Drone-Borne Electromagnetic (DREM) Surveying in The Netherlands

Abstract

Summary In the past decade drones have become available and affordable for civil applications, including monitoring with geophysical sensors. In 2017 and 2019 the feasibility of executing frequency domain electromagnetic (FDEM) method surveys using an off the shelf drone, was investigated at Deltares. This paper reports on the preparatory tests executed to determine the optimal configuration, processing and inversion scheme and on the field validation tests demonstrating the capability of the drone-borne electromagnetic survey. One demonstration example shows how the system can efficiently map shallow groundwater and surface water salinity in areas where seepage of saline water occurs. The other demonstration example shows how the system can map shallow lithology as well as buried metal cables and pipelines. The general findings are that the system provides for the flexibility to fly a combination of FDEM soundings, profiles or grid patterns and its ability and efficiently to fly over inaccessible areas and surface water. Compared to the HLEM surveys, the spatial resolution is much higher which allows for detailed 3D mapping of subsurface and the costs are, certainly for small study areas, relatively low, which also makes monitoring of changes by repeated drone-borne electromagnetic (DREM) surveys affordable.