T. Eltoft et Ka. Hogda, NON-GAUSSIAN SIGNAL, STATISTICS IN OCEAN SAR IMAGERY, IEEE transactions on geoscience and remote sensing, 36(2), 1998, pp. 562-575
In this paper, we have studied the significance of non-Gaussian signal
statistics in some synthetic aperture radar (SAR) images of the ocean
surface, The study consisted of calculating the amplitude histogram o
f the returned echoes from the images and comparing these with the Ray
leigh- and K-v-distributions, corresponding to the Gaussian and non-Ga
ussian statistics, respectively. The images used were some C-band SAR
data from the Canadian airborne SAR collected during the NORCSEX'88 ca
mpaign and some ERS-1 data collected during the NORCSEX'91 campaign, T
he analysis of the NORCSEX'88 data included studies of the dependency
of the signal statistics on incidence angle and meteorological and ima
ging conditions, It was found, specifically at small incidence angles,
that there was a significant deviation from Gaussian statistics, It w
as also found that when the wind was blowing against the wares, the de
viation from Gaussian statistics was more pronounced than when the win
d was blowing in the same direction as the waves were propagating, The
study also showed a correlation between the signal statistics and the
width of the SAR image spectra, At low incidence angles, this agrees
with the interpretation that non-Gaussian statistics may be related to
strong widebanded scattering events, However, since non-Gaussian stat
istics also were observed at incidence angles as high as 50 degrees, i
t is evident that the modulation of the scattering cross section by th
e long waves is also an important factor, In addition, the analysis of
the ERS-1 data shelved that to account for the width of the SAR image
spectra, an azimuth smearing term, due to short scene coherence time,
had to be included, This was in the present work done by modeling the
short-coherence-time-smearing as a Gaussian low-pass filter, By this
procedure, we were able to obtain realistic estimates for the average
scene coherence time of the SAR scenes.