Abstract :
Synthetic aperture radar (SAR) imagery has found
important applications due to its clear advantages over optical
satellite imagery one of them being able to operate in various
weather conditions. However, due to the physics of the radar
imaging process, SAR images contain unwanted artifacts in the
form of a granular look which is called speckle. The assumptions
of the classical SAR image generation model lead to a Rayleigh
distribution model for the histogram of the SAR image. However,
some experimental data such as images of urban areas show impulsive
characteristics that correspond to underlying heavy-tailed
distributions, which are clearly non-Rayleigh. Some alternative
distributions have been suggested such as theWeibull, log-normal,
and the k-distribution which had success in varying degrees depending
on the application. Recently, an alternative model namely
the -stable distribution has been suggested for modeling radar
clutter. In this paper, we show that the amplitude distribution
of the complex wave, the real and the imaginery components of
which are assumed to be distributed by the -stable distribution,
is a generalization of the Rayleigh distribution. We demonstrate
that the amplitude distribution is a mixture of Rayleighs as is
the k-distribution in accordance with earlier work on modeling
SAR images which showed that almost all successful SAR image
models could be expressed as mixtures of Rayleighs. We also
present parameter estimation techniques based on negative order
moments for the new model. Finally, we test the performance of
the model on urban images and compare with other models such
as Rayleigh, Weibull, and the k-distribution.
