Accurate Maps of Reef-Scale Bathymetry with Synchronized Underwater Cameras and GNSS

We investigate the utility of towed underwater camera systems with tightly coupled Global Navigation Satellite System (GNSS) positions to provide reef-scale bathymetric models millimeter centimeter resolutions and accuracies Structure-from-Motion (SfM) photogrammetry. Successful development these techniques would allow for detailed assessments benthic conditions, including accretion erosion reefs adjacent sediment deposits, without need ground control points. use a multi-camera system by small vessel map over 70,000 m2 complex shallow (2–8 m water depth) bedrock reef, boulder fields, fine (sand gravel) sediments Lake Tahoe, California. find that multiple synchronized cameras increase overall mapping coverage wider survey line spacing. The accuracy was sub-millimeter local length measurements less than meter, reproducibility found scale GNSS (3–5 cm), although this could be improved sub-centimeter inclusion one or more co-registered, but unsurveyed, For future applications, we guidance on conducting field operations, correcting image color, optimizing SfM workflows. conclude GNSS-coupled array is promising technique at high resolution control.