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118 results on '"Lambot, Sebastien"'

5. Digital Soil Mapping Using Drone-Borne Ground-Penetrating Radar

Author

Wu, Kaijun, Lambot, Sébastien, Kostianoy, Andrey, Series Editor, Carpenter, Angela, Editorial Board Member, Younos, Tamim, Editorial Board Member, Scozzari, Andrea, Editorial Board Member, Vignudelli, Stefano, Editorial Board Member, Kouraev, Alexei, Editorial Board Member, Di Mauro, Anna, editor, and Soldovieri, Francesco, editor

Published
2022
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12. Prediction of Antenna Reflection Coefficient in Presence of Multilayer Media: A Fast Spectral Domain Approach

Author

Roohi, Ramin, Attari, Amir Reza, Majedi, Mohammad Saeed, and Lambot, Sebastien

Abstract

Asphalt thickness estimation using ground-penetrating radar (GPR) is an important application in transportation infrastructure inspections. Thin asphalt measurement needs to use super-resolution or full-wave methods to process the GPR signals with overlapped echoes. We propose a model for antenna reflection coefficient in the presence of multilayer medium by omitting considerations of evanescent waves and interactions between the antenna and the medium. We formulated it within the spectral domain, enabling the explicit incorporation of the antenna’s radiation pattern. This model is about 100 times faster than the existing full-wave models. In this model, we calculate the plane wave expansion (PWE) of the antenna radiated field. Ignoring the evanescent waves, the PWE of the radiated field is calculated from the far-field pattern of the antenna. Simulation and measurement results confirm the validity and effectiveness of this model in asphalt thickness measurement.

Published
2024
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20. Ground-penetrating radar for observing tree trunks and other cylindrical objects

Author

Jezova, Jana, Mertens, Laurence, and Lambot, Sebastien

Subjects
Non-destructive testing -- Analysis, Ground penetrating radar -- Destruction -- Analysis, Forest management -- Analysis, Business, Construction and materials industries
Abstract

ABSTRACT To improve forest management and to prevent collapses of trees, it is necessary to investigate the internal part of tree trunks. In order to do it non-invasively, ground-penetrating radar [...]

Published
2016
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28. Filtering soil surface and antenna effects from GPR data to enhance landmine detection

Author

Lopera, Olga, Slob, Evert C., Milisavljevic, Nada, and Lambot, Sebastien

Subjects
Antennas (Electronics) -- Analysis, Ground penetrating radar -- Analysis, Business, Earth sciences, Electronics and electrical industries
Abstract

The detection of antipersonnel landmines using ground-penetrating radar (GPR) is particularly hindered by the predominant soil surface and antenna reflections. In this paper, we propose a novel approach to filter out these effects from 2-D off-ground monostatic GPR data by adapting and combining the radar antenna subsurface model of Lambot et al. with phase-shift migration. First, the antenna multiple reflections originating from the antenna itself and from the interaction between the antenna and the ground are removed using linear transfer functions. Second, a simulated Green's function accounting for the surface reflection is subtracted. The Green's function is derived from the estimated soil surface dielectric permittivity using full-wave inversion of the radar signal for a measurement taken in a local landmine-free area. Third, off-ground phase-shift migration is performed on the 2-D data to filter the effect of the antenna radiation pattern. We validate the approach in laboratory conditions for four differently detectable landmines embedded in a sandy soil. Compared to traditional background subtraction, this new filtering method permits a better differentiation of the landmine and estimation of its depth and geometrical properties. This is particularly beneficial for the detection of landmines in low-contrast conditions. Index Terms--Clutter reduction, ground-penetrating radar (GPR), inverse modeling, landmine detection, phase-shift migration.

Published
2007

30. Modeling of ground-penetrating radar for accurate characterization of subsurface electric properties

Author

Lambot, Sebastien, Slob, Evert C., van den Bosch, Idesbald, Stockbroeckx, Benoit, and Vanclooster, Marnik

Subjects
Ground penetrating radar -- Usage, Business, Earth sciences, Electronics and electrical industries
Abstract

The possibility to estimate accurately the subsurface electric properties from ground-penetrating radar (GPR) signals using inverse modeling is obstructed by the appropriateness of the forward model describing the GPR subsurface system. In this paper, we improved the recently developed approach of Lambot et aL whose success relies on a stepped-frequency continuous-wave (SFCW) radar combined with an off-ground monostatic transverse electromagnetic horn antenna. This radar configuration enables realistic and efficient forward modeling. We included in the initial model: 1) the multiple reflections occurring between the antenna and the soil surface using a positive feedback loop in the antenna block diagram and 2) the frequency dependence of the electric properties using a local linear approximation of the Debye model. The model was validated in laboratory conditions on a tank filled with a two-layered sand subject to different water contents. Results showed remarkable agreement between the measured and modeled Green's functions. Model inversion for the dielectric permittivity further demonstrated the accuracy of the method. Inversion for the electric conductivity led to less satisfactory results. However, a sensitivity analysis demonstrated the good stability properties of the inverse solution and put forward the necessity to reduce the remaining clutter by a factor 10. This may partly be achieved through a better characterization of the antenna transfer functions and by performing measurements in an environment without close extraneous scatterers. Index Terms--Frequency domain, ground-penetrating radar (GPR), inverse modeling, linear systems, soil dielectric properties, soil water content.

Published
2004

34. GPR System Performance Compliance According to COST Action TU 1208 Guidelines

Author

Pajewski, Lara, Vrtunski, Milan, Bugarinovic, Željko, Ristic, Aleksandar, Govedarica, Miro, Van Der Wielen, Audrey, Gregoire, Colette, Van Geem, Carl, Derobert, Xavier, Borecký, Vladislav, Salih Serkan, Artagan, Fontul, Simona, Marecos, Vania, and Lambot, Sebastien

Subjects
signal linearity in the time axis, Ground Penetrating Radar (GPR), system performance compliance, signal-to-noise ratio, antennas, calibration, signal stability
Abstract

Ground Penetrating Radar (GPR) systems shall be periodically calibrated and their performance verified, in accordance with the recommendations and specifications of the manufacturer. Nevertheless, most GPR owners in Europe employ their instrumentation for years without ever having it checked by the manufacturer, unless major flaws or problems become evident, according to the results of a survey carried out in the context of COST (European Cooperation in Science and Technology) Action TU1208 “Civil engineering applications of Ground Penetrating Radar.” The D6087–08 standard, emitted by the American Society for Testing Materials (ASTM International), describes four procedures for the calibration of GPR systems equipped with air-coupled antennas. After a critical analysis of those procedures, four improved tests were proposed by a team of Members of the COST Action TU1208, which can be carried out to evaluate the signal-to-noise ratio, short-term stability, linearity in the time axis, and long-term stability of the GPR signal. This paper includes a full description of the proposed tests and presents the results obtained by scientists from Belgium, Czech Republic, Portugal, and Serbia, who executed the tests on their GPR systems. Overall, five pulsed control units and nine antennas were tested (five horn and four ground-coupled antennas, with central frequencies from 400 MHz to 1.8 GHz). While the performed measurements are not representative enough to establish absolute thresholds for the tests, they provide a valuable indication about values that one could obtain when testing GPR equipment, if the equipment is working reasonably well. Moreover, by periodically repeating the tests on the same equipment, it is possible to detect any significant shift from previously obtained values, which may imply that the GPR unit or antenna under test is not working in a normal or satisfactory manner. We also believe that executing the tests described in this paper is a useful exercise to gain awareness about the behaviour of a GPR system, its accuracy and limits, and how to best utilize it. Ground Penetrating Radar (GPR) systems shall be periodically calibrated and their performance verified, in accordance with the recommendations and specifications of the manufacturer. Nevertheless, most GPR owners in Europe employ their instrumentation for years without ever having it checked by the manufacturer, unless major flaws or problems become evident, according to the results of a survey carried out in the context of COST (European Cooperation in Science and Technology) Action TU1208 “Civil engineering applications of Ground Penetrating Radar.” The D6087–08 standard, emitted by the American Society for Testing Materials (ASTM International), describes four procedures for the calibration of GPR systems equipped with air-coupled antennas. After a critical analysis of those procedures, four improved tests were proposed by a team of Members of the COST Action TU1208, which can be carried out to evaluate the signal-to-noise ratio, short-term stability, linearity in the time axis, and long-term stability of the GPR signal. This paper includes a full description of the proposed tests and presents the results obtained by scientists from Belgium, Czech Republic, Portugal, and Serbia, who executed the tests on their GPR systems. Overall, five pulsed control units and nine antennas were tested (five horn and four ground-coupled antennas, with central frequencies from 400 MHz to 1.8 GHz). While the performed measurements are not representative enough to establish absolute thresholds for the tests, they provide a valuable indication about values that one could obtain when testing GPR equipment, if the equipment is working reasonably well. Moreover, by periodically repeating the tests on the same equipment, it is possible to detect any significant shift from previously obtained values, which may imply that the GPR unit or antenna under test is not working in a normal or satisfactory manner. We also believe that executing the tests described in this paper is a useful exercise to gain awareness about the behaviour of a GPR system, its accuracy and limits, and how to best utilize it.

Published
2018

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