A method for fan imaging of ground penetrating radar data

Abstract

The application provides a geological radar data fan imaging method, which performs boundary extension on two-dimensional rectangular profile data of a geological radar, and then performs third-order interpolation between channels and triangular projection transformation. Through conversion of the two-dimensional rectangular profile to the fan profile, the morphological characteristics of the geological radar measuring line in the three-dimensional space can be more clearly and accurately described, and target positioning and interpretation in the three-dimensional space can be realized.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration, specifically a method for fan-shaped imaging of ground-penetrating radar data. This method transforms a two-dimensional rectangular profile into a fan-shaped profile through third-order interpolation and triangular projection transformation, which more clearly and accurately describes the morphological characteristics of ground-penetrating radar lines in three-dimensional space and is beneficial for target positioning in three-dimensional space. Background Technology

[0002] During coal mining, geological structural changes are easily triggered, and hidden geological anomalies (such as faults, collapse columns, and folds) can easily lead to mining accidents. Major mining accidents include roof collapse, coal and gas outbursts, and mine water inrush. Ground-penetrating radar (GPR), as an effective geophysical exploration tool, is suitable for detecting geological structural anomalies such as faults, collapse columns, and folds. Three-dimensional scanning GPR, by rotating the antenna angle, is used for three-dimensional spatial exploration in front of the working face, and can also be used for directional exploration of sidewalls, mining areas, etc., enabling rapid identification and three-dimensional imaging of geological structures.

[0003] Three-dimensional spatial scanning ground-penetrating radar transmits high-frequency broadband electromagnetic waves in pulse form to the working face. A portion of these waves travels directly from the transmitting antenna to the receiving antenna, forming a coupled wave. Another portion, after being transmitted, is reflected back from the air-surface interface without penetrating underground, forming a direct wave. Coupled waves and direct waves are often collectively referred to as direct-coupled waves, frequently used to determine the zero-time point as a reference for judging the depth of underground targets. The remaining electromagnetic waves propagate into the medium ahead of the working face. When they encounter targets with electrical differences (such as faults, collapse columns, folds, etc.) or interfaces between different media, the electromagnetic waves are reflected back to the working face and received by the receiving antenna. After acquisition, processing, and storage, the received signals become ground-penetrating radar data containing information about the medium ahead of the working face.

[0004] Three-dimensional spatial scanning ground-penetrating radar (GPR) uses the angle of the rotating GPR antenna to detect three-dimensional space in front of the working face. The shape of the survey line in three-dimensional space is arc-shaped, with the antenna position as the center. Therefore, the GPR profile should present a fan shape. The present invention provides a fan-shaped imaging method for GPR data, which can realize the conversion from a two-dimensional rectangular profile to a fan-shaped profile, and more clearly and accurately describe the morphological characteristics of the GPR survey line in three-dimensional space. Summary of the Invention

[0005] The purpose of this invention is to convert a two-dimensional rectangular profile into a sector profile by using third-order interpolation and triangular projection transformation based on the characteristics of ground-penetrating radar data.

[0006] This method converts a two-dimensional rectangular section into a sector section according to the following steps:

[0007] Step (A1): For the ground-penetrating radar data D(i,j), where i = 1, 2, ..., n, j = 1, 2, ..., m, perform boundary extension to obtain...

[0008]

[0009] Where j′=1,2,...,m,m+1,...,m+N, then perform third-order inter-track interpolation.

[0010]

[0011] Where k is the channel number of the interpolated ground-penetrating radar data, and d l for and The distance, l = 1, 2, ..., N, where N is the number of interpolation sampling channels, usually N = 6;

[0012] Step (A2): Ground Penetrating Radar Data Where i = 1, 2, ..., n, k = 1, 2, ..., m, m+1, ..., 2m, after triangular projection transformation, a sector-shaped section is obtained.

[0013]

[0014] Where i = 1, 2, ..., n, k = 1, 2, ..., m, m+1, ..., 2m, and (-α, +α) is the angular range of the sector profile during antenna rotation scanning. This is the result of a sector-shaped cross-sectional imaging.

[0015] The present invention has the following advantages:

[0016] 1. The triangular projection transformation function proposed in this invention can convert a two-dimensional rectangular section into a sector section.

[0017] 2. The sector-shaped profile can more clearly and accurately describe the morphological characteristics of the ground-penetrating radar survey line in three-dimensional space, which is beneficial for target positioning and interpretation in three-dimensional space. Attached Figure Description

[0018] Figure 1 Flowchart of Ground Penetrating Radar Data Enhancement in this Invention

[0019] Figure 2 Two-dimensional rectangular profile of ground-penetrating radar data of this invention

[0020] Figure 3 This invention provides a sector profile of ground-penetrating radar data. Detailed Implementation

[0021] This invention addresses the characteristics of three-dimensional spatial scanning ground-penetrating radar antennas rotating to acquire data. By using third-order interpolation and triangular projection transformation, it converts two-dimensional rectangular profiles into sector-shaped profiles, which can more clearly and accurately describe the morphological characteristics of ground-penetrating radar survey lines in three-dimensional space, thus facilitating target localization and interpretation in three-dimensional space.

[0022] The present invention provides a method for sector imaging of ground-penetrating radar data, which is divided into two cases. In the first case, after third-order interpolation between traces, the number of traces is greater than the number of sampling points (2m>n). The specific steps are as follows:

[0023] (1) Ground Penetrating Radar Data Where i = 1, 2, ..., n, k = 1, 2, ..., m, m+1, ..., 2m, after triangular projection transformation, a sector-shaped section is obtained.

[0024]

[0025] Where i = 1, 2, ..., n, k = 1, 2, ..., m, m+1, ..., 2m, and (-α, +α) is the angular range of the sector profile during antenna rotation scanning. This is the result of a sector-shaped cross-sectional imaging.

[0026] In the second case, after third-order interpolation between traces, the number of traces is less than or equal to the number of sampling points (2m≤n). The specific steps are as follows: (1) For the ground-penetrating radar data Where i = 1, 2, ..., n, k = 1, 2, ..., 2m, boundary extension yields...

[0027]

[0028] Where k′=1,2,...,2m,2m+1,...,2m+N, then perform third-order inter-track interpolation.

[0029]

[0030] Where k″ is the channel number of the interpolated ground-penetrating radar data, d l for and The distance is given by l = 1, 2, ..., N, where N is the number of interpolation sampling channels, typically N = 6. If the number of channels is less than or equal to the number of sampling points (4m ≤ n), the interpolation is repeated until λm > n, where λm is the number of channels after interpolation. The interpolated data is...

[0031] (2) Ground Penetrating Radar Data Where i = 1, 2, ..., n, p = 1, 2, ..., m, m+1, ..., λm, after triangular projection transformation, a sector-shaped profile is obtained.

[0032]

[0033] Where i = 1, 2, ..., n, p = 1, 2, ..., m, m+1, ..., λm, and (-α, +α) is the angular range of the sector profile during antenna rotation scanning. This is the result of a sector-shaped cross-sectional imaging.

Claims

1. A method for sector imaging using ground-penetrating radar (GPR) data, which uses two-dimensional GPR data as a basis and forms a sector profile based on the geometric characteristics of GPR survey lines in three-dimensional space. The specific steps are as follows: Step (A1): For the ground-penetrating radar data D(i,j), where i = 1, 2, ..., n, j = 1, 2, ..., m, perform boundary extension to obtain: Where j′=1 ,2 ,...,m ,m+1 ,...,m+N, then perform third-order inter-track interpolation: in, k is the trace number of the interpolated ground-penetrating radar data, d l for and The distance, l = 1, 2, ..., N, where N is the number of interpolation sampling channels, N = 6; Step (A2): Ground Penetrating Radar Data Where i = 1, 2, ..., n, k = 1, 2, ..., m, m+1, ..., 2m, after triangular projection transformation, a sector profile is obtained: Where i = 1, 2, ..., n, k = 1, 2, ..., m, m+1, ..., 2m, and (-α, +α) is the angular range of the sector profile when the antenna rotates for scanning. This is the result of a sector-shaped cross-sectional imaging.

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