EDO8036 - Caswell; geophysical survey 2024

‘The survey was undertaken using four Bartington Grad601 sensors mounted at 1m intervals onto a rigid carrying frame allowing for a 1m traverse interval. The system was programmed to take readings at a frequency of 10Hz (allowing for a 10-15cm sample interval) on roaming traverses spaced 4m apart in order to secure comprehensive coverage. The magnetometer 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 of each data point; +/- 1cm for each reading. At the start of each day the magnetometer was left idle whilst switched on for approximately 30 minutes to allow the instrument to acclimatise to the site conditions. The instrument was thereafter re-balanced when necessary to compensate for instrument drift. The data was stored on an external weatherproof laptop and later downloaded for processing and interpretation. Anomaly GeoSurvey v1.12.3 (Lichenstone Geoscience) and QGIS v.3.28.5 software was used to process and present the data respectively. Only a single irregularly shaped enclosure, has been interpreted as of probable archaeological origin although several discrete anomalies adjacent to the enclosure are assessed as of possible archaeological origin. This enclosure borders the A37 Dorchester Road, which is presumed to follow the line of the Roman road between Ilchester and Dorchester. This appears to be an isolated area of archaeological interest as no other anomalies of obvious archaeological origin have been recorded in any other part of the site. The survey has recorded a number of weak linear and curvilinear anomalies as well as magnetically elevated clustered and isolated discrete anomalies throughout the site but the lack of any clear pattern or any evidence to support an archaeological interpretation has resulted in these anomalies being ascribed an uncertain origin. Numerous anomalies of agricultural origin, indicative of boundary removal, modern ploughing and land drainage, have been recorded. The location of two former ponds have also been confirmed by the survey and an area of possible mineral extraction has also been identified. The suitability of the bedrock geology to magnetic prospection combined with the general absence of any overlying superficial deposits (except the alluvial deposits bordering minor watercourses) suggests that the survey results likely provide a reliable indication of the archaeological potential of the site. Consequently, based solely on the survey data, the archaeological potential of the site is assessed as low except in the area in and around the enclosure that borders the likely Roman road where it is assessed as moderate to high.’