Magnetometry Survey at Malice Farm, Thorney, Peterborough, Cambridgeshire

The survey was carried out using a SenSys Magneto MXPDA� magnetometer survey system. The cart system which CFA employs can easily be configured to be towed by quad, pushed by hand, or carried depending on what is most suitable for the site configuration and conditions. The geophysical magnetometer survey was undertaken across the c.83.7ha area comprising the planning application boundary. The non-magnetic modular system records data through a configuration of five vertical-difference fluxgate gradiometer probes which measure a range of �10,000 nT or �8,000 nT. The sensors were calibrated during the manufacturing process, which includes calibration in a shielded chamber (offset and noise calibration) and a rotation calibration in ambient field. The sensors undergo re-calibration by the manufacturer at the recommended time intervals. Data was collected across a 2m swath and sample interval of 0.50m, using an integrated IP67 Tablet PC with RTK DGPS, accurate to 0.008m + 1ppm in the horizontal and 0.015m + 1ppm in the vertical. All data was stored using an SD card on a tough pad, where it was processed in the field to ensure the accuracy of the survey, and where it was automatically backed up to CFA's servers at the end of each day. Survey data was processed through two software packages: Magneto� v3.x dedicated software package, which allows for analysis and visualisation of geophysical magnetic data and DWC Terrasurveyor64 v4.1 which allows additional treatment of the data for best visualisation. The data was compensated using a sensor and track based median during the processing of the data. The data recorded as magnetic measurements and GNSS positions were synchronised by the hardware and the result was recorded by the MonMX software as a point cloud which was later gridded by the MAGNETO and Terrasurveyor software as bilinear and visualised as square pixels. Processing conformed to the EAC guidelines for 'minimally enhanced data' (Schmidt et al. 2016). During processing, several different ranges were examined to best identify and examine the type of potential anomalies recorded in the raw data. The data collected by the sensors is best viewed as a greyscale, with the shade representing the gradient of the sensors, total data being either positive or negative. Multiple greyscale images at different plotting ranges can be useful for data interpretation and have been provided for reference where these prove useful. The anomalies identified by the survey have been assigned a category based on the strength and type of response they provided, and by interpretation of the possible type of feature they represent. The interpretation of the results is not intended as an accurate map of below ground features. Any anomalies detected relied on sufficient contrast with the background readings to be identifiable, and as a result the interpretation of the features in this report is subjective. The only way to confirm the presence and/or dates and type of these features is to undertake ground-truthing in areas of the survey area where these anomalies are located. CFA Archaeology Ltd successfully carried out a fluxgate magnetometer survey over an area of c. 83.7ha area on agricultural land at Malice Farm, Thorney, Peterborough, Cambridgeshire. A small area of the Site was unsurveyable in Field B due to ground conditions. However, this comprised less than 0.2ha of the total area and did not impact the interpretation of the potential archaeology present. The geophysical survey has detected a range of anomalies consistent with archaeological, agricultural, geological and undetermined origins. Archaeological activity was concentrated towards the east of the Survey area in Fields C, E, F, G, H and I. This comprised a series of enclosures, trackways, farmsteads, field systems and four potential roundhouses, indicative of a Romano-British rural settlement.