Development and integration of an electromagnetic induction system on an unmanned aircraft system for subsurface electrical conductivity mapping

Detection and mapping of subsurface electrical conductivity using electromagnetic induction method have broad applications in detecting buried metal, locating unexploded ordinances (UXOs), exploring ground water and minerals, etc. An unmanned aircraft system (UAS) provides an unprecedented platform for quick geophysical data acquisition with high spatial resolution. To leverage a UAS platform for quick acquisition of subsurface electrical conductivity, we developed a light-weight electromagnetic induction (EMI) system for a UAS. This system consists of a multi-turn current loop for a transmitter, a multi-turn receiver loop, a waveform (saw wave) signal generator, a power amplifier, a microcontroller board, an onboard data storage, and a GPS receiver unit as shown in Fig. 1. We characterized and optimized this system after its completion and tested it over an area with real UXOs and UXO simulators. Data collected from this system include GPS position of the center of the system, transmitter signal and concurrent receiving signal. Subsurface electrical conductivity was inverted from the decay rate of current in the receiver during the off-duty sub-periods of the transmitter. Electrical conductivity or resistivity maps were eventually obtained. This presentation will show the detailed design, optimization, test results of this sensor and its integration to a UAS system.