Mobile Impulse Electromagnetic Soundings. Assessment of the Possibilities of Using UAVs

On the example of transient electromagnetic sounding (TEM) of moraine deposits the efficiency of the TEM-FAST technology is demonstrated. This technology uses a compact 25 m × 12.5 mcombined transmitterreceiver antenna for measuring transient responses in the microsecond range. The research depth with specific resistance of sandy-clayey deposits of 30–300 Ohm·mis notless than 50 mwith a “dead” zone thickness of not more than 6 m. For mobile pedestrian sounding, an antenna fixed on 4 flexible poles at a height of 2.5 mabove the earth′ssurface was used. The measuring system, with a total mass of 2.5 kg, was transported along the profiles by a team of 4 people at a speed of ~1 m/s. Every 20 seconds after processing 13,000 pulses, the system in the “autopilot” mode recorded the measurement results and coordinates. The repetition rate of current pulses with an amplitude of I = 3.3Аwasf = 3.2 kHz, the measured range of transient response timest = 4 — 64 μs. Vibration noises arising during movement due to deformations of the antenna contour in the Earth′smagnetic field reduced the sounding depth to 50–60 m. Based on the area sounding data, 3D geoelectric model of the territory was constructed, which was used to assess the capabilities of the TEM-FAST system in flight mode. Transient responses were synthesized, corresponding to different antenna heights above the surface of the studied environment. Despite the decrease in response amplitudes when raising the antennas to a 30 mheight, the sounding depth remained within 50 m. Based on mass-produced light UAVs (unmanned aerial vehicles) equipped with real-time dynamic positioning systems, it is proposed to tow the TEM system with a convoy of devices flying or hovering above the earth′ssurface in autopilot mode. When positioning antenna angles with decimeter accuracy, the noise threshold of transient response measurements will not exceed the levels obtained during mobile pedestrian sounding, and the research depth will not fall below 50 m.

transient electromagnetic sounding, TEM-FAST technology, measurement noise threshold