Repeatability of Towed Magnetic Data for Archaeological Prospection within a Sand and Gravel Mineral Deposit

The Geophysical Exploration Equipment Platform (GEEP) was used to survey an area of known archaeological interest in Shelford, Nottinghamshire. The site consisted of varying depths of sand and gravel deposits reaching a maximum thickness just under 10 meters, although the archaeological remains are likely to be much closer to the surface. An array of six caesium magnetometer sensors were set up at 0.6m separations on the GEEP and towed across the site. A section of the site was surveyed again the following day to determine the repeatability of the towing method used. Sand and gravel deposits in the region produced a level of background magnetic variation across the traverses and archaeological features were clearly observed outside this trend. A differential GPS system was mounted on the GEEP to provide positional data ensuring a reliable comparison between datasets was achieved. Data obtained on the repeat survey shows extreme likeness to that observed on the original dataset indicating the repeatability of the GEEP towing method for small separation magnetic surveys in sand and gravel environments. It took the GEEP operator three and a half hours to collect the original 6 hectare dataset, and an additional forty minutes to complete the repeated section.