Three-dimensional ground penetrating radar wet road surface detection and correction method

Abstract

The invention provides a three-dimensional ground penetrating radar wet road surface detection and correction method, and the method specifically comprises the following steps: selecting a wet road surface test region, and respectively collecting a wet road surface radar signal and a copper plate reflection radar signal of a corresponding region through employing the same parameters; fourier transform is adopted to convert the wet road surface radar signal and the copper plate reflection radar signal into a frequency domain form; selecting a main correction frequency by using an empirical method; or calculating a main correction frequency by calculating a frequency value which enables the wet road surface radar signal and the copper plate reflection radar signal to be closest to each other; correcting the wet road surface radar signal in the main correction frequency range; correcting the wet road surface radar signals outside the main correction frequency range to enable the signals to be continuous; and performing inverse Fourier transform on the corrected radar signal of the wet road surface, converting a frequency domain into a time domain form, and further performing thickness and compactness analysis. According to the technical scheme, the problem that in the prior art, a wet road surface affects radar signals of the ground penetrating radar is solved.

Description

Technical Field

[0001] The present invention relates to the field of three-dimensional geological radar detection, and in particular to a three-dimensional ground penetrating radar wet road surface detection and correction method. Background Art

[0002] The physical principle of 3D geological radar detection technology is based on the interaction between electromagnetic waves and the subsurface medium. By recording the amplitude, phase, and spectral characteristics of reflected and scattered waves and combining them with a dielectric constant distribution model, the 3D subsurface structure can be reconstructed. This technology has established a standardized application system in road engineering inspection, primarily enabling precise measurement of pavement structural layer thickness and intelligent identification of internal defects. Innovative application research has also been conducted in the non-destructive testing of asphalt pavement compaction. Research has shown that because the dielectric constant of water (ε = 81) is significantly higher than that of conventional road materials (ε = 4-9), the presence of water can significantly alter the electromagnetic wave propagation velocity and reflection coefficient. Consequently, the current industry standard (JTG 3450-2019) explicitly stipulates that radar inspections should be conducted on dry pavement surfaces, prohibiting data collection under wet conditions. However, in engineering practice, when rainfall conditions occur or when roller wheel spraying is used to prevent adhesion, the presence of water in the pavement is unavoidable. This creates a technical bottleneck for key quality control processes such as real-time compaction monitoring. Therefore, establishing a correction method for 3D geological radar data under wet conditions has become a core scientific issue in improving the environmental adaptability of detection technology.

[0003] Therefore, a three-dimensional ground penetrating radar wet road surface detection correction method is needed to reduce the impact of road surface wetness on ground penetrating radar radar signals and correct wet road surface radar data. Summary of the Invention

[0004] The main purpose of the present invention is to provide a three-dimensional ground penetrating radar wet road surface detection and correction method to solve the problem in the prior art that the wet road surface has an impact on the radar signal of the ground penetrating radar.

[0005] To achieve the above objectives, the present invention provides a three-dimensional ground penetrating radar wet road surface detection and correction method, which specifically includes the following steps:

[0006] S1, select a wet road surface test area, use the same parameters to collect the wet road surface radar signal y wet (t) and the radar signal y reflected by the copper plate in the corresponding area copper (t).

[0007] S2 uses Fourier transform to convert the wet road surface radar signal and the copper plate reflected radar signal into frequency domain form.

[0008] S3, select the main correction frequency using an empirical method; or calculate the main correction frequency by calculating the frequency value that makes the wet road surface radar signal and the copper plate reflected radar signal closest to each other.

[0009] S4, correcting the wet road surface radar signal within the main correction frequency range.

[0010] S5, correcting the wet road surface radar signal outside the main correction frequency range to make the signal continuous.

[0011] S6, performs inverse Fourier transform on the corrected wet road surface radar signal, converting the frequency domain into the time domain, and then performs thickness and compaction analysis.

[0012] Furthermore, the parameters in step S1 include: acquisition frequency, time window, number of signal superpositions and driving speed.

[0013] Furthermore, the frequency domain form of the wet road surface radar signal in step S2 is Y wet (f), the frequency domain form of the radar signal reflected by the copper plate is Ycopper(f).

[0014] Furthermore, the calculation of the main correction frequency in step S3 specifically includes the following steps:

[0015] S3.1. Calculate the minimum value R required to proportionally reduce the difference between the wet road surface radar signal and the copper plate reflected radar signal:

[0016]

[0017] Where a is a constant, argmin is the parameter value for obtaining the minimum value, and the upper limit of the frequency range f where the interpolation between the radar signal reflected from the copper plate and the radar signal on the wet road surface is the minimum after correction is obtained. l and the lower limit f h , f is the frequency, MSE is the mean square error loss, S e is the mean square error of the function at a certain frequency.

[0018] S3.2, by calculating the wet road surface within a certain frequency range, find the e The upper or lower limit of the minimum value is used to calculate the main correction frequency f0:

[0019]

[0020] Furthermore, the correction formula in step S4 is:

[0021] Y wet_corrected (f) = Y copper (f)×|||Y wet (f0)|÷|Y copper (f0)|||,f∈(f0,f1);

[0022] Among them, Y wet_corrected (f) The wet road surface radar signal after correction within the main correction frequency range, where f1 is the upper limit frequency of the metal plate correction.

[0023] Furthermore, the correction formula in step S5 is:

[0024]

[0025] Among them, Y wet_corrected’ (f) Wet road surface radar signal after correction outside the main correction frequency range, f max It is the maximum effective frequency in the frequency domain of the wet road surface.

[0026] Furthermore, the inverse Fourier transform in step S6 is:

[0027] y wet_corrected (t) = F -1 (Y wet_corrected’ (f));

[0028] Among them, F -1 is the inverse Fourier transform, y wet_corrected (t) Corrected time domain wet road surface radar signal.

[0029] The present invention has the following beneficial effects:

[0030] (1) Real-time correction of radar data under humid conditions was achieved, significantly improving the accuracy of the data.

[0031] (2) By combining frequency domain analysis with empirical rules, the selection of correction parameters is optimized, making the algorithm more adaptable and generalizable.

[0032] (3) Reduced manual intervention costs and provided more reliable data support in complex construction environments.

[0033] (4) Improved the detection reliability of radar technology in adverse weather conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0035] Figure 1 A flow chart of a three-dimensional ground penetrating radar wet road surface detection and correction method of the present invention is shown.

[0036] Figure 2 The mean square error for different main correction frequency lower limits is shown.

[0037] Figure 3 The mean square error for different upper limits of the main correction frequency is shown.

[0038] Figure 4 The frequency domain comparison of radar signals on wet road surfaces before and after correction and on dry road surfaces is shown.

[0039] Figure 5 The time domain comparison of radar signals on wet road surfaces before and after correction and on dry road surfaces is shown. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] like Figure 1 The method for detecting and correcting wet road surfaces using a three-dimensional ground penetrating radar is shown, and specifically comprises the following steps:

[0042] S1, select a wet road surface test area, use the same parameters to collect the wet road surface radar signal y wet (t) and the radar signal y reflected by the copper plate in the corresponding area copper (t). A copper plate-reflected radar signal is acquired by placing a copper plate on the road surface and placing a radar on it. According to radar principles, reflection from a metal plate is considered total reflection, meaning that all electromagnetic wave signals are reflected back to the receiving antenna without being transmitted. The structure of its reflection pattern is believed to be similar to that of a dry road surface. Therefore, by selecting a reference point, the copper plate-reflected radar signal can be proportionally reduced within a certain frequency range to replace the wet road surface radar signal.

[0043] S2 uses Fourier transform to convert the wet road surface radar signal and the copper plate reflected radar signal into frequency domain form.

[0044] S3, select the main correction frequency using an empirical method; or calculate the main correction frequency by calculating the frequency value that makes the wet road surface radar signal and the copper plate reflected radar signal closest to each other.

[0045] S4, correcting the wet road surface radar signal within the main correction frequency range.

[0046] S5, correcting the wet road surface radar signal outside the main correction frequency range to make the signal continuous.

[0047] S6, performs inverse Fourier transform on the corrected wet road surface radar signal, converting the frequency domain into the time domain, and then performs thickness and compaction analysis.

[0048] The presence of moisture significantly enhances the overall amplitude of the radar signal in the time domain, especially the amplitude strength of the first wave signal reflected from the road surface; in the frequency domain, it significantly enhances the amplitude characteristics of high-frequency signals in a specific frequency band, while having little observable effect on the signal amplitude in the low-frequency range. This dual-domain mechanism leads to a systematic overestimation of the measured dielectric constant compared to the true dielectric constant of the dry road surface. In view of the technical implementation difficulties of time domain signal correction, although the conventional bandpass filtering method can directly filter out high-frequency components, it will cause excessive attenuation of the effective signal, thereby reducing the robustness and signal-to-noise ratio of the acquired signal. Therefore, the present invention adopts a frequency domain signal overall correction strategy, using the principle that the copper plate reflection and the dry road surface reflection are both single medium reflections and their waveforms are basically the same. The core parameters are determined by comparative analysis of the wet road surface and copper plate reflection signals: first, the main correction frequency is determined, and then the main correction frequency is used as a reference to implement dynamic gain adjustment on the copper plate reflection signal within the cutoff frequency range to replace the wet road surface reflection signal.

[0049] Specifically, the parameters in step S1 include: acquisition frequency, time window, number of signal superpositions, and driving speed.

[0050] Specifically, the frequency domain form of the wet road surface radar signal in step S2 is Y wet (f), the frequency domain form of the radar signal reflected by the copper plate is Ycopper(f).

[0051] Specifically, the calculation of the main correction frequency in step S3 includes the following steps:

[0052] S3.1. Calculate the minimum value R required to proportionally reduce the difference between the wet road surface radar signal and the copper plate reflected radar signal:

[0053]

[0054] Where a is a constant, argmin is the parameter value for obtaining the minimum value, and the upper limit of the frequency range f where the interpolation between the radar signal reflected from the copper plate and the radar signal on the wet road surface is the minimum after correction is obtained. l and the lower limit f h , f is the frequency, MSE is the mean square error loss, S e is the mean square error of the function at a certain frequency.

[0055] S3.2, by calculating the wet road surface within a certain frequency range, find the e The upper or lower limit of the minimum value is used to calculate the main correction frequency f0:

[0056]

[0057] The empirical method in step S3 is: 0.45 GHz is selected for 1 GHz radar, 0.85 GHz is selected for 2 GHz radar, and 1.2 GHz is selected for 3 GHz radar.

[0058] Specifically, the correction formula in step S4 is:

[0059] Y wet_corrected (f) = Y copper (f)×|||Y wet (f0)|÷|Y copper (f0)|||,f∈(f0,f1);

[0060] Among them, Y wet_corrected (f) The wet road surface radar signal after correction within the main correction frequency range. f1 is the upper limit frequency of the metal plate correction, which is set to 1.5 times the antenna main frequency. For example, for a 1 GHz radar, 1.5 GHz is selected, and for a 2 GHz radar, 3 GHz is selected.

[0061] Specifically, the correction formula in step S5 is:

[0062]

[0063] Among them, Y wet_corrected’ (f) Wet road surface radar signal after correction outside the main correction frequency range, f max It is the maximum effective frequency in the frequency domain of the wet road surface and can be taken as twice of the center frequency.

[0064] Specifically, the inverse Fourier transform in step S6 is:

[0065] y wet_corrected (t) = F -1 (Y wet_corrected’ (f));

[0066] Among them, F -1 is the inverse Fourier transform, y wet_corrected (t) Corrected time domain wet road surface radar signal.

[0067] In order to verify the engineering applicability of this method, a field application test was conducted during the construction of an asphalt pavement on a highway. The AC-16 modified asphalt mixture structure layer was selected as the test object. The water spraying rate of the roller was kept at 0.8L / m 3Radar data was collected synchronously under humidity conditions. First, data acquisition conditions were configured, with equipment parameters set at a 2GHz air-coupled antenna and a 15ns sampling window. Calibration was performed using a 500mm diameter copper standard reflector. Environmental requirements included an air temperature of 25±3°C and a wind speed of less than 1.5m / s. Field data collection was then performed. Finally, the wet road surface correction method was used.

[0068] First, fix the upper limit of the main correction frequency to 1.5 GHz with the highest probability in the frequency domain, and calculate the mean square error Se of different main correction frequency lower limits, as follows: Figure 2 As shown, the minimum value appears at about 0.5GHz, so take fl l is 0.5GHz.

[0069] Then fix the lower limit of the main correction frequency to 0.5GHz, calculate the mean square error Se of different main correction frequency upper limits, and the minimum value appears at about 1.1GHz, as shown in Figure 3 As shown, take f H It is 1.1GHz.

[0070] Then calculate the main correction frequency

[0071] Perform corrections according to steps S4-S6 to obtain frequency domain and time domain diagrams, such as Figure 4 and Figure 5 shown.

[0072] Table 1 Comparative analysis of results

[0073]

[0074] As shown in Table 1, the proposed method can correct radar detection under wet road conditions to approximate dry road conditions, demonstrating significant application value in monitoring compaction processes. This achievement overcomes the traditional radar detection system's reliance on dry surfaces and provides a new technical path for continuous nondestructive testing of road projects.

[0075] like Figure 4 and Figure 5 This indicates that the amplitudes were too large before correction, but after correction, they are close to dry road surface signals. The method provided by the present invention has broad application potential and market prospects in the field of road engineering detection. By improving the accuracy and reliability of radar data under wet conditions, more accurate quality assessments can be provided during road construction and maintenance. This will not only support the construction of transportation infrastructure, but can also be widely used in other industries requiring high-precision underground detection, such as mining exploration and urban construction. With the continuous improvement of technology and the growth of market demand, the application prospects are expected to be broad.

[0076] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A three-dimensional ground penetrating radar wet road surface detection and correction method, characterized in that: The specific steps include: S1, select a wet road surface test area, use the same parameters to collect the wet road surface radar signal y wet (t) and the radar signal y reflected by the copper plate in the corresponding area copper (t); S2, uses Fourier transform to convert the wet road surface radar signal and the copper plate reflected radar signal into frequency domain form; S3, select the main correction frequency by empirical method; or calculate the main correction frequency by calculating the frequency value that makes the wet road surface radar signal and the copper plate reflected radar signal closest to each other; S4, correcting the wet road surface radar signal within the main correction frequency range; S5, correcting the wet road surface radar signal outside the main correction frequency range to make the signal continuous; S6, performs inverse Fourier transform on the corrected wet road surface radar signal, converting the frequency domain into the time domain, and then performs thickness and compaction analysis.

2. A three-dimensional ground penetrating radar wet road surface detection and correction method according to claim 1, characterized in that: The parameters in step S1 include: acquisition frequency, time window, number of signal superpositions and driving speed.

3. The three-dimensional ground penetrating radar wet road surface detection and correction method according to claim 1, characterized in that: The frequency domain form of the wet road surface radar signal in step S2 is Y wet (f), the frequency domain form of the radar signal reflected by the copper plate is Ycopper(f).

4. The three-dimensional ground penetrating radar wet road surface detection and correction method according to claim 1, characterized in that: Calculating the main correction frequency in step S3 specifically includes the following steps: S3.

1. Calculate the minimum value R required to proportionally reduce the difference between the wet road surface radar signal and the copper plate reflected radar signal: S e =MSE|||Y wet (f)|-R|Y copper (f)||| 2 ; Where a is a constant, argmin is the parameter value for obtaining the minimum value, and the upper limit of the frequency range f where the interpolation between the radar signal reflected from the copper plate and the radar signal on the wet road surface is the minimum after correction is obtained. l and the lower limit f h , f is the frequency, MSE is the mean square error loss, S e is the mean square error of the function at a certain frequency; S3.2, by calculating the wet road surface within a certain frequency range, find the e The upper or lower limit of the minimum value is used to calculate the main correction frequency f0:

5. The three-dimensional ground penetrating radar wet road surface detection and correction method according to claim 1, characterized in that: The correction formula in step S4 is: Y wet_corrected (f)=Y copper (f)×|||Y wet (f0)|÷|Y copper (f0)|||,f∈(f0,f1); Among them, Y wet_corrected (f) The wet road surface radar signal after correction within the main correction frequency range, where f1 is the upper limit frequency of the metal plate correction.

6. The three-dimensional ground penetrating radar wet road surface detection and correction method according to claim 1, characterized in that: The correction formula in step S5 is: Among them, Y wet_corrected '(f) is the wet road surface radar signal after correction outside the main correction frequency range, f max It is the maximum effective frequency in the frequency domain of the wet road surface.

7. The method for detecting and correcting wet road surface using a three-dimensional ground penetrating radar according to claim 1, wherein: The inverse Fourier transform in step S6 is: y wet_corrected (t)=F -1 (Y wet_corrected ’(f)); Among them, F -1 is the inverse Fourier transform, y wet_corrected (t) Corrected time domain wet road surface radar signal.

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