Antonio Iodice

A novel across-track SAR interferometry simulator

A novel across-track interferometric synthetic aperture radar (SAR) raw signal simulator is presented. It is based on an electromagnetic backscattering model of the scene and an accurate description of the SAR system impulse response function. A set of meaningful examples are also presented. They show that the proposed simulator is structurally consistent and correctly simulates the decorrelation effect, both in the mean and in the distribution sense.

A Novel Approach for Disaster Monitoring: Fractal Models and Tools

In this paper, we present a complete framework to support the monitoring of natural and man-made disasters by means of synthetic aperture radar (SAR) images. The fractal geometry is the most appropriate mathematical instrument in describing the irregularity of a natural observed scene, by means of few effective and reliable parameters. Therefore, fractal concepts can be used to model and identify geometrical changes that occurred in areas hit by disasters. We present an overall framework employing fractal-based models, algorithms, and tools to support the identification of natural area changes due to natural or man-made disasters. Such a framework includes an algorithm used to extract fractal parameters from a 2-D signal, a fractal interpolation tool, and a SAR raw-signal simulator. The combined use of these tools provides an innovative instrument for disaster monitoring applications. In this paper, we implement the fractal framework to obtain a relation between the fractal parameters of a SAR image and those of the relative imaged area. In addition, a case study is discussed, showing the potentiality of our framework for flooding detection

Effects of secondary antenna oscillations on X-SAR/SRTM performance

A theoretical approach to the problem of SRTM mast bending is presented. Effects on final images and interferograms are qualitatively evaluated by theoretical analysis and quantitatively estimated by simulated SAR data.

Angle Independence Properties of Fractal Dimension Maps Estimated From SAR Data

The extremely remarkable properties of angle independence exhibited by an innovative SAR product, the fractal dimension map estimated from a single SAR image, are discussed. The theoretical analysis is supported by a noticeable data set of actual SAR images acquired, with look angles varying from 20° to 45°, in the stripmap operational mode by the COSMO-SkyMed constellation. The behavior of the fractal dimension maps at different look angles is discussed for both natural and urban scenarios and emphasis is also posed on areas within the same image that, according to the scene macroscopic topography, are characterized by different incidence angles. The whole analysis is aimed at highlighting, on the one hand, the specific independencies of natural surface fractal dimension maps from the look angle and from the local incidence angle, which can be very useful in information extraction and SAR post-processing techniques and, on the other hand, the different fractal dimension maps behavior whereas urban areas are analyzed.

Boundary Perturbation Theory for Scattering in Layered Rough Structures

The electromagnetic wave interaction with layered structures constitutes a crucial topic of current interest in theoretical and experimental research. Generally speaking, several modelling and design problems, encountered, for instance, in SAR (Synthetic Aperture Radar) application, GPR (Ground Penetrating Radar) sensing, radar altimeter for planetary exploration, microstrip antennas and MMICs (Monolithic Microwave Integrated Circuits), radio-propagation in urban environment for wireless communications, through-the-wall detection technologies, optics, biomedical diagnostic of layered biological tissues, geophysical and seismic exploration, lead to the analysis of the electromagnetic wave interaction with multilayered structure, whose boundaries can exhibit some amount of roughness. This chapter is aimed primarily at providing a comprehensive analytical treatment of electromagnetic wave propagation and scattering in three-dimensional multilayered structures with rough interfaces. The emphasis is placed on the general formulation of the scattering problem in the analytic framework of the Boundary Perturbation Theory (BPT) developed by Imperatore et al. A systematic perturbative expansion of the fields in the layered structure, based on the gently rough interfaces assumption, enables the transferring of the geometry randomness into a non-uniform boundary conditions formulation. Subsequently, the fields’ expansion can be analytically evaluated by using a recursive matrix formalism approach encompassing a proper scattered field representation in each layer and a matrix reformulation of non-uniform boundary conditions. A key-point in the development resides in the appropriate exploitation of the generalized reflection/transmission notion, which has strong implications in order to make the mathematical treatment manageable and to effectively capture the physics of the problem. Two relevant compact closed-form solutions, derived in the first-order limit of the perturbative development, are presented. They refer to two complementary bi-static configurations for the scattering, respectively, from and through layered structures with arbitrary number of rough interfaces. The employed formalism is fully-polarimetric and suitable for applications. In addition, it is demonstrated how the symmetrical character of the BPT formalism reflects the inherent conformity with the reciprocity theorem of the electromagnetic theory. 1

SAR simulation of ocean scenes covered by oil slicks with arbitrary shapes

The identification of oil slicks on the ocean surface from SAR data requires quantitative sound models accounting for the most important characteristics (ocean spectrum, slick viscosity, slick shape, and so on). In this paper we present the implementation of an innovative SAR raw signal and image simulator, which is able to reproduce images relative to ocean surfaces covered by oil slicks with arbitrary shapes. The attention is mainly focused on slicks with fractal contours. The fractal Weierstrass-Mandelbrot function is used to generate slicks with fixed fractal dimension. A box counting technique is employed to evaluate the fractal dimensions of the generated slicks and the corresponding SAR images. Radiometric properties of the area covered by oil are also estimated in order to show how the simulated data provide a powerful set for processing algorithms.

Characterization of local regularity in SAR Imagery by means of multiscale techniques: application to oil spill detection

Thanks to their capability to cover large areas, in all weather conditions, during the day as well as during the night, spaceborne Synthetic Aperture Radar (SAR) techniques constitute an extremely promising alternative to traditional surveillance methods. Nevertheless, in order to assure further usability of SAR images, specific data mining tools are still to be developed to provide an efficient automatic interpretation of SAR data. The aim of this paper is to introduce texture analysis performed in the framework of time - frequency theory, as a means to detect oil spills in the sea surface. In particular, an algorithm permitting a precise quantitative characterization of the border between the oil spill candidate and the sea, will allow a novel classification of oil spills and look-alikes.

Retrieval of soil surface parameters via a polarimetric two-scale model in hilly or mountainous areas

Recently we proposed a Polarimetric Two-Scale Model (PTSM) [1-3], able to retrieve surface roughness, ground permittivity and soil moisture content by processing polarimetric Synthetic Aperture Radar (SAR) data. In our model we consider a bare soil surface as composed of large-scale variations on which a small-scale roughness is superimposed. In particular, the large-scale roughness is locally treated by replacing the surface with a slightly rough tilted facet, whose slope is the same of the smoothed surface at the center of the pertinent facet. The facet slopes along azimuth and range directions are modeled as independent Gaussian variables. Unlike what is described in [1-3], here the facet slope means are not forced to be equal to zero and then our retrieval algorithm can be applied even on not flat areas, just considering information provided by Digital Elevation Models (DEM). The facets tilt causes the rotation of the local incidence plane around the line of sight and the variation of the local incidence angle around the radar look angle. We accounted for both these effects to evaluate analytically the normalized radar cross sections (NRCS), employed to retrieve the roughness and the soil moisture content using the co-pol/cross-pol method.

Perturbative solution for the scattering from multilayered structure with rough boundaries

The objective of this paper is to investigate analytically the fully polarimetric electromagnetic wave scattering and emission from a three-dimensional layered structure with N-rough interfaces in the framework of SPM method. Assuming that deviations and slopes - with respect to the reference mean plane - exhibited by rough interfaces are small enough, we firstly perform a perturbative expansion of the fields in the rough-interfaces layered structure, following the classical scheme employed to deal with a rough surface. Subsequently, by using effectively the concept of generalized reflection/transmission coefficients, the unknown expansion coefficients of scattered wave propagating upward in the upper half-space are derived via a recursive method. This approach can be also applied to the evaluation of the second-order contribution, opening the way to the accurate calculation of thermal emission from complex layered structure.

Monitoring of Flooding in Urban Areas

Urban areas are crowded environments, where a disaster can bring dramatic consequences, if not adequately forecasted and faced. Remote sensing instruments can be fruitfully used for both prediction and aid organization purposes. In particular, in this paper we present innovative synthetic aperture radar (SAR) techniques for the detection of a flooded area in urban settlements. A SAR raw signal simulator is presented and used, in order to improve the comprehension of the main physical phenomena and to plan the most adequate sensor characteristics for detection purposes. The single and multiple scattering phenomena, in conjunction with strong layover effects make the SAR images relative to urban areas extremely involved. The presented study is focused on a canonical environment, in order to provide a complete and powerful instrument for the comprehension of the complex texture of urban area SAR images.