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17 pages, 11252 KiB

Open AccessArticle

Detection of Soil Pipes Using Ground Penetrating Radar

by Anita Bernatek-Jakiel and Marta Kondracka

Remote Sens. 2019, 11(16), 1864; https://doi.org/10.3390/rs11161864 - 9 Aug 2019

Cited by 19 | Viewed by 6386

Abstract

Soil piping leads to land degradation in almost all morphoclimatic regions. However, the detection of soil pipes is still a methodological challenge. Therefore, this study aims at testing ground penetrating radar (GPR) to identify soil pipes and to present the complexity of soil [...] Read more.

Soil piping leads to land degradation in almost all morphoclimatic regions. However, the detection of soil pipes is still a methodological challenge. Therefore, this study aims at testing ground penetrating radar (GPR) to identify soil pipes and to present the complexity of soil pipe networks. The GPR surveys were conducted at three sites in the Bieszczady Mountains (SE Poland), where pipes develop in Cambisols. In total, 36 GPR profiles longitudinal and transverse to piping systems were made and used to provide spatial visualization of pipe networks. Soil pipes were identified as reflection hyperbolas on radargrams, which were verified with the surface indicators of piping, i.e., sagging of the ground and the occurrence of pipe roof collapses. Antennas of 500 MHz and 800 MHz were tested, which made possible the penetration of the subsurface up to 3.2 m and 2 m, respectively. Concerning ground properties, antenna frequencies and processing techniques, there was a potential possibility to detect pipes with a minimum diameter of 3.5 cm (using the antenna of lower frequency), and 2.2 cm (with the antenna of higher frequency). The results have proved that soil pipes meander horizontally and vertically and their networks become more complicated and extensive down the slope. GPR is a useful method to detect soil pipes, although it requires field verification and the proper selection of antenna frequency. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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31 pages, 17225 KiB

Open AccessArticle

Reconstruction of a Segment of the UNESCO World Heritage Hadrian’s Villa Tunnel Network by Integrated GPR, Magnetic–Paleomagnetic, and Electric Resistivity Prospections

by Annalisa Ghezzi, Antonio Schettino, Pietro Paolo Pierantoni, Lawrence Conyers, Luca Tassi, Luigi Vigliotti, Erwin Schettino, Milena Melfi, Maria Elena Gorrini and Paolo Boila

Remote Sens. 2019, 11(15), 1739; https://doi.org/10.3390/rs11151739 - 24 Jul 2019

Cited by 5 | Viewed by 5456

Abstract

Hadrian’s Villa is an ancient Roman archaeological site built over an ignimbritic tuff and characterized by abundant iron oxides, strong remnant magnetization, and elevated magnetic susceptibility. These properties account for the high-amplitude magnetic anomalies observed in this site and were used as a [...] Read more.

Hadrian’s Villa is an ancient Roman archaeological site built over an ignimbritic tuff and characterized by abundant iron oxides, strong remnant magnetization, and elevated magnetic susceptibility. These properties account for the high-amplitude magnetic anomalies observed in this site and were used as a primary tool to detect deep archaeological features consisting of air-filled and soil-filled cavities of the tuff. An integrated magnetic, paleomagnetic, radar, and electric resistivity survey was performed in the Plutonium-Inferi sector of Hadrian’s Villa to outline a segment of the underground system of tunnels that link different zones of the villa. A preliminary paleomagnetic analysis of the bedrock unit and a high-resolution topographic survey by aerial photogrammetry allowed us to perform a computer-assisted modelling of the observed magnetic anomalies, with respect to the archaeological sources. The intrinsic ambiguity of this procedure was reduced through the analysis of ground penetrating radar and electric resistivity profiles, while a comprehensive picture of the buried archaeological features was built by integration of the magnetization model with radar amplitude maps. The final subsurface model of the Plutonium-Inferi complex shows that the observed anomalies are mostly due to the presence of tunnels, skylights, and a system of ditches excavated in the tuff. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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26 pages, 20724 KiB

Open AccessArticle

The Messapic Site of Muro Leccese: New Results from Integrated Geophysical and Archaeological Surveys

by Catia Bianco, Lara De Giorgi, Maria T. Giannotta, Giovanni Leucci, Francesco Meo and Raffaele Persico

Remote Sens. 2019, 11(12), 1478; https://doi.org/10.3390/rs11121478 - 21 Jun 2019

Cited by 9 | Viewed by 4437

Abstract

The regular application of geophysical survey techniques to evaluate archaeological sites is well established as a method for locating, defining, and mapping buried archaeological materials. However, it is not always feasible to apply a range of different methods over a particular site or [...] Read more.

The regular application of geophysical survey techniques to evaluate archaeological sites is well established as a method for locating, defining, and mapping buried archaeological materials. However, it is not always feasible to apply a range of different methods over a particular site or landscape due to constraints in time or funding. This paper addresses the integrated application of three geophysical survey methods over an important archaeological site located in south Italy. In particular, it is focused on the results achieved from a past geophysical survey and the ongoing excavations performed by archaeologists in the site of Muro Leccese. Muro Leccese (Lecce) is one of the most important Messapian archaeological sites in southern Italy. The archaeological interest of the site was generated since the discovery of the remains of Messapian walls (late 4th–3rd centuries BC). With the aim of widening the archaeological knowledge of the Messapian settlement, several integrated methods, including magnetometry, ground-penetrating radar, and electrical resistivity tomography were used on site to fulfill a number of different research objectives. Since the most important targets were expected to be located at shallow soil depth, a three-dimensional (3D) ground-penetrating radar (GPR) survey was carried out in two zones, which were labeled respectively as zone 1 and zone 2, and were both quite close to the archaeological excavations. The GPR investigations were integrated with a 3D electrical resistivity tomography (ERT) survey in zone 1 and with a magnetometric, in gradiometry configuration survey in zone 2. The integration of several techniques allowed mapping the structural remains of this area and leading the excavation project. The geophysical results show a good correspondence with the archaeological features that were found after the excavation. Current work on the geophysical survey data using different codes for the processing of the data and merging different datasets using a Geographic Information System allowed achieving a user-friendly visualization that was presented to the archaeologists. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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29 pages, 10086 KiB

Open AccessArticle

Kinematic GPR-TPS Model for Infrastructure Asset Identification with High 3D Georeference Accuracy Developed in a Real Urban Test Field

by Nikolaj Šarlah, Tomaž Podobnikar, Domen Mongus, Tomaž Ambrožič and Branko Mušič

Remote Sens. 2019, 11(12), 1457; https://doi.org/10.3390/rs11121457 - 19 Jun 2019

Cited by 11 | Viewed by 10384

Abstract

This paper describes in detail the development of a ground-penetrating radar (GPR) model for the acquisition, processing and visualisation of underground utility infrastructure (UUI) in a controlled environment. The initiative was to simulate a subsurface urban environment through the construction of regional road, [...] Read more.

This paper describes in detail the development of a ground-penetrating radar (GPR) model for the acquisition, processing and visualisation of underground utility infrastructure (UUI) in a controlled environment. The initiative was to simulate a subsurface urban environment through the construction of regional road, local road and pedestrian pavement in real urban field/testing pools (RUTPs). The RUTPs represented a controlled environment in which the most commonly used utilities were installed. The accuracy of the proposed kinematic GPR-TPS (terrestrial positioning system) model was analysed using all the available data about the materials, whilst taking into account the thickness of the pavement as well as the materials, dimensions and 3D position of the UUI as given reference values. To determine the reference 3D position of the UUI, a terrestrial geodetic surveying method based on the established positional and height geodetic network was used. In the first phase of the model, the geodetic network was used as a starting point for determining the 3D position of the GPR antenna with the efficient kinematic GPR surveying setup using a GPR and self-tracking (robotic) TPS. In the second phase, GPR-TPS system latency was quantified by matching radargram pairs with a set of fidelity measures based on a correlation coefficient and mean squared error. This was followed by the most important phase, where, by combining sets of “standard” processing routines of GPR signals with the support of advanced algorithms for signal processing, UUI were interpreted and visualised semi-automatically. As demonstrated by the results, the proposed GPR model with a kinematic GPR-TPS surveying setup for data acquisition is capable of achieving an accuracy of less than ten centimetres. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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17 pages, 5542 KiB

Open AccessArticle

Data Processing and Interpretation of Antarctic Ice-Penetrating Radar Based on Variational Mode Decomposition

by Siyuan Cheng, Sixin Liu, Jingxue Guo, Kun Luo, Ling Zhang and Xueyuan Tang

Remote Sens. 2019, 11(10), 1253; https://doi.org/10.3390/rs11101253 - 27 May 2019

Cited by 10 | Viewed by 3971

Abstract

In the Arctic and Antarctic scientific expeditions, ice-penetrating radar is an effective method for studying the bedrock under the ice sheet and ice information within the ice sheet. Because of the low conductivity of ice and the relatively uniform composition of ice sheets [...] Read more.

In the Arctic and Antarctic scientific expeditions, ice-penetrating radar is an effective method for studying the bedrock under the ice sheet and ice information within the ice sheet. Because of the low conductivity of ice and the relatively uniform composition of ice sheets in the polar regions, ice-penetrating radar is able to obtain deeper and more abundant data than other geophysical methods. However, it is still necessary to suppress the noise in radar data to obtain more accurate and plentiful effective information. In this paper, the entirely non-recursive Variational Mode Decomposition (VMD) is applied to the data noise reduction of ice-penetrating radar. VMD is a decomposition method of adaptive and quasi-orthogonal signals, which decomposes airborne radar data into multiple frequency-limited quasi-orthogonal Intrinsic Mode Functions (IMFs). The IMFs containing noise are then removed according to the information distribution in the IMF’s components and the remaining IMFs are reconstructed. This paper employs this method to process the real ice-penetrating radar data, which effectively eliminates the interference noise in the data, improves the signal-to-noise ratio and obtains the clearer inner layer structure of ice. It is verified that the method can be applied to the noise reduction processing of polar ice-penetrating radar data very well, which provides a better basis for data interpretation. At last, we present fine ice structure within the ice sheet based on VMD denoised radar profile. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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16 pages, 4559 KiB

Open AccessArticle

Characterization of Electromagnetic Properties of In Situ Soils for the Design of Landmine Detection Sensors: Application in Donbass, Ukraine

by Timothy Bechtel, Stanislav Truskavetsky, Gennadiy Pochanin, Lorenzo Capineri, Alexander Sherstyuk, Konstantin Viatkin, Tatyana Byndych, Vadym Ruban, Liudmyla Varyanitza-Roschupkina, Oleksander Orlenko, Pavlo Kholod, Pierluigi Falorni, Andrea Bulletti, Luca Bossi and Fronefield Crawford

Remote Sens. 2019, 11(10), 1232; https://doi.org/10.3390/rs11101232 - 24 May 2019

Cited by 13 | Viewed by 4911

Abstract

To design holographic and impulse ground penetrating radar (GPR) sensors suitable for humanitarian de-mining in the Donbass (Ukraine) conflict zone, we measured critical electromagnetic parameters of typical local soils using simple methods that could be adapted to any geologic setting. Measurements were recorded [...] Read more.

To design holographic and impulse ground penetrating radar (GPR) sensors suitable for humanitarian de-mining in the Donbass (Ukraine) conflict zone, we measured critical electromagnetic parameters of typical local soils using simple methods that could be adapted to any geologic setting. Measurements were recorded along six profiles, each crossing at least two mapped soil types. The parameters selected to evaluate GPR and metal detector sensor performance were magnetic permeability, electrical conductivity, and dielectric permittivity. Magnetic permeability measurements indicated that local soils would be conducive to metal detector performance. Electrical conductivity measurements indicated that local soils would be medium to high loss materials for GPR. Calculation of the expected attenuation as a function of signal frequency suggested that 1 GHz may have optimized the trade-off between resolution and penetration and matched the impulse GPR system power budget. Dielectric permittivity was measured using both time domain reflectometry and impulse GPR. For the latter, a calibration procedure based on an in-situ measurement of reflection coefficient was proposed and the data were analyzed to show that soil conditions were suitable for the reliable use of impulse GPR. A distinct difference between the results of these two suggested a dry (low dielectric) soil surface, grading downward into more moist (higher dielectric) soils. This gradation may provide a matching layer to reduce ground surface reflections that often obscure shallow subsurface targets. In addition, the relatively high dielectric deeper (10 cm–20 cm) subsurface soils should provide a strong contrast with plastic-cased mines. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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21 pages, 17229 KiB

Open AccessArticle

Step-Frequency Ground Penetrating Radar for Agricultural Soil Morphology Characterisation

by Federico Lombardi and Maurizio Lualdi

Remote Sens. 2019, 11(9), 1075; https://doi.org/10.3390/rs11091075 - 7 May 2019

Cited by 15 | Viewed by 6262

Abstract

Soil morphology plays a fundamental role in the vertical and lateral movements of solutes and water transport, providing knowledge regarding spatial distribution of its textural properties and subsurface dynamics. In this framework, the measured values of electrical conductivity are able to reveal the [...] Read more.

Soil morphology plays a fundamental role in the vertical and lateral movements of solutes and water transport, providing knowledge regarding spatial distribution of its textural properties and subsurface dynamics. In this framework, the measured values of electrical conductivity are able to reveal the heterogeneity of soil that is present in a particular agricultural field and they are affected by more than one important physical characteristic: soil texture, organic matter, moisture content, and the depth of the clay pan. In the microwave region, these dynamics are known to exhibit a frequency dependent behaviour. This study explores the application of a Step Frequency Continuous Wave Ground Penetrating Radar (SFCW GPR) to shed light on the practical impact that these dependencies have on the imaging results, not only regarding the electrical characterisation of the subsurface morphology, but also in its correct interpretation. This information is of notable importance for determining water-use efficiency and planning precision-agriculture programs. The results clearly show visible and significant fluctuations of the amplitude levels, depending on the considered central frequency, demonstrating that the frequency dependence of electromagnetic properties of heterogeneous soil are significant and cannot be ignored if the aim is to properly define the subsurface attributes. The measurements also suggest that correlating the delineated variations might help in the identification of extended features and the classification of areas that possess similar properties in order to increase the confidence in monitoring soil resources. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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16 pages, 5915 KiB

Open AccessArticle

Dam Leakage Detection by Borehole Radar: A Case-History Study

by Sixin Liu, Xudong Wang, Qi Lu, Honqing Li, Yuanxin Wang and Li Deng

Remote Sens. 2019, 11(8), 969; https://doi.org/10.3390/rs11080969 - 23 Apr 2019

Cited by 14 | Viewed by 5805

Abstract

A borehole radar investigation was performed at the Sanzuodian reservoir, Chifeng, China to assess possible leakage paths located in the deep dam foundation. The key methodologies used include both single-hole reflection and cross-hole radar tomography, which make a high-resolution identification of the hydraulic [...] Read more.

A borehole radar investigation was performed at the Sanzuodian reservoir, Chifeng, China to assess possible leakage paths located in the deep dam foundation. The key methodologies used include both single-hole reflection and cross-hole radar tomography, which make a high-resolution identification of the hydraulic connection paths between upstream and downstream sides possible. The leakage paths are characterized by direct wave loss due to high electromagnetic attenuation in the single-hole reflection profile and the nearly horizontal-banded low-velocity zone in the cross-hole velocity tomography due to possible large internal erosion. Meanwhile, some small structures inside the dam, including the core wall thickness changing point, the connecting point between asphalt and concrete walls, and the contacting interface between the dry and the water-saturated formations can be identified from the single-hole reflection profile clearly. Interpreted leakage paths are proven by the water flow measurement. Borehole radar is a useful high-resolution tool, suitable for deep leakage detection and evaluation. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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13 pages, 56309 KiB

Open AccessArticle

GPR Survey on an Iron Mining Area after the Collapse of the Tailings Dam I at the Córrego do Feijão Mine in Brumadinho-MG, Brazil

by Jorge Luís Porsani, Felipe Augusto Nascimento de Jesus and Marcelo Cesar Stangari

Remote Sens. 2019, 11(7), 860; https://doi.org/10.3390/rs11070860 - 10 Apr 2019

Cited by 49 | Viewed by 7843

Abstract

This article shows the interesting results of a pioneer effort by IAG/USP researchers to use ground-penetrating radar (GPR) for humanitarian purposes, guiding the rescue of victims in the tragedy of Brumadinho. The tailings Dam I at the Córrego do Feijão iron ore mine, [...] Read more.

This article shows the interesting results of a pioneer effort by IAG/USP researchers to use ground-penetrating radar (GPR) for humanitarian purposes, guiding the rescue of victims in the tragedy of Brumadinho. The tailings Dam I at the Córrego do Feijão iron ore mine, located in the Brumadinho complex, Minas Gerais State, Brazil, collapsed on 25 January 2019. About 11.7 million m³ of mining mud was spilled from the dam, burying bodies, equipment, structural buildings, buses, and cars along a length of 8.5 km up to the Paraopeba River. Additionally, the contaminated mud traveled more than 300 km along the bed of the Paraopeba River toward the São Francisco River. This work shows the results of a geophysical investigation using the GPR method 17 days after the event. To carry out the geophysical survey, an excavator was used for soil compaction. The data acquisition was performed on the tracks left by the excavator chain using SIR-4000 equipment and antennas of 200 and 270 MHz (GSSI). The GPR studies aimed to map bodies, structural buildings, and equipment buried in the mud. The location of the profiles followed preferably the edge of the slope due to the higher probability of finding buried bodies and objects. The GPR results allowed the detection of subsoil structures, such as concentrations of iron ore and accumulations of sand from the dam filter. The GPR was effective because the iron ore sludge in the mixing process became porous and the pores were filled with air, which provided penetration and reflection of the GPR electromagnetic waves up to a depth of 3.5 m. The results were surprising. Although no bodies or underground equipment were found, the results of this research served to eliminate the studied areas from future excavations, thus redirecting the rescue teams and optimizing the search process. These important results can serve as an additional motivation for the use of GPR in future humanitarian work in areas of tragedies. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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24 pages, 4320 KiB

Open AccessArticle

Accounting for Surface Roughness Scattering in the Characterization of Forest Litter with Ground-Penetrating Radar

by Frédéric André, François Jonard, Mathieu Jonard, Harry Vereecken and Sébastien Lambot

Remote Sens. 2019, 11(7), 828; https://doi.org/10.3390/rs11070828 - 7 Apr 2019

Cited by 7 | Viewed by 4274

Abstract

Accurate characterization of forest litter is of high interest for land surface modeling and for interpreting remote sensing observations over forested areas. Due to the large spatial heterogeneity of forest litter, scattering from litter layers has to be considered when sensed using microwave [...] Read more.

Accurate characterization of forest litter is of high interest for land surface modeling and for interpreting remote sensing observations over forested areas. Due to the large spatial heterogeneity of forest litter, scattering from litter layers has to be considered when sensed using microwave techniques. Here, we apply a full-waveform radar model combined with a surface roughness model to ultrawideband ground-penetrating radar (GPR) data acquired above forest litter during controlled and in situ experiments. For both experiments, the proposed modeling approach successfully described the radar data, with improvements compared to a previous study in which roughness was not directly accounted for. Inversion of the GPR data also provided reliable estimates of the relative dielectric permittivity of the recently fallen litter (OL layer) and of the fragmented litter in partial decomposition (OF layer) with, respectively, averaged values of 1.35 and 3.8 for the controlled experiment and of 3.9 and 7.5 for the in situ experiment. These results show the promising potentialities of GPR for efficient and non-invasive characterization of forest organic layers. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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19 pages, 15858 KiB

Open AccessArticle

Rock Location and Quantitative Analysis of Regolith at the Chang’e 3 Landing Site Based on Local Similarity Constraint

by Bin Hu, Deli Wang, Ling Zhang and Zhaofa Zeng

Remote Sens. 2019, 11(5), 530; https://doi.org/10.3390/rs11050530 - 5 Mar 2019

Cited by 21 | Viewed by 3868

Abstract

Structural analysis of lunar regolith not only provides important information about lunar geology but also provides a reference for future lunar sample return missions. The Lunar Penetrating Radar (LPR) onboard China’s Chang’E-3 (CE-3) provides a unique opportunity for mapping the subsurface structure and [...] Read more.

Structural analysis of lunar regolith not only provides important information about lunar geology but also provides a reference for future lunar sample return missions. The Lunar Penetrating Radar (LPR) onboard China’s Chang’E-3 (CE-3) provides a unique opportunity for mapping the subsurface structure and the near-surface stratigraphic structure of the regolith. The problem of rock positioning and regolith-basement interface highlighting is meaningful. In this paper, we propose an adaptive rock extraction method based on local similarity constraints to achieve the rock location and quantitative analysis for regolith. Firstly, a processing pipeline is designed to image the LPR CH-2 A and B data. Secondly, we adopt an f-x EMD (empirical mode decomposition)-based dip filter to extract low-wavenumber components in the two data. Then, we calculate the local similarity spectrum between the filtered CH-2 A and B. After a soft threshold function, we pick the local maximums in the spectrum as the location of each rock. Finally, according to the extracted result, on the one hand, the depth of regolith is obtained, and on the other hand, the distribution information of the rocks in regolith, which changes with the path and the depth, is also revealed. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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19 pages, 27693 KiB

Open AccessArticle

Particle Center Supported Plane for Subsurface Target Classification based on Full Polarimetric Ground Penetrating Radar

by Xuan Feng, Haoqiu Zhou, Cai Liu, Yan Zhang, Wenjing Liang, Enhedelihai Nilot, Minghe Zhang and Zejun Dong

Remote Sens. 2019, 11(4), 405; https://doi.org/10.3390/rs11040405 - 17 Feb 2019

Cited by 13 | Viewed by 3733

Abstract

The subsurface target classification of ground penetrating radar (GPR) is a popular topic in the field of geophysics. Among the existing classification methods, geometrical features and polarimetric attributes of targets are primarily used. As polarimetric attributes contain more information of targets, polarimetric decomposition [...] Read more.

The subsurface target classification of ground penetrating radar (GPR) is a popular topic in the field of geophysics. Among the existing classification methods, geometrical features and polarimetric attributes of targets are primarily used. As polarimetric attributes contain more information of targets, polarimetric decomposition methods, such as H-Alpha decomposition, have been developed for target classification of GPR in recent years. However, the classification template used in H-Alpha classification is preset depending on the experience of synthetic aperture radar (SAR); therefore, it may not be suitable for GPR. Moreover, many existing classification methods require excessive human operation, particularly when outliers exist in the sample (the data set containing the features of targets); therefore, they are not efficient or intelligent. We herein propose a new machine learning method based on sample centers, i.e., particle center supported plane (PCSP). The sample center is defined as the point with the smallest sum of distances from all points in the same sample, which is considered as a better representation of the sample without significant effect of the outliers. In this proposed method, particle swarm optimization (PSO) is performed to obtain the sample centers; the new criterion for subsurface target classification is achieved. We applied this algorithm to full polarimetric GPR data measured in the laboratory and outdoors. The results indicate that, comparing with support vector machine (SVM) and classical H-Alpha classification, this new method is more efficient and the accuracy is relatively high. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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13 pages, 1307 KiB

Open AccessArticle

Nonintrusive Depth Estimation of Buried Radioactive Wastes Using Ground Penetrating Radar and a Gamma Ray Detector

by Ikechukwu K. Ukaegbu, Kelum A. A. Gamage and Michael D. Aspinall

Remote Sens. 2019, 11(2), 141; https://doi.org/10.3390/rs11020141 - 12 Jan 2019

Cited by 11 | Viewed by 5018

Abstract

This study reports on the combination of data from a ground penetrating radar (GPR) and a gamma ray detector for nonintrusive depth estimation of buried radioactive sources. The use of the GPR was to enable the estimation of the material density required for [...] Read more.

This study reports on the combination of data from a ground penetrating radar (GPR) and a gamma ray detector for nonintrusive depth estimation of buried radioactive sources. The use of the GPR was to enable the estimation of the material density required for the calculation of the depth of the source from the radiation data. Four different models for bulk density estimation were analysed using three materials, namely: sand, gravel and soil. The results showed that the GPR was able to estimate the bulk density of the three materials with an average error of 4.5%. The density estimates were then used together with gamma ray measurements to successfully estimate the depth of a 658 kBq ceasium-137 radioactive source buried in each of the three materials investigated. However, a linear correction factor needs to be applied to the depth estimates due to the deviation of the estimated depth from the measured depth as the depth increases. This new application of GPR will further extend the possible fields of application of this ubiquitous geophysical tool. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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24 pages, 12117 KiB

Open AccessArticle

Underground Object Classification for Urban Roads Using Instantaneous Phase Analysis of Ground-Penetrating Radar (GPR) Data

by Byeongjin Park, Jeongguk Kim, Jaesun Lee, Man-Sung Kang and Yun-Kyu An

Remote Sens. 2018, 10(9), 1417; https://doi.org/10.3390/rs10091417 - 6 Sep 2018

Cited by 52 | Viewed by 10032

Abstract

Ground-penetrating radar (GPR) has been widely used to detect subsurface objects, such as hidden cavities, buried pipes, and manholes, owing to its noncontact sensing, rapid scanning, and deeply penetrating remote-sensing capabilities. Currently, GPR data interpretation depends heavily on the experience of well-trained experts [...] Read more.

Ground-penetrating radar (GPR) has been widely used to detect subsurface objects, such as hidden cavities, buried pipes, and manholes, owing to its noncontact sensing, rapid scanning, and deeply penetrating remote-sensing capabilities. Currently, GPR data interpretation depends heavily on the experience of well-trained experts because different types of underground objects often generate similar GPR reflection features. Moreover, reflection visualizations that were obtained from field GPR data for urban roads are often weak and noisy. This study proposes a novel instantaneous phase analysis technique to address these issues. The proposed technique aims to enhance the visibility of underground objects and provide objective criteria for GPR data interpretation so that the objects can be automatically classified without expert intervention. The feasibility of the proposed technique is validated both numerically and experimentally. The field test utilizes rarely available GPR data for urban roads in Seoul, South Korea and demonstrates that the technique allows for successful visualization and classification of three different types of underground objects. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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16 pages, 6640 KiB

Open AccessArticle

A Microwave Tomography Strategy for Underwater Imaging via Ground Penetrating Radar

by Giovanni Ludeno, Luigi Capozzoli, Enzo Rizzo, Francesco Soldovieri and Ilaria Catapano

Remote Sens. 2018, 10(9), 1410; https://doi.org/10.3390/rs10091410 - 5 Sep 2018

Cited by 18 | Viewed by 4751

Abstract

Detection and monitoring of underwater structures is one of the most challenging applicative scenarios for remote sensing diagnostic techniques, among which ground penetrating radar (GPR). With this aim, an imaging strategy belonging to the family of microwave tomographic approaches is proposed herein. This [...] Read more.

Detection and monitoring of underwater structures is one of the most challenging applicative scenarios for remote sensing diagnostic techniques, among which ground penetrating radar (GPR). With this aim, an imaging strategy belonging to the family of microwave tomographic approaches is proposed herein. This strategy allows the imaging of objects located into a wet sand medium below a freshwater layer and it can find application in investigation of lakes, rivers, and hydraulic structures. The proposed strategy accounts for the layered structure of the scenario under test by exploiting a spatially variable equivalent permittivity in the inverse scattering model. This allows a reliable reconstruction of depth and horizontal size of underwater hidden objects. The imaging capabilities of the strategy are verified by processing experimental data referred to a laboratory environment reproducing a submerged archeological site at scale 1:1. The results are compared with those obtained by modelling the reference scenario as a homogeneous medium, in order to verify the effective improvement in terms of reconstruction accuracy. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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15 pages, 12751 KiB

Open AccessLetter

Application of Laplace Domain Waveform Inversion to Cross-Hole Radar Data

by Xu Meng, Sixin Liu, Yi Xu and Lei Fu

Remote Sens. 2019, 11(16), 1839; https://doi.org/10.3390/rs11161839 - 7 Aug 2019

Cited by 7 | Viewed by 3371

Abstract

Full waveform inversion (FWI) can yield high resolution images and has been applied in Ground Penetrating Radar (GPR) for around 20 years. However, appropriate selection of the initial models is important in FWI because such an inversion is highly nonlinear. The conventional way [...] Read more.

Full waveform inversion (FWI) can yield high resolution images and has been applied in Ground Penetrating Radar (GPR) for around 20 years. However, appropriate selection of the initial models is important in FWI because such an inversion is highly nonlinear. The conventional way to obtain the initial models for GPR FWI is ray-based tomogram inversion which suffers from several inherent shortcomings. In this paper, we develop a Laplace domain waveform inversion to obtain initial models for the time domain FWI. The gradient expression of the Laplace domain waveform inversion is deduced via the derivation of a logarithmic object function. Permittivity and conductivity are updated by using the conjugate gradient method. Using synthetic examples, we found that the value of the damping constant in the inversion cannot be too large or too small compared to the dominant frequency of the radar data. The synthetic examples demonstrate that the Laplace domain waveform inversion provide slightly better initial models for the time domain FWI than the ray-based inversion. Finally, we successfully applied the algorithm to one field data set, and the inverted results of the Laplace-based FWI show more details than that of the ray-based FWI. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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17 pages, 11310 KiB

Open AccessTechnical Note

A posteriori GPR Evaluation of Tree Stability: A Case Study in Rome (Italy)

by Pier Matteo Barone and Carlotta Ferrara

Remote Sens. 2019, 11(11), 1301; https://doi.org/10.3390/rs11111301 - 31 May 2019

Cited by 4 | Viewed by 3901

Abstract

Following the frequent and harmful collapses of trees that have plagued the municipal territory of Rome in recent years, a protocol of understanding was initiated between the Department of Environmental Protection of ROMA CAPITALE, the American University of Rome, the Research Centre for [...] Read more.

Following the frequent and harmful collapses of trees that have plagued the municipal territory of Rome in recent years, a protocol of understanding was initiated between the Department of Environmental Protection of ROMA CAPITALE, the American University of Rome, the Research Centre for Forestry and Wood of the– Council for Agricultural Research and Economics (CREA)–, and Sensors and Software, Inc. This protocol aims to start an experimental project by conducting a series of non-destructive geophysical measurements using ground-penetrating radar (GPR) technology and assessing the effectiveness of this methodology to investigate the root system and tree trunks located along paved roads in two sample areas of the city. The test will use the GPR technique to confirm some hypothetical assumptions about tree stability based on a posteriori evaluations made by the Department of Environmental Protection of ROMA CAPITALE. All phases of this test showed the effectiveness of the method and the rapidity of the data acquisition. Full article

(This article belongs to the Special Issue Recent Progress in Ground Penetrating Radar Remote Sensing)

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