Three-dimensional ISAR imaging: a review

Three-dimensional (3D) inverse synthetic aperture radar (ISAR) imaging has been proven feasible by combining traditional ISAR imaging and interferometry. Such technique, namely inteferometric ISAR (In-ISAR), allows for the main target scattering centres to be mapped into a 3D spatial domain as point clouds. Specifically, the use of an In-ISAR system can overcome the main geometrical interpretation issues imposed by the monostatic acquisition geometry as the problem of cross-range scaling and unknown image projection plane (IPP). However, some issues remain such as scatterer scintillation, shadowing effects, poor SNR etc., which limit the effectiveness of 3D imaging. A solution to such unsolved issues can be found in the use of multiple 3D views, which can be obtained exploiting either multi-temporal or multi-perspective configurations or a combination of both. This study aims to review the main concepts to produce multi-view 3D ISAR images by using In-ISAR systems also presenting real data collected with a multi-static In-ISAR system

Firm Complexity and Capital Structure: Evidence from Italian Diversified Firms

International audienceThis paper examines the links between product diversification, international diversification and capital structure for a panel of medium and large Italian firms. The results indicate that the interaction between these two dimensions of diversification strategy has a negative and significant impact on leverage. Furthermore, debt maturity analysis reveals that firms pursuing a simultaneous dual diversification strategy have, in particular, lower long‐term debt ratios. Our findings support the hypothesis that the complexity that comes from diversification reduces debt levels. Copyright © 2014 John Wiley & Sons, Ltd

3D interferometric ISAR imaging of noncooperative targets

Inverse synthetic aperture radar (ISAR) images are frequently used in target classification and recognition applications. Nevertheless, the interpretation of ISAR images remains problematic for several reasons. One of these is the fact that the image plane cannot be defined by the user but instead depends on the target's own motions and on its relative position with respect to the radar. In order to overcome the problem of interpreting two-dimensional (2D) ISAR images, a method for three-dimensional (3D) reconstruction of moving targets is presented. This method is based on the use of a dual interferometric ISAR system. The interferometric phases measured from two orthogonal baselines are used to jointly estimate the target's effective rotation vector and the heights of the scattering centers with respect to the image plane. The scattering center extraction from the ISAR image is performed by applying a multichannel CLEAN technique. Finally, a 3D image of the moving target is reconstructed from the 3D spatial coordinates of the scattering centers. The effectiveness and robustness of the proposed algorithm is first proven theoretically and then tested against several radar-target scenarios as well as in the presence of noise

3D InISAR target reconstruction using airborne PAMIR data

In this paper a method for three dimensional target imaging from a multichannel airborne radar is presented. With data collected in cross-channel configuration, at least two interferometric phases are formed. Each scatterer position in cross-range and height is estimated from the interferometric phases and the scatterer Doppler location. The effect of moving radar platform and its antenna steering is considered is demonstrated on simulated and real data

Detection of ships from SAR images

The observation of maritime activity has been a field of research ever since SAR images of the ocean surface became available. This is because SAR images provide global scale coverage, independently of the weather and of the night/day cycle, and high spatial resolutions. More specifically, ship detection and classification from SAR images are effective tools for fishing activity monitoring and detection of ships responsible for marine oil pollution. Furthermore, SAR images are used for detecting illegally operating ships that increase marine crimes including smuggling and sea-jacking by piracy

Multistatic 3D ISAR image reconstruction

InISAR imaging has proven an effective tool to produce 3D target reconstruction. 3D target reconstruction solves the problems related to the ISAR image interpretation, due to the unknown target's projection onto the image projection plane. Nevertheless, problems related to shadowing are not solved as scatterers that are not visible cannot be detected and located in a 3D coordinate system. To overcome this problem, a multistatic InISAR system is introduced. A method for multistatic 3D target reconstruction that is based on an incoherent technique is proposed and analysed

Blue port traffic monitoring via 3D InISAR radar imaging system

Nowadays, maritime traffic control is mainly performed via the VTS (vessel traffic service) system, which exploits information from AIS (automatic identification system) systems installed on board of cooperative vessels, remote radar site (RRS) and GPS system. The AIS allows the port authorities to know with adequate accuracy absolute geographic coordinates, velocity, trajectory, type, size, draught and cargo of each cooperative vessel (equipped with AIS) thus providing the means for controlling and monitoring the area of interest