Inversion of the HF radar Doppler spectrum for ocean wave measurement

An unambiguous measurement of the directional spectrum is obtained. The estimates are amplitudes on a nonuniform 2-D wavenumber grid with a short-wave cut-off (due to a requirement to linearise the integral equation) which is at 0.2 Hz at 7MHz (a radar frequency which provides a long-range measuring capability) and 0.3Hz at 27 MHz. There is a long wave cut-off which varies with spectral quality and ocean conditions but which is at about 0.05 Hz. Beyond the short wave cut-off the spectral estimates are those of the initialisation