A review of propagation and scattering factors in remote-sensing and ship-tracking by HF radar

The propagation-loss, noise and scattering mechanisms involved in ground-wave radar for sea state sensing and ship-tracking are first reviewed, taking as an example a coastal installation in the U.K. Techniques for extracting surface-current, surface-wind and directional sea-wave spectrum from first and second-order sea-echo are described, with reference to the influence of the antenna directivity and propagation factors. The special factors affecting ship-tracking in range, azimuth and Doppler are illustrated. The use of sky-wave radar for sea-state sensing and for assessing the ionospheric layer configuration and propagation mode patterns is discussed. Sea-state sensing is shown to require real-time propagation assessment for effective frequency-management. Rapid sweep frequency, sweep-azimuth and Doppler analysis are shown to be desirable.