Estimation of groundwater level by GPR in an area with multiple ambiguous reflections

Nakashima, Yuichi; Zhou, Hui; Suzuki, Motoyuki

doi:10.1016/s0926-9851(01)00068-4

Cited by 71 publications

(35 citation statements)

References 8 publications

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“…Figure 3 shows a schematic representation of the CMP method with transmitting and receiving antennas located symmetrically about a CMP position while measuring their common mid-point at different antenna offsets. Traditionally this is performed by stepwise movement of the Tx and Rx antennas away from each other manually [28,29,34,35]. Today, with the increasing availability of arrayed antenna GPR systems, such CMP gather can in principal be acquired without having to move the GPR system at all.…”

Section: Gpr Soil Moisture Estimation By Means Of Cmp Velocity Analysismentioning

confidence: 99%

“…It should be emphasized that the non-normalized cross-correlation takes into account the true amplitudes and thus adapts only high amplitude reflections [29]. In this way, the chance of picking up unwanted multiple reflections is greatly reduced.…”

Section: Gpr Soil Moisture Estimation By Means Of Cmp Velocity Analysismentioning

confidence: 99%

“…In the presence of a water saturated layer, like a groundwater aquifer, it can easily be identified by its RMS velocity due to the sharp contrast compared to the unsaturated zone [22,27]. Several studies have discussed the effect of the velocity analysis on the stacked CMP gather for quantitative retrieval of the subsurface soil water content [28][29][30].…”

Section: Introductionmentioning

confidence: 99%

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In-Situ Measurement of Soil Permittivity at Various Depths for the Calibration and Validation of Low-Frequency SAR Soil Moisture Models by Using GPR

et al. 2017

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At radar frequencies below 2 GHz, the mismatch between the 5 to 15 cm sensing depth of classical time domain reflectometry (TDR) probe soil moisture measurements and the radar penetration depth can easily lead to unreliable in situ data. Accurate quantitative measurements of soil water contents at various depths by classical methods are cumbersome and usually highly invasive. We propose an improved method for the estimation of vertical soil moisture profiles from multi-offset ground penetrating radar (GPR) data. A semi-automated data acquisition technique allows for very fast and robust measurements in the field. Advanced common mid-point (CMP) processing is applied to obtain quantitative estimates of the permittivity and depth of the reflecting soil layers. The method is validated against TDR measurements using data acquired in different environments. Depth and soil moisture contents of the reflecting layers were estimated with root mean square errors (RMSE) on the order of 5 cm and 1.9 Vol.-%, respectively. Application of the proposed technique for the validation of synthetic aperture radar (SAR) soil moisture estimates is demonstrated based on a case study using airborne L-band data and ground-based P-band data. For the L-band case we found good agreement between the near-surface GPR estimates and extended integral equation model (I 2 EM) based SAR retrievals, comparable to those obtained by TDR. At the P-band, the GPR based method significantly outperformed the TDR method when using soil moisture estimates at depths below 30 cm.

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Section: Gpr Soil Moisture Estimation By Means Of Cmp Velocity Analysismentioning

confidence: 99%

Section: Gpr Soil Moisture Estimation By Means Of Cmp Velocity Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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In-Situ Measurement of Soil Permittivity at Various Depths for the Calibration and Validation of Low-Frequency SAR Soil Moisture Models by Using GPR

et al. 2017

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“…In literature, in fact, the prevailing approach is to neglect the presence of multiples in order to simplify the analysis [5,6] or apply generic clutter removal techniques [7], and only a few recent works can be cited that try to explicitly face the problem. Standard filtering techniques, such as predictive deconvolution [8] and two-dimensional f −k filtering [9], are generally employed, but some application-oriented algorithms can be anyway found, as in [10], where the 'wave field prediction and removal method' have been devised to enhance GPR images for the quality assessment of back-filled grouting in a shield tunnel.…”

Section: Introductionmentioning

confidence: 99%

Towards the Detection of Multiple Reflections in Time-Domain Em Inverse Scattering of Multi-Layered Media

Caorsi¹,

Stasolla²

2012

PIER B

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Abstract-In this paper, a new theoretical approach for the classification of multiple reflections in time-domain e.m. inverse scattering of multi-layered media is presented. The existence of multiples limits the capabilities of inversion algorithms, thus suitable identification and suppression techniques should be applied to reduce this undesired effect. Assuming a scenario composed of loss-less and non-dispersive media, and providing an accurate time delay estimation (TDE) of backscattered signals, the proposed method allows not only to evaluate the presence of multiples and discriminate them from primary reflections, but also to determine their propagation paths. Preliminary tests performed on FDTD simulated data have shown its potentialities to effectively handle multiple reflections and therefore to enhance the e.m. signals backscattered by primary reflectors.

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“…The groundwater table, horizontal or inclined joints and other subsurface discontinuities could also create these reflections (Nakashima et al 2001;Porsani et al 2006). In addition, hyperbolic diffraction patterns will be generated as radar waves are scattered by deep caves or underground solid diffractors (Bruschini et al 1998;Beres et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Analysis of Standing Waves on GPR Hyperbolic Travel-Time Responses - Case Studies in a Fractured Granitic Rock and a Deteriorating Coastal Structure

Chen¹,

Chow²,

Chen³

2007

Terr. Atmos. Ocean. Sci.

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ABSTRACT1 Institute of Applied Geoscience, National Taiwan Ocean University, Keelung, Taiwan, ROC 2 Institute of Geophysics, National Central University, Chung-Li, Taiwan, ROC * Corresponding author address: Prof. Joseph Jinder Chow, Institute of Applied Geoscience, National Taiwan Ocean University, Keelung, Taiwan, ROC; E-mail: jdchow@mail.ntou.edu.tw doi: 10.3319/ TAO.2007.18.5.879(T) Utilizing Ground Penetrating Radar (GPR), emitted electromagnetic (EM) standing waves can be generated in underground voids. This phenomenon can be employed for the detection of subterranean voids and fractures when one has a proper understanding of relation between the widest inner length in an underground vacant space and half an EM wavelength. In this study, indoor and outdoor small-scale experiments verified the generation of EM standing waves. These responses were then applied in an arched-top cave covered by a single layer of backfill at Gongzihliao, Taiwan. Further studies were carried out at two other sites, including a fracture located in a granite mountain without regolith on the surface at Kinmen, and a deteriorating fishing port in Nanfangao, northeast Taiwan. Applying a band-pass filter with bandwidth narrower than a typical two-octave bandwidth produced the required standing waves with recognizable positions of minimum amplitude. A hyperbolic travel-time (HTT) curve revealing the minimum amplitude, known as standing-wave nodes, indicates the presence of an underground hollow diffractor with the widest inner length in the vacant space being larger than half an EM wavelength. However, a HTT curve without nodal points signifies a hollow object with the widest inner length smaller than half an EM wavelength or an underground solid diffractor. An underground arched-top cave was detected by nodal points in the arc-like curves. When emitting the radar waves toward a wall, the Terr. Atmos. Ocean. Sci., Vol. 18, No. 5, December 2007 880 interval of the nodes was used for estimating the wavelength of receiving GPR signals. Identifying the occurrence of nodal points in HTT or HTTlike curves in radargrams may assist the GPR interpreting work for underground tunnels, drainages, cavities, fractures, or solid objects.

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Estimation of groundwater level by GPR in an area with multiple ambiguous reflections

Cited by 71 publications

References 8 publications

In-Situ Measurement of Soil Permittivity at Various Depths for the Calibration and Validation of Low-Frequency SAR Soil Moisture Models by Using GPR

In-Situ Measurement of Soil Permittivity at Various Depths for the Calibration and Validation of Low-Frequency SAR Soil Moisture Models by Using GPR

Towards the Detection of Multiple Reflections in Time-Domain Em Inverse Scattering of Multi-Layered Media

Analysis of Standing Waves on GPR Hyperbolic Travel-Time Responses - Case Studies in a Fractured Granitic Rock and a Deteriorating Coastal Structure

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