Abstract

In this article, a temporal convolutional network (TCN)-based model is proposed to retrieve significant wave height ( $H_s$ ) from X-band nautical radar images. Three types of features are first extracted from radar image sequences based on signal-to-noise ratio (SNR), ensemble empirical mode decomposition (EEMD), and gray level cooccurrence matrix methods, respectively. Then, feature vectors are input into the proposed TCN-based regression model to produce $H_s$ estimation. Radar data are collected from a moving vessel at the East Coast of Canada, as well as the simultaneous wave data measured by several wave buoys deployed nearby are used for model training and testing. Experimental results after averaging show that TCN-based model further improves the $H_s$ estimation accuracy, with reductions of root-mean-square errors by 0.33 and 0.10 m, respectively, compared to the SNR-based and the EEMD-based linear fitting methods. It has also been found that under the same feature extraction scheme, TCN outperforms other machine learning-based algorithms including support vector regression and the gated recurrent unit network.

Highlights

  • Accurate measurement of sea surface wave parameters, especially the significant wave height (Hs), is critical for a variety of maritime applications, such as offshore wind farm development, oil and gas exploitation, ship navigation, breakwater construction, and cross-sea bridge building [1]

  • Since data collections were interrupted due to system failure for some periods, and the radar data collected under rain condition are excluded, a total of 1448 radar image sequences are utilized in this study. 50% of radar image sequences collected in three time periods are used for model training, while the other half are used for testing the estimation accuracy. 5-fold cross validation is applied to the training set

  • In order to validate the effectiveness of the extracted features (SNR, ensemble empirical mode decomposition (EEMD), and gray level co-occurrence matrix (GLCM) feature) in wave height estimation, different feature combinations are input to the temporal convolutional network (TCN) model for Hs estimation analysis

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Summary

Introduction

Accurate measurement of sea surface wave parameters, especially the significant wave height (Hs), is critical for a variety of maritime applications, such as offshore wind farm development, oil and gas exploitation, ship navigation, breakwater construction, and cross-sea bridge building [1]. In situ sensors such as wave buoys are employed for wave measurements. They only provide Hs data at the current position of interest [2]. Among different types of radars sensors, the nautical X-band radar is a favorable choice for real-time wave estimation due to its high temporal and spatial resolution. It can be mounted at different locations including moving ships, fixed offshore platforms, and nautical traffic control towers with relatively low cost for deployment and maintenance [3]

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