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
Conventional localization systems typically rely on fixed transmission parameters and signal types, limiting their effectiveness in variable and dynamic underwater environments. The present work investigates the potential of adaptable transmission strategies to enhance signal detection estimation for localization purposes. Two widely used signal types, Linear Frequency Modulated (LFM) chirps and BPSK-modulated Msequences, are selected due to their strong autocorrelation properties and robustness to noise. A matched-filter detection approach based on peak correlation is implemented and evaluated. The analysis examines the impact of varying transmission parameters, namely transmission power and signal duration, on detection performance, which inherently influences time-based localization. Results demonstrate that reconfiguring signal parameters significantly reduces estimation dispersion. Moreover, the optimal signal type is shown to depend on the acoustic scenario, with no single waveform consistently outperforming the other. These findings highlight the value of reconfigurable acoustic systems capable of adapting acoustic systems characteristics based on environmental or system feedback, thereby improving localization performance in navigation tasks and dynamic underwater conditions. © 2025 Marine Technology Society.

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.

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
In the present paper, we propose a control approach to perform docking of an autonomous surface vehicle (ASV) while avoiding surrounding obstacles. This control architecture is composed of two sequential controllers. The first outputs a feasible trajectory between the vessel's initial and target state while avoiding obstacles. This trajectory also minimizes the vehicle velocity while performing the maneuvers to increase the safety of onboard passengers. The second controller performs trajectory tracking while accounting for the actuator's physical limits (extreme actuation values and the rate of change). The method's performance is tested on simulation, as it enables a reliable ground truth method to validate the control architecture proposed.