Landfalls are where underwater cables or pipelines come to shore and are typically complex and dynamic environments, that are difficult to characterise due to accessibility, safety, and environmental challenges posed by coastal sites. Beach environments can be dangerous and are often subject to restricted access and working hours due to tides, sheer cliffs as well as salt flats, marshes and estuaries which are typically vast. The geology of landfalls can also contribute to the difficulty in performing a landfall survey due to highly variable ground conditions which can change rapidly over time due to longshore drift, storm surges and migrating channels.
From Geo Business by Sinead Morgan.
Geo-4D are a geoscience specialist, who have developed an efficient toolkit and workflow for characterising challenging coastal sites. Geo-4D were recently tasked with performing a multidisciplinary beach landfall characterisation survey in Cornwall, UK, to assist with the engineering and design of a telecommunication cable installation.
To acquire information to meet the needs of the engineers, Geo-4D collected topographical, geotechnical, magnetometer and aerial imagery data, to aid in the selection of the route and cable engineering, using an unmanned aerial vehicle (UAV) supplemented by traditional surveying techniques.
Topographical data can be acquired aerially using a combination of photogrammetry and LiDAR. Photogrammetry utilises high-resolution cameras to take overlapping photos which are accurately triangulated into ultra-high resolution colourised 3D terrain models. The data is accurately georeferenced using accurate GPS receivers onboard the UAVs, and accurately surveyed ground control points. LiDAR uses time of flight measurements of reflected light pulses, along with accurate inertial motion sensors to build accurate terrain models and is capable of penetrating through vegetation allowing true ground elevations to be surveyed.
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