1.1.3 The use of UAVs
Although many sensors are currently available on ground, airborne, and space-based platforms, methods using unmanned aerial vehicles are rapidly developing among all modern methods for exogenous processes monitoring (Marzolff & Poesen, 2009; Marzolff et al. , 2011). The possibility of obtaining three-dimensional (3D) information about the terrain with high accuracy and spatial resolution opens up new horizons for studying landslide processes (Gafurov, 2017; Eker et al. , 2018; Gafurov, 2021). The first studies involving UAV for exogenous processes monitoring started relatively recently. The authors note the perspective of photogrammetry technology; however, they conclude that at that time, DEMs obtained using budget airborne surveys are not accurate enough to study the rill network, in contrast to DEMs obtained using ground-based laser systems, which allow a better reconstruction of the soil surface topography.
Particular attention should be given to methodological and technical works in which UAVs are compared with other, already proven methods. For example, when comparing models obtained by TLS and UAV with the results of total station surveys, in grass vegetation covers, the UAV gives a model even more accurate than the TLS (GruszczyƄski et al. , 2017; Gafurov, 2018). When comparing the TLS and UAV models, the errors vary within 5 mm (Eltner et al. , 2013) from using the ICP method. For erosion field calibration stand, the average error was 0.03 mm with a standard deviation of 5 mm (Nouwakpo et al. , 2016; Wilkinsonet al. , 2016).