Diffraction‐based velocity estimates from optimum offset seismic data

Cross, Guy; Knoll, Michael D.

doi:10.1190/1.1443019

Cited by 5 publications

(3 citation statements)

References 14 publications

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“…In order to convert travel time into depth, the GPR signal velocities in the subsoil were estimated using a hyperbola fitting technique through the diffraction of some hyperbolas caused by concrete irrigation piles found throughout the study area (Cross and Knoll ; Jacob and Urban ). Finally, an average velocity of 0.08 m ns –1 (values ranging from 0.06 to 0.10 m ns –1 ) was established and used to estimate the depth of the strata.…”

Section: Data Collection and Methodsmentioning

confidence: 99%

The Integration of VHR Satellite Imagery, GPR Survey and Boring for Archaeological Prospection at the Longcheng Site in Anhui Province, China

2018

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This paper is focused on the joint use of non-invasive and minimal intervention techniques for supporting archaeological prospection. Very high resolution (VHR) satellite imagery analysis and ground-penetrating radar (GPR) and boring surveys were integrated for the study of the Longcheng site, located near Hefei city in Anhui Province, China, to test their effectiveness and efficiency in prospecting archaeological remains and evaluating their degree of preservation. First, target locations of potential archaeological structures were identified on a WorldView-2 (WV-2) satellite image through spatial and radiometric enhancement, interpretation and object-oriented classification. Second, archaeological features extracted from the WV-2 imagery were further investigated by a GPR survey that provided detailed crosschecking information about buried remains. Finally, a subsequent boring survey was conducted across those prospective archaeological structures in order to map the stratigraphic sequences on the basis of colour, compactness and the inclusions contained in the soil, and then to test their correspondence with the GPR data. The boring led to detailed confirmation of the results produced by the remote sensing analyses and GPR surveys, as well as the discovery of datable artefacts. On the basis of all the integrated data, the preliminary layout and structure of the Longcheng site was reconstructed in GIS. Furthermore, the widths, lengths, heights and burial depths of these buried archaeological structures were estimated in detail.

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Section: Data Collection and Methodsmentioning

confidence: 99%

The Integration of VHR Satellite Imagery, GPR Survey and Boring for Archaeological Prospection at the Longcheng Site in Anhui Province, China

2018

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“…The GPR signal velocity may also be estimated from GPR profile data collected perpendicular to a subsurface ‘point scatterer’ (Cross and Knoll ; al Hagrey and Müller ; Conyers ). This method is based on the increasing travel time associated with the increasing path length as the distance increases away from the point scatterer.…”

Section: Methods Of Determining the Velocitymentioning

confidence: 99%

Ground-Penetrating Radar Velocity Determination and Precision Estimates Using Common-Midpoint (CMP) Collection with Hand-Picking, Semblance Analysis and Cross-Correlation Analysis: A Case Study and Tutorial for Archaeologists

Jacob

Urban

2015

Archaeometry

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The most crucial parameter to be determined in an archaeological ground-penetrating radar (GPR) survey is the velocity of the subsurface material. Precision velocity estimates comprise the basis for depth estimation, topographic correction and migration, and can therefore be the difference between spurious interpretations and/or efficient GPR-guided excavation with sound archaeological interpretation of the GPR results. Here, we examine the options available for determining the GPR velocity and for assessing the precision of velocity estimates from GPR data, using data collected at a small-scale iron-working site in Rhode Island, United States. In the case study, the initial velocity analysis of common-offset GPR profile data, using the popular method of hyperbola fitting, produced some unexpectedly high subsurface signal velocity estimates, while analysis of common midpoint (CMP) GPR data yielded a more reasonable subsurface signal velocity estimate. Several reflection analysis procedures for CMP data, including hand and automated signal picking using cross-correlation and semblance analysis, are used and discussed here in terms of efficiency of processing and yielded results. The case study demonstrates that CMP data may offer more accurate and precise velocity estimates than hyperbola fitting under certain field conditions, and that semblance analysis, though faster than hand-picking or cross-correlation, offers less precision. bs_bs_banner or strata is constrained by the achievable resolution, which is in turn limited by the wavelengthin both the horizontal and vertical planes (Rial et al. 2007; Annan 2009)-and the survey design, particularly in the horizontal plane (Urban et al. 2014a,b). The wavelength is governed by the antenna frequency and the substrate velocity. When the subsurface velocity is known, the wavelength in the medium can therefore be determined, and the vertical resolution can be estimated as a fraction of the wavelength (Appendix A).Knowledge of the subsurface velocity is also necessary for the implementation of several other GPR processing procedures that are important for successful archaeological investigations. First, the accuracy and precision of depth estimates are dependent on knowledge of the subsurface velocity; for example, Leckebusch (2007) shows that errors in velocity complicate depth determination. Second, topographic corrections, often undertaken for GPR surveys on uneven surfaces (e.g., Forte and Pipan 2008), can be crucial to archaeological interpretation in some instances in that they mitigate any distortion within spatial correlations for reflected phases. Third, the commonly used procedure of migration is often implemented to eliminate the tails of diffraction hyperbolas (e.g., Böniger and Tronicke 2010). Successful migration generates GPR profile images that are more intuitive and have more appropriate dimensions for the embedded features that caused the diffraction hyperbolas. This latter procedure can be of great importance, particularly in archaeology, where interpre...

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“…Case studies in this paper relied primarily on the technique of hyperbola fitting to estimate velocity. When a GPR profile is collected perpendicular to a point-scatter (i.e., an anomaly in the ground that results in a diffraction hyperbola) velocity may be estimated from the resulting hyperbolic curve on the basis of increasing travel time associated with increasing path length with regard to horizontal distance from the sub-surface anomaly [8,9]. The relationship of antenna position x, point-scatter depth d, travel time T, velocity v, and T 0 (the time at which the antenna is directly above the point-scatterer) can be described in simple terms by (Equation (1))…”

Section: Ground-penetrating Radar (Gpr) In Frozen and Partially Frozementioning

confidence: 99%

Frozen: The Potential and Pitfalls of Ground-Penetrating Radar for Archaeology in the Alaskan Arctic

et al. 2016

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Ground-penetrating radar (GPR) offers many advantages for assessing archaeological potential in frozen and partially frozen contexts in high latitude and alpine regions. These settings pose several challenges for GPR, including extreme velocity changes at the interface of frozen and active layers, cryogenic patterns resulting in anomalies that can easily be mistaken for cultural features, and the difficulty in accessing sites and deploying equipment in remote settings. In this study we discuss some of these challenges while highlighting the potential for this method by describing recent successful investigations with GPR in the region. We draw on cases from Bering Land Bridge National Preserve, Cape Krusenstern National Monument, Kobuk Valley National Park, and Gates of the Arctic National Park and Preserve. The sites required small aircraft accessibility with light equipment loads and minimal personnel. The substrates we investigate include coastal saturated active layer over permafrost, interior well-drained active layer over permafrost, a frozen thermo-karst lake, and an alpine ice patch. These examples demonstrate that GPR is effective at mapping semi-subterranean house remains in several contexts, including houses with no surface manifestation. GPR is also shown to be effective at mapping anomalies from the skeletal remains of a late Pleistocene mammoth frozen in ice. The potential for using GPR in ice and snow patch archaeology, an area of increasing interest with global environmental change exposing new material each year, is also demonstrated.

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Diffraction‐based velocity estimates from optimum offset seismic data

Cited by 5 publications

References 14 publications

The Integration of VHR Satellite Imagery, GPR Survey and Boring for Archaeological Prospection at the Longcheng Site in Anhui Province, China

The Integration of VHR Satellite Imagery, GPR Survey and Boring for Archaeological Prospection at the Longcheng Site in Anhui Province, China

Ground-Penetrating Radar Velocity Determination and Precision Estimates Using Common-Midpoint (CMP) Collection with Hand-Picking, Semblance Analysis and Cross-Correlation Analysis: A Case Study and Tutorial for Archaeologists

Frozen: The Potential and Pitfalls of Ground-Penetrating Radar for Archaeology in the Alaskan Arctic

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