Derivation of MSL riverbank line from UAV DSM data based on tidal slope analysis

Abstract

Deriving a riverbank line at a tidal river is complicated, since dynamic factors such as tide and slope topography influence its location. Hence, this study utilises the Unmanned Aerial Vehicle (UAV), geodetic, and tidal data to identify the exact riverbank line based on Mean Sea Level (MSL) value from UAV products. We carried out two epochs of UAV data collection during low and high tide conditions. Orthometric height (H) has been applied in UAV data processing to produce a high accuracy of orthophoto and Digital Surface Model (DSM). UAV-MSL derived riverbank lines have been identified from the UAV orthophoto image using supervised classification and feature extraction techniques. DSM model provides the topographical height in three-dimensional (3D) view and enables identifying low and high tide, MSL, and lowest astronomical tides (LAT) at the riverbank. The study found that UAV-MSL derived riverbank line was identified in between the MSL value (at 2.302 m) and chart datum (at 1.043 m). This study also identified the correlation model, R2 value at 0.9288 between UAV-MSL derived riverbank line with MSL-tide gauge data. This study provides an alternative for researchers to determine riverbank lines based on UAV derived MSL instead of using only tide gauge data.