Fast and Accurate ISAR Focusing Based on a Doppler Parameter Estimation Algorithm

This letter deals with inverse synthetic aperture radar (ISAR) autofocusing of noncooperative moving targets. The relative motion between the target and the sensor, which provides the angular diversity necessary for ISAR imagery, is also responsible for unwanted range migration and phase changes generating defocusing. In the case of noncooperative targets, the relative motion is unknown: the ISAR needs, hence, to implement an autofocus step [motion compensation (MoCo)] to achieve high resolution imaging. This task is typically carried out via the optimization of functionals based on general image quality parameters. In this letter, we propose the use of a fast and accurate MoCo algorithm based on the estimation of the Doppler parameters, thus fully coping with the nature of the imaging system. The effectiveness of the proposed method is proven on both simulated data and data acquired by operational systems

A general framework and related procedures for multiscale analyses of DInSAR data in subsiding urban areas

In the last decade Differential Synthetic Aperture Radar (DInSAR) data were successfully tested in a number of case studies for the detection, mapping and monitoring of ground displacements associated with natural or anthropogenic phenomena. More recently, several national and regional projects all around the world provided rich data archives whose confident use, however, should rely on multidisciplinary experts in order to avoid misleading interpretations. To this aim, the present work first introduces a general framework for the use of DInSAR data; then, focusing on the analysis of subsidence phenomena and the related consequences to the exposed facilities, a set of original procedures is proposed. By drawing a multiscale approach the study highlights the different goals to be pursued at different scales of analysis via high/very high resolution SAR sensors and presents the results with reference to the case study of the Campania region (southern Italy) where widespread ground displacements occurred and damages of different severity were recorded

Multiresolution Detection of Persistent Scatterers: A Performance Comparison Between Multilook GLRT and CAESAR

Persistent scatterers (PS) interferometry tools are extensively used for the monitoring of slow, long-term ground deformation. High spatial resolution is typically required in urban areas to cope with the variability of the signal, whereas in rural regions, multilook shall be implemented to improve the coverage of monitored areas. Along this line, SqueeSAR and later Component extrAction and sElection SAR (CAESAR) were introduced for the monitoring of both persistent and (decorrelating) distributed scatterers (DS). Multilook generalized likelihood ratio test (MGLRT) is a detector derived in the context of tomographic SAR processing that has been investigated for a fixed multilook degree. In this work, we address MGLRT and CAESAR in the multiresolution context characterized by a spatially variable multilook degree. We compare the two schemes for the multiresolution selection of PS and DS, highlighting the pros and cons of each scheme, particularly the peculiarities of CAESAR that have important implications at the implementation stage. A performance analysis of both detectors in case of model mismatch is also addressed. Experiments carried out with data acquired by the COSMO-SkyMed constellation support both the theoretical argumentation and the results achieved by resorting to Monte Carlo simulations

Chapter Mapping of the risk of coastal erosion for two case studies: Pianosa island (Tuscany) and Piscinas (Sardinia)

This study focuses on the use of remote sensing to generate coastal erosion risk maps for Pianosa Island (Tuscany) and Piscinas dune system (Sardinia). The method made use of both ancillary and satellite data (Sentinel-2), in addition to SAR images (COSMO SkyMed and Sentinel-1B). TOA radiance products were atmospherically corrected and processed using Sen2Coral and BOMBER in order to map different marine substrates and bathymetry. The coastal erosion risk maps have been generated based on these output and the results confirm that the coasts of these sites don’t have coastal erosion problems

Transport Infrastructure Surveillance and Monitoring by Electromagnetic Sensing: The ISTIMES Project

The ISTIMES project, funded by the European Commission in the frame of a joint Call “ICT and Security” of the Seventh Framework Programme, is presented and preliminary research results are discussed. The main objective of the ISTIMES project is to design, assess and promote an Information and Communication Technologies (ICT)-based system, exploiting distributed and local sensors, for non-destructive electromagnetic monitoring of critical transport infrastructures. The integration of electromagnetic technologies with new ICT information and telecommunications systems enables remotely controlled monitoring and surveillance and real time data imaging of the critical transport infrastructures. The project exploits different non-invasive imaging technologies based on electromagnetic sensing (optic fiber sensors, Synthetic Aperture Radar satellite platform based, hyperspectral spectroscopy, Infrared thermography, Ground Penetrating Radar-, low-frequency geophysical techniques, Ground based systems for displacement monitoring). In this paper, we show the preliminary results arising from the GPR and infrared thermographic measurements carried out on the Musmeci bridge in Potenza, located in a highly seismic area of the Apennine chain (Southern Italy) and representing one of the test beds of the project

Inversion Algorithms and PS Detection in SAR Tomography. Case Study of Bucharest City

Synthetic Aperture Radar (SAR) tomography can reconstruct the elevation profile of each pixel based on a set of co-registered complex images of a scene. Its main advantage over classical interferometric methods consists in the capability to improve the detection of single persistent scatterers as well as to enable the detection of multiple scatterers interfering within the same pixel. In this paper, three tomographic algorithms are compared and applied to a dataset of 32 images to generate the elevation map of dominant scatterers from a scene. Targets which present stable proprieties over time - Persistent Scatterers (PS) are then detected based on reflectivity functions reconstructed with Capon filtering

SAR Interferometry and Tomography: Theory and Applications

Synthetic Aperture Radar (SAR) is among of the most used remote sensing systems for Earth observation and has wide application in security in both marine and terrestrial environments. The last decade has been a period of extraordinary development of SAR systems with an impressive growth in the number of launch and operational deployment of spaceborne SAR remote sensing systems. Enabling an extensive range of new applications is the advent of several very high resolution spaceborne SARs, such as TerraSAR-X/Tandem-X and the COSMO-SKYMED constellation. Very fine details of Earth surface are provided on a regular basis by data acquired and processed by those sensors. A significant contribution to the desire to field such systems has been the development of coherent processing techniques, in particular interferometry, that have dominated SAR applications since their first demonstration in the late 70's and early 80's. Evidence of the importance and versatility of radar interferometry is its application to such diverse area as the monitoring of volcanoes, earthquakes, landslides, ice sheet motion and anthropogenic sources such as ground pumping of water and oil. Development of innovative processing techniques, like permanent scatterer interferometry, polarimetric-interferometry and tomography have expanded the number of applications and data sets that can be successfully exploited. For example, permanent scatterer interferometry and tomography have revolutionized what can be done by SARs in urban environments. In this article we aim to provide a description of the some of the major developments in SAR interferometry and SAR tomography with particular emphasis on the digital signal processing aspects. We will illustrate SAR tomography using urban and infrastructures applications although it has other applications such as in forest and ice structure. Examples of applications of interferometry and tomography are provided to demonstrate the practical usefulness of the technological advances occurring on both the SAR system and data processing. With respect to other published tutorial on interferometry, we focus on the development of multibaseline/multipass coherent processing approach from a signal processing perspective with the aim to provide to readers a comprehensive description of the topics demanding to the reference bibliography deeper investigations

Tomographic Imaging and Monitoring of Buildings with Very High Resolution SAR Data

Layover is frequent in imaging and monitoring with synthetic aperture radar (SAR) areas characterized by a high density of scatterers with steep topography, e.g., in urban environment. Using medium-resolution SAR data tomographic techniques has been proven to be capable of separating multiple scatterers interfering (in layover) in the same pixel. With the advent of the new generation of high-resolution sensors, the layover effect on buildings becomes more evident. In this letter, we exploit the potential of the 4-D imaging applied to a set of TerraSAR-X spotlight acquisitions. Results show that the combination of high-resolution data and advanced coherent processing techniques can lead to impressive reconstruction and monitoring capabilities of the whole 3-D structure of buildings

Non-Linear Least Squares Algorithm for Detection of Simple and Double Persistent Scatterers

Synthetic Aperture Radar (SAR) Tomography is a multi-temporal technique which can reconstruct the 3D profile of a scene. One of its main features consists in the ability to detect the presence of multiple Persistent Scatterers (PS) within the same resolution cell. This paper aims to investigate the super-resolution capabilities of SAR Tomography, by detecting targets situated at a distance which is close to Rayleigh resolution. Elevation positions of scatterers are determined with Capon estimation, which is characterized by higher side-lobs reduction. An adapted form of multi-looking is proposed for extraction of targets contribution from reconstructed reflectivity functions and for estimation of reflectivity power textures. An algorithm for detection of dominant and secondary PSs will be conducted based on the derived reflectivity estimates, trying to preserve the advantages of Capon filtering used for reflectivity reconstruction

Applications of SAR Tomography on Persistent Scatterers detection, based on Beam-Forming filtering

The main advantage of Synthetic Aperture Radar (SAR) Tomography over classical interferometry consists in capacity to detect the presence of multiple scatterers within the same resolution cell. In this paper we present an algorithm for detection of Persistent Scatterers (PS) based on the variation of reflectivity function in elevation direction reconstructed with Beam-Forming technique. Then, we extract the contribution of dominant scatterers from each resolution cell and reapply the detection algorithm to identify the presence of secondary PSs in scene's pixels. The methods were implemented on a dataset of high-resolution Single Look Complex (SLC) images acquired by TerraSAR-X sensor, on which the residual component of interferometric phase was estimated and compensated locally