Abstract
Detailed knowledge of nearshore topography and bathymetry is required for a wide variety of purposes, including ecosystem protection, coastal management, and flood and erosion monitoring and research, among others. Both topography and bathymetry are usually studied separately; however, many scientific questions and challenges require an integrated approach. LiDAR technology is often the preferred data source for the generation of topobathymetric models, but because of its high cost, it is necessary to exploit other data sources. In this regard, the main goal of this study was to present a methodological proposal to generate a topobathymetric model, using low-cost unmanned platforms (unmanned aerial vehicle and unmanned surface vessel) in a very shallow/shallow and turbid tidal environment (Bahía Blanca estuary, Argentina). Moreover, a cross-analysis of the topobathymetric and the tide level data was conducted, to provide a classification of hydrogeomorphic zones. As a main result, a continuous terrain model was built, with a spatial resolution of approximately 0.08 m (topography) and 0.50 m (bathymetry). Concerning the structure from motion-derived topography, the accuracy gave a root mean square error of 0.09 m for the vertical plane. The best interpolated bathymetry (inverse distance weighting method), which was aligned to the topography (as reference), showed a root mean square error of 0.18 m (in average) and a mean absolute error of 0.05 m. The final topobathymetric model showed an adequate representation of the terrain, making it well suited for examining many landforms. This study helps to confirm the potential for remote sensing of shallow tidal environments by demonstrating how the data source heterogeneity can be exploited.
Highlights
The marine coastal zone is a highly energetic environment occurring along a continuum of coastal land, intertidal area, and aquatic systems [1]
The main goal of this study is to present a methodological proposal to generate a topobathymetric model by using low-cost unmanned platforms (UAV and USV) in a very shallow/shallow tidal environment
A continuous terrain model was built with a spatial resolution of approximately 0.08 (TPC) and 0.50 m (BPC)
Summary
The marine coastal zone is a highly energetic environment occurring along a continuum of coastal land, intertidal area, and aquatic systems [1]. In recent years, unmanned platforms, like UAV (unmanned aerial vehicle) or USV (unmanned surface vessel), have emerged as a promising technology for surveying, providing new opportunities for collecting useful data in remote or inaccessible areas. The latest technologies in topographic surveying are related to the development of a powerful approach called Structure from Motion (SfM), which combines well-established photogrammetric principles (basically, image matching and bundle adjustment) with modern computational methods [6] This trend is confirmed in many studies involving topographic surveys over coastal zones [7,8,9,10,11,12]. Tonkin et al.’s study [13] makes reference to a new methodological frontier for acquiring topographic data based on UAV-SfM, of great interest for scientists working in geomorphology
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