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.

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.

Analysis for Scattering of Non-homogeneous Medium by Time Domain Volume Shooting and Bouncing Rays

2021 ◽  
Vol 36 (3) ◽  
pp. 245-251
Author(s):  
Jun Li ◽  
Huaguang Bao ◽  
Dazhi Ding
Keyword(s):  
Time Domain ◽  
Electromagnetic Scattering ◽  
Electromagnetic Waves ◽  
High Efficiency ◽  
Homogeneous Medium ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Transient Electromagnetic ◽  
Frequency Domain Methods ◽  
Scattered Fields

In order to evaluate scattering from hypersonic vehicles covered with the plasma efficiently, time domain volume shooting and bouncing rays (TDVSBR) is first introduced in this paper. The new method is applied to solve the transient electromagnetic scattering from complex targets, which combines with non-homogeneous dielectric and perfect electric conducting (PEC) bodies. To simplify the problem, objects are discretized into tetrahedrons with different electromagnetic parameters. Then the reflection and transmission coefficients can be obtained by using theory of electromagnetic waves propagation in lossy medium. After that, we simulate the reflection and transmission of rays in different media. At last, the scattered fields or radiation are solved by the last exiting ray from the target. Compared with frequency-domain methods, time-domain methods can obtain the wideband RCS efficiently. Several numerical results are given to demonstrate the high efficiency and accuracy of this proposed scheme.

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>

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.

Interaction of plane electromagnetic waves with a moving compressible plasma fluid

1969 ◽  
Vol 47 (4) ◽  
pp. 375-387 ◽  
Author(s):  
H. Fujioka ◽  
F. Nihei ◽  
N. Kumagai
Keyword(s):  
Electric Field ◽  
Electromagnetic Waves ◽  
Surface Charge Density ◽  
Magnetohydrodynamic Wave ◽  
Reflection And Transmission ◽  
Numerical Examples ◽  
Compressible Plasma ◽  
Transmission Coefficients ◽  
Moving Interface ◽  
Magnetoacoustic Waves

The problem of reflection and transmission of plane electromagnetic waves by a semi-infinite compressible plasma fluid moving parallel to its own interface with vacuum is investigated. Solutions are obtained for both incident E wave and H wave. It is found that (i) for the case of incident E wave which excites only two distinct magnetoacoustic waves, the reflection and transmission coefficients add to unity; however, (ii) for the incident H wave which excites only the transverse magnetohydrodynamic wave, both coefficients do not add to unity in general, because of the interaction of the electric field of the transmitted wave with surface charge density at the moving interface. Other interesting features due to the movement of the medium are discussed, and a few numerical examples are given.

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.

TRANSFORMATION OF SOUND AND ELECTROMAGNETIC WAVES IN NON-STATIONARY MEDIA

2010 ◽  
Vol 24 (18) ◽  
pp. 1951-1961 ◽  
Author(s):  
A. R. MKRTCHYAN ◽  
A. G. HAYRAPETYAN ◽  
B. V. KHACHATRYAN ◽  
R. G. PETROSYAN
Keyword(s):  
Energy Flux ◽  
Sound Wave ◽  
Electromagnetic Waves ◽  
Reflection And Transmission Coefficients ◽  
Sound Waves ◽  
Reflection And Transmission ◽  
Reflected Waves ◽  
Transmission Coefficients

Transformation (reflection and transmission) of sound and electromagnetic waves are considered in non-stationary media, properties of which abruptly change in time. Reflection and transmission coefficients for both amplitudes and intensities of sound and electromagnetic waves are obtained. Quantitative relations between the reflection and transmission coefficients for both sound and electromagnetic waves are given. The sum of the energy flux reflection and transmission coefficients for both types of waves is not equal to one (for sound waves it is greater than one). The energy of both waves is not conserved, that is, exchange of the energy occurs between the corresponding waves and medium. As a result, the sound wave obtains a notable property: the transmitting wave carries energy equal to the sum of the energies of the incident and reflected waves. A possibility of the amplification of sound waves and transformation of their frequencies is illustrated.

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.

Sign in / Sign up

Export Citation Format

Share Document