Validating GEV Model for Reflection Symmetry-Based Ocean Ship Detection with Gaofen-3 Dual-Polarimetric Data

Rui Guo,Guobin Jing,Shuangxi Zhang,Jingyu Cui,Mengdao Xing

doi:10.3390/rs12071148

Abstract

The spaceborne synthetic aperture radar (SAR) is quite powerful in worldwide ocean observation, especially for ship monitoring, as a hot topic in ocean surveillance. The launched Gaofen-3 (GF3) satellite of China can provide C-band and multi-polarization SAR data, and one of its scientific applications is ocean ship detection. Compared with the single polarization system, polarimetric systems can be used for more effective ship detection. In this paper, a generalized extreme value (GEV)-based constant false alarm rate (CFAR) detector is proposed for ship detection in the ocean by using the reflection symmetry metric of dual-polarization. The reflection symmetry property shows big differences between the metallic targets at sea and the sea surface. In addition, the GEV statistical model is employed for reflection symmetry statistical distribution, which fits the reflection symmetry probability density function (pdf) well. Five dual-polarimetric GF3 stripmap ocean data sets are introduced in the paper, to show the contrast in enhancement by using reflection symmetry and to investigate the GEV model fit to the reflection symmetry metric. Additionally, with the detection experiments on the real GF3 datasets, the effectiveness and efficiency of the GEV model for reflection symmetry and the model-based ocean ship detector are verified.

Highlights

Detection of ships in the ocean is a traditional task and one of the key applications for the earth obsevation remote sensing activities
The reflection symmetry metric, namely the correlation between co- and cross-polarization for dual-polarimetric ocean data, was analyzed for ship detection in the sea surface with the generalized extreme value (GEV) statistical distribution model, which was firstly considered for ocean target detection
The reflection symmetric property reveals the natural characteristics of the sea clutter and metallic targets, so the reflection symmetry metric was explored for ship detection, as it enlarges the contrast between the targets and the sea clutter

Summary

Introduction

Detection of ships in the ocean is a traditional task and one of the key applications for the earth obsevation remote sensing activities. Ship detection with SAR data has gained intensive attention for various potential remote sensing applications, including marine surveillance, vessel traffic services and military operations. The world-wide-developed satellite SAR systems supplies more opportunities to realize ocean ship detection, as the launched new advanced SAR systems can provide more complete information of target scattering characterization, such as the polarimetric SAR systems (e.g., TerraSAR-X, ALOS-PALSAR, Radarsat-2, Sentinel-1, ComoSky-Med and so on) [1,2,3,4]. Polarimetric scattering characteristic parameters, such as the polarimetric entropy [7], polarimetric cross entropy (PCE) [8], the degree of polarization [9,10] and eigenvalue from polarimetric decomposition [11,12], have been developed for targets observation or target detection at sea

Methods

Discussion

Conclusion