High-resolution depth and coastline over major atolls of South China Sea from satellite altimetry and imagery

Yu Shen Hsiao, Chein-way Hwang*, Yung Sheng Cheng, Liang Chien Chen, Hung Jui Hsu, Jung Huo Tsai, Chien Liang Liu, Ching Chieh Wang, Ya Chi Liu, Yu Chi Kao

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

42 Scopus citations


Current bathymetric models for the South China Sea (SCS) are largely based on predicted depths from gravity and sparse single-beam echo-sounder measurements. Such models lack high-resolution coastlines and shallow-water bottom features around atolls and islands. This study refines the gravity field of the SCS using sea surface heights from measurements of satellite altimeter Geosat/GM, ERS-1/GM, Jason-1/GM and the original Cryosat-2. A new one-minute gravity anomaly grid is determined. The modeled gravity anomalies show a 6-mgal RMS discrepancy with shipborne measurements in shallow waters. An altimeter-only bathymetric model is derived from the new gravity grid by the gravity-geological method that uses the latest global and regional models of the ocean depth and marine gravity as a priori knowledge. The new model outperforms current SCS bathymetric models and is accurate to 100. m, based on comparison with multi-beam depth measurements. Optical images from IKONOS-2, QuickBird-2, GeoEye-1, WorldView-1-2 and -3, are rectified and digitized to derive the zero (coastline) and 20-m depth contours (reef lines) around 44 atolls, which are integrated with the altimeter-only depths, giving significantly improved accuracies and spatial resolutions in modeled depths. The improvement percentages of coastlines by the satellite imagery range from 50% to 97% at 41 of the 44 atolls. We establish a webpage for free access to the optical and depth images, and the depth and gravity grids. We will continue to update satellite images, altimeter-derived gravity grids and bathymetric models over major atolls of the SCS.

Original languageEnglish
Pages (from-to)69-83
Number of pages15
JournalRemote Sensing of Environment
StatePublished - 1 Apr 2016


  • Atoll depth
  • Gravity
  • Satellite altimetry
  • Satellite imagery
  • South China Sea


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