Advanced Methods for the Analysis of Radar Sounder and VHR SAR Signals

In the last decade the interest in radar systems for the exploration of planetary bodies and for Earth Observation (EO) from orbit increased considerably. In this context, the main goal of this thesis is to present novel methods for the automatic analysis of planetary radar sounder (RS) signals and very high resolution (VHR) synthetic aperture radar (SAR) images acquired on the Earth. Both planetary RSs and VHR SAR systems are instruments based on relatively recent technology which make it possible to acquire from orbit new types of data that before were available only in limited areas from airborne acquisitions. The use of orbiting platforms allows the acquisition of a huge amount of data on large areas. This calls for the development of effective and automatic methods for the extraction of information tuned on the characteristics of these new systems. The work has been organized in two parts. The first part is focused on the automatic analysis of data acquired by planetary RSs. RS signals are currently mostly analyzed by means of manual investigations and the topic of automatic analysis of such data has been only marginally addressed in the literature. In this thesis we provide three main novel contributions to the state of the art on this topic. First, we present a theoretical and empirical statistical study of the properties of RS signals. Such a study drives the development of two novel automatic methods for the generation of subsurface feature maps and for the detection of basal returns. The second contribution is a method for the extraction of subsurface layering in icy environments, which is capable to detect linear features with sub-pixel accuracy. Moreover, measures for the analysis of the properties of the detected layers are proposed. Finally, the third contribution is a technique for the detection of surface clutter returns in radargrams. The proposed method is based on the automatic matching between real and clutter data generated according to a simulator developed in this thesis. The second part of this dissertation is devoted to the analysis of VHR SAR images, with special focus on urban areas. New VHR SAR sensors allow the analysis of such areas at building level from space. This is a relatively recent topic, which is especially relevant for crisis management and damage assessment. In this context, we describe in detail an empirical and theoretical study carried out on the relation between the double-bounce effect of buildings and their orientation angle. Then, a novel approach to the automatic detection and reconstruction of building radar footprints from VHR SAR images is pre-sented. Unlike most of the methods presented in the literature, the developed method can extract and reconstruct building radar footprints from single VHR SAR images. The technique is based on the detection and combination of primitive features in the image, and introduces the concept of semantic meaning of the primitives. Qualitative and quantitative experimental results obtained on real planetary RS and spaceborne VHR SAR data confirm the effectiveness of the proposed methods.