Prospecting frost-wedge pseudomorphs and their polygonal network using the electromagnetic induction sensor EM38DD

Electromagnetic induction was used to locate near-surface Pleistocene frost-wedge pseudomorphs at a test site where a polygonal network was exposed. The soil apparent electrical conductivity (ECa) was measured simultaneously with the EM38DD in the vertical and horizontal orientation, allowing the profile ratio (PR) to be calculated. Based on a fuzzy k-means classification the PR map was classified into two zones with a mean PR difference of 10%. A detailed drawing of the polygonal network served as a validation. A cross-tabulation yielded an overall accuracy of 81% when only wedges wider than 0.25 m wide were considered. The overall accuracy increased to 83% by introducing an uncertainty zone. Due to differences in composition between the wedge fillings and the host material, the PR was found to be a useful indicator of these phenomena.