Archaeological geophysics in Britain

I describe the approach followed by the Ancient Monuments Laboratory in adapting the instrumentation and techniques of resistivity and magnetic prospecting to the near-surface problems of mapping buried archaeological sites. Such sites demand rapid and intensive ground coverage and the highest possible spatial resolution and instrument sensitivity. Resistivity is used largely for planning building foundations. Optimized resistivity results have required comparative studies of electrode configurations and the effect on resistivity of climatic variations in different lithologies. Magnetic prospecting is especially effective for detecting (1) fired structures such as kilns, and (2) excavated features such as ditches and pits filled with topsoil of relatively high susceptibility (which is further enhanced by human activities). Speed and resolution requirements have caused the proton magnetometer to be abandoned in favor of the fluxgate gradiometer. Valuable information about human activity can also be obtained from magnetic susceptibility measurements on topsoil.