A practical approach to correct attenuation effects in GPR data

Background and Scope Because of the crucial role coarse roots (>2 mm diameter) play in plant functions and terrestrial ecosystems, detecting and quantifying the size, architecture, and biomass of coarse roots are important. Traditional excavation methods are labor intensive and destructive, with limited quantification and repeatability of measurements over time. As a nondestructive geophysical tool for delineating buried features in shallow subsurface, ground penetrating radar (GPR) has been applied for coarse root detection since 1999. This article reviews the state-ofknowledge of coarse root detection and quantification using GPR, and discusses its potentials, constraints, possible solutions, and future outlooks. Some useful suggestions are provided that can guide future studies in this field. Conclusions The feasibility and accuracy of coarse root investigation by GPR have been tested in various site conditions (mostly in controlled conditions or within plantations) and for different plant species (mostly tree root systems). Thus far, single coarse root identification and coarse root system mapping have been conducted using GPR, including roots under pavements in urban environment. Coarse root diameter and biomass have been estimated from indexes extracted from root GPR radargrams. Coarse root development can be observed by repeated GPR scanning over time. Successful GPR-based coarse root investigation is site specific, and only under suitable conditions can reliable measurements be accomplished. The best quality of root detection by GPR is achieved in well-drained and electrically-resistive soils (such as sands) under dry conditions. Numerous factors such as local soil conditions, root electromagnetic properties, and GPR antenna frequency can impact the reliability and accuracy of GPR detection and quantification of coarse roots. As GPR design, data processing software, field data collection protocols, and root parameters estimation methods are continuously improved, this noninvasive technique could offer greater potential to study coarse roots.

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“…When penetrating through media, radar energy decays exponentially with propagation time (Neto and de Medeiros 2006):…”

Section: Gpr Principlementioning

confidence: 99%

“…Thus, resolution is positively correlated with antenna frequency. Unfortunately, GPR wave energy attenuation is increased with antenna frequency (Neto and de Medeiros 2006). Therefore, a trade-off exists between penetration depth and resolution (Fig.…”

Section: Limiting Factors Of Gpr-based Coarse Root Detection and Quanmentioning

confidence: 99%

Application of ground penetrating radar for coarse root detection and quantification: a review

et al. 2012

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“…Grasmueck et al . ) because soils and materials infilling karst voids or resulting from carbonate rock weathering might be electrically conductive and, as a result, penetration depth and signal resolution might be greatly reduced due to attenuation (Xavier Neto and Medeiros ). In addition, fractures and faults might cause a significant amount of GPR wave scattering.…”

Section: Introductionmentioning

confidence: 99%

“…Cassidy ; Economou et al . ) or improvements on specific flow steps, for example, ringing noise removal (Kim, Cho and Yi ), propagation effects compensation (Xavier Neto and Medeiros ), and background removal (Rashed and Harbi ; Montiel‐Zafra et al . ).…”

Section: Introductionmentioning

confidence: 99%

Enhancing stratigraphic, structural and dissolution features in GPR images of carbonate karst through data processing

Oliveira

Medeiros

Santana

et al. 2019

Near Surface Geophysics

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Obtaining high‐quality ground penetrating radar (GPR) images in karst is difficult because materials resulting from the weathering of carbonate rocks might be electrically conductive. As a consequence, penetration depth and signal resolution might be greatly reduced due to attenuation. In addition, fractures and faults might cause a significant amount of electromagnetic wave scattering. We present a 2D data processing flow which allows improving the quality of GPR images in carbonate karst. The processing flow is composed of the following steps: obtaining a zero‐offset section by removing the direct wave, low‐frequency noise removal, geometrical spreading and exponential gain compensation, spectral balancing, Kirchhoff migration, bandpass filtering, amplitude‐volume enhancement, and topographic correction. For a 200‐MHz dataset, we present in detail each step of the processing flow, exemplifying how to parameterize every step. Spectral balancing is of key importance because it can approximately replenish the high‐frequency content lost due to propagation effects. In this step, we recommend to shift the centroid frequency as much as possible to high‐frequency values, even exceeding the nominal value of the antenna center frequency, but still looking for a band‐limited spectrum as the goal. Despite the difficulty of migrating GPR data, we show that migration (even assuming a constant velocity) might enhance the lateral continuity of the reflection events and allows identification of discontinuities such as faults and fractures. If imaged in a better way, these structures can have special importance as they are often the boundaries of dissolution features. Obtaining images based on amplitude‐volume enhancement techniques allows to better visualize karst voids and deep‐rooted discontinuities because these features are often associated with low‐amplitude zones, which are highlighted in such images. Due to this processing flow, stratigraphic, structural and dissolution features can be enhanced, allowing the interpreter to establish spatial and genetic associations among these elements to obtain a better understanding of the karst formation process.

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“…43 Pensar a produção documental periférica dentro dessa conjuntura passa por reconhecer a materialidade de um engajamento político, aspecto que emergiu com força nos anos 1960 e que até os dias de hoje impulsiona a confecção do "documentário engajado", 44 cuja fidelidade política aparece em primeiro plano para lidar com os problemas sociais.…”

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Pontos de vista em documentários de periferia: estética, cotidiano e política

Silva¹

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A practical approach to correct attenuation effects in GPR data

Cited by 58 publications

References 16 publications

Application of ground penetrating radar for coarse root detection and quantification: a review

Application of ground penetrating radar for coarse root detection and quantification: a review

Enhancing stratigraphic, structural and dissolution features in GPR images of carbonate karst through data processing

Pontos de vista em documentários de periferia: estética, cotidiano e política

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