Moderate fly insect population average body length estimation method based on polarization weather radar

Abstract

The invention discloses a migratory fly insect population average body length estimation method based on a polarization weather radar. According to the method, migration insect individuals are equivalent to long ellipsoid scatterers under the Rayleigh scattering condition, statistical averaging is carried out on insect body axis orientations, migration number density is introduced to serve as constraint parameters, and the migration insect population average body length inversion method based on the weather radar differential phase shift rate is constructed. And the model is verified and calibrated by combining electromagnetic scattering numerical simulation with weather radar and insect radar combined observation data, so that stable estimation of the average body length of the migrated insect population is realized. Compared with a traditional method depending on radar reflectivity and other amplitude information, the method is not sensitive to factors such as insect number fluctuation and distance attenuation, and the stability and reliability of the migrated insect body length estimation result are fundamentally improved. According to the method, the body shape effect and the group scale effect are effectively distinguished, and migrant fly group length inversion with clear physical significance is realized.

Description

Technical Field

[0001] This manual belongs to the field of radar remote sensing and biometeorological monitoring technology, specifically involving a method for estimating the average body length of migratory insect populations based on the joint constraints of differential phase shift rate and migration number density of polarimetric weather radar. Background Technology

[0002] Migratory insects are important carriers of agricultural pests and the transport of ecological materials. Their migration activities are typically characterized by cross-regional, long-distance, and highly gregarious activities, which have a significant impact on agricultural production safety, ecosystem stability, and biodiversity conservation. Continuous monitoring and species identification of migratory insect populations are essential foundations for pest early warning, control decision-making, and ecological process research.

[0003] Currently, vertical insect radar can accurately measure parameters such as individual insect length, quantity, and flight altitude. However, limited by transmission power and antenna size, its detection range is usually small, making it difficult to meet the needs of monitoring migratory insects on a regional or even larger scale. In contrast, S-band dual-polarization weather radar has advantages such as wide detection range, stable operation, and continuous coverage, and has been widely used in precipitation monitoring and biological target detection.

[0004] However, existing weather radar systems are primarily designed for meteorological targets, and their spatial resolution and observation parameters are insufficient to directly reflect insect body length and other structural information, thus limiting the identification of migratory insect species. A systematic and clear technical solution is still lacking for establishing a quantitative relationship between polarization parameters such as differential phase shift rate provided by polarimetric weather radar and the body size of migratory insects. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, the present invention aims to provide a method for estimating the body length of migratory insects based on polarimetric weather radar. This method fully utilizes the highly sensitive polarimetric phase observation capability of polarimetric weather radar for non-spherical biological targets, and combines it with migratory insect number density information to establish a stable quantitative relationship between radar polarimetric observations and the body length of migratory insects at the population scale. This enables reliable inversion of the average body length of large-scale, high-altitude migratory insect populations.

[0006] The technical solution of the present invention is as follows: A method for estimating the body length of migratory insects based on polarimetric weather radar includes: The first step involves acquiring dual-polarization observation data from a polarimetric weather radar within the target observation area, and simultaneously acquiring migratory insect monitoring data. The polarimetric weather radar observation data undergoes clutter suppression, noise suppression, phase correction, and phase unwrapping processing. Phase information of the horizontal and vertical polarization channels is extracted, and the differential phase shift rate is calculated along the radar radial distance direction. Statistical processing is then performed on the migratory insect monitoring data to obtain migratory insect number density data consistent with the radar observation volume and time scale. The second step is to establish an equivalent scattering model for individual migratory insects. Given that the geometric dimensions of individual migratory insects are much smaller than the operating wavelength of polarimetric weather radar, a single migratory insect is equivalent to a long ellipsoidal scatterer with anisotropic electromagnetic response characteristics. The major axis of the long ellipsoid is used to characterize the body axis direction of the migratory insect, and the minor axis is used to characterize the lateral dimensions of the insect's body. An equivalent dielectric constant is introduced to describe the response characteristics of the insect's tissues to electromagnetic waves, thus establishing a scattering response model for individual migratory insects under polarimetric electromagnetic wave incident conditions. The third step involves analyzing the polarization propagation characteristics of migratory insect populations. Treating the numerous discretely distributed migratory insects in space as an equivalent sparse medium, and neglecting the interference effects of individual scattering, the influence of the migratory insect population on the propagation of radar polarized electromagnetic waves is expressed as an incoherent superposition of the scattering contributions of all individuals. Based on the equivalent medium theory, the propagation constants of horizontally polarized waves and vertically polarized waves in the migratory insect population medium are determined, and the difference between the two polarization propagation constants is obtained. The real part of this phase propagation constant difference corresponds to the differential phase shift rate observable by polarimetric weather radar, and its data is related to the number density of migratory insects and their average scattering characteristics. The fourth step involves constructing a quantitative model of the average body length of the colony. Considering the randomness of individual attitudes and spatial orientations of migratory insects during flight, the aforementioned individual scattering model of migratory insects is statistically averaged across all possible spatial orientations to eliminate the influence of individual orientation differences on polarization scattering characteristics, thus obtaining the average scattering characteristics of the colony independent of individual orientation. This average scattering characteristic is then incorporated into the polarization propagation analysis results to establish a model relating the average body length of the migratory insect colony to the differential phase shift rate observed by radar. To avoid the ambiguity caused by variations in the size of the migratory insect colony on the differential phase shift rate observation results, the number density of migratory insects is explicitly introduced as a key input parameter in the inversion relationship, thus forming a deterministic body length inversion model with differential phase shift rate and migratory insect number density as inputs and the average body length of the migratory insect colony as the output. Mathematically, this model expresses a power-law relationship between the average body length of the migratory insect colony and the ratio of differential phase shift rate to number density, where the exponent is a constant less than 1, reflecting the nonlinear physical characteristics of the body size's response to the polarization phase. The fifth step is to verify the model's rationality through electromagnetic scattering simulation experiments. Under the condition that the insect distribution is relatively sparse and the distance between individuals is much greater than their size, the interference effect between individual scattered waves can be ignored. The influence of the population on electromagnetic wave propagation can be considered as an incoherent superposition of the scattering contributions of all individuals. A hybrid modeling approach of "individual scattering + population superposition" is adopted in the simulation. The correspondence between insect population length, number density, and differential phase shift rate is obtained through simulation experiments. The rationality of the quantitative relationship model of the average body length of the population is verified by analyzing the experimental results.

[0007] Step 6: Calculate the average body length of the migratory insect population. The differential phase shift rate data and the migratory insect number density data are time-synchronized and spatially registered to correspond to the same observation volume. The registered differential phase shift rate and migratory insect number density are then substituted into the quantitative body length relationship model as input parameters to calculate the estimated average body length of the migratory insect population within the target observation area. The relevant parameters in the quantitative body length relationship model can be pre-calibrated or optimized based on the parameters of the polarimetric weather radar system to adapt to the application requirements of different polarimetric weather radar system parameters and different types of migratory insects.

[0008] Beneficial effects First, this invention utilizes the differential phase shift rate of polarimetric weather radar, a polarimetric observation with phase information as its core, to perform body length inversion. Compared with traditional methods that rely on amplitude information such as radar reflectivity, it is less sensitive to factors such as fluctuations in insect populations and distance attenuation, fundamentally improving the stability and reliability of the body length estimation results for migratory insects.

[0009] Second, this invention explicitly introduces the number density of migratory insects as a key constraint parameter in the body length inversion model, effectively distinguishing between the body size effect and the population size effect, avoiding the problem of high parameter coupling in existing empirical models, and realizing the inversion of the average body length of migratory insect populations with clear physical meaning.

[0010] Third, this invention constructs the body length inversion relationship based on a well-defined electromagnetic scattering theory and an equivalent medium propagation model. It has a clear physical basis and good generalizability, and can be adapted to polarized weather radar systems with different configurations and different types of migratory insect targets through parameter calibration.

[0011] Fourth, this invention can automatically and quantitatively invert the body length characteristics of high-altitude migratory insect populations over a large spatial scale and continuous time range, providing an efficient, objective and repeatable technical means for monitoring and early warning of agricultural pests and diseases, ecological research on migratory insects, and assessment of material and energy transport in ecosystems. Attached Figure Description

[0012] Figure 1A schematic flowchart illustrating a method for estimating the body length of migratory insects based on polarimetric weather radar, provided in the embodiments of this specification. Figure 2 1. A schematic diagram illustrating the data processing of differential phase shift rate, number density, and body length of migratory insects under actual measurement conditions, provided in the embodiments of this specification. Figure 3 A schematic diagram of the geometric relationship for insect target observation based on a long ellipsoid model, provided as an embodiment of this specification; Figure 4 A schematic diagram illustrating the conversion process from individual parameters of migratory insects to equivalent parameters of a population, provided in the embodiments of this specification. Figure 5 1. A schematic diagram illustrating the establishment of a quantitative relationship model for insect populations provided in the embodiments of this specification; Figure 6 A schematic diagram illustrating the processing of differential phase shift rate, number density, and body length data of migratory insects under simulated conditions, provided as an embodiment of this specification. Figure 7 A schematic diagram illustrating the process of estimating the average body length of migratory insects under actual measurement conditions, provided as an embodiment of this specification. Detailed Implementation

[0013] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0014] It should be noted that, in the absence of conflict, the following embodiments and features can be combined with each other; and, based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0015] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0016] This application provides a method for estimating the average body length of migratory insect populations based on polarimetric weather radar observations. Taking joint weather radar and insect radar observation data from July to August 2024 as an example, the overall framework of this method is as follows: Figure 1 As shown, the steps of this method include: The first step involves acquiring and preprocessing polarimetric weather radar observation data and insect monitoring data. In this embodiment, a dual-polarimetric weather radar is used, operating in the S-band at centimeter-scale wavelengths, with a volumetric scanning mode including low elevation scanning. During observation, the radar simultaneously acquires echo signals from both the horizontal and vertical polarization channels and records the corresponding phase information. The raw radar data is sequentially processed with ground clutter suppression and system noise suppression to reduce interference from non-target echoes on phase observations. Subsequently, the phase data from the horizontal and vertical polarization channels are unwrapped, and system phase deviations are corrected. Based on this, a differential phase shift rate observation is generated by calculating the phase gradient along the radar's radial distance direction. The differential phase shift rate obtained through the above processing is used to characterize the phase accumulation difference of polarized electromagnetic waves along their propagation path caused by the presence of non-spherical scatterers.

[0017] Simultaneously, high-resolution insect radar was used to acquire the migration density information of insects within the target area. The insect radar is a coherent system with a blind range of 150 m; the antenna is a dual-polarized parabolic surface with a 1 m aperture, a 1.5° beamwidth, and a total bandwidth of 800 MHz, achieving a range resolution of 0.2 m. The volumetric number density of migratory insects was calculated by statistically analyzing the number of effective insect individuals detected per unit time and unit spatial volume, denoted as [missing information]. N The above process is as follows: Figure 2 As shown.

[0018] The second step involves equivalent modeling of the electromagnetic scattering characteristics of individual migratory insects. Considering that the typical body length of migratory insects is much smaller than the operating wavelength of polarimetric weather radar, satisfying the Rayleigh scattering approximation condition, Rayleigh scattering theory can be used to describe the electromagnetic scattering behavior of individual insects. In this embodiment, a single migratory insect is equivalent to a uniform medium ellipsoid, with its major axis corresponding to the insect's head-to-tail direction and its minor axis corresponding to the insect's lateral scale. The parameters considered in the modeling are as follows: Figure 3 As shown. Let the length of the major axis of the elongated ellipsoid be... L The length of the minor axis is D The ratio of these two factors is defined as the ellipsoidal axis ratio. For the same type of migratory insect, this axis ratio is taken as a fixed value of 4:1 to describe its typical morphological characteristics. In addition, by introducing an equivalent complex permittivity, the electromagnetic response characteristics of insect body tissues are parametrically described, thereby fully characterizing the scattering polarization characteristics of a single insect under polarized electromagnetic wave incident conditions.

[0019] The third step is to analyze the polarization propagation characteristics of migratory insect swarms. Spatially, migratory insect swarms appear as numerous discretely distributed individual scatterers. Therefore, by statistically analyzing the polarization scattering characteristics of these individuals, the polarization propagation characteristics and parametric features of the swarm can be analyzed, such as... Figure 4 As shown.

[0020] Based on the equivalent medium theory, the propagation constant of polarized electromagnetic waves in this migratory insect colony can be expressed as a form related to the number of insects per unit volume and their average scattering characteristics. The propagation constants differ between horizontally polarized and vertically polarized waves. This difference stems from the anisotropic scattering response caused by the non-spherical geometry of individual insects, and can be expressed as:

[0021] That In the middle is the polarizability tensor of the long ellipsoid model. The propagation ratio constant, Let be the effective relative permittivity. Let the difference between the horizontal and vertical polarization propagation constants be... The differential phase shift rate observed by polarimetric weather radar can then be expressed as the cumulative result of the real part of the difference along the propagation path, i.e.:

[0022] Wherein, represents the statistically significant difference in the average scattering characteristics of migratory insect populations. C 1 represents a scaling factor related to radar operating parameters. The above relationship indicates that, all other things being equal, the differential phase shift rate increases with the increase of the number density of migratory insects.

[0023] The fourth step is to construct a quantitative model of the average body length of the colony. Considering that the body axis orientation of insects typically exhibits a random distribution during actual migration, scattering models established under a single orientation are difficult to directly use for colony-scale inversion. Therefore, the scattering model of a single insect is statistically averaged across all possible spatial orientations. By integrating and averaging the body axis orientation angles, a colony-average scattering expression independent of the insect's body axis orientation can be obtained. Substituting this average scattering characteristic into the aforementioned colony propagation analysis formula and performing mathematical simplification, the average body length of the migratory insect colony can be established. L Differential phase shift rate and migratory insect number density N Quantitative relationships between them, such as Figure 5 As shown. This relationship can be expressed in the following power-law form:

[0024] Among them, the proportionality coefficient C 2. The average body length of the migratory insect population is determined by parameters such as the radar operating wavelength, the equivalent dielectric constant of the insect, and the geometric axis ratio of the elongated ellipsoid. The above relationships indicate that, given the known number density of migratory insects, the average body length of the migratory insect population can be directly inverted using the differential phase shift rate obtained from radar observations.

[0025] The fifth step is to verify the model's rationality through simulation experiments. Based on the above theory, electromagnetic scattering simulation experiments are conducted using FEKO, with input parameters as follows: Figure 6 As shown, individual simulations were used as the "basis function" for scattering by individuals within a swarm. The scattering responses of randomly oriented individuals were represented by incident angles at different azimuths, and the average polarization characteristics of the entire swarm were obtained through incoherent superposition. The incident wave frequency was set to 2.8 GHz, and the scattered electric field components under H / V polarization conditions were calculated, including the real and imaginary parts and phase distribution in both directions. The adjacent range gates were spaced 250 m apart, and it was assumed that each range gate contained several individuals. The average power of the overall echo was obtained by incoherently superimposing the squares of the scattered field intensity at each incident angle and statistically analyzing the results. In the experiment, the insect body length was varied to perform electromagnetic scattering on the target model. The body length was obtained from the simulation experiment and post-processing. L , N The correspondence between these relationships yields the following fitting formula. This fitting formula is highly similar to the body length model described above, which verifies the model's rationality.

[0026] .

[0027] Step 6: Calculate the average body length of the migratory insect population. Strict time synchronization and spatial registration are performed on the radar differential phase shift rate data and insect number density data to ensure they correspond to the same observation volume and time window. Subsequently, the registered differential phase shift rate and migratory insect number density data are input into the aforementioned body length inversion model. The model calculates the estimated average body length of the migratory insect population within the target area, as follows: Figure 7 As shown. To improve the accuracy and stability of the inversion results, the scaling factors in the body length inversion model can be calibrated through numerical simulation experiments based on rigorous electromagnetic scattering theory, or statistically fitted using joint observation data from weather radar and insect radar. The calibrated model can be stably applied to the body length inversion task of migratory insects in different times and regions.

[0028] Taking the combined observation data of weather radar and insect radar from July to August 2024 as an example, the body length data obtained by using the method proposed in the embodiments is compared with the actual observed body length data. As shown in Table 1, it can be seen that the body length estimation accuracy of the method proposed in the embodiments is high, and it has good estimation performance under different number density conditions.

[0029] Table 1. Detection performance indicators of various existing RGBT fusion target detection methods and the proposed method.

[0030] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for estimating the body length of migratory insects based on polarimetric weather radar, characterized in that, The steps of this method include: The first step involves acquiring dual-polarization observation data from a polarimetric weather radar within the target observation area, and simultaneously acquiring migratory insect monitoring data. The polarimetric weather radar observation data is then processed with clutter suppression, noise suppression, phase correction, and phase unwrapping. Phase information of the horizontal and vertical polarization channels is extracted, and the differential phase shift rate is calculated along the radar radial distance direction. Statistical processing is performed on the migratory insect monitoring data to obtain migratory insect number density data consistent with the radar observation volume and time scale. The second step is to establish an equivalent scattering model for individual migratory insects. Under the condition that the geometric size of individual migratory insects is much smaller than the working wavelength of polarimetric weather radar, a single migratory insect is equivalent to a long ellipsoidal scatterer with anisotropic electromagnetic response characteristics. The major axis of the long ellipsoid is used to characterize the body axis direction of the migratory insect, the minor axis is used to characterize the lateral size of the insect's body, and an equivalent dielectric constant is introduced to describe the response characteristics of the insect's body tissue to electromagnetic waves, thereby establishing a scattering response model for individual migratory insects under polarimetric electromagnetic wave incident conditions. The third step is to analyze the polarization propagation characteristics of migratory insect populations. A large number of discretely distributed migratory insects in space are considered as an equivalent sparse medium. Ignoring the mutual interference effects of individual scattering, the influence of the migratory insect population on the propagation of radar polarized electromagnetic waves is expressed as an incoherent superposition of the scattering contributions of all individuals. Based on the equivalent medium theory, the propagation constants of horizontally polarized waves and vertically polarized waves in the migratory insect population medium are determined, and the difference between the two polarization propagation constants is obtained. The real part of this phase propagation constant difference corresponds to the differential phase shift rate observable by the polarization weather radar, and its data is related to the number density of migratory insects and their average scattering characteristics. The fourth step involves constructing a quantitative model of the average body length of the colony. Considering the randomness of the individual attitude and spatial orientation of migratory insects during flight, the aforementioned individual scattering model of migratory insects is statistically averaged across all possible spatial orientations to eliminate the influence of individual orientation differences on polarization scattering characteristics, thus obtaining the average scattering characteristics of the colony independent of individual orientation. This average scattering characteristic is then incorporated into the polarization propagation analysis results to establish a model relating the average body length of the migratory insect colony to the differential phase shift rate observed by radar. To avoid the confusion caused by changes in the size of the migratory insect colony on the differential phase shift rate observation results, the number density of migratory insects is explicitly introduced as a key input parameter in the inversion relationship, thus forming a deterministic body length inversion model with differential phase shift rate and migratory insect number density as inputs and the average body length of the migratory insect colony as the output. Mathematically, this model expresses a power-law relationship between the average body length of the migratory insect colony and the ratio of differential phase shift rate and number density, where the power exponent is a constant less than 1, reflecting the nonlinear physical characteristics of the body size scale's response to the polarization phase. The fifth step is to verify the rationality of the model through electromagnetic scattering simulation experiments. Under the condition that the insects are relatively sparsely distributed and the distance between individuals is much greater than their size, the mutual interference effect between individual scattered waves can be ignored. The influence of the group on the propagation of electromagnetic waves can be regarded as the incoherent superposition of the scattering contributions of all individuals. In the simulation, a hybrid modeling approach of "individual scattering + group superposition" is adopted. The correspondence between insect group length, number density and differential phase shift rate is obtained through simulation experiments. By analyzing the experimental results, the rationality of the above quantitative relationship model of average body length of the group is verified. The sixth step is to calculate the average body length of the migratory insect population; to perform time synchronization and spatial registration processing on the differential phase shift rate data and the migratory insect number density data so that they correspond to the same observation volume; to substitute the registered differential phase shift rate and migratory insect number density as input parameters into the quantitative relationship model of body length, and to calculate the estimated result of the average body length of the migratory insect population in the target observation area; wherein, the relevant parameters in the quantitative relationship model of body length can be pre-calibrated or optimized according to the parameters of the polarimetric weather radar system to adapt to the application requirements of different polarimetric weather radar system parameters and different types of migratory insects.

2. The method as described in claim 1, characterized in that, In the third step, the propagation constants of horizontally polarized waves and vertically polarized waves differ. This difference originates from the anisotropic scattering response caused by the non-spherical geometry of the insect individual, and is expressed as: ； in For the polarizability tensor of the long ellipsoid model, The propagation ratio constant, Let be the effective relative permittivity; let the difference between the horizontal and vertical polarization propagation constants be . The differential phase shift rate observed by polarimetric weather radar can then be expressed as the cumulative result of the real part of the difference along the propagation path, i.e.: ； Wherein, represents the statistically significant difference in the average scattering characteristics of migratory insect populations. C 1 is a scaling factor related to radar operating parameters.

3. The method as described in claim 1, characterized in that, In the fourth step, the average body length of the migratory insect population is established. L Differential phase shift rate and migratory insect number density N The quantitative relationship between them can be expressed in the following power-law form: ； Among them, the proportionality coefficient C 2. It is determined by parameters such as the radar operating wavelength, the insect's equivalent dielectric constant, and the geometric axis ratio of the elongated ellipsoid.

4. The method as described in claim 1, characterized in that, In the fifth step, the body length... L Migratory insect population density N The correspondence between them is fitted by the following formula: 。

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