Monitoring coastal morphology: the potential of low‐cost fixed array action cameras for 3D reconstruction

Abstract

The combination of structure‐from‐motion with multi‐view stereo (SfM‐MVS) photogrammetry has become an increasingly popular method for the monitoring and three‐dimensional (3D) reconstruction of coastal environments. Climate change is driving the potential for increased coastal landward retreat meaning geomorphological monitoring using methods such as SfM‐MVS has become essential for detecting and tracking impacts. SfM‐MVS has been well‐researched with a variety of platforms and spatial and temporal resolutions using mainly rectilinear digital cameras in coastal settings. However, there has been no assessment of the potential of fixed multi‐camera arrays to monitor landward retreat or on the significance of camera placement in relation to the scene. This study presents an innovative method of image acquisition using a purpose‐built camera grid and GoPro© action camera to evaluate the combined effects of camera height, obliqueness and overlap at a site of known landward retreat. This approach examines the effect of camera placement on scene reconstruction to aid the design of a multi‐camera array. SfM‐MVS dense point clouds display millimetre accuracy when compared to equivalent terrestrial laser scans and strong image network geometry with internal precision estimates of < 3 mm. Comparable point cloud reconstruction can be achieved with a small number of images stationed in appropriate positions. Initial results show as few as five images positioned at a cliff to camera ratio of 3:4.18 and camera obliqueness of 40° can provide reconstruction in the range of millimetres (mean error of 4.79 mm). These findings illustrate the importance of camera placement when using multiple cameras and aid the design of a low‐cost, fixed multi‐camera array for use at sites of small‐scale landward retreat. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

Low-Cost Sensors for Monitoring Coastal Climate Hazards: A Systematic Review and Meta-Analysis

“…Information on coastal topography derived from variables such as DEM/DSM, 3D point clouds, sand level variation, and beach profile helps in the quantification of volumetric changes in sediments quantifying accretion or erosion rates in beach-dune systems and hence have been categorised under coastal topography, as seen from the table below. DEM/DSM and 3D point clouds are derived from images taken either on ground [ 60 , 61 , 62 , 63 ] or from an aerial platform such as a drone [ 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 ] or a kite [ 108 ] fitted with an RGB camera.…”

“…Terrestrial photogrammetry has been successfully applied to quantify erosion on coastal cliffs [ 58 ], and terrestrial photogrammetry combined with SfM has been used to monitor coastal cliff morphological changes by deriving high-resolution topographic data of the site monitored [ 59 , 60 , 61 , 62 ].…”

“…Ref. [ 61 ] evaluated the potential of a fixed multi-camera array for the reconstruction of retreating coastal cliffs and investigated the effects of camera height and obliqueness on image reconstruction, making use of an action camera (GoPro Hero4 black), which is unconventional in the sense that the large field of view (FOV) incorporates greater radial distortion; however, Ref. [ 61 ] found that this could be compensated for with the use of commercial software such as Agisoft Metashape, generating point clouds that were at times even better than the TLS survey carried out for validation.…”

An Optimum Deployment Algorithm of Camera Networks for Open-Pit Mine Slope Monitoring

“…In addition, the algorithm can be used for the calculation of other slope deployment scenarios (e.g., modeling of cultural heritage objects [ 35 ], 3D robot localization [ 36 ], monitoring coastal morphology [ 37 ], etc.). The algorithm can be improved by considering more photogrammetric geometry factors (e.g., the angle of intersection, the length of the photographic baseline, etc.)…”

How strong are salt marshes? Geotechnical properties of coastal wetland soils

“…While there is a general consensus among existing studies that such processes contribute to marsh edge erosion, observations of such erosion are rare and difficult to capture (e.g. Godfrey et al, 2020). As such, the erosion processes causing retreat are generally inferred from marsh morphology change after erosion has taken place and are therefore poorly understood.…”