Underwater Topography Detection and Analysis of the Qilianyu Islands in the South China Sea Based on GF-3 SAR Images

Longyu Huang,Jungang Yang,Jie Zhang,Junmin Meng

doi:10.3390/rs13010076

Longyu Huang, Jungang Yang + Show 2 more

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https://doi.org/10.3390/rs13010076

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Abstract

Shallow sea underwater topography plays an important role in the development of islands and reefs. The Qilianyu Islands, located in Xisha, South China Sea, are a key area for the development and utilization of the South China Sea. Compared with traditional underwater topography detection methods, synthetic aperture radar (SAR) has the advantages of low cost, short time consumption, and the large-scale detection of shallow water topography. The GF-3 satellite is the first SAR satellite launched by China, and its ability to probe shallow sea topography has never been assessed. To detect the underwater topography of the Qilianyu Islands and test the application of GF-3 SAR data in shallow sea underwater topography detection, this paper implements the SAR shallow sea underwater topography detection model, the tidal information corresponding to the imaging time of the SAR image, and six GF-3 SAR images to detect the underwater topography of the Qilianyu island and reefs. The detection results have been analyzed from different imaging times, different water depths and different polarization modes, and the first four SAR images show promising detection results. The average absolute error (MAE) and average relative error (MRE) of the results are 1.5 m and 14.33%, respectively, which demonstrates that GF-3 SAR images have an impressive performance in underwater topography detection of South China Sea island reefs.

Highlights

Remote Sens. 2021, 13, 76.The construction of the South China Sea is an important measure to protect the country’s maritime rights and interests
The area with a water depth of 0–5 m is mainly located on the edge of the reef and some small areas in the inner area of the reef, and the area of
Based on the synthetic aperture radar (SAR) shallow sea underwater topography inversion model, this paper uses 6 GF-3 SAR images to carry out research on underwater topography detection in the Qilianyu Islands of the South China Sea, and analyzes the relationship between the tidal field and the underwater topography gradient at the time of SAR image imaging

Summary

Introduction

The construction of the South China Sea is an important measure to protect the country’s maritime rights and interests. The Qilianyu Islands are undeveloped islands in the South China Sea. The distances among the islands are short, and the entire reef is shallow, making it suitable for reclamation. Underwater topography is an important environmental parameter that needs to be known for land reclamation projects. Traditional shallow sea underwater topography detection technology mainly includes the on-site measurement of ship platforms, using technologies such as sonar or multibeam scanners [1]

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