A multi-point electromagnetic parameter measurement method and device for cross-modal data

Abstract

An embodiment of the present invention provides a multi-point electromagnetic parameter measurement method for cross-modal data. The present invention provides a multi-point electromagnetic parameter measurement method for cross-modal data, which utilizes point cloud data reconstructed from multi-view oblique photography images, marks measurement points based on the three-dimensional coordinates of the point cloud, and achieves the optimal arrangement of transmitting points and receiving points for large-scale electromagnetic parameter measurement in urban environments, measures initial electromagnetic parameters based on the free space method, detects abnormal initial electromagnetic parameters using the isolation forest algorithm, determines the cause of the abnormality based on the image segmentation result, calibrates the initial electromagnetic parameters, and achieves accurate correction of electromagnetic parameters of multi-medium cross-modal data fusion. An embodiment of the present invention also provides a multi-point electromagnetic parameter measurement device for cross-modal data.

Description

Technical Field

[0001] The present invention relates to a multi-point electromagnetic parameter measurement method and device, and in particular to a multi-point electromagnetic parameter measurement method and device for cross-modal data. Background Art

[0002] In urban environments, various facilities are densely distributed, the types of electromagnetic media are diverse, and there may be shadows or mixed distribution problems between objects. The electromagnetic parameter measurement in open environments based on instruments may have large errors and is difficult to support the needs of refined electromagnetic medium modeling. As the core parameter for measuring the electromagnetic properties of materials, the dielectric constant has always been the focus of related research in the field of electromagnetic parameter measurement.

[0003] At present, there are two main methods in the research of electromagnetic parameter measurement:

[0004] 1) Transmission / reflection method

[0005] This method is based on the scattering network theory. The medium is placed in a coaxial line or a rectangular waveguide. The position of the medium sample is independent of its position in the coaxial line or waveguide. The scattering parameters of the sample area are extracted using a vector network analyzer, and then the dielectric constant of the medium is inverted using the scattering equation.

[0006] 2) Resonant Cavity Method

[0007] This method places the material to be tested at the point where the magnetic field is maximum and the electric field is minimum in the resonant cavity. When a thin film or rod-shaped material to be tested is placed in a closed or open cavity, the inherent quality factor, inherent resonance rate and field distribution of the material in the cavity change. The electromagnetic parameters are calculated by the changes in the quality factor and resonant frequency parameters before and after the cavity is placed.

[0008] The problem with method 1) is that the position, thickness and length of the sample will lead to measurement errors. If the thickness of the sample to be measured is greater than the corresponding waveguide wavelength, there are multiple solutions for the propagation constant. Measuring extremely thin samples will increase the measurement uncertainty. This method can only be used for indoor measurements.

[0009] The problem with method 2) is that this method is a lossy measurement and is mainly suitable for measuring the equivalent electrical parameters of dielectric materials such as thin films and sheet dielectrics that require precise processing. It has high requirements for material preparation and places high demands on the resolution of measuring instruments such as frequency meters and vector network analyzers. Summary of the invention

[0010] In order to solve the problems in the prior art, the present invention provides a multi-point electromagnetic parameter measurement method for cross-modal data.

[0011] The point cloud data reconstructed from multi-view oblique photography images is used to achieve the optimal arrangement of transmitting points and receiving points for large-scale electromagnetic parameter measurements in urban environments. The initial electromagnetic parameters are measured based on the free space method and assigned values ​​on the point cloud. The abnormal initial electromagnetic parameters are detected using the isolation forest algorithm. The cause of the anomaly is determined based on the image segmentation results. The initial electromagnetic parameters are calibrated to achieve precise correction of the electromagnetic parameters of multi-medium media using cross-modal data fusion.

[0012] The technical solution adopted by the present invention is as follows:

[0013] A multi-point electromagnetic parameter measurement method for cross-modal data includes the following steps:

[0014] A. Design the deployment plan of electromagnetic signal measurement instruments based on point cloud data: pre-mark the measurement points on the point cloud data, and use the coordinate data of the points to place electromagnetic signal transmitting antennas at fixed intervals on one side of the building along the road. If the buildings are densely packed, multiple transmitting antennas can be placed on a single building; place the same number of receiving antennas on the other side of the building. The placed transmitting antennas and receiving antennas must cover all marked points, and each point must be measured multiple times;

[0015] B. Measure the initial electromagnetic parameters based on the free space method and assign them on the point cloud: obtain the reflection parameters by using the ratio of the coupling signal to the reference signal, obtain the transmission parameters by using the ratio with the reference signal, set the network under test as a two-port network, calculate the initial electromagnetic parameters of the medium by measuring the reflection parameters and transmission parameters of the electromagnetic medium, and assign the initial electromagnetic parameters to the corresponding points on the point cloud according to the points marked by the measurement deployment plan;

[0016] C. Detect abnormal initial electromagnetic parameters: Based on the isolation forest algorithm, the abnormal scores of the initial electromagnetic parameters at multiple points of different measurement media are calculated respectively, and the electromagnetic parameters with abnormal scores close to 1 are regarded as abnormal points;

[0017] D. Use the image segmentation results to determine the cause of the abnormality and perform calibration: According to the coordinates of the abnormal electromagnetic parameter point, obtain the mapping position of the point in the oblique photography image. According to the electromagnetic medium type segmentation results of the oblique photography image, determine whether the abnormal electromagnetic parameter is caused by measurement error or interference caused by different types of electromagnetic media. For the former, the median value of the measurement value of other points of the measurement medium can be used for correction. For the latter, adjust the position of the receiving and transmitting antennas and re-measure the electromagnetic parameters of the point.

[0018] In step A, the point cloud data refers to: three-dimensional point cloud data of urban features reconstructed based on multi-view oblique photography images, and the points in the point cloud contain three-dimensional coordinate information of the medium to be measured.

[0019] In step B, the free space method refers to: using a focusing lens antenna to radiate electromagnetic waves into free space, forming a stable quasi-TEM beam near the focal plane of the antenna, and vertically incident on the sample surface. Based on the discontinuity at the surface of the medium, the electromagnetic waves are reflected and transmitted multiple times at the interface between the medium and the air. The reflected signal is received by the transmitting antenna and sent to port 1 of the vector network analyzer. The transmitted signal is received by the receiving antenna and sent to port 2 of the vector network analyzer to obtain reflection parameters and transmission parameters.

[0020] In step D, the electromagnetic medium type segmentation result refers to: depicting the contours of different urban objects based on image segmentation technology to distinguish different electromagnetic media.

[0021] On the other hand, the present invention provides a multi-point electromagnetic parameter measurement device for cross-modal data, comprising the following modules:

[0022] Initial electromagnetic parameter calculation module: Pre-mark multiple measurement points on the point cloud data, and arrange multiple electromagnetic signal transmitting antennas according to the points on one side of the building along the road, and place the same number of electromagnetic signal receiving antennas as the transmitting antennas on the other side of the building, so that the placed transmitting antennas and receiving antennas cover all the marked points; This module calculates the reflection parameters using the ratio of the coupling signal obtained from these multiple points to the reference signal, and calculates the transmission parameters using the ratio of the transmission signal to the reference signal, and finally calculates the initial electromagnetic parameters of the medium based on the reflection parameters and the transmission parameters;

[0023] Cross-modal electromagnetic parameter calibration module: Based on the isolation forest algorithm, the initial electromagnetic parameter abnormal points of different measurement objects are detected, the mapping position of the point in the oblique photography image is obtained according to the coordinates of the abnormal electromagnetic parameter point, and the cause of the abnormality is determined in combination with the electromagnetic medium type segmentation result.

[0024] The technical solution and measuring device provided by the present invention have the following beneficial effects:

[0025] Among the above components, based on the three-dimensional point cloud data of urban objects, the transmitting and receiving antennas of the large-scale electromagnetic parameter measurement scheme are optimized. The free space method is used to measure the initial electromagnetic parameters and assign values ​​on the point cloud. The abnormal initial electromagnetic parameters are detected based on the isolation forest algorithm. Based on the image segmentation results, the initial electromagnetic parameters are calibrated to achieve accurate correction of the electromagnetic parameters of multi-medium cross-modal data fusion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 This is a schematic flow chart of a multi-point electromagnetic parameter measurement method for cross-modal data disclosed in this application.

[0028] Figure 2 This is a schematic diagram of the initial electromagnetic parameter measurement deployment scheme disclosed in this application. DETAILED DESCRIPTION

[0029] To make the purpose, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application. Example

[0030] Delineate the area to be measured and use multi-angle oblique photography images from drones to reconstruct three-dimensional point cloud data of urban features.

[0031] Pre-mark the measurement points on the 3D point cloud data, and use the coordinate data of the points to place electromagnetic signal transmitting antennas at fixed intervals on one side of the building along the road. If the buildings are densely packed, multiple transmitting antennas can be placed on a single building, and the same number of receiving antennas can be placed on the other side of the building. The placed transmitting antennas and receiving antennas must cover all marked points.

[0032] According to the points marked in the measurement deployment plan, the vector network analyzer, transmitting antenna and receiving antenna are arranged, the quasi-TEM beam is emitted to the medium to be measured and the reflected and transmitted signals are received. The reflection parameters are obtained by using the ratio of the coupled signal to the reference signal, and the transmission parameters are obtained by using the ratio with the reference signal. The network to be measured is set as a two-port network, and the initial electromagnetic parameters of the medium are calculated by measuring the reflection parameters and transmission parameters of the electromagnetic medium. The initial electromagnetic parameters are assigned to the corresponding points on the point cloud.

[0033] The isolation forest algorithm is used to calculate the abnormal scores of the initial electromagnetic parameters of multiple points of each measurement medium, and the electromagnetic parameters with abnormal scores close to 1 are regarded as abnormal points. According to the coordinates of the abnormal electromagnetic parameter point, the mapping position of the point in the oblique photography image is obtained. According to the electromagnetic medium type segmentation result of the oblique photography image, it is judged whether the abnormal electromagnetic parameter is a measurement error or interference caused by different types of electromagnetic media. For the former, the median of the measurement values ​​of other points of the measurement medium can be used for correction. For the latter, the position of the receiving and transmitting antennas is adjusted and the electromagnetic parameters of the point are re-measured. Based on the cross-modal fusion of image data and instrument measurement data, accurate correction of electromagnetic parameters is achieved.

[0034] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

Claims

1. A multi-point electromagnetic parameter measurement method for cross-modal data, characterized in that: The following steps are involved: A. Design the deployment plan of electromagnetic signal measurement instruments based on point cloud data: pre-mark the measurement points on the point cloud data, and use the coordinate data of the points to place electromagnetic signal transmitting antennas at fixed intervals on one side of the building along the road. If the buildings are densely packed, multiple transmitting antennas can be placed on a single building; Place the same number of receiving antennas on the other side of the building. The placed transmitting antennas and receiving antennas must cover all marked points, and each point needs to be measured multiple times. B. Measure the initial electromagnetic parameters based on the free space method and assign them on the point cloud: obtain the reflection parameters by using the ratio of the coupling signal to the reference signal, obtain the transmission parameters by using the ratio with the reference signal, set the network under test as a two-port network, calculate the initial electromagnetic parameters of the medium by measuring the reflection parameters and transmission parameters of the electromagnetic medium, and assign the initial electromagnetic parameters to the corresponding points on the point cloud according to the points marked by the measurement deployment plan; C. Detect abnormal initial electromagnetic parameters: Based on the isolation forest algorithm, the abnormal scores of the initial electromagnetic parameters at multiple points of different measurement media are calculated respectively, and the electromagnetic parameters with abnormal scores close to 1 are regarded as abnormal points; D. Use the image segmentation results to determine the cause of the abnormality and perform calibration: According to the coordinates of the abnormal electromagnetic parameter point, obtain the mapping position of the point in the oblique photography image. According to the electromagnetic medium type segmentation results of the oblique photography image, determine whether the abnormal electromagnetic parameter is caused by measurement error or interference caused by different types of electromagnetic media. For the former, the median value of the measurement value of other points of the measurement medium can be used for correction. For the latter, adjust the position of the receiving and transmitting antennas and re-measure the electromagnetic parameters of the point.

2. A multi-point electromagnetic parameter measurement method for cross-modal data according to claim 1, characterized in that: In the step A, the point cloud data refers to: three-dimensional point cloud data of urban features reconstructed based on multi-view oblique photography images, and the points in the point cloud contain three-dimensional coordinate information of the medium to be measured.

3. A multi-point electromagnetic parameter measurement method for cross-modal data according to claim 1, characterized in that: In the step B, the free space method refers to: using a focusing lens antenna to radiate electromagnetic waves into free space, forming a stable quasi-TEM beam near the focal plane of the antenna, and vertically incident on the sample surface. Based on the discontinuity at the surface of the medium, the electromagnetic waves are reflected and transmitted multiple times at the interface between the medium and the air. The reflected signal is received by the transmitting antenna and sent to port 1 of the vector network analyzer. The transmitted signal is received by the receiving antenna and sent to port 2 of the vector network analyzer to obtain reflection parameters and transmission parameters.

4. A multi-point electromagnetic parameter measurement method for cross-modal data according to claim 1, characterized in that: In the step D, the electromagnetic medium type segmentation result refers to: depicting the contours of different urban objects based on image segmentation technology to distinguish different electromagnetic media.

5. A multi-point electromagnetic parameter measurement device for cross-modal data, which refers to the method of claim 1, characterized in that: Includes the following modules: Initial electromagnetic parameter calculation module: Pre-mark multiple measurement points on the point cloud data, and arrange multiple electromagnetic signal transmitting antennas according to the points on one side of the building along the road, and place the same number of electromagnetic signal receiving antennas as the transmitting antennas on the other side of the building, so that the placed transmitting antennas and receiving antennas cover all the marked points; This module calculates the reflection parameters using the ratio of the coupling signal obtained from these multiple points to the reference signal, and calculates the transmission parameters using the ratio of the transmission signal to the reference signal, and finally calculates the initial electromagnetic parameters of the medium based on the reflection parameters and the transmission parameters; Cross-modal electromagnetic parameter calibration module: Based on the isolation forest algorithm, the initial electromagnetic parameter abnormal points of different measurement objects are detected, the mapping position of the point in the oblique photography image is obtained according to the coordinates of the abnormal electromagnetic parameter point, and the cause of the abnormality is determined in combination with the electromagnetic medium type segmentation result.

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