Comparison of magnetic, electrical and ground penetrating radar surveys to detect buried forensic objects in semi-urban and domestic patio environments

Abstract

Near-surface geophysical techniques should be routinely utilized by law enforcement agencies to locate shallowly buried forensic objects, saving human and other resources. However, there has been little published research on optimum geophysical detection method(s) and configurations beyond metal detectors. This paper details multi-technique geophysical surveys to detect simulated unmarked illegal weapons, explosive devices and arms caches that were shallowly buried within a semi-urban environment test site. A concrete patio was then overlaid to represent a common household garden environment before re-surveying. Results showed that the easily utilized magnetic susceptibility probe was optimal for target detection in both semi-urban and patio environments, while basic metal detector surveys had a lower target detection rate in the patio scenario with some targets remaining undetected. High-frequency (900 MHz) ground penetrating radar antennae were optimum for target detection in the semi-urban environment, while 450 and 900 MHz frequencies had similar detection rates in the patio scenario. Resistivity surveys at 0.25 m probe and sampling spacing were good for target detection in the semi-urban environment. 2D profiles were sufficient for target detection, but resistivity datasets required site de-trending to resolve targets in map view. Forensic geophysical techniques are rapidly evolving to assist search investigators to detect hitherto difficult-to-locate buried forensic targets.