Bringing up the Bodies: High Resolution and Target Definition Using GPR

摘要

Ground Penetrating Radar (GPR) is an extremely useful non-destructive testing (NDT) and detection technique applied in many different spheres of activity from the common ones of utility detection, concrete investigation, road monitoring and archaeology to the more rarely used ability for forensic and security investigations. Target detection and imaging are inter-related both in terms of the frequency of antenna used and the survey parameters applied. Even for strong reflectors, the density of data collected can make a significant difference to identification, particularly where this is based on pattern recognition. The definition capability of a 4 GHz antenna used primarily in structural investigations is described. Taking as an example the two graves discovered beneath the floor of the Cosmati Pavement in front of the High Altar of Westminster Abbey, this paper examines the evidence for extant skeletal remains in GPR data generated using a 4 GHz antenna. These results are then compared with results from a more traditional lower frequency antenna (400 MHz) used for the detection of graves within the Abbey (including the two beneath the mosaic pavement) in forensic searches for missing persons believed to have been buried in open ground and in the archaeological investigation of an area known to contain mediaeval graves. Although faunal remains have been found in such searches, the recognition of weak reflectors such as human remains more often relies upon the recognition of associated material rather than the signals returned by the bodies themselves. The reasons for this are briefly discussed. The potential effect of increasing data density is discussed with particular reference to the data (4 GHz and 400 MHz) from Westminster Abbey and suggestions made as to how the effect of more intensive survey might assist in the identification of buried human remains, whether in a legitimate grave or not.