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).