Physics-Guided Spatiotemporal Learning for Coastal Wave Peak Period Estimation from Video
This research introduces a new deep learning framework designed to estimate the peak period of ocean waves—a critical metric for coastal management and climate resilience—directly from standard coastal video footage. While traditional monitoring methods like buoys are accurate, they are expensive and have limited coverage. This study provides a cost-effective, automated alternative that uses video analysis to track wave behavior without requiring complex, manual preprocessing steps like constructing time-stack images or performing spectral analysis.
How the Approach Works
The framework uses a three-stage transfer learning process to bridge the gap between raw video data and accurate physical measurements. First, the system is pre-trained on synthetic video sequences generated using Airy wave theory, which teaches the model the fundamental physics of how waves propagate. Second, it is trained on a large "silver" dataset of real-world coastal videos with automatically generated labels. Finally, the model is fine-tuned using a "golden" dataset of high-quality, expert-annotated videos to ensure it aligns with real-world conditions.
To improve accuracy, the framework includes an automated region-of-interest (ROI) detector. By analyzing the temporal variance of pixels, the system identifies the active surf zone and ignores static elements like land or sky. Additionally, the model incorporates a physics-guided loss function that penalizes predictions falling outside the physically plausible range of 8 to 20 seconds, ensuring the results remain consistent with oceanographic reality.
Key Findings and Performance
The study compared several architectures, including transformer-based models and recurrent-convolutional networks. The results indicated that transformer-based architectures were superior for achieving high accuracy in instantaneous predictions. In contrast, lightweight recurrent-convolutional models were better suited for operational use, offering higher temporal stability.
Ablation studies confirmed that the physics-guided regularization was essential for maintaining trend-following consistency and preventing physically impossible predictions. Furthermore, explainability audits showed that the model successfully focused its attention on hydrodynamically active regions, aligning closely with how waves actually behave in nature.
Important Considerations
While the framework shows great promise for long-term, cost-efficient coastal monitoring, there are limitations to note. The current "golden" dataset of expert-annotated videos is relatively small, which limited the researchers' ability to perform a fully independent held-out test partition in this study. Consequently, the reported performance metrics reflect the model's behavior on the data used during the fine-tuning phase. Future work aims to expand this dataset to allow for more rigorous, independent testing across a wider variety of coastal environments.
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