Enhancement of the normalized scalar product method for surface current measurement using nautical radar

An algorithm to improve the normalized scalar product (NSP) method of extracting sea surface currents from X-band nautical radar image sequences is presented. In the NSP method, two-dimensional searching over a suitable range of current velocities with an appropriate resolution is required to determine the velocity that maximizes the normalized scalar product. The search may take an extremely long time if the range is wide or a high resolution is sought. In order to reduce the computation involved in the procedure, the proposed algorithm uses variable ranges and resolutions instead of fixed ones. Simulated inversion results for a variety of current velocities are obtained in order to check the internal consistency of the algorithm. With this algorithm, it is observed that the search time can be reduced significantly while obtaining high precision. The performance of the algorithm is also validated using real radar data collected on the east coast of Canada.