An underwater bathymetry reversion in the radial sand ridge group region of the southern Huanghai Sea using the remote sensing technology

The variation of underwater bathymetry in the radial sand ridge group of the southern Huanghai Sea is complex and changeable owing to abundant sediment supply of different sources and varied hydrodynamic processes. Remote sensing has potential and is imperative for the surveying and monitoring variation of under water topography with quick and largearea data acquisition abilities. So based on the experiences of water depth in the Changjiang Estuary and coastal area with the remote sensing rever sion,a typicalregion in radial sand ridge was chosen for bat hymetry reversion viaremo tesensing technology. Tidal current and content of suspended sediments were surveyed synchronously during the measurement of water depth. Spectral characteristics of suspended sediments were analyzed and a spectrum based on sedimentrever sion parameter was obtained to reduce its influence on water depth information contained in MODIS image. And then real observed bathymetry data were used to establish a remote sensing rever sion model. The under water to pography of about 1.5×10⁴km² in the radial sand ridge group region was then acquired with a fairly good precision. The correlation coefficient square between the reversed water depth and the measured reached 0.664. The mean absolute error was approximately 1.52m and the mean relative error was about 24%. The best reversion results appearat water depth range of 5 to 15m. The mean relative error was only 18%. It is indicated that this remote sensing based on the rever sion technology was suitable for the under water bathy metry reversion in a complex coastal area especially with a relatively shallow water depth.