Hierarchical Fusion Method for SAR-Based Coastal Bathymetric Inversion in Short-Period Wave-Dominated Areas: A Case Study of the Wengtian Coast, Hainan Island

Coastal bathymetric information is essential for marine engineering, navigation safety, and coastal management. Coastal bathymetric inversion based on wave characteristics extracted from synthetic aperture radar (SAR) images is a widely used technique. Existing studies that apply this method have mostly focused on long-period wave-dominated areas. However, in short-period wave-dominated areas, this method suffers from large errors and poor stability, limiting its practical application. To address this problem, this study proposes a hierarchical fusion method for SAR-based coastal bathymetric inversion in short-period wave-dominated areas. The proposed method significantly reduces bathymetric inversion errors by hierarchically fusing multi-angle wavelength estimation results and multi-temporal SAR bathymetry inversion results, thereby achieving more robust underwater topography mapping. A validation experiment was conducted on the Wengtian coast, Hainan Island. Compared with the best single-temporal inversion results, the proposed method reduces the MAE by 19.5% and the RMSE by 23.5%. Finally, the effects of the dispersion relation and the selection of the fusion strategy on the bathymetric inversion results are discussed. These results show that the proposed method significantly improves bathymetric inversion accuracy in short-period wave-dominated areas.