## 3 Results of Experimental and Real Unmanned Aerial Vehicle (UAV)-Gamma Surveys with Small Detectors
### Case 1. Spectrometric Surveys with Small Scintillation Detectors  
The Tageran site is located near the shore of Lake Baikal. The purpose of the experimental work on it was to study the quality of the data obtained from the results of low-altitude UAV spectrometry with small detectors. In order to confirm the sufficient quality of the survey, its results must be, first, structural, i.e., anomalous geological objects on the field maps can be distinguished and, secondly, they are reproducible, i.e., the main anomalies of low and high gamma background during ordinary and control surveys should not change their position, and maps created based on the results of ordinary and control surveys should have a high correlation. The attenuation of the gamma field with height was also studied. The following types of research were carried out:  
* Terrestrial survey using the SRP-68 radiometer. * UAV gamma survey in radiometric mode with detector CsI 6.5 cm\({}^{3}\). The survey was carried out twice along the same profiles, in the forward and opposite directions--in order to assess the convergence and reproducibility of the results. The quality of UAV and ground data was also compared. Figure 4: Location of survey sites (coordinates in EPSG 28418). UAV gamma survey in radiometric and spectrometric modes using a CsI 100 cm\({}^{3}\) detector. The survey was carried out twice along the same profiles, in the forward and opposite directions, in order to assess the convergence and reproducibility of the results. The radiometric data with the data obtained by a smaller detector (previous item) was compared. The survey was carried out at an altitude of 25 m, the distance between the survey profiles was also 25 m, the flight speed was 20 km/h (Figure 5). The area of the site is about 1 km\({}^{2}\). A geological map for this site (apart from the Russian state small-scale maps M1:200,000 and 1:000,000) was not available, however, its geological structure is quite simple and can be easily interpreted from the gamma survey data. The intensity of the gamma field of the site is low (in comparison with the regional background), the maximum values do not exceed 10 uR/h. The site is most likely formed by two complexes of rocks, the rocks in the central part of the site (visually metamorphished carbonates) are characterised by low radioactivity. Along the edges there are presumably highly metamorphosed granite-gneisses, their radioactivity is higher, but the contrast ratio of the anomalies is low--about 2-2.5. As can be seen from Figure 6, granite graisses are characterised by increased concentrations of all radionuclides (U, Th, K-40) in comparison with carbonate rocks. Such a situation, when various stratigraphic complexes are characterised by synchronously different contents of all radionuclides, is, unfortunately, typical of the promising areas for gold in Eastern Siberia, where UAV-geophysical methods were used. A more interesting case would be to study the gamma field in a situation where different anomalies are caused by different radionuclides, but accessible areas with a priori suitable geological conditions in the Irkutsk region are not known to us. In this situation, the maps of individual radionuclides should approximately coincide with the integral channel. Figure 5: Scheme of survey profiles at the Tazheran site (coordinates in EPSG 28418). Figure 6a,b,d shows that despite the fact that the anomalies attenuate with height, when classifying the survey results by the quantile method, geological information is not lost. Even minor anomalies are geometrised and mapped correctly. Figure 7 shows a comparison of radiometric data obtained with small (6.5) and large (100) detectors during flights in the forward and opposite directions.