Using Unmanned Aerial Vehicles (UAV) for High-Resolution Reconstruction of Topography: The Structure from Motion Approach on Coastal Environments

Abstract

Abstract:The availability of high-resolution Digital Surface Models of coastal environments is of increasing interest for scientists involved in the study of the coastal system processes. Among the range of terrestrial and aerial methods available to produce such a dataset, this study tests the utility of the Structure from Motion (SfM) approach to low-altitude aerial imageries collected by Unmanned Aerial Vehicle (UAV). The SfM image-based approach was selected whilst searching for a rapid, inexpensive, and highly automated method, able to produce 3D information from unstructured aerial images. In particular, it was used to generate a dense point cloud and successively a high-resolution Digital Surface Models (DSM) of a beach dune system in Marina di Ravenna (Italy). The quality of the elevation dataset produced by the UAV-SfM was initially evaluated by comparison with point cloud generated by a Terrestrial Laser Scanning (TLS) surveys. Such a comparison served to highlight an average difference in the vertical values of 0.05 m (RMS = 0.19 m). However, although the points cloud comparison is the best approach to investigate the absolute or relative correspondence between UAV and TLS OPEN ACCESSRemote Sens. 2013, 5 6881 methods, the assessment of geomorphic features is usually based on multi-temporal surfaces analysis, where an interpolation process is required. DSMs were therefore generated from UAV and TLS points clouds and vertical absolute accuracies assessed by comparison with a Global Navigation Satellite System (GNSS) survey. The vertical comparison of UAV and TLS DSMs with respect to GNSS measurements pointed out an average distance at cm-level (RMS = 0.011 m). The successive point by point direct comparison between UAV and TLS elevations show a very small average distance, 0.015 m, with RMS = 0.220 m. Larger values are encountered in areas where sudden changes in topography are present. The UAV-based approach was demonstrated to be a straightforward one and accuracy of the vertical dataset was comparable with results obtained by TLS technology.

Application of Low-Cost Fixed-Wing UAV for Inland Lakes Shoreline Investigation

“…Despite their increased capabilities, the use of drones in geophysical sciences is usually restricted to image acquisition for generating highresolution maps (Tauro et al 2016). Some authors offered a solution-the use of UAV systems to reconstruct topography in coastal environment (Mancini et al 2013), shallow braided rivers (Javernick et al 2014) and lakes. More sensors will be developed over time allowing, for example, in situ measurements (Kageyama et al 2016;Koparan and Koc 2016), pollution meters (Zang et al 2012) and so on.…”

Comparison of pre- and self-calibrated camera calibration models for UAS-derived nadir imagery for a SfM application

“…10s -100s m) Terrestrial Laser Scanners (TLS) are increasingly used, offering millimetre range precision; in-combination with instruments such as differential GPS (dGPS) and Total Stations, they can prove to be very effective for detecting and measuring morphology and morphological change (Rosser et al, 2005;Bangen et al, 2014). The expense of airborne techniques, the lack of control over timing of national Lidar-mapping programmes, and possibly the accessibility limitations of some of these approaches has led some scientists to explore the potential of Unmanned Aerial Systems (UASs) for the acquisition of high resolution imagery and elevation mapping through low-altitude aerial photogrammetry (Boon et al, 2016;Clapuyt et al, 2016;Fonstad et al, 2013;Mancini et al, 2013;Ouédraogo et al, 2014).…”

“…There is an increasing demand for the availability of high resolution environmental topographic datasets (Mancini et al, 2013). Topographic data such as Digital Surface Models (DSMs) offer a valuable insight into the landscape, morphology and elevation structure of an environment (Hutchinson and Gallant, 2000).…”

SF3M software: 3-D photo-reconstruction for non-expert users and its application to a gully network

“…While recent UAV technologies have the capacity of surveying large areas of the landscape (Mathews and Jensen, 2013;Mancini et al, 2013), not all stakeholders (e.g. researchers, technicians and land owners) have the technical and financial resources to use such sophisticated techniques.…”