Abstract
For the context of a mobile tracking system, an underwater acoustic positioning system was developed, using three hydrophones to compute the direction of an acoustic source relative to an Autonomous Surface Vehicle (ASV). The paper presents an algorithm for the Direction of Arrival (DoA) of an acoustic source, which allows to estimate its position. Preliminary results will be shown in this paper relative to the detection and identification (ID) of the acoustic sources, as well as an analysis of the proposed algorithm. The solution allows the position estimation of an acoustic source, which can be used in tracking solutions. The system can be applied in an ASV or fixed buoys, as long as the baseline's hydrophones are at equal angular distances. The main objective is to track targets with the DoA algorithm as well to estimate their position, improving what was done in [1].

Abstract
This paper presents an autonomous robotic system, IRIS, designed for lost fishing gear recovery. The vehicle was developed in the context of the NetTag project. This is a European Union project funded by EASME the Executive Agency for Small and Medium Enterprises addressing marine litter, and the reduction of quantity and impact of lost fishing gears in the ocean. NetTag intends to produce new technological devices for location and recovery of fishing gear and educational material about marine litter, raise awareness of fisheries industry and other stakeholders about the urgent need to combat marine litter and increase scientific knowledge on marine litter problematic, guaranteeing the engagement of fishers to adopt better practices to reduce and prevent marine litter derived from fisheries. The design of IRIS is presented in detail, addressing the mechanical design, hardware architecture, sensor system and navigation and control. Preliminary tests in tank and in controlled sea conditions are presented and ongoing developments on the recovery system are discussed.

Abstract
Autonomous Surface Vehicles (ASVs), operating near ship harbors or relatively close to shorelines must be able to steer away from incoming vessels and other possible obstacles, be they dynamic or not. To do this, one must implement some type of multi-target tracking and obstacle avoidance algorithms that lets the vehicle dodge obstacles. This paper presents a radar-based multi-target tracking system developed for obstacle detection in a small unmanned surface vehicle. The system was designed for ROAZ II ASV belonging to INESC TEC/ISEP and implemented in Robot Operating System (ROS) for easier integration with the already existing software.

Abstract
In hyperspectral remote sensing, it is common to perform direct analysis of reflectance signals to identify key absorption features, and to apply techniques like the Spectral Angle Mapper to compare spectra and generate a similarity score. In this paper, we introduce the first application of the Continuous Wavelet Transform (CWT) in the context of hyperspectral remote sensing of marine plastic litter. First, we use the CWT to decompose plastic litter reflectance spectra from publicly available datasets and analyze its structure from the perspective of its frequency content at different wavelengths. Then, we propose a matching technique based on the cosine similarity of the magnitude gradients of the CWTs, named CWT Gradient Matching (CWTGM). Our results show that the CWT can be used to identify features which may otherwise prove difficult to analyze, and may also be useful in guiding sensor design. We also demonstrate that the CWTGM technique may be a viable option to measure similarity based on the frequency content of spectral reflectance signals. © 2025 Marine Technology Society.

Abstract
Wireless communication over the ocean surface is challenged by the absence of infrastructure, dynamic propagation conditions, variations in node position and orientation, and signal degradation from reflections, scattering, and absorption. To evaluate the feasibility of long-range, low-power communication in such environments, field trials were conducted using LoRa's Chirp Spread Spectrum (CSS) modulation with E22-900T22S modules operating at 868 MHz. Tests were performed over nearshore ocean water using omnidirectional antennas. One antenna was mounted on a buoy close to the surface, and the other on a movable station, while varying transmission power, bit rate, and distance. Performance was assessed through signal quality, Packet Delivery Ratio (PDR), and throughput measurements, with results indicating that a log-distance Received Signal Strength Indicator (RSSI) model, with fitted parameters showing high correlation, can describe the observed behavior across configurations. LoRa achieved up to 1.7 km range with over 60% PDR at 10 dBm and 2.4kbs-1, demonstrating its potential for ocean-surface communication and aiding in optimal configuration for maritime applications. © 2025 Marine Technology Society.

Abstract
We present a pilot study where spectral unmixing is applied to hyperspectral images captured in a controlled environment with a threefold purpose in mind: validation of our experimental setup, of the data processing pipeline, and of the usage of spectral unmixing algorithms for the aforementioned research avenue. Results from this study show that classical techniques such as VCA and FCLS can be used to distinguish between plastic and nonplastic materials, but struggle significantly to distinguish between spectrally similar plastics, even in the presence of multiple pure pixels.