Earth Resistivity

Earth resistivity has been chosen as a complementary geophysical method to magnetic prospection. This active prospection method implies the use of metal electrodes that allow electric current to flow in the topsoil in order to detect places with higher or lower resistivity. The instrument used is an Elmes ADA-5 with a twin-probe array. Earth resistivity is used on areas chosen through magnetic prospection as potentially containing subsoil architectural remains.

Earth resistivity survey using Elmes ADA-5

Earth resistivity survey using Elmes ADA-5

In the southern part of the camp earth resistivity measurements have been conducted over the presumed outline of the east fortified wall of the Roman fort. The results have shown an area of lower resistivity where the wall should run and higher outside the fort, on the side of the east annexe, identified as buildings outside the fort. This confirmed the course of the fortifications that the archaeological plans implied and the presence of subsoil structures outside the fort in its close proximity.

Further measurements in the eastern annexe have revealed a series of high resistivity areas that can be – by present knowledge – identified as buried architectural remains, indicating a settlement complex existing east of the fort.

Earth resistivity results at area B - the vicinity of the fort wall (37-147 Ωm) combined with magnetic prospection results

Earth resistivity results at area B – the vicinity of the fort wall (37-147 Ωm) combined with magnetic prospection results

In the area west of the fort, small open spaces between modern buildings have been a subject of earth resistivity measuring. Few enclosed high resistivity anomalies surrounded by an area of rather uniform lower resistivity might indicate existence of a settlement pattern. Yet further tests and survey has to anwser the question about the origin and composition of the source of these anomalies.

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