GI5.4 | Ground Penetrating Radar and other geophysical techniques: Applications and Advancements

GI5.4

Ground Penetrating Radar and other geophysical techniques: Applications and Advancements
Co-organized by EMRP2/SSP1
Convener: Raffaele Persico | Co-conveners: Salvatore Piro, Martina BevacquaECSECS, Valentina SchenoneECSECS, Ilaria Catapano, Vincenzo Lapenna, Jean Dumoulin
Orals
| Mon, 24 Apr, 08:30–10:15 (CEST)
 
Room 0.51
Posters on site
| Attendance Mon, 24 Apr, 14:00–15:45 (CEST)
 
Hall X4
Posters virtual
| Attendance Mon, 24 Apr, 14:00–15:45 (CEST)
 
vHall ESSI/GI/NP
Orals |
Mon, 08:30
Mon, 14:00
Mon, 14:00
Ground penetrating radar and geophysical applications have been and are evolving thanks to the increasing need of environmental control and monitoring. The instruments are continuously improving while their price is progressively decreasing too. In particular, geophysical instruments are useful to geologists, archaeologists, engineers, policemen, soldiers, hydro-geophysicists, architects and so on with regard to topic as safety, resilience, cultural heritage and so on. Such a topic deserves, we think, occasions for discussion and exchanging ideas, also at the EGU conference.
The hopefully progressively overcoming of the COVID-19 pandemic encourages to propose a session were new systems, new applications, new data processing can be proposed, together with case histories of meaningful interest for the scientific community.
Consequently, contributions are welcome with regard to all the aspects of the GPR technique, ranging from the hardware of the systems to the data processing and any theoretical aspect, including innovative applications or procedures as well as results of particular relevance, possibly achieved within an integrated measurement campaign founded on a plurality of geophysical techniques.
Hope to see you in Vienna.

Orals: Mon, 24 Apr | Room 0.51

Chairperson: Raffaele Persico
08:30–08:35
08:35–08:55
|
EGU23-9597
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GI5.4
|
solicited
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On-site presentation
James Irving, Chongmin Zhang, Mathieu Gravey, and Grégoire Mariéthoz

3D GPR data, where measurements are acquired along a series of parallel survey lines, offer much potential for gaining important information about complex subsurface environments. Such data are, however, extremely time consuming to collect, and a typical trade-off is that the survey line spacing is set to be significantly larger than the trace spacing along the lines. This introduces a strong resolution bias in the 3D dataset, and spatial aliasing is commonly present in the across-line direction. Although simple interpolation methods may be considered to address this problem, they generally lead to overly smoothed and unrealistic results.

Here, we present a means of overcoming this issue via multiple-point geostatistics (MPS) simulation. Considering that we have a limited number of sparsely distributed 2D GPR profiles to begin with, we reconstruct the densely spaced 3D GPR data set using a series of separate 2D simulations in both the along-line and across-line directions. Training images, which are necessary for the application of MPS, come from the existing GPR profiles. To deal with the discontinuities in 3D spatial structures caused by performing independent 2D simulations, target profiles are selected randomly but simulations are performed alternately in both directions. Test results show that this methodology provides significantly better reconstructions than standard interpolation, in particular as the spacing between the GPR survey lines increases.

How to cite: Irving, J., Zhang, C., Gravey, M., and Mariéthoz, G.: Increasing the sampling density of 3D GPR data using multiple-point geostatistics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9597, https://doi.org/10.5194/egusphere-egu23-9597, 2023.

08:55–09:05
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EGU23-1884
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GI5.4
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ECS
|
On-site presentation
Ianis Gaudot, Matéo Leroy, Adnand Bitri, and François Bretaudeau

It is now established that existing telecom fiber optic cables (FOC) may be used to record interpretable DAS seismic signals at seismological and reservoir scales, but their use at geotechnical scales remains an active topic of research.

In this work, we present a comparison study of DAS surface waves records on a 600 m long FOC containing both tight and loose standard fiber optics spliced between each other. 2x300 m portion of the FOC are deployed next to each other horizontally at 40 cm depth in a shallow trench located along a road. The first 300 m portion of the FOC lays on the bottom of a PVC pipe (gravity coupling), and the second 300 m portion of the FOC is buried in the soil (soil coupling) ; so that a total of 4 couplings is tested along an optical path totalizing 1200 m: (1) gravity coupling on loose fiber optic, (2) soil coupling of loose fiber optic, (3) gravity coupling on tight fiber optic, and (4) soil coupling on tight fiber optic. We performed hammer shots recorded using DAS with 2.4 m, 4 m, 6 and 10 m gauge length. The resulting DAS data are compared to data from standard vertical and horizontal geophones regularly spaced along the line, as well as data from gimbal mounted vertical geophones towed behind a vehicle along the line.

Our results show that gravity coupling on loose fiber optic using gauge length shorter than 5 m gives interpretable surface waves dispersion image up to 50 Hz for the fundamental Rayleigh wave mode, with a quality which is competitive with results from gimbal data. Therefore, our results suggest that the leveraging of existing telecom FOC for low-cost and fast geotechnical characterization is promising.

How to cite: Gaudot, I., Leroy, M., Bitri, A., and Bretaudeau, F.: Comparison of DAS surface waves records at geotechnical scales using telecom fiber optic with different cable and ground coupling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1884, https://doi.org/10.5194/egusphere-egu23-1884, 2023.

09:05–09:15
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EGU23-10974
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GI5.4
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Highlight
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On-site presentation
Annalisa Ghezzi, Antonio Schettino, Alberto Collareta, Claudio Nicola Di Celma, Pietro Paolo Pierantoni, and Luca Tassi

The Ica Desert of southern Peru presents one of the most important marine Lagerstätten worldwide, characterized by excellent preservation and abundance of outcropping vertebrate fossils of whales, sharks, and dolphins. Even more fossils are potentially buried at shallow depth, which could be exposed by excavation and become the focus of new paleontological research. We investigated a small area at the top of Cerro Los Quesos, one of the most rich fossil-bearing localities in the Ica Desert, formed by sub-horizontal layers of diatomaceous sediments belonging to the Pisco Formation. Although most of these sediments are fine-grained, specific geochemical processes that occured in this area determined the formation of several beds of coarse cemented material, populated by large dolomitic nodules and underlain by two characteristic layers: a black manganese oxyde lamina and a thin reddish dolomite enriched in iron oxyde. Most of the fossils outcropping in the Ica Desert appear to be incapsulated in large dolomitic nodules, which can also be detected at shallow depth by ground penetrating radar (GPR) techniques. Here we describe an approach that can be used to identify the presence of fossils using a GPR system, which requires a detailed analysis of radar profiles and traces. In particular, it is shown that a sequence of distinctive reflected wavelets characterizes the bottom of the dolomitic nodules that wrap the skeletons

How to cite: Ghezzi, A., Schettino, A., Collareta, A., Di Celma, C. N., Pierantoni, P. P., and Tassi, L.: Ground Penetrating Radar for the Detection of Vertebrate Fossils: An Example from the Ica Desert Fossil-Lagerstätte, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10974, https://doi.org/10.5194/egusphere-egu23-10974, 2023.

09:15–09:25
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EGU23-14429
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GI5.4
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ECS
|
On-site presentation
Marc Dumont, Itzel Isunza Manrique, Hadrien Michel, Tom Debouny, David Caterina, and Frédéric Nguyen

Ancient metallurgical sites, such as those found in post-industrial cities, present both challenges and opportunities for the development of resilient cities. The legacy of these industries, including mining, smelting, and blast furnace, has left behind vast quantities of residues in the form of unrecorded slag heaps. The challenge of those ancient metallurgical sites is to combine the remediation of the polluted soil while leveraging the valuable resources it contains to support sustainable economic development. This requires a detailed understanding of the structure and composition of the slag heaps in order to safely and effectively extract valuable materials while minimizing environmental impacts.

For decades, the regeneration of past metallurgical sites has relied on extensive drilling surveys and geochemical analysis. However, this approach has proven to be costly, time-consuming, and potentially hazardous for the operators involved. In this context, we present an integrated methodology for characterizing slag heaps using non-invasive geophysics. Developed as part of the NWE-REGENERATIS Interreg project, our approach consists of four main steps: (i) historical studies of the site activities and deposits to identify areas of interest, (ii) electromagnetic induction mapping of the identified areas of interest; (iii) 2D electrical resistivity tomography (ERT) and induced polarization (IP) to image the structure of the slag heap; and (iv) conducting a limited sampling survey to validate the geophysical interpretation and define the bulk composition of the deposit. Our approach is not only less time-consuming and less costly than the traditional method but also safer for the operators.

This study has been applied to a former zinc production site nearby Liège city in Wallonia, Belgium. The application of the NWE-REGENERATIS methodology has allowed the imaging of the 3D structure of the anthropogenic deposits. The combination of ERT and IP measurements has revealed the presence of two types of residues, with the main part of the deposit composed of inert waste, and metallic slag lenses are present on the surface. These insights provide valuable information for assessing the feasibility of urban mining and developing effective regeneration plans for the site. The application of the NWE-REGENERATIS methodology in this study has proven to be a valuable tool for understanding the complexities of ancient metallurgical sites. Our approach is not only less time-consuming and less costly than the traditional method but also safer for the operators.

How to cite: Dumont, M., Isunza Manrique, I., Michel, H., Debouny, T., Caterina, D., and Nguyen, F.: Applied geophysics for regeneration of past metallurgical sites, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14429, https://doi.org/10.5194/egusphere-egu23-14429, 2023.

09:25–09:35
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EGU23-11627
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GI5.4
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On-site presentation
Csongor Gedeon, Gábor Szatmari, Mátyás Árvai, Laura Sherrod, and Janos Meszaros

Endangered burrowing mammals are good indicators of ecosystem quality as they frequently play a crucial role in the functioning of grassland ecosystems, maintaining their diversity, functions, or services. However, the non-destructive estimation of their population size, spatial and temporal population dynamics remains a challenge. The number of burrow openings is a good proxy for estimating actual population sizes if one individual occupies one burrow system and the ratio of openings per burrow system is known. Remote, semi-automated counting of animals’ surface burrows has been successful, and we now focus on detecting subsurface animal burrows. For this purpose, we investigate the applicability of GPR surveys to non-destructively identify and locate artificial burrows of the same size dimensions as burrows of protected ground squirrels.  Based on the results we present an approach to non-invasively map ground squirrel burrows.

A Mala system with 160 and 750MHz antennas was used for the GPR surveys. Artificial burrows (ABs) (5-7cm wide, 1m long) were drilled in the wall of a ditch (depth of 2m, length of 20m). Each burrow location was known and placed between 5 and 160cm depth perpendicular to the direction of the GPR survey. Burrow locations were marked both in the field and radargram. The survey area was a grassland (similar to natural ground squirrel habitats) with short vegetation and even ground surface.

A standard processing of the raw GPR data was used in Reflexw2D, including: compressing original data (deleting every 2nd trace), bandpass filtering, time-zero correction using the automatic correct max phase option, and move-starttime. Processed radargrams were also (fk) migrated and gain adjusted for better display of burrows on images. The last step was the time-depth conversion with constant velocity of 0.1 m/ns. The processing sequence was saved and applied to each raw data file with the same data acquisition parameters.

Preliminary results indicate that although many of ABs can be found through the use of GPR, this method has some drawbacks. Penetration depth was limited to less than 150cms. Since, sousliks dig deeper in the soil, that depth could be one of the limiting factors in mapping entire burrow systems. A general difficulty of locating ABs was that ABs’ reflections were often indistinguishable from unknown subsurface objects despite the prior knowledge of their exact location in the soil. Although reverse polarity of the reflected wave was expected due to the air-filled burrows in the soil, the data did not show this phenomenon clearly. ABs in the upper ~30cm, opposite to ABs deeper, were identifiable more with less plotscale colour intensity.

In summary, while some ABs were detected by GPR, many were not, even though their exact location was known. This experience has indicated a different approach for mapping animal burrows may be necessary. Multiple-point geostatisitcs (MPS) could be a good approach for modelling non-linear burrows. Information about burrows can be obtained from burrow maps used as training images could be combined with GPR data to enable modelling of multiple-point relations and complex zig-zag patterns.

How to cite: Gedeon, C., Szatmari, G., Árvai, M., Sherrod, L., and Meszaros, J.: Preliminary results of the study of using ground-penetrating radar (GPR) as a tool to locate artificial burrows similar to souslik burrows and future directions of mapping burrow systems of sousliks or other burrowing mammals alike, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11627, https://doi.org/10.5194/egusphere-egu23-11627, 2023.

09:35–09:45
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EGU23-17111
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GI5.4
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On-site presentation
Patrizia Capizzi, Raffaele Martorana, Alessandra Carollo, and Alessandro Canzonieri

The archaeological museum of the Giuseppe Whitaker Foundation (Mozia island, Sicily), exhibits the Greek statue of the Auriga, which has been the subject of geophysical investigations to evaluate the degradation of the marble. In particular, a 3D ultrasonic tomography (UST) and some georadar investigations were performed. For the UST 114 measurement points were used, selected on the surface of the statue. The results of the US tomography show an average velocity of the marble equal to about 4700 m/s, which indicates a good mechanical resistance of the marble. There are widespread areas with lower velocity (around 3000 m/s), which however fall within the range of variability of the material. A comparison was made with ultrasound data acquired in January 2012, during a previous diagnostic campaign. Georadar profiles were performed to highlight any internal discontinuity surfaces, which can be interpreted with the presence of fractures and/or lesions. In all the georadar profiles acquired, the internal signal of the material shows a general homogeneity, which allows to exclude the presence of fracturing surfaces and/or internal lesions.

How to cite: Capizzi, P., Martorana, R., Carollo, A., and Canzonieri, A.: GPR and Ultrasonic investigations to study the degradation of the Auriga statue (Mozia island, Sicily), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17111, https://doi.org/10.5194/egusphere-egu23-17111, 2023.

09:45–10:09
10:09–10:15

Posters on site: Mon, 24 Apr, 14:00–15:45 | Hall X4

Chairperson: Salvatore Piro
X4.164
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EGU23-2106
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GI5.4
Raffaele Persico, Gianfranco Morelli, Giuseppe Esposito, and Ilaria Catapano

Commonly exploited migration algorithms or also well-established linear inverse scattering algorithms [1] for the focusing of GPR data are often based on the hypothesis of a homogeneous soil. However, this assumption is not valid always, and it provides deformed results when it is applied to image scenarios where it is not valid. More complex models of the scattering can afford the situation of a stratified medium, but only if the layers are flat and parallel to each other these model assumes analytic forms. In any case, commonly available commercial codes do not allow to implement the reflections and refraction of the waves associated to these cases [2]. More recently, time reverse migration algorithms have been introduced. They can account efficiently of non-homogeneous soils, but their performances in case of large and strong scattering targets are not yet completely established and they make use of forward numerical solvers, not all the times available and user friendly. At the conference, we will describe a strategy based on suitable combination of migration results achieved from different homogeneous media, accompanied by a time-depth conversion accounting for the occurrence of different values of the wave propagation velocity in the investigated domain. We will show how an improvement of the imaging result is achieved even in the lack of a correct mathematical model of the scattering phenomenon. Last but not least, the proposed strategy exploits software routines easy to be implemented.

How to cite: Persico, R., Morelli, G., Esposito, G., and Catapano, I.: Combined migrations and time-depth conversions: first results, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2106, https://doi.org/10.5194/egusphere-egu23-2106, 2023.

X4.165
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EGU23-15344
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GI5.4
Lourdes Farrugia, Raffaele Persico, Andrea Cataldo, Iman Farhat, and Raissa Schiavoni

The use of time domain reflectometry (TDR) techniques for in-situ, non-destructive measurement of water content has revolutionized soil water management and it is a rapidly growing area of interest. Additionally, monitoring other soil parameters such as levels of contaminants in soil is becoming an active field of research due to increasing environmental pollution and thus enforcement of contamination levels from policy makers. As a result, in recent years there have been advancements of TDR probe capability in terms of operating range, proven design, multiplexing and automated data collection. However, there is still a strong need for systems that are user-friendly and low cost which provide for quasi-real time and in situ monitoring with high sensitivity of soil parameters with adequate accuracy.

In this paper, we present a system consisting of a bifilar TDR probe interfaced with a miniaturized Vector network analyser which enabled measurements of the reflection coefficient in the frequency-domain.   The reflection coefficient is then related to soil parameters, such as soil water content and percentage of diesel oil (as an example of soil contaminant) through an innovative numerical procedure that retrieves the Debye parameters of different soil samples under different conditions.

This numerical procedure consisted of two main steps:

Firstly, the accurate modelling of the bifilar TDR probe in CST Microwave Studio such that the model is an accurate representation of the experimental setup used in the laboratory. This model was also validated using well-characterised materials such as Methanol and Prop-2-ol, utilising Debye parameters as published in [1].

Finally, the bifilar probes were immersed in soil samples having different moisture levels (dry up to 30%, in steps of 5%) and contaminated soil with different percentages of diesel oil (0%, 5%, 7.5% and 10%) and the Debye parameters were retrieved using the validated model in the first step.

Results illustrate that there exists a correlation between the retrieved Debye parameters and the moisture levels and percentage of diesel oil in soil. This proves that the Debye parameters provide the necessary information to differentiate between water or contaminant content and thus can be used for monitoring purposes rather than conducting measurements of the dielectric permittivity.

 

References

[1] Gregory, A.P.; Clarke, R.N. Tables of the Complex Permittivity of Dielectric Reference Liquids at Frequencies up to 5 GHz; National Physical Laboratory Report; 2012. Available online: https://eprintspublications.npl.co.uk/2076/ (accessed on 13 September 2022).

How to cite: Farrugia, L., Persico, R., Cataldo, A., Farhat, I., and Schiavoni, R.: Using the Debye parameters of soil for water content and contamination level determination., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15344, https://doi.org/10.5194/egusphere-egu23-15344, 2023.

X4.166
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EGU23-12812
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GI5.4
|
Highlight
Ilaria Catapano, Giovanni Ludeno, Gianluca Persichetti, Romeo Bernini, and Lorenzo Crocco

Effective usage of water resources is a relevant topic to move towards smart and resilient cities, and it demands technologies aimed at monitoring water distribution networks at avoiding wastefulness and assuring environmental safety.

In this frame, research activities designing technological solutions assuring time-constant monitoring and, simultaneously, providing high spatial resolution images from which infer accurate information about the position and extension of the leakage are carried out.

Being this request difficult to be satisfied by means of a single sensor, the pursued idea is the joint and cooperative use of the distributed optical fiber sensor based on the Brillouin scattering phenomenon [1] and the microwave tomography (MWT) enhanced ground penetrating radar (GPR) [2]. The first technology, if integral to the pipe, is able to detect temperature and/or thermal conductivity variations occurring in the soil hosting the pipe and due to water leakages. Therefore, it appears suitable to assure continuous monitoring and to provide low spatial resolution information about leakage detection. Conversely, GPR allows on-demand non-invasive surveys providing high spatial resolution images of the investigated scenario, if the collected raw data are processed properly. An effective way to do it is the use of MWT approaches, which face GPR imaging as an inverse scattering problem [3].

In order to provide a proof of concept assessing the benefits and limits of the cooperative use of the above technologies, a joint experimentation was carried out. Specifically, an ad-hoc experimental scenario allowing to reproduce a water leakage was built. The scenario is a scaled reproduction of a realistic test case and a plastic pipe filled with fresh water and buried in a river-sand terrain makes it up. The optical fiber sensor was buried in the sand few cm underneath the pipe, while GPR data were collected along and across directions with respect to the pipe.

The achieved results confirmed the expected potentialities and encourage going on this activity.

A detailed presentation of the experimental setup and the achieved results will be provided at the conference.

Acknowledgment: The authors would like to thank the SMART WATERTECH project “Smart Community per lo Sviluppo e l’Applicazione di Tecnologie di Monitoraggio e Sistemi di Controllo Innovativi per il Servizio Idrico Integrato” by which the present work has been financed.

 

[1] Bernini R., Minardo A., Zeni L. (2004) Accuracy enhancement in Brillouin distributed fiber-optic temperature sensors using signal processing techniques, IEEE Photonics Technology Letters 16 (4), pp. 1143-1145.

[2] Catapano, I., Gennarelli, G., Ludeno, G., Persico, R., Soldovieri, F. (2019). Ground Penetrating Radar: Operation Principles and Data, Wiley Encyclopedia of Electrical and Electronics Engineering.

[3] Catapano, I., Palmeri, R., Soldovieri, F., Crocco, L. (2022). GPR Water Pipe Monitoring and Leaks Characterization: A Differential Microwave Tomography Approach. In: Di Mauro, A., Scozzari, A., Soldovieri, F. (eds) Instrumentation and Measurement Technologies for Water Cycle Management. Springer Water. Springer, Cham.

How to cite: Catapano, I., Ludeno, G., Persichetti, G., Bernini, R., and Crocco, L.: Water pipe monitoring via fiber optical sensor and ground penetrating radar: a joint laboratory experiment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12812, https://doi.org/10.5194/egusphere-egu23-12812, 2023.

X4.167
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EGU23-12688
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GI5.4
Francesco Soldovieri, Gianluca Gennarelli, Giovanni Ludeno, Giuseppe Esposito, and Ilaria Catapano

Nowadays, Ground Penetrating Radar (GPR) systems working in contactless way deserve huge attention because, if mounted onboard of moving platforms like terrestrial and aerial vehicles, they allow the collection of a large amount of data, while keeping low complexity and time of the measurement step [1,2]. At the same time, multiple input multiple output (MIMO) GPR systems are worth being exploited because, being capable of gathering multiview and multistatic data, they allow an improvement of the reconstruction capabilities [3, 4]. However, the effective use of a contactless MIMO GPR requires the availability of properly designed data processing strategies able to manage the information acquired by this kind of systems and to provide an accurate reconstruction of the scenario under test.

This contribute proposes a microwave tomographic approach, which faces the GPR imaging as a linear inverse scattering problem and it is suitable to process contactless multi-view and multi-static data. The approach is referred to the 2D scalar case, exploits a ray-based model of the scattering phenomenon, and accounts for the presence of the air-soil interface. Specifically, the approach extends to the case of MIMO systems the concept of the Interface Reflection Point (IPR) previously exploited to process contactless data gathered by means of a multi-monostatic GPR [2,5].

At the conference, the approach formulation will be described in detail and results referred to virtual experiments will be provided in order to state the achievable imaging capabilities.

[1] Miccinesi, L., Beni, A., & Pieraccini, M. (2022). UAS-Borne Radar for Remote Sensing: A Review. Electronics, 11(20), 3324.

[2] Catapano, G. Gennarelli, G. Ludeno, C. Noviello, G. Esposito, and F. Soldovieri, "Contactless ground penetrating radar imaging: state of the art, challenges, and microwave tomography-based data processing," IEEE Geosci. Rem. Sens. Mag., vol. 10, no. 1, pp. 251-273, 2022.

[3] García-Fernández, M., López, Y. Á., & Andrés, F. L. H. (2020). Airborne multi-channel ground penetrating radar for improvised explosive devices and landmine detection. IEEE Access, 8, 165927-165943.

[4] Leone, G., & Soldovieri, F. (2003). Analysis of the distorted Born approximation for subsurface reconstruction: Truncation and uncertainties effects. IEEE Transactions on geoscience and remote sensing, 41(1), 66-74.

[5] Catapano, L. Crocco, Y. Krellmann, G. Triltzsch, and F. Soldovieri, “Tomographic airborne ground penetrating radar imaging: achievable spatial resolution and on-field assessment,”, ISPRS J. Photogram. Remote Sens., vol. 92, pp. 69–78, June 2014.

How to cite: Soldovieri, F., Gennarelli, G., Ludeno, G., Esposito, G., and Catapano, I.: A microwave tomographic approach for contactless Multiple Input Multiple Output GPR systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12688, https://doi.org/10.5194/egusphere-egu23-12688, 2023.

X4.168
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EGU23-12013
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GI5.4
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ECS
Tom Debouny, David Caterina, and Frédéric Nguyen

Over time, urbanized areas have undergone continuous development and growth as they adapt to the changing needs of their residents. This has often involved the construction of new buildings, roads, and infrastructures, as well as the renovation and expansion of existing structures. Subsurface characterization is thus a crucial aspect of urban development, as it is essential for the planning, construction and monitoring of new or existing infrastructures. Urbanized environments may be challenging for conventional subsurface characterization methods such as drilling or excavation due to difficulty of access or the presence of buried networks that are not always properly mapped. Geophysical methods can be seen as an interesting alternative to these traditional characterization approaches but require to be adapted to work properly in such environment. This led to the development of the urban geophysics discipline.

Among the different geophysical methods available, Electrical resistivity tomography (ERT) appears as a useful and robust tool for studying subsurface materials and structures in urban environments. It has already been used to investigate underground utilities such as tunnels, cellars, pipes, tank storages and building foundations as well as natural structures. While ERT minimizes site disturbance, the use of fully non-invasive electrodes is sometimes required for the preservation of investigated sites. The best example remains the investigation of archeological structures. For that purpose, a diversity of non-invasive electrodes such as flat electrodes, bentonite mud or conductive gel has already been used overtime for different purposes but showed different outcomes in terms of contact resistance, measurement uncertainty, durability or signal to noise ratio. To our knowledge, few systematic comparison has been done between the different types of non-invasive electrodes and their impact in terms of imaging/monitoring in specific conditions for urban applications.

The present study proposes an assessment of the use of different non-conventional electrodes on various surfaces often encountered in urban environments at controlled lab-scale. The tested electrodes can be divided into two main categories, the electrolytic and the weight electrodes. The analysis focuses on contact resistance, electrical current transmission, noise measurements, strength and stability of the signal over time. The ease and time of deployment are also taken into account for future uses in larger scale fieldworks. Based on preliminary results, the electrodes based on electrolytic contact demonstrate better performances in highly resistive environments, where a better grounding resistance can globally be achieved compared to weight-based electrodes. However, their implementation are more fastidious slowing the acquisition.

How to cite: Debouny, T., Caterina, D., and Nguyen, F.: Benchmark of multiple non-invasive electrodes for a relevant use in urban environments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12013, https://doi.org/10.5194/egusphere-egu23-12013, 2023.

X4.169
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EGU23-14562
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GI5.4
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Highlight
Jean Dumoulin, Alexis Renier-Robin, Diego Reale, Thibaud Toullier, Simona Verde, and Francesco Soldovieri

After the collapse of the Genoa Bridge in August 2018, a renewed interest in permanent monitoring of the structural behavior of civil infrastructures [2] was observed. Such monitoring has to encompass the need to survey a very large number of structures that reach critical age but also new structures. In addition, recent technological advances have helped to make the installation and operation of continuous monitoring systems more practical and economical. In parallel, monitoring approaches based on the use of data acquired by satellite Synthetic Aperture Radar (SAR) may complete and enlarge the observation scale of such ground based monitoring systems, to enhance Structural Health Monitoring (SHM) performances.

Monitoring of civil structures is frequently based on vibration analysis. Anyway, one limitation to the use of SHM algorithms based on modal parameter analysis is its sensitivity to environmental effects and not to damage. Among them, the subsidence around and at structure’s foundation level is a factor that has a great influence on natural frequencies.

In this study, we address quasi-periodic monitoring and subsidence characterization using surface deformation measurements achieved through the Differential Interferometric SAR (DInSAR) technology [1]. Peculiarities of DInSAR have to be taken into account with reference to the application to structures monitoring:

  • Robustness of estimated ground deformation obtained throught the combination of the Line-of-sight (LOS) deformation measurements carried out by the processing of complementary ascending and descending orbits data, for which the measurements points and date of acquisition could be different;
  • Sparse, or absence of, measurements points on some areas induced by strong decorrelation phenomena;
  • Limited range of the actual structure deformation that could reach the accuracy of the DInSAR technology.

Bibliographic study showed that it could be difficult to exploit the DInSAR data directly for the SHM because of the problems mentioned above. The proposed procedure aims at reconstructing the deformations over an area of interest using a regularly spaced grid whose deformations would be interpolated on the available sparse measurements dataset. The interpolation is carried out on each orbit trajectory and for each acquisition date. This allows both to:

  • Estimate measurements point on the same, possibly regular, grid for different orbits;
  • Estimate deformation in areas lacking of measurement points;

Inspired from research works of Chen et al. [3] we implemented and studied a neural network (NN) kriging based interpolation (introducing the spatial dimension inside the NN). It allows the modelisation of the points correlation (variograms) directly from the data instead of predefined functions.

An overview of the studied method and developed software applied on 2 use-cases will be presented and analysed. Perspectives towards improvements of such approach will be also discussed.

References

[1] Antonio Pepe and Fabiana Calò. “A Review of Interferometric Synthetic Aperture RADAR (InSAR) Multi-Track Approaches for the Retrieval of Earth’s Surface Displacements”. In: Applied Sciences 7.12 (2017). doi: 10.3390/app7121264. 

[2] Riccardo Lanari et al. “Comment on “Pre-Collapse Space Geodetic Observations of Critical Infrastructure: The Morandi Bridge, Genoa, Italy” by Milillo et al. (2019)”. In: Remote Sensing 12.24 (2020). doi:10.3390/rs12244011.

[3] Wanfang Chen et al. “DeepKriging: Spatially Dependent Deep Neural Networks for Spatial Prediction”. In: arXiv:2007.11972 (May 23, 2022).

How to cite: Dumoulin, J., Renier-Robin, A., Reale, D., Toullier, T., Verde, S., and Soldovieri, F.: Feasibility study of Neural Networks interpolation applied to Synthetic Aperture Radar Deformations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14562, https://doi.org/10.5194/egusphere-egu23-14562, 2023.

Posters virtual: Mon, 24 Apr, 14:00–15:45 | vHall ESSI/GI/NP

Chairperson: Vincenzo Lapenna
vEGN.18
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EGU23-5339
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GI5.4
Alessandro Fedeli, Valentina Schenone, Matteo Pastorino, and Andrea Randazzo

The inspection of underground scenarios is a challenging task required in several applications, from geophysical to archeological and civil areas. The ground penetrating radar (GPR) is a common tool that has been widely adopted to provide qualitative imaging of the underground scenario [1]. Recently, several approaches to process GPR data and retrieve quantitative images to characterize the inspected region have been developed [2-3]. Moreover, to compensate for the loss of information that usually happens in this scenario, GPR systems have been implemented not only in monostatic and bistatic configurations but also in multistatic settings [4].

In this contribution, a quantitative inverse scattering approach is proposed to retrieve the distribution of the complex dielectric permittivity of a buried region, starting from scattering parameters collected through a multistatic GPR configuration. The approach is based on a finite-element (FE) formulation of the electromagnetic inverse scattering problem and, as solving procedure, a reconstruction method in variable exponent Lebesgue spaces is adopted [5]. On the one hand, the FE model embedded in the method is exploited to describe the structure of the measurement configuration without simplifying assumptions (except for the two-dimensional hypotheses and the numerical discretization of the problem). On the other hand, the inversion procedure in variable exponent Lebesgue spaces has been found quite effective to face the ill-posedness and nonlinearity of the problem. A numerical validation of this approach is reported.

 

References

[1] R. Persico, “Introduction to ground penetrating radar: Inverse scattering and data processing.” Hoboken, New Jersey: Wiley, 2014.

[2] M. Pastorino and A. Randazzo, “Microwave imaging methods and applications.” Boston, MA: Artech House, 2018.

[3] V. Schenone, A. Fedeli, C. Estatico, M. Pastorino, and A. Randazzo, “Experimental assessment of a novel hybrid scheme for quantitative GPR imaging”, IEEE Geoscience and Remote Sensing Letters, vol. 19, pp. 1–5, 2022.

[4] M. Ambrosanio, M. T. Bevacqua, T. Isernia, and V. Pascazio, “Performance analysis of tomographic methods against experimental contactless multistatic ground penetrating radar”, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 14, pp. 1171–1183, 2021.

[5] V. Schenone, C. Estatico, G. L. Gragnani, M. Pastorino, A. Randazzo, and A. Fedeli, “Microwave-based subsurface characterization through a combined finite element and variable exponent spaces technique”, Sensors, vol. 23, no. 1, p. 167, 2023.

How to cite: Fedeli, A., Schenone, V., Pastorino, M., and Randazzo, A.: Quantitative inverse scattering analysis for ground penetrating radar imaging, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5339, https://doi.org/10.5194/egusphere-egu23-5339, 2023.

vEGN.19
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EGU23-14265
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GI5.4
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Salvatore Piro, Daniela Zamuner, Daniele Verrecchia, and Tommaso Leti Messina

Important research and technical issues are related to the prospection in urban area to locate subsurface cavities and/or archaeological remains and to produce hazard mapping. In many cases, cavities, voids and collapses represent disruptions to the geometry of an originally near-horizontal layered system. Geophysical techniques can be employed to identify the feature geometries by contrasts in the physical properties, but can be strongly conditioned by cultural features that interfere with instrument measurements (utilities, structures, surficial debris).

The most promising non-destructive geophysical prospection method for use in urban area is GPR. GPR measurements are less affected by the presence of metallic structures compared to magnetometer prospection and they result in the largest amount of data of all commonly employed near-surface geophysical methods, providing detailed three-dimensional information about the subsurface [1], [4]. In thist paper the surveys made with GPR to investigate different sites in the area of S. Giovanni in Laterano and Santa Croce in Gerusalemme in Rome, as part of the ERC funded Rome Transformed project (2019-2024) are presented and discussed. The aim of the GPR survey is to identify Roman and high-medieval age remains which could enhance understanding of the ancient topography and the urban evolution of the study area.

For the surveys a GPR SIR3000 (GSSI), equipped with a 400 MHz (GSSI) bistatic antenna with constant offset, a 70 MHz (Subecho Radar) monostatic antenna and a SIR4000 system equipped with dual frequency antenna with 300/800 MHz were employed.

All the GPR profiles were processed with GPR-SLICE v7.0 Ground Penetrating Radar Imaging Software. The basic radargram signal processing steps included: (i) post processing pulse regaining; (ii) DC drift removal; (iii) data resampling; (iv) band pass filtering; (v) background filter and (vi) migration. With the aim of obtaining a planimetric vision of all possible anomalous bodies, the time-slice representation technique was applied using all processed profiles up to a depth of about 2.5 m, [2], [3]. Ground Penetrating Radar (GPR) survey at the selected areas has produced significant and fruitful results that will be discussed during the presentation.

 

References

1 - I. Trinks, P. Karlsson, A. Biwall and A. Hinterlaitner, Mapping the urban subsoil using ground penetrating radar – challenges and potentials for archaeological prospection, ArchaeoScience, revue d’archeometrié, 2009, suppl. 33,  pp. 237-240.

2 - D. Goodman and S. Piro, GPR Remote sensing in Archaeology, 2013, Springer (Ed), ISBN 978-3-642-31856-6, ISBN 978-3-642-31857-3 (eBook), DOI 10.1007/978-3-642-31857-3. Springer, Berlin, (Germany).

3 - S. Piro S. and D. Goodman, Integrated GPR data processing for archaeological surveys in urban area. The case of Forum (Roma, Italy), 2008, 12th International Conference on Ground Penetrating Radar, June 16-19, 2008, Birmingham, UK. Proceedings Extanded Abstract Volume.

4 - Piro S., Zamuner D., 2016. Investigating the urban archaeological sites using Ground Penetrating Radar. The cases of Palatino Hill and St John Lateran Basilica (Roma, Italy). Acta IMEKO, Vol. 5, issue 2, pp 80-85. ISSN: 2221-870X. DOI: 10.21014/acta imeko/v5i2.234 .

 

How to cite: Piro, S., Zamuner, D., Verrecchia, D., and Leti Messina, T.: Employment of multiple GPR surveys in urban area, as part of the ERC Rome Transformed project., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14265, https://doi.org/10.5194/egusphere-egu23-14265, 2023.