Ground‐penetrating radar velocity tomography in heterogeneous and anisotropic media

Geophysics ◽  
1997 ◽  
Vol 62 (6) ◽  
pp. 1758-1773 ◽  
Author(s):  
Don W. Vasco ◽  
John E. Peterson ◽  
Ki Ha Lee
Keyword(s):  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Numerical Technique ◽  
Anisotropic Media ◽  
Perturbation Approach ◽  
Low Velocity ◽  
Weak Anisotropy ◽  
Geological Features ◽  
Velocity Anomalies ◽  
Ground Penetrating

A ray series solution for Maxwell's equations provides an efficient numerical technique for calculating wavefronts and raypaths associated with electromagnetic waves in anisotropic media. Using this methodology and assuming weak anisotropy, we show that a perturbation of the anisotropic structure may be related linearly to a variation in the traveltime of an electromagnetic wave. Thus, it is possible to infer lateral variations in the dielectric permittivity and magnetic permeability matrices. The perturbation approach is used to analyze a series of crosswell ground‐penetrating radar surveys conducted at the Idaho National Engineering Laboratory. Several important geological features are imaged, including a rubble zone at the interface between two basalt flows. Linear low‐velocity anomalies are imaged clearly and are continuous across well pairs.

REFLECTION COEFFICIENT OF AN ELECTROMAGNETIC WAVE IN CONDUCTIVE MEDIA

2018 ◽  
pp. 100-106
Author(s):  
M. S. Sudakova ◽  
M. L. Vladov ◽  
M. R. Sadurtdinov
Keyword(s):  
Reflection Coefficient ◽  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Water Contamination ◽  
Survey Design ◽  
Direct And Inverse Problems ◽  
The Difference ◽  
Ground Penetrating ◽  
Ideal Dielectric

Within the ground penetrating radar bandwidth the medium is considered to be an ideal dielectric, which is not always true. Electromagnetic waves reflection coefficient conductivity dependence showed a significant role of the difference in conductivity in reflection strength. It was confirmed by physical modeling. Conductivity of geological media should be taken into account when solving direct and inverse problems, survey design planning, etc. Ground penetrating radar can be used to solve the problem of mapping of halocline or determine water contamination.

scholarly journals Study Effect of Objects Orientation in the Mediums On GPR Signal Reflections Using FDTD Simulation

2018 ◽  
Vol 3 (11) ◽  
pp. 73-77
Author(s):  
Aye Mint Mohamed Mostapha ◽  
Gamil Alsharahi ◽  
Abdellah Driouach
Keyword(s):  
Finite Difference ◽  
Time Domain ◽  
Ground Penetrating Radar ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Ground Surface ◽  
Propagation Path ◽  
Fdtd Simulation ◽  
Ground Penetrating ◽  
Dielectric Objects

Ground penetrating radar (GPR) is a very effective tool for detecting and identifying objects below the ground surface.  based on  the propagation and reflection of high-frequency electromagnetic waves. The GPR reflection can be affected by many things like the type of objects orientation, their shapes ..ect. The purpose of this paper is to  study by simulation the effect of objects orientation in two different mediums (dry and wet sand) on the GPR signal reflection using Reflexw software which is based on a numerical method known as finite difference in time domain (FDTD).  The simulations that have been realized included a conductor  and dielectric objects. The results obtained have led us to find that the propagation path, the reflection strength and the signal form change with the change of object orientation and nature. To confirm the validity of the results, we compared them with experimental results previously published by researchers under the same conditions.

WISDOM Antenna Pattern in the presence of Rover and Soil

2021 ◽  
Author(s):  
Wolf-Stefan Benedix ◽  
Dirk Plettemeier ◽  
Christoph Statz ◽  
Yun Lu ◽  
Ronny Hahnel ◽  
...  
Keyword(s):  
Pattern Matching ◽  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Complete System ◽  
Near Field ◽  
System Model ◽  
Soil Types ◽  
Broadband Antenna ◽  
Shallow Subsurface ◽  
Ground Penetrating

<p>The WISDOM ground-penetrating radar aboard the 2022 ESA-Roscosmos Rosalind-Franklin ExoMars Rover will probe the shallow subsurface of Oxia Planum using electromagnetic waves. A dual-polarized broadband antenna assembly transmits the WISDOM signal into the Martian subsurface and receives the return signal. This antenna assembly has been extensively tested and characterized w.r.t. the most significant antenna parameters (gain, pattern, matching). However, during the design phase, these parameters were simulated or measured without the environment, i.e., in the absence of other objects like brackets, rover vehicle, or soil. Some measurements of the rover's influence on the WISDOM data were performed during the instrument's integration.</p><p>It was shown that the rover structure and close surroundings in the near-field region of the WISDOM antenna assembly have a significant impact on the WISDOM signal and sounding performance. Hence, it is essential to include the simulations' environment, especially with varying surface and underground.</p><p>With this contribution, we outline the influences of rover and ground on the antenna's pattern and particularly on the footprint. We employ a 3D field solver with a complete system model above different soil types, i.e., subsurface materials with various combinations of permittivity and conductivity.</p>

scholarly journals The Processing Algorithm for Wideband Signals Propagating in Media with Frequency Dispersion

2020 ◽  
Vol 12 (3) ◽  
pp. 2-7
Author(s):  
Andrei A. Kalshchikov ◽  
Vitaly V. Shtykov ◽  
Sergey M. Smolskiy
Keyword(s):  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Flaw Detection ◽  
Frequency Dispersion ◽  
Debye Model ◽  
Processing Algorithm ◽  
Chirp Pulse ◽  
Wideband Signals ◽  
Dispersion Media ◽  
Ground Penetrating

The new processing algorithm for wideband signals, which are propagating in frequency dispersion media, is developed in the context of the ground penetrating radar technology. The mathematical substantiation of offered method is presented on the base of linear functional spaces. The method is described for calculation acceleration on the base of the recursive approach. Results of numerical modeling of this method are presented for electromagnetic waves propagating in frequency dispersion media at utilization of chirp pulse signals. The Debye model is used as the model of electrical medium properties. The frequency dispersion of losses in the medium is taken into consideration at modeling. Results of operation modeling of the ground penetrating radar are described. Results of this paper will be useful for the ground penetrating radar technology and the ultrasonic flaw detection.

Ground-penetrating radar data diffraction focusing without a velocity model

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. H13-H24
Author(s):  
Nikos Economou ◽  
Antonis Vafidis ◽  
Maksim Bano ◽  
Hamdan Hamdan ◽  
Jose Ortega-Ramirez
Keyword(s):  
Ground Penetrating Radar ◽  
Constant Velocity ◽  
Electromagnetic Waves ◽  
Ground Truth ◽  
Velocity Model ◽  
Migration Velocity ◽  
Dominant Frequency ◽  
Limited Information ◽  
Velocity Range ◽  
Ground Penetrating

Ground-penetrating Radar (GPR) sections commonly suffer from strong scattered energy and weak reflectors with distorted lateral continuity. This is mainly due to the gradual variation of moisture with depth, dense lateral sampling of common-offset GPR traces (which are considered as zero-offset data), along with the small wavelength of the electromagnetic waves that is comparable to the size of the shallow subsurface dielectric heterogeneities. Focusing of the diffractions requires efficient migration that, in the presence of highly heterogeneous subsurface formations, can be improved by a detailed migration velocity model. Such a velocity model is difficult to develop because the common-offset antenna array is mostly used for its reduced time and cost in the data acquisition and processing stages. In such cases, migration processes are based on limited information from velocity analysis of clear diffractions, cores, or other ground truth knowledge, often leading to insufficient imaging. We have developed a methodology to obtain GPR sections with focused diffractions that is based on multipath summation, using weighted stacking (summation) of constant-velocity migrated sections over a predefined velocity range. The success of this method depends on the assignment of an appropriate weight, for each constant-velocity migrated section to contribute to the final stack, and the optimal width of the velocity range used. Additionally, we develop a postmultipath summation processing step, which consists of time-varying spectral whitening, to deal with the decrease of the dominant frequency due to attenuation effects and the additional degraded resolution expected by the constant migration summed images. This imaging strategy leads to GPR sections with sufficiently focused diffractions, enhancing the lateral and the temporal resolution, without the need to explicitly build a migration velocity model.

scholarly journals Estimation of Moisture Content in Railway Subgrade by Ground Penetrating Radar

2020 ◽  
Vol 12 (18) ◽  
pp. 2912
Author(s):  
Sixin Liu ◽  
Qi Lu ◽  
Hongqing Li ◽  
Yuanxin Wang
Keyword(s):  
Moisture Content ◽  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Geophysical Methods ◽  
Dielectric Constants ◽  
Thin Layers ◽  
Velocity Spectrum ◽  
Railway Transportation ◽  
Interval Velocities ◽  
Ground Penetrating

China is strongly dependent on railway transportation, but the frost heaving of the subgrade in cold regions has seriously affected the safety and comfort of trains. Moisture content is an essential parameter in the subgrade frost heave. Non-destructive and efficient geophysical methods have great potential in measuring the moisture content of railway subgrade. In this paper, we use the common mid-point (CMP) measurement of ground penetrating radar (GPR) to estimate the propagation velocity of electromagnetic waves in a subgrade application. We establish a synthetic model to simulate the railway subgrade structure. The synthetic CMP gathers acquired from shallow and thin layers are seriously disturbed by multiple waves and refraction waves, which make the routine velocity analysis unable to provide accurate velocities. Through the analysis of numerical simulation results, it is found that the primary reflection waves, multiple waves, and refraction waves are dominant in different offset ranges of CMP gather. Therefore, we propose a solution of the optimal gather at a certain range of offset dominated by the primary reflection wave to calculate the velocity spectrum and extract the accurate velocities for the subgrade model. The relative dielectric constants of the corresponding layers are calculated after the stacking velocities are converted into the interval velocities. Then, the moisture content is obtained by the Topp formula, which expresses the relationship between dielectric constant and moisture content. Finally, we apply the optimal gather scheme and the above interpretation process to the GPR data acquired at the railway site, and we form a long moisture content profile of the railway subgrade. Compared with the polarizability measured by the induced polarization (IP) method, it is found that the regions with high moisture content correspond to polarizability anomalies with different strengths. The comparison shows the reliability of GPR results to some extent.

Simulation and Experiments on Signals of Ground-Penetrating Radar in Soil Cement

2020 ◽  
pp. 2158003
Author(s):  
Zhezhe Hou ◽  
Yanliang Du
Keyword(s):  
Dielectric Constant ◽  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Soil Layer ◽  
Center Line ◽  
Reflected Waves ◽  
Soil Cement ◽  
Subgrade Soil ◽  
Ground Penetrating ◽  
Radar Wave

Subgrade bedding is a key element of railway structure in stability and durability, and it is almost made of soil cement. The dielectric constant, compaction and curing ages of soil cement with different moisture contents were measured. The relation among curing ages, moisture content, compaction of soil cement and electromagnetic features was analyzed. The model of layered soil cement was established to simulate ground-penetrating radar (GPR) electromagnetic waves in the soil cement. The variation rules of dielectric constant and amplitude of radar signals were obtained. The electromagnetic features, i.e. velocity, frequency and amplitude, were analyzed. Ground-penetrating radar was used to detect the railway subgrade soil layer. Based on the center line of the subgrade, there were nine detection lines for every 1[Formula: see text]m to detect the density and smoothness of the subgrade soil layer. Based on the radar wave events and reflected waves, the subgrade condition can be judged.

A review of ground-penetrating radar studies related to peatland stratigraphy with a case study on the determination of peat thickness in a northern boreal fen in Quebec, Canada

2013 ◽  
Vol 37 (6) ◽  
pp. 767-786 ◽  
Author(s):  
Sandra Proulx-McInnis ◽  
André St-Hilaire ◽  
Alain N. Rousseau ◽  
Sylvain Jutras
Keyword(s):  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Open Water ◽  
Coefficient Of Determination ◽  
Cross Sectional ◽  
Soil Thickness ◽  
Shallow Subsurface ◽  
Observation Method ◽  
Time Required ◽  
Ground Penetrating

Ground-penetrating radar (GPR) is a non-intrusive geophysical observation method based on propagation and reflection of high-frequency electromagnetic waves in the shallow subsurface. The vertical cross-sectional images obtained allow the identification of thickness and lithologic horizons of different media, without destruction. Over the last decade, several studies have demonstrated the potential of GPR. This paper presents a review of recent GPR applications to peatlands, particularly to determine peat stratigraphy. An example study of acquisition and comparison of peatland soil thickness of a fen-dominated watershed located in the James Bay region of Quebec, using (1) a meter stick linked to a GPS RTK and (2) a GSSI GPR, is given. A coefficient of determination ( r2) of 56% was obtained between the ordinary krigings performed on data gathered using both techniques. Disparities occurred mainly in the vicinity of ponds which can be explained by the attenuation of GPR signal in open water. Despite these difficulties – the higher time required for analysis and the error margin – it seems more appropriate to use a GPR, instead of a graduated rod linked to a GPS, to measure the peat depths on a site like the one presented in this study. Manual measurements, which are user-dependent in the context of variable mineral substrate densities and with the presence of obstacles in the substrate, may be more subjective.

scholarly journals GROUND PENETRATING RADAR DATA ANALYSIS BY USING MODELLING WITH FINITE DIFFERENCE METHOD: CASE STUDY IN BELAWAN PORT

2016 ◽  
Vol 11 (1) ◽  
pp. 15-24
Author(s):  
Hans Elmaury Andreas Siregar
Keyword(s):  
Numerical Simulation ◽  
Finite Difference ◽  
Data Acquisition ◽  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Processing Technique ◽  
Radar Image ◽  
Clayey Sand ◽  
Near Surface ◽  
Ground Penetrating

Ground Penetrating Radar (GPR) is one of non destructive geophysics methods which is appropriate used to identify subsurface object with depth penetration less than 70 meter. High data resolution as well as relatively unprolonged and manageable data acquisition make this method becoming convenient supporting method to increase near surface data for other geophysics methods.  The depth penetration of GPR varies with the frequency of antenna. Getting optimum depth penetration before field acquisition data some numerical simulation should be accomplished in order to perceive antenna frequency and processing technique that used, so the depth of target zone can be achieved. The Finite Difference (FD) is one one of numerical anaysis technique that mostly used to determine differential equation. By using FD method, the solution of electromagnetic waves equation can be obtained and the image of numerical simulation can be displayed. In line with this radar image from numerical simulation, the relationship of frequency and depth penetration on the media used is acquired.  Media used in this simulation are sand, clay, sandy clay, clayey sand and concrete. Through numerical simulation from this research, we conclude that GPR method able to distinguish boundary layer among each medium. Processing technique is accomplished to comprehend suitable  processing stages for high resolution radar image that can be interpreted. Data acquisition and processing technique from simulation have been implemented in field experiment and very helpful to apprehend GPR characteristic signal in subsurface map in Belawan port.

Ray‐based synthesis of bistatic ground‐penetrating radar profiles

Geophysics ◽  
1995 ◽  
Vol 60 (1) ◽  
pp. 87-96 ◽  
Author(s):  
Jun Cai ◽  
George A. McMechan
Keyword(s):  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Dynamic Properties ◽  
Reflection And Transmission ◽  
Attenuation Coefficients ◽  
Transmission Coefficients ◽  
Dallas County ◽  
Austin Chalk ◽  
Wave Effects ◽  
Ground Penetrating

An algorithm has been developed to numerically synthesize 2-D bistatic (common‐offset), ground‐penetrating radar (GPR) profiles using the principles of geometrical ray theory. By assuming nondispersive propagation, kinematic properties of electromagnetic waves are simulated by ray tracing. Dynamic properties are simulated by computing transmitter and receiver directivities, reflection and transmission coefficients, geometrical spreading, and attenuation coefficients. The main limitations are that wave effects, such as diffractions, and offline (3-D) effects are not included. The algorithm is applied to iterative modeling of multioffset, multifrequency GPR data acquired over an outcrop of fractured Austin Chalk in Dallas County in northeast Texas. Modeling is able to simulate realistically the main time and amplitude behaviors observed in GPR reflections at 50, 100, and 200 MHz at each of 1, 3, and 5 meter antenna separations from a single model. Detailed modeling produces quantitative estimates of the spatial distributions of electrical properties that are consistent with the geologic environment.

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