Underwater photogrammetry and in particular systematic visual surveys of the deep sea are by far less developed than similar techniques on land or in space. The main challenges are the rough conditions with extremely high pressure, the accessibility of target areas (container and ship deployment of robust sensors, then diving for hours to the ocean floor), and the limitations of localization technologies (no GPS). The absence of natural light complicates energy budget considerations for deep diving flash-equipped drones. Refraction effects influence geometric image formation considerations with respect to field of view and focus, while attenuation and scattering degrade the radiometric image quality and limit the effective visibility. As an improvement on the stated issues, we present an AUV-based optical system intended for autonomous visual mapping of large areas of the seafloor (square kilometers) in up to 6000 m water depth. We compare it to existing systems and discuss tradeoffs such as resolution vs. mapped area and show results from a recent deployment with 90,000 mapped square meters of deep ocean floor.

The Cabo Verde Archipelago is related to a mantle plume located close to the rotational pole of the African Plate. It consists of islands and seamounts arranged in a horseshoe‐shaped pattern open to the west, thus forming two volcanic chains, each with a weak east‐west age progression. High‐resolution swath bathymetry of 12 Cabo Verde seamounts is used here to assign each seamount to its pre‐shield, shield or post‐shield evolutionary stage, respectively. The eastern seamounts exhibit degraded and partially eroded morphologies, and are mainly in their post‐shield stage. A new ⁴⁰Ar‐³⁹Ar date for Senghor Seamount at 14.872 ± 0.027 Ma supports old ages for the eastern seamounts. The western seamounts generally exhibit younger volcanic‐edifice‐construction morphologies, showing fresh effusive and explosive volcanics, including rarely observed deep‐water explosive volcanism in the Charles Darwin Volcanic Field. Furthermore, the two previously unknown seamounts Sodade and Tavares in the westernmost termini of both volcanic chains exhibit pristine volcanic morphologies, in agreement with present‐day volcanism and seismic activity recorded from the western seamounts. The islands and seamounts rest on three submarine platforms to the east, northwest and southwest, respectively. Taken together, the seamount and island data suggest a shift in igneous activity from the eastern to the other platforms at about 8–6 Ma. However, the complex evolution pattern for both volcanic chains includes the simultaneous occurrence of pre‐shield or shield edifices at any time, followed by erosional and rejuvenation stages. The new seamount data still demonstrate ongoing westward submarine‐growth in both volcanic chains.

In this technical report, we discuss several approaches to in-core rendering of large volumetric datasets in Unreal Engine 5 (UE5). We explore the following methods: the TBRayMarcher Plugin, the Niagara Fluids Plugin , and various approaches using Sparse Volume Textures (SVT), with a particular focus on Heterogeneous Volumes (HV). We found the HV approach to be the most promising. The biggest challenge we encountered with other approaches was the need to chunk datasets so that each fits into volume textures smaller than one gigavoxel. While this enables display of the entire dataset at reasonable frame rates, it introduces noticeable artifacts at chunk borders due to incorrect lighting, as each chunk lacks information about its neighbors. After addressing some (signed) int32 overflows in the Engine's SVT-related source code by converting them to to (unsigned) uint32 or int64, the SVT-based HV system allows us to render sparse datasets up to 32k x 32k x 16k voxels, provided the compressed tile data (including MIP data and padding for correct interpolation) does not exceed 4 gigavoxels. In the future, we intend to extend the existing SVT streaming functionality to support out-of-core rendering, in order to eventually overcome VRAM limitations, graphics API constraints, and the performance issues associated with 64-bit arithmetic in GPU shaders.

Underwater high resolution 3D mapping implies a very accurate sensor pose estimation to fuse the sensor readings over time into one consistent model. In the case of optical mapping systems, the needed accuracy can easily lie outside of the specification of Doppler Velocity Logs normally used for pose estimation by remotely operated and autonomous underwater vehicles. This is especially the case for difficult terrains or for low altitude situations. Therefore, to improve performance in such situations, a self-referenced laser system is proposed performing micro navigation to significantly improve the resolution of optical underwater 3D seabed mapping.