G. Engen et al., DIRECTIONAL WAVE SPECTRA BY INVERSION OF ERS-1 SYNTHETIC-APERTURE RADAR OCEAN IMAGERY, IEEE transactions on geoscience and remote sensing, 32(2), 1994, pp. 340-352
An algorithm that extracts the directional ocean wave spectrum from sy
nthetic aperture radar (SAR) ocean image spectra is implemented and ap
plied to spaceborne c-band SAR data obtained from the ERS-1 satellite.
The nonlinear iterative algorithm is based on the Hasselmann's forwar
d spectral transform extended to include the range bunching effect. An
analytic expression for the wave spectral increment is derived based
on the exact gradient of the quasi-linear ocean-to-SAR transform. Enha
nced wave spectra have been obtained using first-guess wave spectra ei
ther from the numerical wave model WINCH operated by the Norwegian Met
eorological Institute or synthesized from nondirectional wave data and
meteorological conditions. The inverted spectra are compared to in si
tu directional wave data. It is concluded that the wave imagery from E
RS-1 appears to be of excellent quality, and as soon as the backscatte
r modulation transfer functions are properly understood, satellite SAR
data will be an important tool for enhancing and extending convention
al wave measurements and results from numerical wave models.