Home About us Contact
|
Home About us Contact | ||
|
|
||
Ground-penetrating Radar (ground-penetrating + radar)
Terms modified by Ground-penetrating Radar Selected AbstractsHydrological connectivity of soil pipes determined by ground-penetrating radar tracer detectionEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2004Joseph Holden Abstract Soil pipes are common and important features of many catchments, particularly in semi-arid and humid areas, and can contribute a large proportion of runoff to river systems. They may also signi,cantly in,uence catchment sediment and solute yield. However, there are often problems in ,nding and de,ning soil pipe networks which are located deep below the surface. Ground-penetrating radar (GPR) has been used for non-destructive identi,cation and mapping of soil pipes in blanket peat catchments. While GPR can identify subsurface cavities, it cannot alone determine hydrological connectivity between one cavity and another. This paper presents results from an experiment to test the ability of GPR to establish hydrological connectivity between pipes through use of a tracer solution. Sodium chloride was injected into pipe cavities previously detected by the radar. The GPR was placed downslope of the injection points and positioned on the ground directly above detected soil pipes. The resultant radargrams showed signi,cant changes in re,ectance from some cavities and no change from others. Pipe waters were sampled in order to check the radar results. Changes in electrical conductivity of the pipe water could be detected by the GPR, without data post-processing, when background levels were increased by more than approximately twofold. It was thus possible to rapidly determine hydrological connectivity of soil pipes within dense pipe networks across hillslopes without ground disturbance. It was also possible to remotely measure travel times through pipe systems; the passing of the salt wave below the GPR produced an easily detectable signal on the radargram which required no post-processing. The technique should allow remote sensing of water sources and sinks for soil pipes below the surface. The improved understanding of ,owpath connectivity will be important for understanding water delivery, solutional and particulate denudation, and hydrological and geomorphological model development. Copyright © 2004 John Wiley & Sons, Ltd. [source] Snow density variations: consequences for ground-penetrating radarHYDROLOGICAL PROCESSES, Issue 7 2006A. Lundberg Abstract Reliable hydrological forecasts of snowmelt runoff are of major importance for many areas. Ground-penetrating radar (GPR) measurements are used to assess snowpack water equivalent for planning of hydropower production in northern Sweden. The travel time of the radar pulse through the snow cover is recorded and converted to snow water equivalent (SWE) using a constant snowpack mean density from the drainage basin studied. In this paper we improve the method to estimate SWE by introducing a depth-dependent snowpack density. We used 6 years measurements of peak snow depth and snowpack mean density at 11 locations in the Swedish mountains. The original method systematically overestimates the SWE at shallow depths (+25% for 0·5 m) and underestimates the SWE at large depths (,35% for 2·0 m). A large improvement was obtained by introducing a depth,density relation based on average conditions for several years, whereas refining this by using separate relations for individual years yielded a smaller improvement. The SWE estimates were substantially improved for thick snow covers, reducing the average error from 162 ± 23 mm to 53 ± 10 mm for depth range 1·2,2·0 m. Consequently, the introduction of a depth-dependent snow density yields substantial improvements of the accuracy in SWE values calculated from GPR data. Copyright © 2005 John Wiley & Sons, Ltd. [source] Characterising relict cryogenic macrostructures in mid-latitude areas of the USA with three-dimensional ground-penetrating radarPERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2009James Doolittle Abstract Ground-penetrating radar (GPR) has considerable potential for the detection and identification of sediment-filled wedges and relict polygonal patterns in mid-latitude areas. Relict cryogenic macrostructures have been described previously both within and outside the maximum extent of the Late Wisconsinan glacial border in many regions of the USA. The features were formed under climatic conditions associated with permafrost and periglacial conditions and provide evidence of climate change. In this study, buried relict cryogenic macrostructures were identified with GPR. On some two-dimensional GPR (2D GPR) records, boundaries with the host materials are indistinguishable or blurred resulting in the features being overlooked, misinterpreted and/or imprecisely delineated. Three-dimensional GPR (3D GPR) was able to delineate buried networks of sediment-filled wedges and provided more meaningful information than 2D radar records. When supplemented with adequate ground-truth observations, GPR offers considerable potential for imaging, interpreting and mapping near-surface cryogenic macrostructures in former periglacial environments. Copyright © 2009 John Wiley & Sons, Ltd. [source] GPR, ERT and magnetic investigations inside the Martyrium of St Philip, Hierapolis, TurkeyARCHAEOLOGICAL PROSPECTION, Issue 3 2009Luigia Nuzzo Abstract Hierapolis, Denizli, Turkey, was one of the most important Hellenistic-Roman cities in Asia Minor. Located about 250,km east of Izmir, the area is a UNESCO World Heritage Site because of its magnificent archaeological remains and the white travertine pool formations created by its peculiar geothermal setting. The Italian Archaeological Mission in more than 50 years of activity in Hierapolis has brought to light and restored important vestiges of the ancient city, helping to understand the urban layout in the various epochs of its development. In 2001,2003 geophysical surveys were performed by the University of Lecce in several areas inside the archaeological site of Hierapolis to support the archaeological excavations. This paper reports the results of the integrated geophysical surveys performed in 2003 inside the Martyrium of Saint Philip, a mausoleum built on the place where it is believed that the Apostle was martyred. Ground-penetrating radar (GPR), electrical resistivity tomography (ERT) and magnetic gradient investigations were carried out in the central octagonal room, whereas the accessible lateral rooms were surveyed with GPR and occasionally ERT. The acquisition was performed along a series of closely spaced lines and the processed data were visualized as two-dimensional vertical sections (GPR), map view (magnetic gradiometry), depth slices or three-dimensional volumes (GPR and ERT) to allow an integrated interpretation of the geophysical results. The analysis of the geophysical datasets revealed a series of anomalies in both the central and lateral rooms that could be ascribed to the building foundations and to other possible archaeological structures, probably related to earlier stages of the sacred building and to tombs, as well as other anomalies (voids, fractures) of presumable natural origin. Copyright © 2009 John Wiley & Sons, Ltd. [source] Data processing issues in large-area GPR surveys: correcting trace misalignments, edge discontinuities and stripingARCHAEOLOGICAL PROSPECTION, Issue 2 2008Eileen G. Ernenwein Abstract Ground-penetrating radar (GPR) lags behind other archaeogeophysical methods in terms of speed, efficiency and ability to produce clean site-wide composites owing to complex and time-consuming data processing requirements. Two North American case studies illustrate problems that occur when survey is conducted over long and short periods of time. Some GPR defects have been blamed on differential solar heating of antennae and battery power levels but we show these effects to be negligible. Major problems include gradual changes over time in ground moisture and low-level background noise, which can create discontinuities between adjacent survey blocks when data are collected at different times. These problems are often remedied by globally aligning traces using a stable trace position. Variations in ground moisture through time also cause differences in reflection amplitudes, necessitating different range gain curves to match amplitudes between survey blocks. In some cases changes in ground moisture cause noticeable differences in velocity between survey blocks requiring time-scales to be converted to depths to correctly match the data. These problems must be remedied before horizontal slicing can be considered. Subsequent image processing may also be necessary to generate a seamless mosaic and eliminate striping artefacts commonly seen in slice maps. The latter are probably caused by antenna lift and tilt and can be removed by a de-striping algorithm that uses a one-dimensional low-pass filter to characterize stripes followed by their subtraction from the data. Copyright © 2008 John Wiley & Sons, Ltd. [source] Archaeological prospecting at the Double Ditch State Historic Site, North Dakota, USAARCHAEOLOGICAL PROSPECTION, Issue 1 2008Kenneth L. KvammeArticle first published online: 14 FEB 200 Abstract A four-year programme of remote sensing at the Double Ditch State Historic Site, a fortified earthlodge village in the Great Plains of North Dakota, USA, demonstrates the importance of combined prospecting methods for understanding the multidimensional nature of complex settlements. Aerial survey from a powered parachute acquired high-resolution digital colour and thermal infrared imagery. The former distinguishes houses, borrow pits and ditches from middens and fill areas by changes in vegetation; the latter does the same through temperature variations that also highlight substantial village deposits and century-old excavations. Magnetic gradiometry reveals two previously unknown fortification systems that vastly increase the settlement's area and projected population to perhaps 2000 individuals. Vast numbers of food storage pits that supported that population are also indicated. Vertical soundings and area surveys of magnetic susceptibility aid in the understanding of storage pit magnetism and anthropogenic soil mounding and removal. A high-resolution digital model of topography documents surface expressions caused by ditches, houses, borrow pits and mounds; when combined with overlays of geophysical data understanding of remote sensing responses is improved and relationships between large mounds with village defenses are made clear. Ground-penetrating radar gives insights into mounded midden interior forms and yields details about house interior components, while electrical resistance results improve definition of middens, other depositional areas, houses and borrow pits. This multisensor remote sensing programme reduced excavation costs by allowing a wide variety of archaeological features of interest to be targeted accurately. Excavations confirmed anomaly identifications and established a chronology that documents late fifteenth century origins to an ultimate abandonment about AD 1782. Copyright © 2008 John Wiley & Sons, Ltd. [source] Rapid seismic reflection imaging at the Clovis period Gault site in central TexasARCHAEOLOGICAL PROSPECTION, Issue 4 2007John A. Hildebrand Abstract Using a modified seismic reflection imaging system with rapid translation of receivers, stratigraphic profiles were collected at the Gault site in central Texas. For rapid data collection, spikeless geophone receivers were placed in sand-filled bags at tight spacing, and these receivers were rapidly pulled along the ground surface between shots. Shots were produced by a small hammer strike to a vertical pipe at 20-cm intervals. High quality ultrashallow seismic reflection profiles were collected at a rate of 25,m,h,1, significantly faster than what is possible with conventional seismic reflection imaging using individually planted geophones. Ground-penetrating radar was attempted, but abandoned owing to the poor penetration of the radar signals in the clay soils present at the Gault site. Electromagnetic induction grids were collected surrounding each seismic reflection profile, and provided information on near-surface ground water. Seismic reflection images of Gault site stratigraphy provided greater depth penetration than accessible from backhoe trenching and coring, and helped to better outline the site geological context. Seismic images reveal coherent reflections at shallow depths (0,2.5,m), and extensive scattering at deeper levels (2.5,8,m), underlain by reflection-free zones. These data are interpreted as clay and gravel layers overlaying palaeostream channels carved into the limestone bedrock. Where comparative data were available, the geophysical findings were corroborated by observations of site stratigraphy in archaeological excavation units, backhoe trenches and cores. Seismic reflection studies at the Gault site revealed a palaeochannel filled with pre-Clovis age sediments. Pre-Clovis age sediments are not known to occur at other locations within the Gault site. They provide a unique opportunity to test for cultural remains of great antiquity. Copyright © 2007 John Wiley & Sons, Ltd. [source] Ground-penetrating radar for archaeology.ARCHAEOLOGICAL PROSPECTION, Issue 3 2006Lawrence B. Conyers. No abstract is available for this article. [source] Contribution of geophysics to outlining the foundation structure of the Islamic Museum, Cairo, EgyptARCHAEOLOGICAL PROSPECTION, Issue 3 2005A. M. Abbas Abstract The Islamic museum was erected in 1896. The building is situated in the heart of Cairo (capital of Egypt) and holds marvellous Islamic antiquities and priceless ancient hand-writing and rare books. Recently, a restoration scheme has been planned to secure the old building which suffers from weakened foundations. In addition, the wooden roofs will be replaced by concrete ones and an extra floor will be integrated into the building. Unfortunately, the architecture construction charts were neither available nor obtainable. Therefore, the structure of the foundations and the base walls of the building had to be outlined. At the time of construction, three major fundamental wall designs were dominant and were to be considered during the work approach. Ground-penetrating radar (GPR) and dipole,dipole resistivity imaging have been integrated to (define the structure of the foundation walls of the building. A Ramac2 system connected to a 500,MHz antenna has been utilized for conducting the GPR survey. In addition, a Terrameter SAS 1000 single channel device has been used for performing the resistivity profiles. At accessible spaces around the building GPR and resistivity profiles were obtained. The GPR analysis has revealed the depth of the foundation walls to be about 0.9,m from the ground surface with a width close to 0.6,m. The wall design is close to a straight wall style. Furthermore, the analysis of the dipole,dipole resistivity measurements has matched the geology of the area, where subsoil anomalies may be due to the scattered limestone blocks that occur in the area. Moreover, the foundation walls have resistivity values that fall into the range of fractured limestone or limestone blocks. A step-wise or inclined foundation wall style has not been indicated through the parallel resistivity profiles. Copyright © 2005 John Wiley & Sons, Ltd. [source] Identification and removal of above-ground spurious signals in GPR archaeological prospecting,ARCHAEOLOGICAL PROSPECTION, Issue 2 2005Luigia Nuzzo Abstract Ground-penetrating radar (GPR) is a shallow geophysical method increasingly used in archaeological prospecting to detect buried remains and to map the stratigraphy of the uppermost earth layers embodying the archaeological features. The GPR sections, however, can be contaminated by spurious correlated signals caused by above-ground obstacles (buildings, trees, fences, power lines) placed either in-line or off-line with respect to the profile (surface scattering). In the case study presented this problem is analysed for a 35,MHz GPR survey carried out for stratigraphical purposes in the archaeological site of the Roman Ships near Pisa (Italy). The investigation inside the archaeological excavation, when the level was about 5,m below the ground surface, produced a severe surface scattering problem caused by the iron sheet-piling protecting the excavation walls and bordering some of the partly excavated boats. An attempt to interpret the profiles was carried out in a zone where the relatively simple geometry of the metallic enclosure allowed understanding of the possible origin of spurious events, also thanks to the high density of profiles acquired along two orthogonal directions. Migration at the air velocity and geometrical considerations helped the identification of hyperbolic and slightly slanted features as surface scattering phenomena from different sides of the iron sheet-piling. A simple but original subtraction procedure was successful for the attenuation of some of the spurious reflections. After this partial removal, other spurious signals could be recognized more easily as well as two weak subhorizontal reflections of probable stratigraphical meaning. Subsequently, filtering procedures based on f-k and Radon transform methods were tried to further reduce the spurious signals, thus enhancing the visibility of the interesting reflections. Copyright © 2005 John Wiley & Sons, Ltd. [source] Ground-penetrating radar and geo-electrical simulations of data from the Floridablanca archaeological siteARCHAEOLOGICAL PROSPECTION, Issue 1 2005M. de la Vega Abstract In this work we characterize the electromagnetic response of archaeological remains of a Spanish fortress situated on the Atlantic coast in Patagonia (Argentina). The fortress, part of the Floridablanca colony, founded in the eighteenth century, has been surveyed with non-invasive electromagnetic techniques (ground-penetrating radar (GPR) and the geo-electric method). The surveys indicate the presence of adobe walls of various sizes and width having different preservation states. Use of inversion algorithms alone to interpret the data has not been conclusive in obtaining a reliable model, because many uncertainties remained. To aid the interpretation, we make use of modelling methods to simulate the low- and high-frequency electromagnetic responses of the structures. The walls can be differentiated in spite of the low resistivity contrast with the surrounding media. The resolution of the 500,MHz antenna allows a satisfactory determination of the location of the walls and their conservation state. Similarly, the geo-electrical response has enough sensitivity to detect the inner and major walls. Copyright © 2005 John Wiley & Sons, Ltd. [source] Ground-penetrating radar survey to map the location of buried structures under two churchesARCHAEOLOGICAL PROSPECTION, Issue 4 2002Giovanni LeucciArticle first published online: 21 NOV 200 Abstract The range of ground-penetrating-radar (GPR) applications is very wide and diverse. Ground-penetrating radar provides high-resolution continuous profiles, and it has been used in various fields such as environmental, geology, geotechnical engineering, archaeology, etc. Two surveys with GPR were undertaken inside two churches (the church of St Oronzo and the church of Immacolata) at Novoli village, located a few kilometres northwest of Lecce (Italy). The purpose of the two surveys was to obtain information about the existence of ancient structures beneath the two churches. No document or writing exists to confirm the presence of structures under the two churches. However, there are several oral testimonies handed down over the centuries that suggest the presence of these ancient structures. Both surveys were carried out using a GSSI Sir System2, incorporating 500 MHz centre frequency antenna. The GPR time slices were constructed from closely spaced parallel profiles. The time slices, computed from averaging radar reflections over vertical time windows several nanoseconds thick, are used to map subsoil features associated with the structures, probably of anthropogenic origin. To facilitate the interpretation of the results, a three-dimensional image was constructed using closely spaced parallel profiles, which are linearly interpolated. Copyright © 2002 John Wiley & Sons, Ltd. [source] Ground-penetrating radar and magnetic survey to the west of Al-Zayyan Temple, Kharga Oasis, Al-Wadi Al-Jadeed (New Valley), EgyptARCHAEOLOGICAL PROSPECTION, Issue 2 2002Dr. Hiroyuki Kamei Abstract Al-Zayyan Temple or Qasr Al-Zayyan might be regarded as one in a chain of several fortresses that the Romans built to secure the salver's trade caravan route between Asyut and Sudan, known as Darb Al-Arbain. Al-Zayyan temple lies about 25 km south of Al-Kharga city, the capital of the New Valley, and deviates to the east of Al-Kharga-Paris main road some 2 km along the Al-Zayyan-Aarif minor road. The background information about the temple is very scarce, and even what is known is neither clear nor accurate. Some indications have ascribed it to Amenebis and that it was restored during the reign of Emperor Antoninus (AD 138,161). An integrated ground-penetrating radar (GPR)survey using the SIR 2000 Geophysical Survey Systems, Inc. (GSSI) together with magnetic survey using FM36 (GeoScan) and the three component fluxgate gradiometer TRM-70D (Tokin) have been applied to the western side of the temple. The results show relatively large-scale buried structures in a direction intersecting that of the present temple at about 45°. Some particular features within the structure have been speculatively ascribed on the basis of comprehending their signatures in the GPR sections. The magnetic results have improved the identification of some objects revealed by the GPR and provided ideas about some of the other features. Copyright © 2002 John Wiley & Sons, Ltd. [source] Ultra-wideband Vivaldi antenna design for multisensor adaptive ground-penetrating impulse radarMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2006Ahmet Serdar Turk Abstract This paper describes a partially dielectric-loaded Vivaldi antenna (PDVA) structure that maintains ultra-wideband antenna characteristics over a bandwidth ratio greater than 25:1 so as to improve the impulse radiation characteristics for multisensor adaptive ground-penetrating Radar (GPR) operations. The PDVA is introduced for metal-detector-combined GPR head designs in order to avoid performance degradations based on the sensor interferences. It is shown that high gain, low input reflection, and signal-ringing levels over the wide operational bands are attainable for a PDVA with proper dielectric and absorber loadings. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 834,839, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21491 [source] Investigations regarding Alpine talus slopes using ground-penetrating radar (GPR) in the Bavarian Alps, GermanyEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2001Oliver Sass Abstract The applicability of ground-penetrating radar (GPR) for the investigation of loose debris was tested at two sites (Viererkar and Zugspitzplatt). A pulseEKKO 100 GPR system equipped with 25 MHz antennae was utilized. The aim of the investigation was to record the base of the debris layer, and thereby acquire an estimation of the backweathering rates of the adjacent rockwalls. The study areas are situated in the Northern Alps near the German,Austrian border. The sites are characterized by steep limestone rockwalls and extensive talus accumulations. A total of six profiles was surveyed. The method is suitable and effective for a quick survey in this dry, high-ohmic substrate. The GPR system was able to deliver information about the subsurface stratigraphy to c. 70 m depth. The boundary line to the bedrock was discovered , depending upon the profile surveyed ,5 to 25 m below the surface. The base of the debris material sometimes shows no distinct reflection. Buried features (V-shaped furrows, zones overdeepened by ice action, geological structures) could be detected. Arched structures well below the talus,bedrock interface can be interpreted as drainage systems in the karstic bedrock. A thick scree layer of Late Glacial age was separated from a thinner layer on the talus surface, which was related to the Holocene. The backweathering rates were fixed by a calculation of talus volume to c. 100 mm/103 a during the Holocene (Viererkar) and 150,300 mm/103 a (Zugspitzplatt). The detrital formation in north-exposed sites is twice as intense as in south-exposed sites. These results match the rates of recent rockfall in the same area of investigation. The calculated backweathering for the late glacial period is 150,730 mm/103 a. The magnitude of the calculated rockwall retreat lies well within the range of previous measurements. The discrepancy between some weathering rates highlights the fact that recent and past relief formation must be differentiated. Otherwise recent removal rates may be overestimated. Copyright © 2001 John Wiley & Sons, Ltd. [source] Ground-penetrating radar survey of the Sny Magill Mound Group, Effigy Mounds National Monument, IowaGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 4 2008William E. Whittaker A ground-penetrating radar (GPR) survey of 101 mounds at the Sny Magill Unit of Effigy Mounds National Monument, Iowa, demonstrates that GPR can be an effective tool to evaluate the structure and condition of mounds without damaging them. Ideal survey conditions and improved processing technology allow for the identification of strata within the mounds, as well as areas of post-construction disturbance and possible archaeological features within the mounds. Provisional interpretations indicate that 60 are intact conical mounds with minimal post-construction disturbance, and two show very strong evidence of containing interior burial platforms; 29 are badly damaged by non-cultural or cultural activity; two are probable non-cultural mounds; nine are reasonably intact linear and effigy mounds; one is an excavated effigy mound. GPR and other remote-sensing techniques are highly recommended for mound investigation, but wherever possible such techniques need to be coordinated with mound excavation so as to test the remote-sensing results. © 2008 Wiley Periodicals, Inc. [source] 3D imaging of a reservoir analogue in point bar deposits in the Ferron Sandstone, Utah, using ground-penetrating radarGEOPHYSICAL PROSPECTING, Issue 3 2004Xiaoxian Zeng ABSTRACT Most existing reservoir models are based on 2D outcrop studies; 3D aspects are inferred from correlation between wells, and so are inadequately constrained for reservoir simulations. To overcome these deficiencies, we have initiated a multidimensional characterization of reservoir analogues in the Cretaceous Ferron Sandstone in Utah. Detailed sedimentary facies maps of cliff faces define the geometry and distribution of reservoir flow units, barriers and baffles at the outcrop. High-resolution 2D and 3D ground-penetrating radar (GPR) images extend these reservoir characteristics into 3D to allow the development of realistic 3D reservoir models. Models use geometric information from mapping and the GPR data, combined with petrophysical data from surface and cliff-face outcrops, and laboratory analyses of outcrop and core samples. The site of the field work is Corbula Gulch, on the western flank of the San Rafael Swell, in east-central Utah. The outcrop consists of an 8,17 m thick sandstone body which contains various sedimentary structures, such as cross-bedding, inclined stratification and erosional surfaces, which range in scale from less than a metre to hundreds of metres. 3D depth migration of the common-offset GPR data produces data volumes within which the inclined surfaces and erosional surfaces are visible. Correlation between fluid permeability, clay content, instantaneous frequency and instantaneous amplitude of the GPR data provides estimates of the 3D distribution of fluid permeability and clay content. [source] Detection and analysis of LNAPL using the instantaneous amplitude and frequency of ground-penetrating radar dataGEOPHYSICAL PROSPECTING, Issue 1 2002Luciana Orlando This paper reports the results of using the ground-penetrating radar (GPR) method to detect light non-aqueous phase liquids (LNAPL) floating on the water table in an area where the thickness of LNAPL present ranges from a few centimetres to several decimetres. To understand the GPR response in this context, GPR theoretical models are calculated using information from the literature and hydrogeological field data. The study revealed that in the case of LNAPL floating on the water table in a static condition, there is an increase in the reflection amplitude from the water table due to the decrease in the capillary fringe. Nevertheless the amplitude of reflection from the water table can discriminate the contaminated from the non-contaminated zone. Apart from an analysis of the real traces, the analysis of some attributes of the complex trace, instantaneous amplitude, phase and frequency, are also good tools to detect hydrocarbons floating on the water table. Such attributes, depending on both the signal frequency and the hydrocarbon thickness, can also give information about the thickness of the hydrocarbon layer. It is concluded that analysing the lateral variations in signal amplitude of the real trace and in the amplitude, phase and instantaneous frequency of the complex signal permits the delimiting of the area polluted by the hydrocarbon. [source] An electromagnetic modelling tool for the detection of hydrocarbons in the subsoilGEOPHYSICAL PROSPECTING, Issue 2 2000Carcione Electromagnetic geophysical methods, such as ground-penetrating radar (GPR), have proved to be optimal tools for detecting and mapping near-surface contaminants. GPR has the capability of mapping the location of hydrocarbon pools on the basis of contrasts in the effective permittivity and conductivity of the subsoil. At radar frequencies (50 MHz to 1 GHz), hydrocarbons have a relative permittivity ranging from 2 to 30, compared with a permittivity for water of 80. Moreover, their conductivity ranges from zero to 10 mS/m, against values of 200 mS/m and more for salt water. These differences indicate that water/hydrocarbon interfaces in a porous medium are electromagnetically ,visible'. In order to quantify the hydrocarbon saturation we developed a model for the electromagnetic properties of a subsoil composed of sand and clay/silt, and partially saturated with air, water and hydrocarbon. A self-similar theory is used for the sandy component and a transversely isotropic constitutive equation for the shaly component, which is assumed to possess a laminated structure. The model is first verified with experimental data and then used to obtain the properties of soils partially saturated with methanol and aviation gasoline. Finally, a GPR forward-modelling method computes the radargrams of a typical hydrocarbon spill, illustrating the sensitivity of the technique to the type of pore-fluid. The model and the simulation algorithm provide an interpretation methodology to distinguish different pore-fluids and to quantify their degree of saturation. [source] Measuring thaw depth beneath peat-lined arctic streams using ground-penetrating radarHYDROLOGICAL PROCESSES, Issue 14 2005John H. Bradford Abstract In arctic streams, depth of thaw beneath the stream channel is likely a significant parameter controlling hyporheic zone hydrology and biogeochemical cycling. As part of an interdisciplinary study of this system, we conducted a field investigation to test the effectiveness of imaging substream permafrost using ground-penetrating radar (GPR). We investigated three sites characterized by low-energy water flow, organic material lining the streambeds, and water depths ranging from 0·2 to 2 m. We acquired data using a 200 MHz pulsed radar system with the antennas mounted in the bottom of a small rubber boat that was pulled across the stream while triggering the radar at a constant rate. We achieved excellent results at all three sites, with a clear continuous image of the permafrost boundary both peripheral to and beneath the stream. Our results demonstrate that GPR can be an effective tool for measuring substream thaw depth. Copyright © 2005 John Wiley & Sons, Ltd. [source] Application of ground-penetrating radar to determine the thickness of Pleistocene periglacial slope depositsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2004Daniela Sauer Abstract Wide areas of the mountainous regions of Germany have rock covered by Pleistocene periglacial slope deposits (PPSD), formed by gelifluction during the cold periods of the ice ages in non-glaciated areas. The PPSD provide the parent material for soil development, and their physical characteristics affect several stabile soil properties. Because the PPSD play a significant ecological role, we studied the spatial distribution and properties of the PPSD in order to assess the distribution of the stabile soil properties. The high stone content of the PPSD greatly hinders augering and digging. Hence, we tested the use of ground-penetrating radar (GPR) as a potentially time-saving, non-destructive method to determine the thickness of the PPSD. In several study areas of the Rhenish Massif, GPR investigations of single soil profiles and soil transects along an exposed gas-pipeline ditch were carried out. The GPR images were compared to the actual thickness of the layers of the PPSD exposed in the profiles and the ditch. In the GPR images usually at least one distinct boundary could be identified, which occurs at the transition between the loose material and the hard rock, mostly ranging between 50 and 150,cm depth. In some cases, in which stone content changed abruptly between different layers of the PPSD, also the boundaries between these layers could be identified in the GPR image. On the other hand, in areas where remnants of the Mesozoic-Tertiary weathering mantle are preserved, the boundary between the saprolite and the overlying basal layer of the PPSD is ambiguous or not at all visible. Einsatz von Georadar zur Bestimmung der Mächtigkeit periglaziärer Lagen In den deutschen Mittelgebirgen sind die Gesteine weitflächig von periglaziären Lagen überzogen. Diese entstanden durch Gelifluktion während der Kaltzeiten in den unvergletscherten Bereichen. Sie stellen das Ausgangssubstrat der Bodenbildung dar und bestimmen eine Reihe stabiler Bodeneigenschaften. Die ökologische Bedeutung der periglaziären Lagen gab den Anlass, ihre Verbreitung und Eigenschaften zu erfassen, um daraus flächenhafte Aussagen über diese Eigenschaften abzuleiten. Da Bohrungen und Grabungen in den periglaziären Lagen häufig durch hohe Skelettgehalte erschwert werden, wurde untersucht, ob Georadar zur zeitsparenden, zerstörungsfreien Erfassung der Lagenmächtigkeiten eingesetzt werden kann. In verschiedenen Teilen des Rheinischen Schiefergebirges wurden Georadar-Messungen an Bodenprofilen sowie an Transekten entlang eines Gasleitungsgrabens durchgeführt, die jeweils mit den Mächtigkeiten der periglaziären Lagen verglichen wurden, die an der Graben- bzw. Profilwand aufgeschlossen waren. In den Radargrammen ist in der Regel mindestens eine deutliche Grenze zu erkennen. Diese tritt am Übergang vom Lockermaterial zum Festgestein auf, der in der Regel zwischen 50 und 150,cm Tiefe liegt. In einigen Fällen, in denen sich der Skelettgehalt an den Lagengrenzen abrupt stark verändert, sind auch Grenzen zwischen verschiedenen Lagen im Radargramm zu erkennen. Dagegen ist in Gebieten, in denen Reste der mesozoisch-tertiären Verwitterungsdecke im Untergrund anstehen, die Grenze zwischen der Basislage und dem Gestein im Radargramm nur diffus oder nicht ausgeprägt. [source] Imaging glacial sediment inclusions in 3-D using ground-penetrating radar at Kongsvegen, Svalbard,JOURNAL OF QUATERNARY SCIENCE, Issue 5 2010Tavi Murray Abstract The quiescent-phase surge-type glacier, Kongsvegen, flows confluent with the continuously fast-flowing Kronebreen in northwestern Spitsbergen. The lower regions of Kongsvegen overlie glaciomarine sediments, which have been incorporated into the ice during multiple surge events. The resulting englacial structures are exposed at the surface and on a cliff section. These structures have variously been interpreted as thrusts, formed by compression, or sediment-filled crevasses, formed by extension. We collected a grid of closely spaced ground-penetrating radar profiles in the area adjacent to the cliff section. Several structures were imaged in 3-D, including a strong subhorizontal basal reflector, which was underlain by a second, weaker subhorizontal reflector. The basal reflector was occasionally reverse faulted, suggesting compression. Clear englacial features extended upwards from it, dipping up-glacier at angles of <40° and steepening towards the glacier surface; they had complex geometries that changed rapidly cross-glacier. The structures were orientated at ,30° to ice flow, suggesting modification by lateral compression from Kronebreen. Some of these englacial structures clearly crossed the basal reflector. We conclude that the englacial features imaged are not likely to be derived from crevasse filling and were probably formed by thrusting. The results contribute to our understanding of surge initiation and termination processes, and interpretation of features in the palaeorecord. Copyright © 2009 John Wiley & Sons, Ltd. [source] Measurement of plane-wave spectra of ground penetrating radar antennasMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2005H. R. Lenler-Eriksen Abstract The plane-wave transmitting spectrum (PWTS) of a ground-penetrating radar (GPR) loop antenna close to the air,soil interface is measured by means of a probe buried in soil. Probe correction is implemented based upon knowledge about the complex permittivity of the soil and the current distribution of the probe. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 215,216, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20591 [source] Characterising relict cryogenic macrostructures in mid-latitude areas of the USA with three-dimensional ground-penetrating radarPERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2009James Doolittle Abstract Ground-penetrating radar (GPR) has considerable potential for the detection and identification of sediment-filled wedges and relict polygonal patterns in mid-latitude areas. Relict cryogenic macrostructures have been described previously both within and outside the maximum extent of the Late Wisconsinan glacial border in many regions of the USA. The features were formed under climatic conditions associated with permafrost and periglacial conditions and provide evidence of climate change. In this study, buried relict cryogenic macrostructures were identified with GPR. On some two-dimensional GPR (2D GPR) records, boundaries with the host materials are indistinguishable or blurred resulting in the features being overlooked, misinterpreted and/or imprecisely delineated. Three-dimensional GPR (3D GPR) was able to delineate buried networks of sediment-filled wedges and provided more meaningful information than 2D radar records. When supplemented with adequate ground-truth observations, GPR offers considerable potential for imaging, interpreting and mapping near-surface cryogenic macrostructures in former periglacial environments. Copyright © 2009 John Wiley & Sons, Ltd. [source] Ground penetrating radar survey and stratigraphic interpretation of the Plan du Lac rock glaciers, Vanoise Massif, northern French AlpsPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2008Sébastien Monnier Abstract Internal boundaries of the Plan du Lac rock glaciers in the northern French Alps were investigated using ground-penetrating radar (GPR) and were correlated with the surface morphology. Data collected using 50,MHz antennae along three profiles were processed in a novel manner by applying modulated automatic gain control to discriminate reflection events according to coherence and continuity patterns. Based on the GPR and morphological analyses, the stratigraphy appears complex, with prominent internal boundaries dividing the features into several depositional units, interpreted as sequential creeping or thrusting events. Copyright © 2008 John Wiley & Sons, Ltd. [source] Application of ground-penetrating radar imagery for three-dimensional visualisation of near-surface structures in ice-rich permafrost, Barrow, AlaskaPERMAFROST AND PERIGLACIAL PROCESSES, Issue 4 2007Jeffrey S. Munroe Abstract Three-dimensional ground-penetrating radar (3D GPR) was used to investigate the subsurface structure of ice-wedge polygons and other features of the frozen active layer and near-surface permafrost near Barrow, Alaska. Surveys were conducted at three sites located on landscapes of different geomorphic age. At each site, sediment cores were collected and characterised to aid interpretation of GPR data. At two sites, 3D GPR was able to delineate subsurface ice-wedge networks with high fidelity. Three-dimensional GPR data also revealed a fundamental difference in ice-wedge morphology between these two sites that is consistent with differences in landscape age. At a third site, the combination of two-dimensional and 3D GPR revealed the location of an active frost boil with ataxitic cryostructure. When supplemented by analysis of soil cores, 3D GPR offers considerable potential for imaging, interpreting and 3D mapping of near-surface soil and ice structures in permafrost environments. Copyright © 2007 John Wiley & Sons, Ltd. [source] Detection of subsurface permafrost features with ground-penetrating radar, Barrow, AlaskaPERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2001K. M. Hinkel Abstract A ground-penetrating radar (GPR) survey was conducted in May 1999 on the 1 km2 Circumpolar Active Layer Monitoring (CALM) grid 5 km east of Barrow, Alaska. Spatially continuous measurements were collected along established transects while the active layer remained frozen. The primary objectives were to determine the ,long-term' position of the permafrost table, to recognize ice wedges and ice lenses, and to locate the organic,mineral soil interface. GPR signal and core collection were performed in tandem to verify signal interpretation, to calibrate the instrument, and to determine optimal GPR data-collection parameters. Two-way travel times from the antenna to subsurface reflectors were compared with measured depths obtained from soil cores to estimate an average pulse propagation velocity of 0.13 m/ns through the frozen soil. The most conspicuous subsurface reflectors were ice wedges, which gave high-amplitude hyperbolic reflections. Owing to its higher ice content, the approximate long-term position of the permafrost table could be traced laterally across the profile. Radar interpretations were obscured by the effects of cryoturbation, and because some horizons lack sufficient contrast in electrical properties. Highly detailed information can be obtained by collecting radar data at relatively slow speeds of advance, by using faster scanning rates (>32 scans/s), and by employing high-frequency antennas (>400 MHz). Copyright © 2001 John Wiley & Sons, Ltd. RÉSUMÉ Un levé réalisé avec un radar dont les ondes pénètrent dans le sol a été réalisé en mai 1999 sur un km2 appartenant à la grille établie pour suivre l'évolution de la couche active circumpolaire (CALM), 5 km a l'est de Barrow, Alaska. Des mesures ont été réalisées le long de transects alors que la couche active était gelée. Les premiers objectifs étaient de déterminer la position à long terme de la table du pergélisol, de reconnaître les coins et les lentilles de glace, et de localiser le contact entre les sols organiques et minéraux. Les données radar et des carottes de sondages ont été recueillies au même moment pour vérifier l'interprétation des données radar, calibrer l'instrument et déterminer les meilleurs paramètres d'enregistrement. Deux facons de calculer les temps de parcours depuis l'antenne jusqu'aux réflecteurs souterrains ont été comparés avec des mesures obtenues par sondages, pour estimer une vitesse moyenne de propagation de 0.13 m/ns à travers le sol gelé. Les réflecteurs les plus apparents ont été les coins de glace qui donnent des réflexions hyperboliques de grande amplitude. En raison de leur haute teneur en glace, la position approximative à long terme de la table du pergélisol a pu être reconnue le long des profils. Les interprétations sont obscurcies par les effects des cryoturbations et aussi, parce que certains horizons n'ont pas un contraste suffisant dans leurs propriétés électriques. Une information hautement détaillée peut être obtenue par la méthode radar en utilisant des vitesses lentes d'avancée, de rapides vitesses de scannages (>32 scans/s) et en utilisant des antennes de hautes fréquence (>400 MHz). Copyright © 2001 John Wiley & Sons, Ltd. [source] Efficient, large-scale archaeological prospection using a true three-dimensional ground-penetrating Radar Array systemARCHAEOLOGICAL PROSPECTION, Issue 3 2010Immo Trinks Abstract The Swedish UNESCO World Cultural Heritage site of the Birka and Hovgården Iron Age settlements is well suited for the testing of high-resolution archaeological prospection methods. In May 2006 ground-penetrating radar (GPR) and magnetometer test measurements were conducted at Birka, resulting in data of outstanding quality and new archaeological discoveries, but also demonstrating the need for increased spatial sampling regarding GPR prospection at complex Scandinavian sites. Therefore Birka was selected as a testing ground for a pilot study investigating the suitability of the novel multichannel GPR array system MIRA (MALÅ Imaging Radar Array) for efficient, large-scale GPR surveys with very dense spatial sampling. The study was conducted in May 2008 by MALÅ Geoscience AB in collaboration with the archaeological prospection unit of the Swedish National Heritage Board. The very high-resolution three-dimensional GPR pilot survey demonstrated that it is possible to survey 1,ha and more per day with 8,cm cross-line spacing, mapping archaeological structures in unprecedented resolution, such as postholes of only 25,cm diameter. This paper describes the tested technology and methodology as well as the fieldwork and the results of the study. Copyright © 2010 John Wiley & Sons, Ltd. [source] Stepped frequency ground-penetrating radar survey with a multi-element array antenna: Results from field application on archaeological sites,ARCHAEOLOGICAL PROSPECTION, Issue 3 2010Neil Linford Abstract A series of trial geophysical surveys were conducted with a 3d-Radar GeoScope ground-penetrating radar (GPR) utilizing a multi-element array antenna. This system offers the potential for rapid data acquisition at very high sample densities over a wide frequency bandwidth. Field tests, conducted over the Roman town at Silchester, Hampshire, UK, suggested that a revised antenna configuration was necessary to obtain optimum results from the system, which was then successfully deployed in the collection of over 5,ha of survey data at a sample density of 0.075,m,×,0.075,m. The wide area survey produced a wealth of archaeological detail to complement and expand upon the extensive record of excavation, aerial photography and other geophysical results. Initial trial surveys were conducted with a range of antenna arrays (B2431, B1831 and B1823) incorporating different sized elements to fully exploit the wide potential bandwidth of the system. However, the differing response of elements proved difficult to combine within a single data set and a marked increase in quality was obtained with the use of a prototype V1821 antenna array of identical sized elements. Some concerns remain regarding both the suitability of air-launched antenna arrays to certain site conditions, as one early survey visit to Silchester produced very poor results that remain unexplained, and the maximum penetration depth compared with an impulse GPR using ground-coupled antenna. © 2010 Crown copyright. [source] Geophysical Archaeology Research Agendas for the Future: Some Ground-penetrating Radar ExamplesARCHAEOLOGICAL PROSPECTION, Issue 2 2010Lawrence B. Conyers Abstract Archaeological geophysics research and its applications to archaeology are today positioned to move in a number of directions, building on successes in the past few decades. The basics of data acquisition, processing and interpretation are now commonplace, and along with a variety of new geophysical tools and software, readily available to most dedicated practitioners. It is now time to move beyond the basics to develop new areas of research for the coming decades. Here, we propose some future avenues that can be followed, using ground-penetrating radar (GPR) as an example. One avenue is the application of these techniques to test ideas about culture and history in ways not possible using traditional archaeological methods. Another is the application of sophisticated new equipment and three-dimensional processing methods that can produce greater precision in the products produced, while simplifying data acquisition and revealing more information about buried archaeological features. While we discuss below our ideas with regard to the future of GPR, these basic concepts and future pathways are potentially applicable to the other commonly used near-surface geophysical methods. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||||||||