The Society purchased ground resistance measuring equipment in 2002, having previously conducted some surveys using borrowed equipment.
There are several methods of geophysics for archaeological prospection including magnetometry, ground penetrating radar and ground resistance. EAFS are involved with ground resistance and have our own equipment consisting of a mobile frame, cable, remote probes and a meter to process and store the results for upload to a computer.
Ground resistance consists of passing a small electric current between two mobile probes, one current and one potential, and two fixed probes and measuring variations in electrical resistance due to differences in sub-surface moisture content caused by buried structures such as wall foundations, pits or ditches.
The method used involves setting up a grid, normally 20×20 metres and taking measurements at one metre intervals in a zig-zag pattern, normally starting at the South West corner of the survey area and proceeding North. The results are processed as resistance values in ohms which, after uploading to a computer, can be displayed as a greyscale plan showing higher resistances as darker and lower readings as lighter values.
Surveys have been carried out at Newhailes House at the request of the National Trust for Scotland; in Pittencreiff Park, Dunfermline, at the request of Fife Council; at East Bonhard Farm at the request of RCAHMS; at four sites adjacent to the Roman fort at Cramond; on the Hopetoun Estate; and at Eddleston in conjunction with the Peeblesshire Archaeological Society also a major survey at Cramond, adjacent to the Roman road that leaves Cramond fort in a south-easterly direction; there is some historical evidence that points to this field being the site of a Roman cemetery. Recent years have seen surveying taking place across the Lothians, the Borders and Fife regularly through the summer months.