Visual maps of the seafloor can provide objective information to characterize benthic ecosystems and survey the distribution of mineral deposits on spatial scales that cannot be otherwise assessed. This paper proposes a threedimensional mapping method based on light sectioning that enables the simultaneous capture of both structure and color from the images of a single camera. The advantages of the method include high and consistent resolution of the bathymetry, and the simplicity of the setup and the algorithm used to process the data it obtains. The hardware requirements for collecting the data are a single camera, a line laser, and a light, making it possible to deploy the mapping device along with other sensors and devices on underwater platforms such as autonomous underwater vehicles and remotely operated vehicles that can log navigation data. The system has been deployed on a total of 11 cruises, among others, to survey manganese-rich crust deposits on the slopes of Takuyo #5 seamount in the Pacific at depths of more than 2,000 m. In this paper, we present the data that were obtained on one of these cruises.
Abstract-This article presents a bathymetric SLAM (simultaneous localization and mapping) solution for underwater vehicles by addressing the registration of point clouds gathered from single line laser-based structured light systems. While structured light can be applied to generate millimetre resolution seafloor bathymetry, the accuracy of the maps generated is typically constrained by the localization accuracy of the vehicles used. In this work, relative uncertainties in vehicle localisation are reduced by implementing bathymetric SLAM using temporally constrained submaps. We demonstrate that the method described can overcome misalignments by correcting errors in localisation and can be used to generate self-consistent high-resolution seafloor bathymetric maps.
Manganese crusts (Mn-crusts) are a type of mineral deposit that exists on the surface of seamounts and guyots at depths of >800 m. We have developed a method to efficiently map their distribution using data collected by autonomous underwater vehicles and remotely operated vehicles. Volumetric measurements of Mn-crusts are made using a high-frequency subsurface sonar and a 3-D visual mapping instrument mounted on these vehicles. We developed an algorithm to estimate Mn-crust distribution by combining continuous subsurface thickness measurements with the exposed surface area identified in 3-D maps. This is applied to data collected from three expeditions at Takuyo Daigo seamount at depths of ∼1400 m. The transects add to ∼11 km in length with 12 510 m 2 mapped. The results show that 52% of the surveyed area is covered by Mn-crusts with a mean thickness of 69.6 mm. The mean Mn-crust occurrence is 69.6 kg/m 2 with a maximum of 204 kg/m 2 in the mapped region. The results are consistent with estimates made from samples retrieved from the area, showing more detailed distribution patterns and having significantly lower uncertainty bounds for regional-scale Mn-crust inventory estimation.
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