Synthetic Aperture Radar Oceanographic Investigations.

Strip-map system SAR systems are useful for observing a variety of oceanic phenomena, but are limited primarily by their sensitivity to look direction of the SAR relative to the phenomenon being observed. This restriction is alleviated by use of angle diversity SAR techniques which allow the look direction to be varied independently of the direction of motion of the SAR platform. These techniques may also prove to be useful for gaining information on scene motions or for classifying scene elements based on their look directional dependence. Angle diversity radar data of the oceans can be processed using non-coherent averaging or multiple-look techniques to reduce the effects of background noise. This background noise is multiplicative in nature and is a result of the coherent nature of the SAR. Under low to moderate winds, this system noise or speckle can dominate an image and in some cases mask subtle oceanography features of interest a particularly acute problem in respect to detection of bottom topography. Frequency diversity SAR systems using multiple-wavelength transmissions may also incerase the accuracy of detection and classification of surface patterns, based on the wavelength transmissions may also increase the accuracy of detection and classification of surface patterns, based on the wavelength dependence of the surface reflectivity.