Abstract
The deep-sea environment still presents many challenges for systematic, comprehensive data acquisition. The current generation of SMART cables incorporates low-power sensors in long-range telecommunication cables to improve knowledge of ocean variables, aid in earthquake and tsunami warnings, and enhance coastal protection. The K2D Project seeks to expand SMART cables' capabilities by increasing the diversity of sensors along deep water cables, integrating active devices, and leveraging mobile platforms like deep-water AUVs, thereby improving spatial coverage and advancing ocean monitoring technology. This paper discusses a demonstration of these capabilities, focusing on the description of the main building blocks developed along the project, with results from a sea deployment in September 2023.

Abstract
In man-made marine infrastructures, elements such as pillars, cables or ducts are common, which provide distinctive landmarks for Simultaneous Localization and Mapping purposes. In this work, we concentrate on the application of template matching to acoustic imagery for landmark detection and tracking, building on the modeling of common elements in marine environments. The proposed algorithm extends on the original method by employing a density-based clustering technique for match candidate selection and leveraging vehicle inertial information to identify regions of interest in the acquired images, tackling performance deterioration resulting from motion-induced image deformation and overall acoustic feature ambiguity. Experimental results are provided based on datasets collected in a testing pool environment. © 2024 IEEE.

Abstract

Abstract
This paper investigates the real-time tracking capabilities of the Long Baseline (LBL) acoustic tracking system, developed by INESC TEC, for near-shore monitoring applications with human divers. The study aims to determine the system's suitability for environmental monitoring under challenging conditions, such as very shallow water and areas close to the coastline, where acoustic multipath effects are prevalent and can cause significant measurement errors. To mitigate these errors, a two-stage outlier rejection algorithm was implemented. The algorithm's performance was evaluated by comparing the measurement data at each stage and assessing the reduction in erroneous readings. The tracking performance was evaluated based on accuracy and repeatability. Two dives were performed, during which positions marked using the developed system were compared with GNSS data. © 2024 IEEE.

Abstract
Lack of information and perceptual ambiguity are key problems in sonar-based mapping applications. We propose a technique for mapping of underwater environments, building on the finite, positive, sonar beamwidth. Our approach models the free-space covered by each emitted acoustic pulse, employing volumetric techniques to create grid-based submaps of the unoccupied water volumes through images collected from imaging sonars. A representation of the occupied space is obtained by exploration of the free-space frontier. Special attention is given to acoustic image preparation and segmentation. Experimental results are provided based on real data collected from a dam shaft scenario.