Dual-use of compact HF radars for the detection of mid- and large-size vessels

This paper describes the development of the SeaSonde High Frequency Radar system into a dual-use application for the mapping of ocean surface currents and detection of ships at sea. This development entailed the creation of a new radar waveform that would permit this dual-use as well as a detection algorithm to identify the ships in the radar spectra. The detection algorithm utilizes two methods for calculating a background signal level: an infinite impulse response (IIR) filter and a two-dimensional median filter. These two methods are employed simultaneously with multiple length averaging times to maximize the number of detections. The initial phase of development focused on improving the radar waveform, to maximize the results for ship detection while still retaining the ability to measure surface currents. The latter phase of the development concentrated on testing the detection algorithm on a known vessel in different environmental conditions.