HHU24SWDSCS: A shallow-water depth model over island areas in South China Sea retrieved from Satellite-derived bathymetry

Abstract. Accurate shallow-water depth information for island areas is crucial for maritime safety, resource exploration, ecological conservation, and offshore economic activity. Traditional approaches like shipborne sounding and airborne bathymetric light detection and ranging (LiDAR) surveys are expensive, time-consuming, and are limited in politically sensitive regions. Moreover, satellite altimetry-predicted depths exhibit large errors over shallow waters. In contrast, satellite-derived bathymetry (SDB), estimated from multispectral imagery, provides a rapid, open source, and cost-effective technique to fully characterize the bathymetry of a region. Given the scarcity of in-situ water-depth data for the South China Sea (SCS), a shallow-water depth model, HHU24SWDSCS, was developed by integrating 1298 Ice, Cloud, and land Elevation Satellite (ICESat-2) tracks with 70 Sentinel-2 multispectral images. The model covers >120 islands and reefs in the SCS, with a resolution of 10 m. Validation against independent ICESat-2 depth data produced a root mean square error for the model of 0.81–1.35 m (<5 % of the maximum depth), with an average coefficient of determination of 0.91. Validation against independent airborne LiDAR bathymetry data revealed an accuracy of 1.01 m for the Lingyang Reef. Further comparisons with existing bathymetry models revealed the superior performance of the model. While the existing bathymetry models exhibit errors up to tens of meters or larger for island regions, and should therefore be used with caution, the HHU24SWDSCS model exhibited good accuracy in shallow waters across the SCS. This model thus provides a reference for mapping shallow-water depth close to islands and provides fundamental support for research in oceanography, geodesy, and other disciplines.