Site Event/Activity record ESF29000 - Geophysical Survey - Framlingham Castle

2019: Earth resistance, magnetic, and Ground Penetrating Radar (GPR) surveys together with a vertical electrical resistance section were conducted at Framlingham Castle. The aim of the survey was to identify any significant remains surviving within the Inner Ward of the castle to improve visitor information and better inform the management of the site. For the earth resistance survey, a series of 30m grids were established and surveyed using a Geoscan RM85 resistance meter. This arrangement allowed two separate surveys, with electrode separations of 0.5m and 1.0m, to be collected simultaneously. The 0.5m electrode separation coverage was designed to detect near-surface anomalies in the upper 0.5m of the subsurface whilst the 1.0m separation survey allowed anomalies to a depth of about 1-1.25m to be detected. For the 0.5m electrode separation survey readings were taken at a density of 1.0m x 0.5m whilst for the 1.0m separation survey they were taken at a density of 1.0m x 1.0m. For the magnetometer survey, three grids were surveyed using a bARtington Grad 601 dual fluxgate gardiometer. Measurements were taken at 0.25 m intervals along parallel traverses separated by 1.0m. For the GPR survey, 3d-Radar MkIV GeoScope Continuous Wave Step-Frequency (CWSF) Ground Penetrating Radar (GPR) system was used and data was acquired at a 0.075m x 0.075m sample interval across a continuous wave stepped frequency range from 40MHz to 2.99GHz in 4MHz increments using a dwell time of 5ms. A vertical electrical resistance section was measured along a line extending 55m south from Coad’s east-west excavation section to acquire further information on the structure of the mound at depth. (S1)