Improvement of the AI-Based Estimation of Significant Wave Height Based on Preliminary Training on Synthetic X-Band Radar Sea Clutter Images

Abstract

Marine X-band radar is an important navigational tool that records signals reflected from the sea surface. Theoretical studies show that the initial unfiltered signal contains information about the sea surface state, including wind wave parameters. Physical laws describing the intensity of the signal reflected from the rough surface are the basis of the classical approaches for significant wave height (SWH) estimation. Nevertheless, the latest research claims the possibility of SWH approximation using machine learning models. Both classical and AI-based approaches require in situ data collected during expensive sea expeditions or with wave monitoring systems. An alternative to real data is generation of synthetic radar images with certain wind wave parameters. This Fourier-based approach is capable of modelling the sea clutter images for wind waves of any given height. Assuming a fully-developed sea, we generate synthetic images from the Pierson–Moskowitz wave spectrum. After that, we apply an unsupervised learning using synthetic radar images to train the convolutional part of the neural network as the encoding part of the autoencoder. In this study, we demonstrate how the accuracy of SWH estimation based on radar images changes when the neural network is pretrained on synthetic data.