Assessing Reef-Island Shoreline Change Using UAV-Derived Orthomosaics and Digital Surface Models

Abstract

This study presents an analysis of shoreline change on reef islands using unmanned aerial vehicle (UAV)-derived orthomosaics and digital surface models (DSMs) collected on Sipadan Island, Sabah, Malaysia, and Sasahura Ite Island, Isabel Province, Solomon Islands. The high resolution of UAV-derived orthomosaics enabled changes in the position of the base of beach to be detected with confidence. The accuracy of the UAV-derived DSMs was assessed against equivalent topographic profiles via root-mean-square error, and found to be <0.21 m in all but one case; this demonstrates the potential for using UAV-derived DSMs to interpret three-dimensional island beach morphology and detect patterns of geomorphic change. The correlation between planimetric and volumetric change along selected beach transects was also investigated and found to be variable, indicating that a multifaceted approach including both planimetric (two-dimensional) and volumetric (three-dimensional) metrics is of value when analysing reef-island change. However, interpretations of UAV-derived data must carefully consider errors associated with global positioning system (GPS) positioning, the distribution of ground control points, the chosen UAV flight parameters, and the data processing methodology. Further application of this technology has the potential to expand our understanding of reef-island morphodynamics and their vulnerability to sea-level rise and other stressors.

Multi-Temporal UAV Data and Object-Based Image Analysis (OBIA) for Estimation of Substrate Changes in a Post-Bleaching Scenario on a Maldivian Reef

“…The use of UAV data combined with SfM algorithms has increased in the last several years in different fields of environmental research, such as plastic and marine litter monitoring [73,74], marine habitat mapping [75,76], marine megafauna surveys [76][77][78], coastal geomorphology [79,80], structural geology [58,81] and forestry sciences [71,82]. However, from the first description of the great potential of these coupled techniques in monitoring ecology and geomorphology of the coral reefs by Casella et al (2016) [24], the studies that have improved this methodology in this field are still few in number [48,83,84].…”

Methodology for Carrying out Measurements of the Tombolo Geomorphic Landform Using Unmanned Aerial and Surface Vehicles near Sopot Pier, Poland

“…The analyses performed indicate that currently the most effective and optimal method from the point of view of accuracy, coverage, and rate is the realization of bathymetric surveys in ultra-shallow waters (at depths of less than 1 m) using an USV on which a multi-GNSS receiver and a miniature SBES or a MultiBeam EchoSounder (MBES) can be mounted [71][72][73][74][75]. The measurements performed in the littoral zone can be supplemented with the use of an UAV equipped with a high-resolution camera [76][77][78][79][80]. However, it should be remembered that measurements using unmanned aerial and surface vehicles can be carried out during favorable weather conditions.…”

Unoccupied Aircraft Systems (UAS) for Marine Ecosystem Restoration

“…From both lidar and SfM, 3D point clouds ( Figure 2B and Supplementary Video S1) can be used to create digital surface models, and digital elevation models ( Figure 2C) when data are georectified within a vertical datum. UAS-derived 3D modeling has been conducted in a variety of environments including shorelines (Gonçalves and Henriques, 2015;Seymour et al, 2018;Lowe et al, 2019;Seymour et al, 2019;Casella et al, 2020), several shallow-water/tidal habitats (Long et al, 2016;Ventura et al, 2016;Casella et al, 2017;Kalacska et al, 2018;Windle et al, 2019), and to study hydrological dynamics in wetlands (Capolupo et al, 2015;de Roos et al, 2018;Harvey et al, 2019).…”