This study builds on a preliminary investigation into the efficacy of gamma radiation surveying as a complementary tool for archaeological prospection. Improved surveying and data processing methods were implemented, including the use of a vehicle-mounted Groundhog surveying system, use of alternative software tools and examination of the impacts of individual radionuclides. The study focuses on a range of targets within Insulae VII, XXXV and XXXIII in Silchester Roman town, Hampshire. Targets of interest included a polygonal temple, a house, ditches (including an Iron Age defensive ditch) and several Roman roads. While the survey revealed no measurable differences in the gamma radionuclide content of less substantial structures (such as the temple and house) and the surrounding soil, it successfully delineated major structures. The Roman roads, Iron Age defensive ditch and potentially an indication of a historic field boundary not present in modern records were clearly visible in the generated visualisations. The roads and field boundary appear as distinct linear features of depleted radioactivity. The location of the Iron Age ditch correlates with an area of elevated radioactivity. Notably, the technique not only successfully identified archaeological features but was also able to indicate differences in the properties of similar targets such as variations in road thickness. Further, the gamma radiation data indicates variations in the local geology attributable to historic changes in land use and geochemical composition. This latest study corroborates the findings of the preliminary investigation, demonstrating replicability, scalability and ability to enhance output data quality. Further research, including sampling and non-destructive analysis of materials from the site, is needed to better explain observed results.
Archaeological prospection is continually expanding into new frontiers, examining increasingly large areas, diverse environmental contexts and varying site types. One area that has received only limited focus is historic battlefields. This paper presents results from large-scale geophysical surveys (> 100 ha) at the Napoleonic battlefield of Waterloo (1815) in Belgium, using fluxgate magnetometry and frequency-domain electromagnetic induction. Despite its international historical significance, professional archaeological research at the battlefield is still in its infancy. We demonstrate how important insights can be gained by using geophysical methods for identifying features and artefacts related to the battle and for developing an understanding of the various influences acting on the present landscape. The largest survey of its kind undertaken on a single battlefield site, this approach holds particular potential for battlefield archaeology, given the subtle and low-density nature of the sought-after targets and the extensive area of the site. Such an approach can mitigate (though not entirely resolve) challenges of resolution and scale associated with other methods of investigation. Using a representative range of examples from Waterloo, we consider successes and challenges in undertaking geophysical surveys on battlefield sites. An integrated approach that incorporates targeted sampling and other forms of ancillary data is emphasized for a more robust interpretation of noninvasive sensor data.