Using cross-image spectra in a SAR ocean wave inversion scheme

Cross-image spectra obtained by combining two single look SAR images are utilized in an inversion scheme for extracting the underlying ocean wave spectrum. The cross-image spectra are shown to significantly reduce the speckle noise level while preserving the spectral shape. The SAR cross-image spectra are shown to yield a SNR typically 5 to 8 dB higher than the corresponding standard 3 look image spectra. The noise level is typically reduced with a factor of 2 compared to the 3 look spectra and a factor of 6 compared to the single look spectra. A closed form expression of the ocean-to-SAR spectral transform and its inversion is formulated for the cross-image case. The inherent informations about the wave propagation direction are utilized in the inversion scheme to resolve the 180 degree ambiguity without using any external informations. The method is demonstrated on airborne C-band SAR data