Electrical Conductivity Depth Modelling with a Multireceiver EMI Sensor for Prospecting Archaeological Features

ABSTRACT Multiple apparent electrical conductivity (EC a ) measurements with an electromagnetic induction (EMI) sensor frequently reveal analogue patterns caused by conductive features in the soil. A procedure was proposed to highlight different archaeological anomalies based on combinations of the simultaneous EC a measurements with the DUALEM‐21S instrument. After selection of a 3.5 ha study site, 0.79 ha has been recorded by archaeological excavation. Since the majority of the archaeological features were found between the plough layer and 1.0 m below the soil surface, a set of four equations were developed to model the EC within that predefined depth interval. This set of four equations employed the four depth response curves specific to the four DUALEM‐21S coil configurations. The modelled conductivity between 0.5 and 1.0 m ( ) showed a larger variability across the archaeological features than the raw EC data. To quantify the added value of this modelled conductivity, and measured EC a were compared with the rasterized map of the archaeological traces. Finally, the map proved to be better able to distinguish between the archaeological features and the ‘empty’ background. This technique allowed the highlighting of vague anomalies in the simultaneous DUALEM‐21S EC a measurements. Copyright © 2011 John Wiley & Sons, Ltd.