Unmanned surface vehicles (USVs) have demonstrated impressive practical value and potential in Marine Internet of Things (MIoT) system. Although trajectory-tracking control is among the most common practical technology of USVs, various limitations remain unaddressed. Existing studies have employed simple mathematical models to simulate marine environment without utilizing actual data, resulting in a lack of environmental authenticity. Moreover, a complex marine environment increases the need for robustness and adaptability of the control policy. To overcome these limitations, this study proposes a deep reinforcement learning (DRL)-based policy for USV trajectory-tracking control, which can effectively adapt to complex environmental disturbances. First, we use actual marine data, including ocean currents and winds, to construct a time-varying multi-element marine environment model. Next, an effective Markov decision processes (MDPs) formulation integrating LOS guidance law is elaborately proposed, in which the composite reward function and state transition function are used to avoid ineffective exploration and achieve better convergence ability. Furthermore, a USV trajectory-tracking controller based on hybrid priority twin-delayed deep deterministic policy gradient (TD3) agent is designed; specifically, a hybrid priority experience replay mechanism is developed and integrated within the TD3. It evaluates the significance of an experience by weighing the temporal-difference (TD) error and reward value, thus enabling the USV agent to explore optimal control policies and further accelerate the network convergence. Experimental results show that our method achieves better trajectory-tracking performance than mainstream DRL-based and model-based control approaches, and adapts to different reference trajectories and different intensities of environmental disturbances with high tracking accuracy.

The Kuroshio intrusion into the South China Sea via the Luzon Strait significantly influences regional ocean dynamics. However, predicting this intrusion, especially the Kuroshio Loop Current (KLC), remains challenging due to its complex mesoscale and submesoscale processes. Traditional physical models struggle to capture the nonlinear and multiscale features of the Kuroshio intrusion, while deep learning approaches face challenges in incorporating the essential physical processes that characterize the KLC. To address these challenges, we developed the Kuroshio Intrusion Forecast Network (KIFnet), a multi-prior knowledge guided deep learning model. KIFnet integrates physical oceanographic principles with data-driven predictions, enhancing its ability to capture complex ocean dynamics. KIFnet incorporates an SST-guided SSH prediction module and a vorticity-guided loss function to explicitly model thermal and dynamic features of the KLC, advancing the challenging task of forecasting KLC intrusion events. Experimental results demonstrate the model achieves an accuracy of 88% for KLC intrusion events and provides reliable predictions up to 10 days ahead. Prior limitations in KLC forecasting have constrained SCS climate modeling and marine ecosystem management. KIFnet provides accurate KLC predictions, supporting proactive climate adaptation and sustainable ecosystem strategies.

We study a data pricing problem, where a seller has access to $N$ homogeneous data points (e.g. drawn i.i.d. from some distribution). There are $m$ types of buyers in the market, where buyers of the same type $i$ have the same valuation curve $v_i:[N]\rightarrow [0,1]$, where $v_i(n)$ is the value for having $n$ data points. *A priori*, the seller is unaware of the distribution of buyers, but can repeat the market for $T$ rounds so as to learn the revenue-optimal pricing curve $p:[N] \rightarrow [0, 1]$. To solve this online learning problem, we first develop novel discretization schemes to approximate any pricing curve. When compared to prior work, the size of our discretization schemes scales gracefully with the approximation parameter, which translates to better regret in online learning. Under assumptions like smoothness and diminishing returns which are satisfied by data, the discretization size can be reduced further. We then turn to the online learning problem, both in the stochastic and adversarial settings. On each round, the seller chooses an *anonymous* pricing curve $p_t$. A new buyer appears and may choose to purchase some amount of data. She then reveals her type *only if* she makes a purchase. Our online algorithms build on classical algorithms such as UCB and FTPL, but require novel ideas to account for the asymmetric nature of this feedback and to deal with the vastness of the space of pricing curves. Using the improved discretization schemes previously developed, we are able to achieve $\widetilde{O}(m\sqrt{T})$ regret in the stochastic setting and $\widetilde{\mathcal{O}}(m^{3/2}\sqrt{T})$ regret in the adversarial setting.

Global navigation satellite system reflectometry (GNSS-R) Delay-Doppler map measures the sea surface roughness, which has recently been applied to retrieve sea surface wind speed. However, current studies on GNSS-R wind speed retrieval only use the spatial domain of the delay-Doppler map without considering the variations patterns in the map, which is regarded as frequency domain information of the map. In this study, we propose a joint frequency-spatial-domain wind speed retrieval network (FSNet) based on reflectivity data provided by the Cyclone Global Navigation Satellite System (CyGNSS) mission. We construct a matchup dataset between the CyGNSS satellite data and ECMWF model data from January 1, 2018, to December 31, 2019. The wind speed range is 0–25 m/s. Using the proposed FSNet, frequency and spatial features are simultaneously extracted. The frequency domain feature supplements the spatial-domain information of the mid and high-level features in the neural network. Rather than directly concatenating the frequency-domain features with the spatial-domain features, we designed a feature fusion module to fuse frequency and spatial features for wind speed retrieval adaptively. Experiments show that our FSNet wind speed retrieval has a root mean square error (RMSE) of 1.63 m/s for a wind range of 0-25 m/s. This accuracy is 25.4% better than the operational algorithm provided by the CyGNSS Level 2 wind speed product. For a higher wind range of 16-25m/s, FSNet performed even better, improving the RMSE by 31%.

This article focuses on unsupervised methods for optical aerial image change detection. Existing unsupervised change detection techniques are mainly categorized as patch-based methods and transfer-learning-based methods. However, the first type ignores the spatial information in the images, and the second type may introduce new errors due to knowledge extracted from additional datasets. To effectively tackle these problems, we propose an unsupervised progressive learning framework (UPLF). We first use original estimated change maps as the labeled samples and choose the reliable regions from samples to train the network. We then propose a progressive learning method to expand the reliable labeled region. Briefly, we apply a label selection filter to filter out incorrect change information from the regions to help rectify incorrect labeling in the regions. This leads to a more reliable labeled region and thus, in turn, more accurate detection results. Compared with the patch-based and transfer-learning-based unsupervised techniques, our method takes the entire map as the training sample to avoid the problem associated with using small patches; moreover, our iterative and progressive methods further enhance the change detection performance without involving external knowledge. Indeed, based on our experimental results on the real datasets, the proposed method demonstrates highly competitive performance compared with the state-of-the-art.

Sea fog significantly threatens the safety of maritime activities. This paper develops a sea fog dataset (SFDD) and a dual branch sea fog detection network (DB-SFNet). We investigate all the observed sea fog events in the Yellow Sea and the Bohai Sea (118.1°E-128.1°E, 29.5°N-43.8°N) from 2010 to 2020, and collect the sea fog images for each event from the Geostationary Ocean Color Imager (GOCI) to comprise the dataset SFDD. The location of the sea fog in each image in SFDD is accurately marked. The proposed dataset is characterized by a long-time span, large number of samples, and accurate labeling, that can substantially improve the robustness of various sea fog detection models. Furthermore, this paper proposes a dual branch sea fog detection network to achieve accurate and holistic sea fog detection. The poporsed DB-SFNet is composed of a knowledge extraction module and a dual branch optional encoding decoding module. The two modules jointly extracts discriminative features from both visual and statistical domain. Experiments show promising sea fog detection results with an F1-score of 0.77 and a critical success index of 0.63. Compared with existing advanced deep learning networks, DB-SFNet is superior in detection performance and stability, particularly in the mixed cloud and fog areas.

Sea surface height anomaly (SSHA) is vitally important for climate and marine ecosystems. This article develops a multilayer fusion recurrent neural network (MLFrnn) to achieve an accurate and holistic prediction of the SSHA field, given only as a series of past SSHA observations. The proposed approach learns long-term dependencies within the SSHA time series and spatial correlations among neighboring and remote regions. A new multilayer fusion cell as the building block of the MLFrnn model was designed, which fully fused spatial and temporal features. The daily average satellite altimeter SSHA data in the South China Sea from January 1, 2001, to May 13, 2019, were used to train and test the model. We performed a 21-day ahead SSHA prediction and our MLFrnn model has very high accuracy, with a root mean square error (RMSE) of 0.027 m. Compared with existing deep learning networks, the proposed model was superior both in prediction performance and stability, especially on the wide-scale and long-term predictions.