Some polarimetric aspects of processing sea surface M-ATI SAR data

A brief review is presented of published work on detection and imaging techniques based on matrix group theory for the scalar non-polarimetric two channel along track interferometer and the vector polarimetric two channel across track interferometer. The relevance to ATI of the vector theory for the across track interferometer is discussed as is the problem of extending the theory to the case of the ATI with N beams. Difficulties in developing detection and imaging methods for the general case of N beams have lead to attempts to develop an alternative approach based on linear filtering. It is assumed that image modulations are a result of local fluctuations in mean intensity which can be described by a spherically invariant statistical process with a compound distribution. The unmodulated background consists of Gaussian scatterers. These scatterers and the modulated ones have different Doppler spectra and maximising the normalised standard deviation of the filtered image maximises the visibility of the image modulations. Polarimetric aspects of this approach are discussed and experimental results obtained with an airborne four beam M-ATI are presented illustrating aspects of the discussion.