© Klaus-Werner Gurgel, University of Hamburg, Germany (PostScript version)

A decametric waves radar (HF-Radar) is a shore- or ship-based system, that

• transmits electromagnetic waves of 6 MHz to 30 MHz, (50 m to 10 m wavelength),
• which travel along the sea surface beyond the horizon by ground wave propagation and
• are scattered back from ocean waves of half the electromagnetic wavelength (Bragg scattering);
• measures the Doppler spectrum caused by moving ocean waves;
• measures the speed of the surface current carrying the ocean waves;
• measures ocean wave height and the wave directional spectrum using the second-order sea echos of the Doppler spectrum.

HF-Radar is a tool for synoptic on-line mapping of surface current fields and the spatial distribution of the wave directional spectrum.