The unmanned surface vehicle (USV) is deemed with significant potential to deal with the maritime search and rescue (SAR) missions. This paper investigates the path planning of the USV with SAR tasks, and proposes a novel algorithm based on combined convolutional neural network rapid-exploration random tree and improved artificial potential field (CRRT-IAPF). The proposed scheme can be divided into the global and the local path plannings. The rapid-exploration random tree (RRT) method is employed to generate the global path in the sea chart, which is further discriminated to be optimal or non-optimal through a well-trained convolutional neural network (CNN). The artificial potential field (APF) method is adopted to plan the local path in the environment with small obstacles and SAR task points. To facilitate the path convergence and avoid the oscillation, the potential field function is improved in a more efficient way. In addition, the evaluation functions of search success rate and rescue success rate are established to evaluate the completeness of SAR tasks. Through the simulation, it is verified that the proposed CRRT-IAPF scheme has the superiority over the others.

The article is devoted to the mathematical theories and algorithms necessary for the implementation of a software package that fully automates the calculations necessary in Nautical Astronomy. The article describes a method for calculating the equatorial and horizontal coordinates of the celestial bodies at any moment of time. The authors describe the calculation of the time of the apparent rising (setting) of the Sun, solar illumination and events of other celestial bodies. A formula for calculating astronomical refraction is proposed. A matrix method for implementing the method of least squares for determining the coordinates of a place along the lines of position is described. An algorithm for identifying navigational planets is also described and a method for estimating the error for it is proposed. Based on this, the results of the development of the software package ‘Astronomy Package’ for Nautical Astronomy are presented.

The need for Global Navigation Satellite System (GNSS) receiver testing increases with the advent of widespread Internet of Things (IoT) technologies and other electronic devices dependent on position determination. In this paper, a low-cost GNSS multiband L1+L5 signal recorder and replayer for equipment testing purposes is proposed. It is implemented using Software-Defined Radio (SDR) modules HackRF One with proper time and phase synchronisation. The recorder–replayer has been tested with GPS, GALILEO, BEIDOU and GLONASS satellites and several commercial GNSS receivers. Reduced GNSS signal bandwidth of approximately 10 MHz is sufficient for efficient reception of recorded signals. Performed tests with a driving car show applicability of this GNSS recorder–replayer in dynamic settings.

The first globalisation of the world occurred under the motivation of the Avis dynasty of Portugal, aimed at discovering new lands and wealth, exploring ocean routes, especially with the successful epic journey to India. The political decisions of the Avis dynasty kings, along with Christianity’s interest in expanding into Africa and Asia, were key factors in the success of these maritime explorations. However, the Coriolis force was a significant force of nature for the outcome of this journey. Here we investigate Caminha’s letter, the scribe of Pedro Álvares Cabral’s fleet when he found the lands of Brazil. This letter contains detailed scientific data, distances travelled, dates, geographical features, fauna and flora, initial anthropological information on indigenous peoples, and records of coastal depths. Analysis of these elements and facts lead to a new proposal for the location of Mount Pascoal and the so-called safe harbour, where Cabral’s fleet landed.

Terrain-aided navigation with a three-dimensional (3D) map has both high accuracy and high reliability, which is crucial for applications in the global navigation satellite system (GNSS)-denied scenarios. In this paper, a new terrain matching algorithm with 3D Zernike moments (3D ZMs) is proposed. The redundant items in the even-order 3D ZMs are analysed in theory. The 3D ZMs are also correlated with the standard deviations of terrain further to identify the redundant items. The new 3D ZM descriptors are proposed for the feature vector of the matching algorithm by excluding the redundant items from the descriptors. The simulation results demonstrate that the algorithm with the revised descriptors achieves a higher matching success rate than both that with the existing descriptors and that with the odd-order descriptors under the same conditions.

Maritime piracy represents a significant international challenge, impacting both economic stability and political dynamics. Researchers from diverse disciplines have been drawn to this multifaceted issue, each aiming to understand and address different aspects of piracy’s impact and implications. This study offers a comprehensive overview of maritime piracy research based on bibliographic analysis. Its objective is threefold. First, to delineate the key domains of inquiry within maritime piracy research. These domains encompass a wide range of topics, including the socio-economic drivers of piracy, the legal frameworks governing maritime security, and computer science to analyse piracy acts. Second, to identify major contributions in the field, recognising seminal works, influential authors and significant findings related to maritime piracy. Lastly, to discern emerging research trends within maritime piracy, and to identify novel areas of inquiry, innovative methodologies and promising avenues for future exploration. Furthermore, the most popular datasets from these studies that include relevant information are presented in this work.

The aim of this paper is to establish the correspondence between the twisted localised Pestov identity on the unit tangent bundle of a Riemannian manifold and the Weitzenböck identity for twisted symmetric tensors on the manifold.

This paper studies the probability of active navigational error events for use in ship–bridge allision risk analysis. To estimate the probability of these kinds of events, accident databases, incident reports and AIS data were studied; the case studies herein cover 6 years and 15 bridges in Scandinavia. The main findings of this paper show that there is great variation in the probability of ship–bridge allision due to active navigational errors, and it is not recommended to use the currently common practice of 2% uniform distribution of the number of ship passages on all bridges. Another important finding is that the probability of a ship striking a bridge due to the error type Wrong Course at a Turning point is not uniform along the length of the bridge, but is only likely to occur in a cone formation from the last turning point.

During a regatta, the influence of wind speed on the velocity of the boat, the distance covered and the manoeuvres carried out has not been clarified to date in the 49er and 49erFX classes. Therefore, the main aim of this study was to analyse how these variables are affected by wind speed during a regatta. The sample consisted of 39 Olympic sailors from the 49erFX and 49er classes, who participated in a World Cup. Velocity, velocity made good (VMG), distance and manoeuvres were evaluated in the upwind and downwind legs using global positioning system (GPS) devices. In both classes, it was observed that mean velocity, VMG and distance travelled increased as the wind velocity increased in upwind and downwind legs. The velocity, the distance travelled and the manoeuvres carried out are conditioned by wind speed in both upwind and downwind legs in the 49er and 49erFX classes.

Maritime navigation in low visibility presents a significant challenge, jeopardising seafarers’ situational awareness and escalating collision risks. This study introduces a maritime head-up display (mHUD) to address this issue. The mHUD, a 2-m diameter aluminium ring with dual rows of LEDs, enhances visibility for autonomous ships in adverse conditions on ship bridges and remote operating centres (ROCs). Displaying various modes such as shallow waters, land, lighthouses, beacons, buoys and maritime traffic, the mHUD was evaluated in a ship bridge simulator by 12 navigation students. Results revealed that the mHUD substantially improved situational awareness, proving more efficient and effective than navigating without it in poor visibility conditions. Participants found the mHUD easy to learn and expressed willingness to use it in real-world situations. The study highlights the mHUD’s potential to enhance situational awareness on ship bridges and ROCs for autonomous ships, while suggesting potential enhancements to increase usability and user satisfaction.

Intermittency as it occurs in fast dynamos in the magnetohydrodynamics (MHD) framework is evaluated through the examination of relations between normalized moments at third order (skewness $S$) and fourth order (kurtosis $K$) for both the velocity and magnetic field, and for their local dissipations. As investigated by several authors in various physical contexts such as fusion plasmas (Krommes 2008 Phys. Plasmas 15, 030703), climate evolution (Sura & Sardeshmukh 2008 J. Phys. Oceano. 38, 639-647), fluid turbulence or rotating stratified flows (Pouquet et al. 2023 Atmosphere 14, 01375), approximate parabolic $K(S)\sim S^\alpha$ laws emerge whose origin may be related to the applicability of intermittency models to their dynamics. The results analyzed herein are obtained through direct numerical simulations of MHD flows for both Taylor–Green and Arnold–Beltrami–Childress forcing at moderate Reynolds numbers, and for up to $3.14 \times 10^5$ turn-over times. We observe for the dissipation $0.2 \lesssim \alpha \lesssim 3.0$, an evaluation that varies with the field, the forcing and when filtering for high-skewness intermittent structures. When using the She & Lévêque (1994) Phys. Rev. Lett. 72, 336-339 intermittency model, one can compute $\alpha$ analytically; we then find $\alpha \approx 2.5$, clearly differing from a (strict) parabolic scaling, a result consistent with the numerical data.

Accurate typhoon track nowcasting is vital for navigation and coastal disaster prevention. This research integrates a Large Language Model (LLM) with Retrieval-Augmented Generation (RAG) technology for typhoon path prediction. Leveraging LLMs as the predictive foundation, the approach tailors forecasts to individual typhoon characteristics. The methodology involves collecting satellite imagery, standardizing data, and employing optical flow methods to track typhoons and derive path coordinates. These coordinates are preprocessed and embedded into the LLM. RAG enhances the LLM’s predictive performance, enabling effective forecasting. Increasing typhoon-specific embedded data further improves accuracy. Using the FY-4 dataset, the method achieved an average absolute error of 10.78 km in 12-hour predictions. The study demonstrates that LLM-RAG integration excels in nowcasting.

Global Navigation Satellite System (GNSS) positioning accuracy is challenged due to abnormal signals in harsh environments. This study proposes an approach for multiple and mixed abnormal measurement processing in multi-GNSS positioning and navigation based on the resilient a priori innovation and posterior residual (PR) for harsh environments. Specifically, first, both static and kinematic processing modes are considered when calculating the innovation vector (IV). Second, observations are classified and abnormal measurements are eliminated based on the different observation accuracies of different GNSS systems within the resilient IV method. Finally, the resilient PR method considers the total number of redundant observations. Compared with the traditional IV and PR method, the RIP method improves the positioning accuracy by approximately 30.2% and 58.0% in static experimental datasets No. 1 and No. 2, respectively. In the kinematic experiment, it improves the ambiguity success rate and positioning accuracy by approximately 41.5% and 86.7%, respectively.