Identifying soil patterns at different spatial scales with a multi-receiver EMI sensor

Multi-receiver electromagnetic induction (EMI) sensors are increasingly being used to map soil spatial variability by measuring the apparent electrical conductivity (ECa) of multiple soil volumes. We present a procedure to process such measurements to identify both large-scale soil variability patterns and small-scale features such as archaeological traces. A 2.6-ha arable field in Belgium was selected since aerial surveys indicated the presence of fine archaeological traces being masked partly by what appeared to be a trend in the soil composition. A survey with a DUALEM-21S EMI sensor provided four co-located ECa measurements of varying soil volumes, which were combined in a two-step inversion procedure. Our procedure enhanced the distinction between the archaeological traces and probable ice-wedge casts, with a small lateral and vertical extent, and the large-scale trend of natural soil variability, identified as the varying depth to the interface between two contrasting soil layers