Integrating EMI and GPR data to enhance the three-dimensional reconstruction of a circular ditch system

摘要

Ground Penetrating Radar (GPR) reflections occur at sharp interfaces between contrasting soil layers. Generally, the depth of the interface is expressed as the two-way travel time fromthe transmitting to the receiving antenna. Converting these travel times to depths requires knowledge of the propagation speed of the GPRwave in the soil. This velocity is influenced by the electric properties of the soilwater content,mainly by the dielectric permittivity (ε). The soil electrical conductivity (σ), which also depends on the soil water content, can be accounted for by electromagnetic (EMI) induction prospecting. A procedure was proposed to thoroughly characterize a circular ditch systemby inverting the apparent electrical conductivity (σ_a) measurements from a multi-receiver EMI instrument based on GPR profile data. A fitting procedure allowed to calibrate both the propagation speed of the GPR waves up to the interface between the ditch infilling and the underlying sand and the conductivities of both layers. Integrating the simultaneous EMI measurements and high-resolution GPR depth profiles and – slices improved the non-invasive dimensioning of the circular ditch system.