Three-component VLF using an unmanned aerial system as sensor platform

In a pilot project, very low frequency (VLF) measurements were performed using a prototype unmanned airborne system (UAS) at a test area near Neuchâtel, Switzerland. The VLF system operates over an extended frequency range of 1–250 kHz and consists of a three-component magnetic field sensor and a data logger, both deployed on an unmanned helicopter. Various developments had to be done prior to the first flight. The devices went through a weight reduction process, the noise influence of the aircraft on the devices had to be investigated, and an appropriate suspension had to be developed. This first experiment was conducted on a test site with anomalies due to man-made objects: a buried pipeline and a power cable with known orientation and location. The performance of the system in comparison with ground-based VLF data was investigated. First results demonstrate the feasibility of airborne VLF measurements with a UAS to detect buried pipelines and power cables.