## 3 Results of Experimental and Real Unmanned Aerial Vehicle (UAV)-Gamma Surveys with Small Detectors
### Case 1. Spectrometric Surveys with Small Scintillation Detectors
Figure 12 shows examples of raw data, which makes it possible to assess the correctness of interpolation. Firstly, it is noticeable that the aerospace map does not quite accurately reflect the real geological situation. The most contrasting gamma-field anomaly corresponds to a thin pack of presumably granite-gneiss of the Shebarta complex in the central part of the area. The structure mapped as similar in composition but larger in size in the eastern part of the site has significantly lower radioactivity and, therefore, belongs to a different stratigraphic subdivision. The results obtained, as in the previous case, show that the map of the gamma field in the integral channel does not have significant differences depending on the survey method. The main anomalies, primarily a linear anomaly from a thin pack of granite-gneiss, cutting the area in half, is visible in all cases and at all altitudes and mapped quite accurately. There are similarities not only between terrestrial surveys, but also between UAV and terrestrial. Due to the natural attenuation of the gamma field with the altitude, the anomalies can be significantly smoothed out, although in other cases, apparently with a slightly larger source area, the smoothing anomalies are practically not observed (Figure 14d). The smallest anomalies of increased gamma field values in the north-western part of the site, the source of which seems to be granite micro-outcrops with an area of no more than a few square metres, are mapped somewhat differently, apparently due to inaccuracy in the spatial referencing of the ground survey results. However, even these micro-objects are found in any case, even at an altitude of 60 m, while in real tasks of radioecological observations or geological searches, objects of this size would hardly be of interest. To demonstrate the attenuation of the gamma field with height, graphs of the distribution of the gamma field values over the profiles were built. Figure 14d shows two graphs--for the profile with the best match between terrestrial and UAV data, (profile 4) and the worst (profile 12). Depending on the geological situation, the gamma-field level above the local anomalies decreases by an amount from 1 to 5 uR/h, while the contrast  
Figure 13: Comparison of the results of ground measurements: (**a**) with the SRP-68 radiometer; (**b**) with lightweight radiometer. of the gamma-radioactivity anomalies in this area is not high, and during ground measurements the gamma background does not exceed 12 uR/h. At the same time, regardless of the degree of attenuation of the gamma field, the epicentres of the main anomalies are visible, and from the cartographic positions they remain in their places. This determines the possibility of obtaining correct and informative radiometric maps with an individual classification of each geostatistical surface. Figure 14: Comparison of UAV gamma survey results: (**a**) lightweight radiometer at 30 m; (**b**) lightweight radiometer at 60 m; (**c**) 100 cm\({}^{3}\) spectrometer at 35 m; (**d**) plots of changes in field values on profiles 12 (**top**) and 4 (**bottom**), green—30 m, blue and red—measurements in terrestrial mode with a light radiometer and SRP-68. As in the previous case, it is not possible to see a fundamental increase in geological information during UAV surveys with a \"large\" detector of 100 cm\({}^{3}\) in comparison to a small one (6.5 cm\({}^{3}\)) (Figure 15). This confirms the hypothesis that there is no need to use detectors with a volume of more than 10-15 cm\({}^{3}\) for low-altitude UAV surveys in radiometric mode.