Ground-Penetrating Radar for Anthropological Research
Conyers, Lawrence B., Antiquity
Geophysical archaeology consists of a number of near-surface imaging methods used to produce maps and profiles of buried cultural remains and associated stratigraphy, usually within a few metres of the surface. Various techniques have been commonly employed to accommodate varying ground conditions, the types of remains that might be encountered, the amount of area to be surveyed, the depth of burial and the resolution necessary (Gaffney & Gater 2003). Many of the methods generally employed by the archaeological community were modified directly from other disciplines, where the focus was usually on geotechnical and environmental uses and the search for hydrocarbons and other minerals. As a result, the early practitioners of geophysical archaeology originated not in the archaeology or anthropology fields, but were often recruited from physics, geology or other scientifically-based disciplines (Bevan 1983; Weymouth 1986; Clark 1990; Scollar et al. 1990). The perceived usefulness of the methods within the archaeology community was often based on an ability to find interesting buried materials that could later be excavated using standard archaeological techniques. In the early days of geophysical archaeology, this 'prospection' was often followed by excavation designed to expose features and analyse artefacts in order to interpret aspects of the human past.
This historical application of geophysical archaeology as purely an exploratory tool is still quite prevalent in the minds of many archaeologists, the goal being to search for buried cultural materials for subsequent excavation, or sometimes for their preservation by avoiding development damage. However, a small but growing community of geophysical archaeologists has lately begun to use powerful geophysical imaging techniques for more than mete prospecting, and to incorporate them into their research projects in much more holistic ways. These researchers use geophysical methods (often accompanied by, and integrated with, standard excavation procedures) as a way to ask questions and test anthropological and historical hypotheses about the human past, by relating site layout, feature size and orientation and other aspects of cultural remains to various human behaviours. In this way archaeological geophysical results are beginning to become a primary data source from which to study the human past, not merely a preliminary to standard excavation procedures (Kvamme 2003). This enlarged use of geophysics has recently been made possible by advances in data collection and processing, both of which are the product of more powerful computers and the development of intuitive software.
Four techniques are widely used by the archaeological community: magnetics, electrical resistivity, electromagnetic induction (EM) and ground-penetrating radar (GPR) (Gaffney & Gater 2003; Campana & Piro 2009). Each of these techniques has been refined to the point where data can be rapidly collected and processing can be accomplished almost immediately on a laptop computer. Maps and images of the ground that are produced often lead directly to interpretation.
Geophysics for understanding the past
Magnetic gradiometry, calibrated with augers, cores and limited subsurface excavations, was used to identify prehistoric house features, storage pits and other features in South Dakota, USA (Kvamme 2003). While producing impressive large-scale maps of an ancient fortified village, the clarity of houses and associated cultural features in the maps allowed for an estimation of the village population and the number and volume of storage pits for agricultural products. From those data the potential food storage and distribution could be estimated to arrive at subsistence estimates per household. Episodes of burning were also identified in some areas and a contraction of the village within defensive walls over time showed evidence of warfare and subsistence stress. …