Advanced magnetic prospecting for archaeology with a vehicle-towed array of cesium magnetometers

Abstract Magnetic survey is an important geophysical technique that is particularly well suited to the identification of near-surface archaeological remains, over suitable geology and soils. It is often deployed to complement initial aerial surveys, particularly where the sites or land use may not be ideal for either producing crop marks or preserving topographic features, but the ground-based techniques can often struggle to match the near-landscape scale of coverage offered from the air. This chapter presents the development of a vehicle-towed magnetometer array, in this case utilizing cesium vapor instruments, with the aim of allowing high-density data sets to be rapidly acquired over large areas of coverage. While other sensor technologies, for example, fluxgate gradiometers, can also very successfully be deployed in vehicle-towed arrays, the use of cesium instrumentation was a natural progression from the original hand-pushed system operated by English Heritage (now Historic England). Technical details of the system are presented together with methodological considerations for both data acquisition in the field and appropriate postprocessing to obtain high-sensitivity field measurements over more weakly magnetized sites. Results are presented from a number of recent case studies where the large-area magnetic surveys have been successfully combined with both aerial and other ground-based techniques.