Simulation and analysis on SAR imaging of channel topography changes in the Pearl River Estuary

According to SAR imaging mechanism of underwater bathymetry, a 3-D hydrodynamic model based on SELFE (Semi-implicit Eulerian-Lagrangian Finite Element) is applied to demonstrate the temporal variations of the channel bathymetry changes. A microwave radar imaging of oceanic surface’s program of M4S is used to simulate the variation of normalized radar cross section (NRCS) induced by the ocean surface current. The simulation is carried out to study the effect of water depth changes and current variations on SAR imaging of channel bathymetry. The depth of channel is defined between 5 m to 17 m with an interval of every two meters. Six time of tide are used in the current variation simulation. The NRCS variation demonstrated in the simulated images are compared with in situ data, historical bathymetric maps and calibrated SAR images. All the four kinds of images manifest similar changes of channels, which proves that there is agreement between the simulation model used in this paper and other data. Simulation results also show that bigger depth change induces bigger NRCS variation. In the time of maximum ebb tide, simulated relative NRCS is bigger than others.