Abstract
Nowadays in solving geological problems, the technologies of UAV-geophysics, primarily magnetic and gamma surveys, are being increasingly used. However, for the formation of the classical triad of airborne geophysics methods in the UAV version, there was not enough technology for UAV-electromagnetic sounding, which would allow studying the geological environment at depths of tens and hundreds of meters with high detail. This article describes apparently the first technology of UAV-electromagnetic sounding in the time domain (TDEM, TEM), implemented as an unmanned system based on a light multi-rotor UAV. A measuring system with an inductive sensor—an analogue of a 20 × 20 or 50 × 50 m receiving loop is towed by a UAV, and a galvanically grounded power transmitter is on the ground and connected to a pulse generator. The survey is carried out along a network of parallel lines at low altitude with a terrain draping at a speed of 7–8 m/s, the maximum distance of the UAV’s departure from the transmitter line can reach several kilometers, thus the created technology is optimal for performing detailed areal electromagnetic soundings in areas of several square kilometers. The results of the use of the unmanned system (UAS) in real conditions of the mountainous regions of Eastern Siberia are presented. Based on the obtained data, the sensitivity of the system was simulated and it was shown that the developed technology allows one to collect informative data and create geophysical sections and maps of electrical resistivity in various geological situations. According to the authors, the emergence of UAV-TEM systems in the near future will significantly affect the practice of geophysical work, as it was earlier with UAV-magnetic prospecting and gamma-ray survey.
Highlights
One of the recent innovations in geological prospecting, which first influenced the theory and practice of applied geology, is unmanned aerial systems that allow airborne geophysical surveys to be performed at low altitudes and with a terrain drape
This paper describes the developed unmanned aerial system for UAV-TEM and the surveying technique, gives an example of using the first working prototype of the created unmanned system at one of the promising areas for uranium in the mountains of Eastern Siberia (Russia)
Work on the Very Low Frequency (VLF) method in both ground and airborne and UAV versions was mainly carried out at the same frequency, in order to map the distribution of the derivatives of the electrical resistance of the upper part of the section over the area, so the VLF methods played a role electrical profiling operations, not sounding
Summary
One of the recent innovations in geological prospecting, which first influenced the theory and practice of applied geology, is unmanned aerial systems that allow airborne geophysical surveys to be performed at low altitudes and with a terrain drape. Work on the VLF method in both ground and airborne and UAV versions was mainly carried out at the same frequency, in order to map the distribution of the derivatives of the electrical resistance of the upper part of the section over the area, so the VLF methods played a role electrical profiling operations, not sounding This is due to the shallow depth of VLF methods—the depth of propagation of electromagnetic waves into the geological environment depends on the resistance of rocks, with a low resistance, the depth of VLF methods does not exceed 10–20 m, with a high one it can reach 40–50 m [24,25,27]. Taking into account the above, a lightweight complex for the UAV-TEM was created, the design features and methods of application are described below
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