Geoarchaeological prospection with multi-coil electromagnetic induction sensors
David M. Simpson · Ghent University Academic Bibliography (Ghent University) · 2009
In Flanders, the risk of destruction of archaeologically valuable sites is high due to the intensive building activity. The aim of archaeological prospection is to estimate the archaeological value of a terrain without complete excavation. For this purpose, earth sciences are increasingly adopted to reconstruct the paleo-environment and to increase the archaeological evidence. An important geoarchaeological prospection method is geophysical prospection, where sensors are used to map the natural soil variability and to detect anthropogenic traces without disturbing the soil. The three most applied sensor types for archaeological prospection are the magnetometer, the electrical resistivity meter and the ground penetrating radar. A fourth type, based on electromagnetic induction is less often used, despite its apparent advantages. It can measure two physical properties simultaneously, the electrical conductivity and the magnetic susceptibility. The instrument does not require soil contact and is therefore easily mounted on a motorized platform. Recently, new sensors were developed with multiple receiver coils, each having a specific spatial sensitivity. The potential of these sensors for archaeology was not evaluated until now. The goal of this doctoral research was to test the use of electromagnetic induction sensors for geoarchaeological prospection. First, a motorized sensor platform was developed to measure large areas per day in a high resolution, so that apart from the archaeological site, also its broader context can be mapped. Computer software was written to be able to process the data and to correct errors such as time drift. Second, the sensitivity of the sensor configurations was tested on an experimental site where structures of known dimensions and physical properties were buried. The results proofed that the coil configuration of the sensor has a large impact on the detection level. Third, the electrical and magnetic response of the electromagnetic induction sensors were compared with magnetometer and electrical resistivity sensors. Finally, the sensors were evaluated on different sites with Medieval or Bronze Age traces in varying environmental settings and with field verification by auger observations.