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Portsmouth, United Kingdom

Sala J.,3d Radar AS | Linford N.,Geophysics Team
Near Surface Geophysics

Stepped frequency continuous wave ground penetrating radar (GPR) systems allow highly detailed data sets to be collected across a wide bandwidth using a multi-element array antenna, such as the 3D-radar GeoScope system. Although the final presentation of the results is similar to time-domain systems, the correct processing of the initial frequency domain data acquired in the field is essential to obtain the maximum information from the site. Processing begins with the identification of a suitable frequency window for conversion to the time-domain using an inverse Fourier transform and demonstrates how the use of a varying frequency window with depth can improve the final results. Various methods for background subtraction to minimize the loss of data quality and cope with the strong surface reflection experienced by an air-launched antenna are also explored. The geometry of the air-launched antenna is also considered with specific regard to developing a threedimensional migration model that accounts for the variation in a signal response expected from such a system. This paper explores these themes with relation to data from archaeological sites and also considers the data processing challenges presented by high density (e.g., 0.075 m × 0.075 m) multihectare surveys. © 2012 European Association of Geoscientists & Engineers. Source

Cheyney S.,University of Leicester | Hill I.,University of Leicester | Linford N.,Geophysics Team | Fishwick S.,University of Leicester
Near Surface Geophysics

Topographical anomalies or compressed areas of soil caused by ploughing or more significant relic features such as ridge and furrow produce a response in near-surface magnetic surveys that are usually identified by their repetitive, linear pattern. While they are accurate recordings of the subsurface magnetic properties and micro-topographical features of the site, it is often the anomalies due to deeper features that are the primary focus of the survey. These target anomalies can be masked by the nearsurface pattern and it is therefore often preferable to remove these from the final presentation of the data.Two routines used for removing these features are common in commercial processing software. These are the directional pass/reject and cosine-taper filters. While these filtering techniques can dramatically improve the clarity of the data image, it is shown here that they make significant changes to the data that remain. As interpretation of near-surface magnetic data moves beyond image analysis towards more quantitative methods, it is important to ensure that the final processed data set represents as close as possible the response to the subsurface features of interest. Here an alternative filtering routine dependant on both the azimuth and power-content of the anomalies is proposed that overcomes the problems encountered by the traditional techniques. It is shown that patterns of agricultural linear anomalies can be removed from the data without significantly changing the properties of the desired responses and therefore quantitative interpretation can be subsequently carried out without the data being significantly compromised by the choice of previous processing techniques. © 2012 European Association of Geoscientists & Engineers. Source

Pringle J.K.,Keele University | Giubertoni M.,Polytechnic of Milan | Giubertoni M.,Polytechnic University of Turin | Cassidy N.J.,Keele University | And 4 more authors.
Forensic Science International

There are various techniques available for forensic search teams to employ to successfully detect a buried object. Near-surface geophysical search methods have been dominated by ground penetrating radar but recently other techniques, such as electrical resistivity, have become more common. This paper discusses magnetic susceptibility as a simple surface search tool illustrated by various research studies. These suggest magnetic susceptibility to be a relatively low cost, quick and effective tool, compared to other geophysical methods, to determine disturbed ground above buried objects and burnt surface remains in a variety of soil types. Further research should collect datasets over objects of known burial ages for comparison purposes and used in forensic search cases to validate the technique. © 2014 Elsevier Ireland Ltd. Source

Linford N.,Geophysics Team | Linford P.,Geophysics Team | Payne A.,Geophysics Team
Near Surface Geophysics

Aerial photography combined with airborne lidar can often provide information on the location of archaeological sites at a near landscape level of coverage. Ground-based geophysical techniques may then be deployed to complement the aerial survey, particularly where the soils or land use may not be ideal for either producing crop marks or preserving topographic features. This paper describes the development of a vehicle-towed caesium magnetometer array, from an original handpushed system, to allow high-density datasets to be rapidly acquired over large areas required to provide a meaningful comparison at the scale demanded by the aerial survey results. Technical details of the system are presented together with methodological considerations for both data acquisition in the field and appropriate post processing to obtain high-sensitivity field measurements over more weakly magnetized sites. Results are presented from a number of recent collaborative research projects within the English Heritage Remote Sensing Team to illustrate the benefits of a combined aerial and ground-based approach to mapping the historic environment. © 2015 European Association of Geoscientists & Engineers, Near Surface Geophysics. Source

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