Recent results from the English heritage caesium magnetometer system in comparison with recent fluxgate gradiometers

Results are presented from a cart-mounted caesium magnetometer system developed by English Heritage using an array of specially modified Scintrex SM4 sensors, to investigate the application of high sensitivity magnetic survey. The caesium data are compared with equivalent datasets collected with recently developed fluxgate instruments. The underlying instrument noise level for the magnetometer systems is considered together with attempts to quantify other sources of noise that potentially limit the ability to detect weak magnetic anomalies. Comparative case studies are presented from a number of English sites which demonstrate the equivalence of results that may be obtained, at similar sample densities, between caesium and fluxgate systems over well magnetized causative features. However, the caesium system exhibits a superior ability to detect very weak anomalies (< 0.1 nT) due to features buried beneath alluvium and has revealed additional archaeological information from small-scale changes in magnetization within the plough soil that could not be distinguished from equivalent fluxgate data. (c) Crown copyright 2007. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.