## 1 Introduction  
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. Over the past few years magnetic prospecting methods [1; 2; 3; 4], then gamma surveys [5; 6; 7] have become widely used, they are often combined with lidar scans, multi or hyperspectral surveys [8; 9; 10; 11; 12; 13]. Now it is obvious that in difficult natural conditions, with poor pedestrian permeability of the landscape and highly rugged terrain, the informativeness of low-altitude UAV geophysics methods may even surpass both traditional ground and traditional aerogeophysical works [2; 5]. Namely, such environmental conditions characterize previously underexplored, currently promising areas. UAV surveys are significantly cheaper than terrestrial geophysical work and more accessible than classical airborne geophysics, which is cost-effective only in large volumes. The advantage of UAV geophysics over traditional airborne geophysics in terms of data informativeness is associated with the ability to significantly reduce the altitude and survey speed without risking the aircraft crew even in mountainous conditions, which significantly increases the contrast of geophysical anomalies, which, as is known, rapidly decay with altitude. As a result, to date, at least in Russia and neighboring countries, whose legislation allows for a simplified procedure for the operation of unmanned systems of the light (less than 30 kg) class, UAV-aeromagnetic and gamma-survey, performed with a step between profiles of 50 or 100 m, almost completely displaced land-based methods from the market. It should be noted that there is a trend towards expanding the range of methods, and the integration of several UAV-geophysical methods on one object, which is implemented both by sequential surveys with different payloads, for example, [9; 12; 13], and by placing several sensors on one UAV [10; 11]. Integration of several payloads is not always possible for technical or methodological reasons, but it allows one to increase productivity and reduce the cost of work. An integration of several methods of geological prospecting makes it possible to characterize the geological setting from various angles, various methods of geophysical exploration are objectively characterized by different depths, detail, and other parameters. Expansion of the set of available methods makes it possible to more reasonably solve traditional geological problems, or solve new classes of problems. The existing technologies of UAV-magnetic and gamma-ray imaging are very effective in geological and geophysical mapping, which is especially important at the early stages of geological prospecting of license sites, but they do not allow successfully solving the problems of studying a geological section to the depth. Gamma surveys have 'no depth', and magnetic prospecting is limited in terms of creating detailed geophysical sections or 3D models of the geological environment, especially since the geological environment is not always contrasting in the presence of magnetic minerals. To study the geological environment both in plan and in depth, methods of electromagnetic prospecting are widely used, studying the parameters of electrical resistivity, chargeability and other geoelectric characteristics of rocks and ores [14; 15; 16]. Moreover, the most important task of electrical prospecting at the present stage of geology, when the objects of search are often hidden bodies, are soundings, which make it possible to reconstruct the deep structure of the geological environment in the form of geophysical sections or 3D models of the distribution of geoelectric parameters [17; 18]. In such tasks, the information content, detail, and other capabilities of electrical prospecting methods are significantly superior to magnetic prospecting methods.