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Open AccessArticle

Correcting Image Refraction: Towards Accurate Aerial Image-Based Bathymetry Mapping in Shallow Waters

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Lab of Photogrammetric Vision, Civil Engineering and Geomatics Dept., Cyprus University of Technology, 2-8 Saripolou str., 3036 Limassol, Cyprus
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Department of Topography, School of Rural and Surveying Engineering, National Technical University of Athens, Zografou Campus, 9 Heroon Polytechniou str., 15780 Athens, Greece
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Author to whom correspondence should be addressed.
Remote Sens. 2020, 12(2), 322; https://doi.org/10.3390/rs12020322
Received: 19 November 2019 / Revised: 4 January 2020 / Accepted: 14 January 2020 / Published: 18 January 2020
Although aerial image-based bathymetric mapping can provide, unlike acoustic or LiDAR (Light Detection and Ranging) sensors, both water depth and visual information, water refraction poses significant challenges for accurate depth estimation. In order to tackle this challenge, we propose an image correction methodology, which first exploits recent machine learning procedures that recover depth from image-based dense point clouds and then corrects refraction on the original imaging dataset. This way, the structure from motion (SfM) and multi-view stereo (MVS) processing pipelines are executed on a refraction-free set of aerial datasets, resulting in highly accurate bathymetric maps. Performed experiments and validation were based on datasets acquired during optimal sea state conditions and derived from four different test-sites characterized by excellent sea bottom visibility and textured seabed. Results demonstrated the high potential of our approach, both in terms of bathymetric accuracy, as well as texture and orthoimage quality. View Full-Text
Keywords: bathymetry; UAV; aerial imagery; seabed mapping; coastal mapping; refraction correction; DSM; image correction; SfM; machine learning bathymetry; UAV; aerial imagery; seabed mapping; coastal mapping; refraction correction; DSM; image correction; SfM; machine learning
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Agrafiotis, P.; Karantzalos, K.; Georgopoulos, A.; Skarlatos, D. Correcting Image Refraction: Towards Accurate Aerial Image-Based Bathymetry Mapping in Shallow Waters. Remote Sens. 2020, 12, 322.

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