Validazione sperimentale di metodologie di classificazione per immagini SAR multifrequenza e polarimetriche

INTRODUCTION 1 INTRODUCTION Environmental monitoring, earth-resource mapping, and defence (security systems) may involve broad-area imaging at high and medium resolution. The imagery must often be acquired in inclement weather or during night as well as day. Synthetic Aperture Radar (SAR), both on airborne and spaceborne platforms, provides such a capability. SAR systems take advantage of the long-range propagation characteristics of radar signals and of the complex information processing capability of modern digital electronics to provide high and median resolution imagery. Synthetic Aperture Radar complements photographic and other optical imaging capabilities thanks to the minimum constraints on time-of-day and atmospheric conditions and thanks to the unique responses of terrain and cultural targets to radar frequencies. ERS-1 was the first instrument in a series of orbital SAR planned to have long lifetimes and semi-operational capabilities. Consequently ERS-2, JERS-2 and RADARSAT satellite systems were created. ENVISAT was launched in 2001. These satellites allow dynamic processes to be observed over most of the Earth’s surface by providing a long series of accurate measurements of the backscatter coefficient 1 . This has a significant impact in many scientific domains: vegetation mapping and monitoring, hydrology, sea-ice mapping and geology. Particularly, Synthetic Aperture Radar technology has provided terrain structural information to geologists for mineral exploration, oil spill boundaries on water to environmentalists, sea state and ice hazard maps to navigators, and reconnaissance and targeting information to military operations. There are many other applications or potential applications. Some of these, particularly civilian, have not yet been adequately explored because lower cost electronics are just beginning to make SAR technology economical for smaller scale uses. Spaceborne radar systems use single frequencies and polarization with modest resolution, because of the constraints imposed by their deployment in space. On the contrary, more complex airborne systems have demonstrated the advantages of multiple frequencies and polarizations. These advantages 1 The backscattering or backward scattering coefficient, in unit of m -1 , indicates the attenuation (reduction in light intensity) caused by scattering at angles from 90° to 180°. 1