Ship Profile Imaging Using Multipath Backscattering

Jean-Marc Le Caillec,Ali Khenchaf,Jérôme Habonneau

doi:10.3390/rs11070748

Jean-Marc Le Caillec, Ali Khenchaf + Show 1 more

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https://doi.org/10.3390/rs11070748

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Abstract

This paper addresses the estimation of the height of a point scatterer over a sea surface via multipath exploitation for a High Range Resolution radar that is using pulse range compression, such as Synthetic Aperture Radars. We first focus our attention on the physical model, in particular on the specular/diffuse reflection coefficients, this coefficients being derived from the empirical Miller Brown and Vegh model. The gravity waves are also simulated since they modify the acquisition geometry such as the local grazing angle. Secondly, the signal model is derived, thus allowing an easy derivation of the time delays (direct echo and replicas), these time delays being converted into a height estimation for possible automatic ship recognition applications. Our algorithm is a non-conventional radar signal processing, in other words it uses the backscattered pulse over before range compression and demodulation. The aim of the paper is to understand for which radar and sea parameters, as well as acquisition scenes, it is possible to extract the scatterer height information using the multipath of the backscattered electromagnetic wave.

Highlights

Automatic Target Recognition (ATR) is the most widely used approach for classification of ships for marine surveillance applications
These radar parameters are the central radar frequency fc fixed to three different values, that are, 0.1, 0.5 and 1 GHz, the resolution δr to 0.5, 5 and 10 m, the polarization and, obviously, the sampling frequency fs as previously stated
The number of operable pulses, the relative bias, that is the absolute value of the difference between the estimate mean and the true height value divided by this height value, and the normalized standard deviation are our three metrics of performance

Summary

Introduction

Automatic Target Recognition (ATR) is the most widely used approach for classification of ships for marine surveillance applications. Our approach is based on the scatterer center identification and localization [2,3], which requires a fine understanding of the physical phenomena In this approach, ATR involves locating point scatterers on these ship profiles. Inverse Synthetic Aperture Radar (ISAR) has been investigated for imaging 2-D profiles of ships In this kind of imaging, the motion of the ship, in particular involuntary displacements due to roll pitch and yaw, are used to vertically locate the point scatterer and to create a 2-D profile of the ship. This solution is not valid for small sea states where these motions do not exist. We locally construct a “2-D image” that is the planar coordinates within the radar image plus the scatterer height (as in the ISAR case) by a non-conventional radar approach

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