On the performance of a shipborne current mapping HF radar

High-frequency (HF) radars have been developed to map surface currents offshore by means of land-based stations. Presently available radar systems use frequencies between 25 and 30 MHz and allow a spatial resolution of 1 km and ranges of up to 50 km. This paper reports on the experience with a shipborne radar and discusses problems which arise for the azimuthal resolution on a metal ship, the correction for the ship's speed, and limitations due to pitch-and-roll motions. Current measurements during cruises to the North Atlantic are presented. It has been found that, with the support of the satellite-supported Global Positioning System, the shipborne HF radar can measure surface current velocities with an accuracy of some 5 cm·s^-1