Geophysical Survey at East Anglia GREEN Energy Enablement, Ardleigh, Essex

The survey was undertaken using four Bartington Grad601 sensors mounted at 1m intervals (1m traverse interval) onto a rigid frame. The system was programmed to take readings at a frequency of 10Hz (allowing for a 10-15cm sample interval) on roaming traverses (swaths) 4m apart (Illus 6). These readings were stored on an external weatherproof laptop and later downloaded for processing and interpretation. The system was linked to a Trimble R12 Real Time Kinetic (RTK) differential Global Positioning System (dGPS) outputting in NMEA mode to ensure a high positional accuracy for each data point. MLGrad601 and MultiGrad601 (Geomar Software Inc.) software was used to collect and export the data. Anomaly GeoSurvey v1.12.5 (Lichenstone Geoscience) and QGIS v.3.28.5 software was used to process and present the data respectively. Anomalies primarily of geological and recent agricultural origin have been identified by the survey, including one former field boundary recorded on first edition historic mapping; several other former boundaries are not recorded by the survey. No anomalies of probable archaeological interest are identified. This is in contrast to the findings of a review of historic environment data, which revealed a plethora of cropmarks, indicative of prehistoric and Roman activity in the surrounding landscape but also within the GSA. Those cropmark features within the GSA include a Roman road, and several rectilinear and linear features. It is considered that the most likely reason for the apparent inability of the survey to detect these cropmark features (assuming they haven't been ploughed away since the air photographs were taken) is due to a lack of magnetic contrast between the fill of the features and the surrounding soils, the homogenous sandy nature of the soils possibly accounting for the apparent lack of visibility. Based solely on the results of the geophysical survey, the archaeological potential of the GSA is assessed as low. However, due to the likely poor magnetic contrast on this site, the overall potential should be considered to be uncertain.