Robust of Doppler Centroid for Mapping Sea Surface Current by Using Radar Satellite Data

Abstract

Problem statement: Sea surface current retrieving from Synthetic Aperture Radar (SAR) is required standard methods due to the complexity of sea surface ocean imaging in SAR data. In this context, various analytical models have been developed which describe overall effects of sea surface roughness on the Doppler signal mechanisms. Nevertheless, such models are limited in the complexity of the sea surface current estimation that can be used. In fact, the resolution of the sea surface Doppler velocity in azimuth direction is typically coarser as compared to the normalized radar cross section image. Approach: This study introduced a new method to retrieve sea surface current from RADARSAT-1 SAR Standard beam mode (S2) data. The method was based on the utilization of the Wavelength Diversity Ambiguity Resolving (WDAR) and Multi Look beat Frequency (MLBF) algorithms to remove Doppler centroid (f_DC) ambiguity. Results: The result showed that the proposed methods are able to correct Doppler centroid (f_DC) ambiguity and produced fine spatial sea surface current variations in S2 mode data. The current velocities were ranged between 0.18 and 0.78 m sec^-1 with standard error of 0.11 m sec^-1. Conclusion: In conclusion, RADARSAT-1 SAR standard beam mode (S2) data can be utilized to retrieve real time sea surface current. Both WDAR and MLBF algorithms are able to provide accurately information on Doppler Centroid (f_DC) in which accurately real time sea surface current can be retrieved from SAR data.