EDO8217 - Druitt Gardens, Christchurch; geophysical survey 2019 and 2020

OASIS: The Christchurch Antiquarians carried out a geophysical survey In Druitt Gardens, Christchurch, Dorset, between August 2019 and March 2020. The purpose of the project was to investigate the burh defences of Twinham, which are projected to cross the area of the Druitt Gardens. Previous geophysical surveys in Druitt Gardens had yielded no conclusive results. It was hypothesised that these earlier surveys had not penetrated deep enough to pick up the postulated archaeological features, which were thought to be at a depth of up to two metres below the present ground surface (based on data from previous archaeological excavations in the area). Therefore, the present the present survey proposed to use geophysical methods adapted to sensing down to two metres. The present survey comprised ground-penetrating radar (GPR), electromagnetic conductivity (EM), electrical resistive tomography (ERT) and magnetic gradiometry, each configured to provide penetration to the required depth, undertaken by contractors from the University of St. Andrews and the University of Wales. The survey was carried out as a series of parallel transects running approximately from east to west, orientated such that they should intersect orthogonally the projected line of the defences. The GPR and ERT results revealed consistent linear geophysical anomalies running approximately SSE to NNW that could be interpreted as a bank and ditch. The location of these anomalies lay about 20 m east of the previously postulated position of the line of the defences.