Surface Current Measurement Under Low Sea State Using Dual Polarized X-Band Nautical Radar

In this paper, a comparison of surface current velocity extraction under low sea state from horizontal and vertical polarized X-band nautical radar image sequences is presented. Three different current retrieval algorithms including the classical least-squares (LS) fitting, a modified iterative least-square fitting routine and an improved normalized scalar product (NSP) method have been employed. An adaptive iteration termination criterion provides optimal times of iteration for the iterative LS method. Variable-search ranges and resolutions are proposed to reduce the computational cost for the NSP method. Field data from two X-band radars deployed during a short experiment at the Skerries Bight near St. John´s, Newfoundland is analyzed. Comparison of the results derived from the radar and in-situ buoy data shows that vertical polarization leads to better current measurements than horizontal polarization even under very low sea state. A performance comparison of LS, iterative LS and NSP algorithms indicates that the latter two provide reliable results, with the current measurements from the NSP method being the least variable.