Polarimetric borehole radar experiment was carried out in 2000 in Korea. Two boreholes separated by 20m were used. The host rock is granite. The cavity is located at about 80m depth. Single-hole and cross-hole radar profiles were acquired. We could clearly detect a subsurface cavity filled with air in the raw data. They have shown that cross-hole signal shows "double-dip" attenuation caused by scattering from an air-filled cavity. Although it is a simple technique, we found that it is suitable for detection of subsurface anomaly. Then we checked the attenuation between two boreholes, and showed that we can detect anomalous zone by a ray-based technique. In order to have vertical 2-D image between the boreholes, we developed a reverse time migration technique. In this analysis, we could assume two horizontal layers having different velocities, and we could image the cavity. The location of the cavity could clearly be determined by these signal interpretation.
{"title":"Polarimetric borehole radar application for characterizing subsurface structure","authors":"Motoyuki Sato, T. Abe, Hui Zhou, J. Ra","doi":"10.1117/12.462275","DOIUrl":"https://doi.org/10.1117/12.462275","url":null,"abstract":"Polarimetric borehole radar experiment was carried out in 2000 in Korea. Two boreholes separated by 20m were used. The host rock is granite. The cavity is located at about 80m depth. Single-hole and cross-hole radar profiles were acquired. We could clearly detect a subsurface cavity filled with air in the raw data. They have shown that cross-hole signal shows \"double-dip\" attenuation caused by scattering from an air-filled cavity. Although it is a simple technique, we found that it is suitable for detection of subsurface anomaly. Then we checked the attenuation between two boreholes, and showed that we can detect anomalous zone by a ray-based technique. In order to have vertical 2-D image between the boreholes, we developed a reverse time migration technique. In this analysis, we could assume two horizontal layers having different velocities, and we could image the cavity. The location of the cavity could clearly be determined by these signal interpretation.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124129980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Ney, J. Berthelier, V. Ciarletti, B. Martinat, M. Hamelin, M. Rodríguez-Cassola, F. Dolon, S. Bonaime, A. Reineix, B. Nevejans, C. Duvanaud, F. Costard, P. Paillou
We present in the first part the state of development of the laboratory prototype of the GPR which will allow to check the performances of all the sub-systems. Then some results obtained from numerical simulation are shown to demonstrate the radar capabilities and the anticipated characteristics of the detected signal. Simulated data have been used to study the algorithms which will be employed to analyse the observations and some examples of initial results are presented. Initial field measurements are reported.
{"title":"Ground-penetrating radar of the Netlander mission","authors":"R. Ney, J. Berthelier, V. Ciarletti, B. Martinat, M. Hamelin, M. Rodríguez-Cassola, F. Dolon, S. Bonaime, A. Reineix, B. Nevejans, C. Duvanaud, F. Costard, P. Paillou","doi":"10.1117/12.462294","DOIUrl":"https://doi.org/10.1117/12.462294","url":null,"abstract":"We present in the first part the state of development of the laboratory prototype of the GPR which will allow to check the performances of all the sub-systems. Then some results obtained from numerical simulation are shown to demonstrate the radar capabilities and the anticipated characteristics of the detected signal. Simulated data have been used to study the algorithms which will be employed to analyse the observations and some examples of initial results are presented. Initial field measurements are reported.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126025877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the paper we have derived the following equation 4 f 0 L equi = c/ sqrt(e equi ) where f 0 is the resonant frequency of the antenna input impedance, c is the speed of light, L equi and e equi are respectively the equivalent length of antenna and the equivalent dielectric constant of the medium formed by half-space ground and half-space air. When measuring in air, the dielectric constant is known. One can obtain the antenna equivalent length from the measured f 0, by using the above equation. When L equi is obtained, one then can calculate e equi from a measured f 0 for the case when placing antenna on material interface. One can further estimate the ground dielectric constant by using the equation: e equi = (e iar + e ground )/2. Bow-tie antennas with different flange angles are constructed for experiments, in order to discuss the application of the above equation. The lengths of those antennas are all 30cm (length of the antenna conductor: 15cm). But the flange angles of the antenna conductors are respectively: 15, 40, 60, 75, 90 degrees. The antenna input reflections are measured over the frequency band up to 500 MHz, for cases when the antennas are placed in air and on sand, stone and water surfaces.
在本文中，我们推导出如下公式:4f0lequi = c/ sqrt(e equi)，其中f0为天线输入阻抗的谐振频率，c为光速，lequi和eequi分别为天线的等效长度和由半空间地面和半空间空气构成的介质的等效介电常数。在空气中测量时，介电常数是已知的。利用上述公式，可以从测量的f0得到天线等效长度。当得到lequi后，就可以根据测量到的f0计算出天线放置在材料界面上的情况下的eequi。我们可以用公式eequi = (ear + e ground)/2进一步估计地介电常数。构造不同翼缘角度的领结天线进行实验，探讨上述方程的应用。天线长度均为30cm(天线导体长度为15cm)。但天线导线的法兰角分别为:15度、40度、60度、75度、90度。当天线放置在空气中、沙子、石头和水面上时，天线的输入反射在500兆赫的频带内进行测量。
{"title":"Resonance of input impedance of bow-tie antenna placed on ground surface","authors":"F. Kong","doi":"10.1117/12.462194","DOIUrl":"https://doi.org/10.1117/12.462194","url":null,"abstract":"In the paper we have derived the following equation 4 f 0 L equi = c/ sqrt(e equi ) where f 0 is the resonant frequency of the antenna input impedance, c is the speed of light, L equi and e equi are respectively the equivalent length of antenna and the equivalent dielectric constant of the medium formed by half-space ground and half-space air. When measuring in air, the dielectric constant is known. One can obtain the antenna equivalent length from the measured f 0, by using the above equation. When L equi is obtained, one then can calculate e equi from a measured f 0 for the case when placing antenna on material interface. One can further estimate the ground dielectric constant by using the equation: e equi = (e iar + e ground )/2. Bow-tie antennas with different flange angles are constructed for experiments, in order to discuss the application of the above equation. The lengths of those antennas are all 30cm (length of the antenna conductor: 15cm). But the flange angles of the antenna conductors are respectively: 15, 40, 60, 75, 90 degrees. The antenna input reflections are measured over the frequency band up to 500 MHz, for cases when the antennas are placed in air and on sand, stone and water surfaces.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132098572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper focuses on the accuracy of detection of the first defect from a ground penetrating radar (GPR) signal in a masonry wall. The main conclusions are drawn from a carefully executed piece of experimental research work based upon field work on a masonry wall on the Bell Tower at Cremona. From inspection of the field GPR records, the resolution of detection of the first target or defect was found to be related to the length of the first reflection from the surface of the masonry. Thus conventional geophysics guidelines with respect to target detection related to one-tenth of a wavelength were tested against field observations and found to be inapplicable in relation to the detectability of the first defect. The shallowest detectable target proved to be at a depth of one-third the centre frequency of the antenna.
{"title":"Depth of first detectable defect in a masonry wall using GPR","authors":"S. Colombo, A. Giannopoulos, M. Forde","doi":"10.1117/12.462216","DOIUrl":"https://doi.org/10.1117/12.462216","url":null,"abstract":"This paper focuses on the accuracy of detection of the first defect from a ground penetrating radar (GPR) signal in a masonry wall. The main conclusions are drawn from a carefully executed piece of experimental research work based upon field work on a masonry wall on the Bell Tower at Cremona. From inspection of the field GPR records, the resolution of detection of the first target or defect was found to be related to the length of the first reflection from the surface of the masonry. Thus conventional geophysics guidelines with respect to target detection related to one-tenth of a wavelength were tested against field observations and found to be inapplicable in relation to the detectability of the first defect. The shallowest detectable target proved to be at a depth of one-third the centre frequency of the antenna.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134515114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stimulated by the inquiry of using high frequency electromagnetic ground waves to communicate information among unattended ground sensors, numerical simulations of GPR performance in different near-surface geological settings were conducted. Two sets of 400 MHz GPR field data, one from Fort Richardson, Alaska, and the other one from Hanover, New Hampshire, were used to be the 'ground truth' to compare with numerical simulations. The numerical simulation algorithm we used adapts the finite difference time domain method, with a perfectly matched layer as the absorption boundary condition to truncate outbound waves. The signal impulse has a central frequency of 400 MHz, and the time step is 0.067 ns. We have simulated four cases: a combination of two radiation polarizations (TM and TE), and two geological settings, i.e., a sandy/gravelly half-space overlain by a silty/clayey layer (the case of Fort Richardson, AK), and a silty/clayey half-space overlain by sandy/gravelly layer (the case of Hanover, NH). The results depict the following implication. (1) More EM energy is radiated into the air as an air wave for the TM mode, and more EM energy will be sent into the ground when the TE mode is used, regardless of the geological setting. (2) Where a gravelly sandy half-space overlain by a silty/clayey layer, more EM energy will be trapped in the silty/clayey layer as a ground wave guide in the TE mode with almost no air radiation, when compared with the same radiation mode in the case of silty/clayey half-space overlain by a layer of gravelly sandy. (3) For the geological setting of a sandy/gravelly half-space overlain by a silty/clayey layer, the TE mode only contains ground wave and the TM mode only contains air wave energy. This implies that for this case a far more complete separation of the air wave and the ground wave can be reached. These simulation results imply that transmission mode should consider the on-site geological setting when attempt to use the ground wave as a communication carrier.
{"title":"Numerical simulation of near-surface GPR in TE and TM modes","authors":"Lanbo Liu, S. Arcone","doi":"10.1117/12.462285","DOIUrl":"https://doi.org/10.1117/12.462285","url":null,"abstract":"Stimulated by the inquiry of using high frequency electromagnetic ground waves to communicate information among unattended ground sensors, numerical simulations of GPR performance in different near-surface geological settings were conducted. Two sets of 400 MHz GPR field data, one from Fort Richardson, Alaska, and the other one from Hanover, New Hampshire, were used to be the 'ground truth' to compare with numerical simulations. The numerical simulation algorithm we used adapts the finite difference time domain method, with a perfectly matched layer as the absorption boundary condition to truncate outbound waves. The signal impulse has a central frequency of 400 MHz, and the time step is 0.067 ns. We have simulated four cases: a combination of two radiation polarizations (TM and TE), and two geological settings, i.e., a sandy/gravelly half-space overlain by a silty/clayey layer (the case of Fort Richardson, AK), and a silty/clayey half-space overlain by sandy/gravelly layer (the case of Hanover, NH). The results depict the following implication. (1) More EM energy is radiated into the air as an air wave for the TM mode, and more EM energy will be sent into the ground when the TE mode is used, regardless of the geological setting. (2) Where a gravelly sandy half-space overlain by a silty/clayey layer, more EM energy will be trapped in the silty/clayey layer as a ground wave guide in the TE mode with almost no air radiation, when compared with the same radiation mode in the case of silty/clayey half-space overlain by a layer of gravelly sandy. (3) For the geological setting of a sandy/gravelly half-space overlain by a silty/clayey layer, the TE mode only contains ground wave and the TM mode only contains air wave energy. This implies that for this case a far more complete separation of the air wave and the ground wave can be reached. These simulation results imply that transmission mode should consider the on-site geological setting when attempt to use the ground wave as a communication carrier.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125160443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. S. Freeland, R. E. Yoder, M. L. Miller, S. Koppenjan
Ground-penetrating radar (GPR) technology has supplied invaluable assistance in numerous criminal investigations. However, field personnel desire further development such that the technology is rapidly deployable, and it provides both a simple user interface and sophisticated target identification. To assist in the development of target identification algorithms, our efforts involve gathering background GPR data for the various site conditions and circumstances that often typify clandestine burials. For this study, forensic anthropologists established burial plots at The University of Tennessee Anthropological Research Facility (ARF). These plots contain donated human cadavers lying in various configurations and depths. Each plot includes a fleshed cadaver with varying combinations of human skeletal remains, construction material, and backfill. We scanned the plots using two GPR systems. The first system is a multi-frequency synthetic-aperture unit (GPR-X) developed by the Department of Energy's Special Technologies Laboratory (STL), Bechtel Nevada (Koppenjan et al., 2000). The impulse radar system is a newly released commercial unit (SIR-20) manufactured by Geophysical Survey Systems, Inc. (GSSI). This paper provides example scans from each system, and a discussion of the survey protocol and general performance.
探地雷达技术在许多刑事调查中提供了宝贵的协助。然而，现场人员希望进一步发展，使该技术能够快速部署，并提供简单的用户界面和复杂的目标识别。为了协助发展目标识别算法，我们的工作包括收集各种地点条件和情况的背景探地雷达数据，这些情况通常是秘密埋葬的典型情况。在这项研究中，法医人类学家在田纳西大学人类学研究机构(ARF)建立了墓地。这些地块包含了捐赠的人类尸体，它们躺在不同的形状和深度。每个地块包括一具肉身尸体，其中包含不同组合的人类骨骼遗骸、建筑材料和回填物。我们用两套探地雷达系统扫描了这些地块。第一个系统是多频率合成孔径单元(GPR-X)，由内华达柏克德公司能源部特殊技术实验室(STL)开发(Koppenjan et al.， 2000)。脉冲雷达系统是由地球物理测量系统公司(GSSI)制造的新发布的商业单位(SIR-20)。本文提供了每个系统的扫描示例，并讨论了调查协议和一般性能。
{"title":"Forensic application of sweep-frequency and impulse GPR","authors":"R. S. Freeland, R. E. Yoder, M. L. Miller, S. Koppenjan","doi":"10.1117/12.462241","DOIUrl":"https://doi.org/10.1117/12.462241","url":null,"abstract":"Ground-penetrating radar (GPR) technology has supplied invaluable assistance in numerous criminal investigations. However, field personnel desire further development such that the technology is rapidly deployable, and it provides both a simple user interface and sophisticated target identification. To assist in the development of target identification algorithms, our efforts involve gathering background GPR data for the various site conditions and circumstances that often typify clandestine burials. For this study, forensic anthropologists established burial plots at The University of Tennessee Anthropological Research Facility (ARF). These plots contain donated human cadavers lying in various configurations and depths. Each plot includes a fleshed cadaver with varying combinations of human skeletal remains, construction material, and backfill. We scanned the plots using two GPR systems. The first system is a multi-frequency synthetic-aperture unit (GPR-X) developed by the Department of Energy's Special Technologies Laboratory (STL), Bechtel Nevada (Koppenjan et al., 2000). The impulse radar system is a newly released commercial unit (SIR-20) manufactured by Geophysical Survey Systems, Inc. (GSSI). This paper provides example scans from each system, and a discussion of the survey protocol and general performance.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"79 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114869358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tunnel management system (TMS) is a software system that stores data on current tunnel conditions. The system designs repair strategy necessary to keep waterway tunnels in proper condition. The TMS database includes eye observation records, boring data, GPR-acquired information, etc. GPR has been widely used in Japan to disclose unseen objects behind the lining of waterway tunnels. Application has been limited, however, to comparatively larger diameter tunnels. A GPR rapid-survey system for small-diameter tunnels has been developed to fulfill the need for database completion of the TMS. Through application to many tunnels, GPR has been found effective in terms of obtaining knowledge objects behind the lining. Through theoretical speculation and experience, the interpreting effort has revealed many unseen events such as void, collapsed soil, and water accumulation. Such GPR information gave firm basis to learning the reason of faults (such as cracks, which appeared on the surface), evaluating the degree of risk for collapse, and determining repair methods.
{"title":"GPR rapid survey system for small-diameter tunnels","authors":"Eiji Sakurada, M. Inagaki","doi":"10.1117/12.462266","DOIUrl":"https://doi.org/10.1117/12.462266","url":null,"abstract":"Tunnel management system (TMS) is a software system that stores data on current tunnel conditions. The system designs repair strategy necessary to keep waterway tunnels in proper condition. The TMS database includes eye observation records, boring data, GPR-acquired information, etc. GPR has been widely used in Japan to disclose unseen objects behind the lining of waterway tunnels. Application has been limited, however, to comparatively larger diameter tunnels. A GPR rapid-survey system for small-diameter tunnels has been developed to fulfill the need for database completion of the TMS. Through application to many tunnels, GPR has been found effective in terms of obtaining knowledge objects behind the lining. Through theoretical speculation and experience, the interpreting effort has revealed many unseen events such as void, collapsed soil, and water accumulation. Such GPR information gave firm basis to learning the reason of faults (such as cracks, which appeared on the surface), evaluating the degree of risk for collapse, and determining repair methods.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117122046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The method of computational diagnostics has been recently developed to determine the depth of layers and their electrophysical parameters related to structural diagnostics (monitoring of road pavements, runways, etc.). The method of computational diagnostics is based on minimizing a certain smoothing functional, which includes a functional of discrepancy between the resulting measurements of scattered electromagnetic field and the results of a direct model problem, and also a stabilizing functional accounting for a priori data on the electrophysical and geometrical parameters of a sounded object (medium). The solution minimizing this functional is found both by one of the iterative techniques (simple iteration, steepest descent, conjugate gradients, etc.) and direct techniques. The problem discussed is related to the complexity of searching for a global minimum of the finite dimensional spaces of the layer parameters, when this complexity is brought about by the multiple-extremality of the functional. The examples are presented of the actually restored electrophysical and geometrical medium parameters by using a video pulse ultra-wideband ground penetrating radar.
{"title":"Detecting and classifying of physical and geometrical characteristics of the subsurface through the use of computing diagnostics method for ground-penetrating radar","authors":"V. N. Sablin, A. Grinev, I. A. Chebakov","doi":"10.1117/12.462288","DOIUrl":"https://doi.org/10.1117/12.462288","url":null,"abstract":"The method of computational diagnostics has been recently developed to determine the depth of layers and their electrophysical parameters related to structural diagnostics (monitoring of road pavements, runways, etc.). The method of computational diagnostics is based on minimizing a certain smoothing functional, which includes a functional of discrepancy between the resulting measurements of scattered electromagnetic field and the results of a direct model problem, and also a stabilizing functional accounting for a priori data on the electrophysical and geometrical parameters of a sounded object (medium). The solution minimizing this functional is found both by one of the iterative techniques (simple iteration, steepest descent, conjugate gradients, etc.) and direct techniques. The problem discussed is related to the complexity of searching for a global minimum of the finite dimensional spaces of the layer parameters, when this complexity is brought about by the multiple-extremality of the functional. The examples are presented of the actually restored electrophysical and geometrical medium parameters by using a video pulse ultra-wideband ground penetrating radar.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"106 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116170418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We have carried out borehole radar (BHR) surveys at gold mines in the Witwatersrand Basin. South Africa in order to map the Ventersdorp Contact Reef (VCR). In one such survey 20 kW transmitter and receiver pairs, 32 mm in diameter, with a bandwidth of 10-125 Mllz were used to profile a ~300 metre long section of the reef from a borehole that intersected it at an angle of 26°. Structures on the VCR were visible to a distance of 8Om, before noise started to dominate the signal. We established that the V.C.R. is sufficiently reflective, and its host rocks are transparent enough to open not only the certainty of high resolution echo sounding along the nadir line, but also the possibility of mapping off-axis back-scatterers by applying modified SAR reconstruction techniques to VHF BHR data. One of the problems facing synthetic aperture borehole radar is that it is difficult to build thin, efficient, directional radar antennas. Thin borehole radars are cylindrically omnidirectional and cannot be used to distinguish left from right. In this paper we show that borehole curvature can be used to address the difficulty of determining on which side ofthe survey line a backscattering object might lie.
{"title":"Borehole radar imaging from deviating boreholes","authors":"C. Simmat, N. Osman, J. Hargreaves, I. Mason","doi":"10.1117/12.462207","DOIUrl":"https://doi.org/10.1117/12.462207","url":null,"abstract":"We have carried out borehole radar (BHR) surveys at gold mines in the Witwatersrand Basin. South Africa in order to map the Ventersdorp Contact Reef (VCR). In one such survey 20 kW transmitter and receiver pairs, 32 mm in diameter, with a bandwidth of 10-125 Mllz were used to profile a ~300 metre long section of the reef from a borehole that intersected it at an angle of 26°. Structures on the VCR were visible to a distance of 8Om, before noise started to dominate the signal. We established that the V.C.R. is sufficiently reflective, and its host rocks are transparent enough to open not only the certainty of high resolution echo sounding along the nadir line, but also the possibility of mapping off-axis back-scatterers by applying modified SAR reconstruction techniques to VHF BHR data. One of the problems facing synthetic aperture borehole radar is that it is difficult to build thin, efficient, directional radar antennas. Thin borehole radars are cylindrically omnidirectional and cannot be used to distinguish left from right. In this paper we show that borehole curvature can be used to address the difficulty of determining on which side ofthe survey line a backscattering object might lie.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122436517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Densely sampled GPR data can supplement hydrogeological data for estimating the spatial distribution of porosity and hydraulic conductivity over an aquifer. However, most of the time, the GPR surveys are performed along profiles (2D) and, when 3D models are seeked, the third spatial dimension is assessed by acquiring data over parallel profiles. This configuration is possible when the ground surface is clean and free of any obstacle but these conditions are seldom met in the field. Here, we show the results of a pseudo-3D acquisition protocol when spatial sampling cannot be done on a regular grid. The GPR reflection times are correlated with piezometric and stratigraphic information; cokriging of both data after some mathematical manipulation yields to an estimate of the hydraulic conductivity.
{"title":"New pseudo-3D GPR data method for hydraulic conductivity estimation over an unconfined aquifer","authors":"E. Gloaguen, M. Chouteau, D. Marcotte","doi":"10.1117/12.462257","DOIUrl":"https://doi.org/10.1117/12.462257","url":null,"abstract":"Densely sampled GPR data can supplement hydrogeological data for estimating the spatial distribution of porosity and hydraulic conductivity over an aquifer. However, most of the time, the GPR surveys are performed along profiles (2D) and, when 3D models are seeked, the third spatial dimension is assessed by acquiring data over parallel profiles. This configuration is possible when the ground surface is clean and free of any obstacle but these conditions are seldom met in the field. Here, we show the results of a pseudo-3D acquisition protocol when spatial sampling cannot be done on a regular grid. The GPR reflection times are correlated with piezometric and stratigraphic information; cokriging of both data after some mathematical manipulation yields to an estimate of the hydraulic conductivity.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115973890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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