This paper explores the potential of ground-penetrating radar (GPR) monitoring for an advanced understanding of snow cover processes and structure. For this purpose, the study uses the Hansbreen (SW ...Spitsbergen) records that are among the longest and the most comprehensive snow-cover GPR monitoring records available on Svalbard. While snow depth (HS) is frequently the only feature derived from high-frequency radio-echo sounding (RES), this study also offers an analysis of the physical characteristics (grain shape, size, hardness, and density) of the snow cover structure. We demonstrate that, based on GPR data (800 MHz) and a single snow pit, it is possible to extrapolate the detailed features of snow cover to the accumulation area. Field studies (snow pits and RES) were conducted at the end of selected accumulation seasons in the period 2008–2019, under dry snow conditions and HS close to the maximum. The paper shows that although the snow cover structure varies in space and from season to season, a single snow pit site can represent the entire center line of the accumulation zone. Numerous hard layers (HLs) (up to 30% of the snow column) were observed that reflect progressive climate change, but there is no trend in quantity, thickness, or percentage contribution in total snow depth in the study period. HLs with strong crystal bonds create a “framework” in the snowpack, which reduces compaction and, consequently, the ice formation layers slow down the rate of snowpack metamorphosis. The extrapolation of snow pit data through radar profiling is a novel solution that can improve spatial recognition of snow cover characteristics and the accuracy of calculation of snow water equivalent (SWE).
The problem of detecting and localizing 2-D thin scatterers (i.e., elongated scatterers whose cross sections are small in terms of the probing wavelength) from scattered field measurements is ...considered. To this end, a linear model that neglects mutual scattering and is based on a distributional representation of the unknown is established. An improved imaging technique based on a minimization algorithm, which takes advantage of the inherent sparseness of the considered ground-penetrating radar scenario, is presented and compared to a classical migration algorithm. The comparison is achieved for both synthetically generated and experimental data collected in realistic conditions under a multimonostatic/multifrequency configuration.
Reliable detection of underground infrastructure is essential for infrastructure modernization works, the implementation of BIM technology, and 3D cadasters. This requires shortening the time of data ...interpretation and the automation of the stage of selecting the objects. The main factor that influences the quality of radargrams is noise. The paper presents the method of data filtration with use of wavelet analyses and Gabor filtration. The authors were inspired to conduct the research by the fact that the interpretation and analysis of radargrams is time-consuming and by the wish to improve the accuracy of selection of the true objects by inexperienced operators. The authors proposed automated methods for the detection and classification of hyperboles in GPR images, which include the data filtration, detection, and classification of objects. The proposed object classification methodology based on the analytic hierarchy process method introduces a classification coefficient that takes into account the weights of the proposed conditions and weights of the coefficients. The effectiveness and quality of detection and classification of objects in radargrams were assessed. The proposed methods make it possible to shorten the time of the detection of objects. The developed hyperbola classification coefficients show promising results of the detection and classification of objects.
In order to obtain the typical soil physical properties of reclaimed land more quickly and accurately, the South Dump of the China Coal’s Antaibao Open-Pit Mine in Pingshuo was focussed on in this ...paper, and ground penetrating radar (GPR) technology was utilized to detect the soil physical properties of reclaimed land in the mining area. The soil profile sampling and GPR detection methods were used to acquire the data. The gravel content of surface soil was analyzed by counting the number of isolated gravel signals in GPR images. The change of effective soil thickness was analyzed by establishing the fitting relationship between calibration depth and GPR image depth. The Topp’s model was validated by comparing its inversion with the measured soil volumetric water content. And the Topp’s model was further validated by the soil volumetric water content obtained from the Topp’s model and which obtained from the wave velocity inversion. The results are as follows: (1) Based on the number of isolated gravel signals in GPR images, we could qualitatively analyze the gravel content of surface soil reclaimed in the mining area. As the number of isolated gravel signals was greater, the gravel content of the surface soil was higher. (2) Using the known relative permittivity, electromagnetic wave velocity, and soil volumetric water content, the calibration depth and the reflection depth of the target (calibrator) of the GPR images were segmented, and the correlation between them is high. The fitting relationship (
R
2
) of each segment was higher than 0.940, and the average value of the five-segment
R
2
was 0.966, which indicated more accurate detection of the effective soil thickness of the reclaimed land in the mining area. (3) GPR could be used to detect the soil volumetric water content of reclaimed land in mining area, and Topp’s model was used for calculation of soil volumetric water content. The average deviation rate between the values from Topp’s model and the measured values was 12%, and the average absolute value of the difference was 2%. In summary, the benefits of using GPR to detect soil physical properties of reclaimed land in mining area are as follows: (1) GPR can be used to detect soil layer thickness and surface gravel content faster and more accurately. (2) Topp model can also be used to calculate the soil moisture content of non-natural deposits such as reclaimed land in mining area.
Previous geoarchaeological research on the Akko coastal plain have contributed to the understanding of the ancient coastal interface and added evidence as to the location/shift of the ancient ...anchorages dating from the Middle Bronze Age (beginning of the 2nd Millennium BC) to the Early Hellenistic period (mid of the 2nd century BC) of the ancient site of Tel Akko. The present research provides new insights into the environmental changes and likely anchorage sites along the western edge of Tel Akko in the 1st Millennium BC (Iron Age II and III, periods associated with the Phoenician mariners and Persian army incursion). Our approach for locating the anchorage is based on a detailed investigation of subsurface sediments combining sedimentological and faunal analysis and radiocarbon dating of cores as well as identification of ceramic sherds found in the cores, and ground penetrating radar (GPR) and electrical resistivity tomography (ERT) surveys. Paleoenvironmental changes are compared and contrasted with the results of the archaeological investigations on the tell and in its vicinity. Our new data demonstrates that the Phoenician/Persian maritime interface of Tel Akko was mainly oriented toward the southwestern area of the tell where a natural anchorage was likely to have been located. At that time, the water depth in this area was ca. 2m, allowing for the anchorage of seagoing vessels. Increasing sediment deposition lead to the deterioration of direct, and eventual loss of access, to the sea. These conditions initiated the abandonment of the tell in the Early Hellenistic period as well as the westward shift to habitation on the peninsula, now the ‘Old city of Akko’, the Crusaders' Saint Jean d’Acre.
It is important to identify the thin cracks within the airport pavement layers. To achieve this goal, a practical interferometric approach using the Yakumo multistatic ground-penetrating radar system ...was developed to detect the slight variability in wave propagation velocity and/or thickness caused by the thin cracks. In comparison with the conventional common midpoint (CMP) velocity estimation method, the proposed method can provide much higher-resolution estimations of slight deviations in the velocity and thickness from their corresponding reference values in the undamaged asphalt through the comparison of two CMP datasets. These deviations can be obtained analytically instead of graphically extracted from the CMP velocity spectrum. The proposed approach was not only analyzed using the simulated datasets, but also practically demonstrated at both an experimental model site and an actual airport site. In the simulation tests, velocity deviations on the order of a few millimeters per nanosecond were detected, and the experimental results shows good agreement with the ground truth and coring samples. This method provides a novel way to inspect partially damaged pavement when the thin cracks are difficult to detect using the reflected signals.
This study presented the development of the bowtie antenna system design as the transmitter in the Ground Penetrating Radar (GPR) system. The Artificial Magnetic Conductor (AMC) reflector was ...integrated into the antenna system as a ground plane to obtain a high gain, increase bandwidth and produce a low-profile antenna. The antenna is designed to work at a center frequency of 2.1 GHz with a range of 1.6 - 2.6 GHz and has ultrawideband (UWB) characteristics with a fractional bandwidth of ≥ 25%. In addition, the value of late-time ringing must also be reduced to -30 dB to prevent masking effects on the detected object. Antenna modeling and simulation was done to obtain the optimum prototype design. Bowtie antenna realization was carried out using RT Duroid 5880 as a substrate with dielectric constant (εr) = 2.2 and thickness (h) = 1.57 mm. The AMC reflector was fabricated with FR-4 Epoxy substrate with a dielectric constant (εr) = 4.4 and thickness (h) = 1.6 mm. The antenna realization results show that the antenna has bandwidth = 510 MHz, return loss = -15.17 dB and VSWR = 1.15. The AMC integrated bowtie antenna radiation pattern produces a unidirectional pattern with gain = 4.2 dB. However, the ringing level becomes high by -19.18 dB. Further development is needed to achieve ringing level values that meet the GPR antenna system specifications.
Ground-penetrating radar has recently found wide application in the underground imaging of tree roots. However, ignoring the random and complex nature of the heterogeneous soil and assuming the ...soil's relative permittivity constant throughout the survey region may yield an inaccurate tree root positioning. Meanwhile, the incompatible relative soil permittivity results in low image quality of the roots reconstruction. Furthermore, the soil's spatial heterogeneity introduces unwanted environmental clutter in the mapping of the tree root. A data processing framework is proposed to address these issues for retrieving the tree roots in heterogeneous soil environments. The proposed framework combines four techniques to be applied consecutively: First, a hyperbola extraction method based on a column-connection clustering algorithm is used to extract individual hyperbolae in B-scans, eliminate mutual influence in the process, and suppress noise. Second, an improved Hough transform technique is adopted to estimate the equivalent permittivity of each root's surrounding soil environment for each extracted hyperbola. Third, individual root restoration is done by transferring each hyperbola to a spot using its corresponding soil equivalent permittivity. Finally, individually restored features are combined in the final image. The images obtained via the proposed framework show a well reconstructed two-dimensional tree roots scenario. The applicability and the effectiveness of the proposed framework have been demonstrated through numerical simulations and fieldmeasurements.
Current ASTM specifications provide an approach for directly correlating the top rebar reflection amplitude from ground-penetrating radar (GPR) to deck condition when corrosion is the primary ...mechanism for concrete deterioration. However, current specifications do not offer an approach to compensate for geometric spreading losses caused by the inevitable variability in as-built concrete rebar cover. Even when cover thickness meets specified tolerances, significant errors may occur in mapping the location and quantity of deteriorated concrete when these amplitude variations are unaccounted for in air-coupled or ground-coupled GPR investigations. The significance of this correction is demonstrated by comparing mapped deterioration quantities that have been corrected and not corrected for depth variation, versus those quantities from independent methods such as half-cell corrosion potential, chain drag, or impact echo. One manual and two automated processes for depth correction are presented. These three processes compare favorably with one another on several mapped decks. One of the automated methods, which sets a deterioration threshold calibrated with half-cell and chain drag results, has been shown to be as accurate as manual methods on numerous decks. This approach is recommended for further evaluation and incorporation within ASTM D6087-08: Standard Method for Evaluating Asphalt-Covered Bridge Decks Using Ground-Penetrating Radar.
The effective monitoring of ballasted railway track beds is fundamental for maintaining safe operational conditions of railways and lowering maintenance costs. Railway ballast can be damaged over ...time by the breakdown of aggregates or by the upward migration of fine clay particles from the foundation, along with capillary water. This may cause critical track settlements. To that effect, early stage detection of fouling is of paramount importance. Within this context, ground penetrating radar (GPR) is a rapid nondestructive testing technique, which is being increasingly used for the assessment and health monitoring of railway track substructures. In this paper, we propose a novel and efficient signal processing approach based on entropy analysis, which was applied to GPR data for the assessment of the railway ballast conditions and the detection of fouling. In order to recreate a real-life scenario within the context of railway structures, four different ballast/pollutant mixes were introduced, ranging from clean to highly fouled ballast. GPR systems equipped with two different antennas, ground-coupled (600 and 1600 MHz) and air-coupled (1000 and 2000 MHz), were used for testing purposes. The proposed methodology aims at rapidly identifying distinctive areas of interest related to fouling, thereby lowering significantly the amount of data to be processed and the time required for specialist data processing. Prominent information on the use of suitable frequencies of investigation from the investigated set, as well as the relevant probability values of detection and false alarm, is provided.
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