to the peak value of the electromagnetic wave waveform of the lightning detected by each station from the time delay factor of each candidate location grid point from each station respectively to obtain the corrected lightning signal arrival time; substituting the corrected lightning signal arrival time into the lightning location equation to obtain the lightning position, and selecting the optimal lightning position from the lightning position.

[0130] The apparatus embodiments described above are merely illustrative, wherein the units described as separate components can or can not be physically separate, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed to multiple network units. Part or all of the modules can be selected to achieve the purposes of the embodiments according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0131] Through the description of the above embodiments, those skilled in the art can clearly understand that the embodiments can be realized by means of software and the necessary universal hardware platform, and of course can also be realized by hardware. Based on such understanding, the above technical solutions can be embodied in the form of a software product, which can be stored in a computer readable storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, etc., and includes a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the methods described in each embodiment or some parts of the embodiments.

[0132] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for correcting lightning location under complex propagation paths, characterized in that, include: The study area is gridded, and candidate location grid points for lightning are determined based on the grid points where the initial location of the lightning is located. Extract the time delay factor of each station for each candidate positioning grid point. The time delay factor is the difference between the arrival time of the lightning signal at each candidate positioning grid point when the lightning propagates to each station under a complex path and an ideal ground surface. The arrival time of the lightning signal after correction is obtained by subtracting the time corresponding to the peak value of the electromagnetic wave waveform of the lightning detected by each station from the time delay factor of each station for each candidate positioning grid point. Substitute the corrected lightning signal arrival time into the lightning location equation to solve for the lightning location corresponding to each corrected lightning signal arrival time at each station, and select the optimal lightning location from the lightning locations. Selecting the optimal lightning location from the lightning locations includes: Calculate the difference between the corrected arrival time of the lightning signal at each station and the arrival time of the lightning signal at each lightning location when it travels at the speed of light to the station; The difference is compared with the arrival time of the lightning signal at each lightning location, which travels at the speed of light to the station. The lightning location with the smallest ratio is taken as the optimal lightning location.

2. The lightning location correction method under complex propagation paths according to claim 1, characterized in that, Extract the time delay factor of each station for each candidate positioning grid point, including: A propagation model of lightning electromagnetic waves under complex paths is established based on the two-dimensional finite-difference time-domain algorithm. When lightning is located at the center of each grid, the lightning electromagnetic wave waveform received by each station is simulated by the lightning electromagnetic wave propagation model, and the time corresponding to the peak value of the simulated lightning electromagnetic wave waveform is taken as the arrival time of the lightning signal under complex path. When lightning is located at the center of each grid, the time it takes for the lightning to travel at the speed of light to each station is calculated based on the distance between the lightning and each station as the arrival time of the lightning signal under the ideal ground surface. The difference between the arrival time of lightning signals at each grid point and the arrival time of lightning signals propagating under an ideal ground surface to each station is used as the time delay factor. Based on the time delay factors of all grids corresponding to each station, a time delay factor database is constructed. Extract the time delay factor of each station for each candidate positioning grid point from the time delay factor database.

3. The lightning location correction method under complex propagation paths according to claim 2, characterized in that, The lightning electromagnetic wave waveforms received by each monitoring station are simulated using the lightning electromagnetic wave propagation model, including: The conformal mesh technique is used to simulate the electromagnetic parameters between different media distributed in the cell space of the lightning electromagnetic wave propagation model using equivalent coefficients.

4. The lightning location correction method under complex propagation paths according to claim 2, characterized in that, The lightning electromagnetic wave waveforms received by each monitoring station are simulated using the lightning electromagnetic wave propagation model, including: The simulation speed of lightning electromagnetic wave propagation is accelerated by employing mobile computing domain technology.

5. The lightning location correction method under complex propagation paths according to claim 2, characterized in that, Substituting the corrected lightning signal arrival time into the lightning location equation, the lightning location corresponding to the corrected lightning signal arrival time at each station is obtained, including: The goodness-of-fit χ of the lightning location equation is determined by the following formula. 2 When χ 2 When the minimum value is reached, the solution to the equation is the location of the lightning strike. ； Where N is the total number of monitoring stations. It is the corrected arrival time of the lightning signal at the i-th station. It is the arrival time σ is the calculated speed of light for the lightning location to travel to the i-th station. 2 It is the time measurement error of the lightning detection system.

6. The lightning location correction method under complex propagation paths according to claim 1, characterized in that, The formula for calculating the ratio is as follows: ； Among them, t mi Δt is the time corresponding to the peak value of the electromagnetic wave waveform of lightning measured at the i-th station. i t is the time delay factor of the i-th station for any lightning location. ci It is the time it takes for any lightning location to travel at the speed of light to the i-th monitoring station, and N is the number of monitoring stations.

7. A lightning location correction device under complex propagation paths, characterized in that, include: The filtering module is used to perform gridding processing on the study area and determine candidate location grid points for lightning based on the grid points where the initial location of lightning is located. The extraction module is used to extract the time delay factor of each station for each candidate positioning grid point. The time delay factor is the difference between the arrival time of the lightning signal at each candidate positioning grid point when the lightning propagates to each station under a complex path and an ideal ground surface. The correction module is used to subtract the time corresponding to the peak value of the electromagnetic wave waveform of lightning detected by each station from the time delay factor of each station for each candidate positioning grid point, so as to obtain the corrected arrival time of the lightning signal for each station. The positioning module is used to substitute the corrected arrival time of the lightning signal into the lightning positioning equation, solve for the lightning position corresponding to the corrected arrival time of each lightning signal at each station, and select the optimal lightning position from the lightning positions. The positioning module is specifically used for: Calculate the difference between the corrected arrival time of the lightning signal at each station and the arrival time of the lightning signal at each lightning location when it travels at the speed of light to the station; The difference is compared with the arrival time of the lightning signal at each lightning location, which travels at the speed of light to the station. The lightning location with the smallest ratio is taken as the optimal lightning location.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the lightning location correction method under complex propagation paths as described in any one of claims 1 to 6.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the lightning location correction method under complex propagation paths as described in any one of claims 1 to 6.

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