3.1 Site 1.
At Site 1, an analysis of the abrasion-slope DEM obtained from ground-based laser scanning in 2012-2014 and UAV imagery in 2019 was chosen as the main method of shoreline deformation (Table 2).
The results of scanning were processed in the Trimble Realworks software. The obtained point clouds were exported to the Golden Software Surfer software, whereby triangulation with linear interpolation of the DEM with a spatial resolution of 0.1 m was created. The calculation of volume change was performed using the Volume tool. According to laser scanning results, a specific indicator such as the volume of eroded soil per unit area (V-/S, m3/m2) was used to estimate the intensity of landslide processes.
Photogrammetric processing of UAV survey results was performed in Agisoft Photoscan software. A combined approach was used to align the point clouds obtained by laser scanning and unmanned aerial vehicle. Since the main survey using terrestrial laser scanning was carried out in the relative coordinate system and the UAV data in the global coordinate system, it was decided to recalculate the latter in the relative coordinate system. At the first stage, common stable areas were singled out on the point clouds obtained from different sources: i.e. elements of the pier, corners of buildings and bank protection structures. Based on the obtained matches, the point clouds were re-aligned using the ICP method to minimize the georeferencing error (Table 3). The obtained errors are considered to be permissible in landslide process studies (Peppa et al. , 2016; Zang et al. , 2019).