Joint Ship Detection Based on Time-Frequency Domain and CFAR Methods with HF Radar

Zhiqing Yang,Xinjun Xu,Hao Zhou,Biyang Wen,Jianjiang Tang,Yingwei Tian

doi:10.3390/rs13081548

Abstract

Compact high-frequency surface wave radar (HFSWR) plays a critical role in ship surveillance. Due to the wide antenna beam-width and low spatial gain, traditional constant false alarm rate (CFAR) detectors often induce a low detection probability. To solve this problem, a joint detection algorithm based on time-frequency (TF) analysis and the CFAR method is proposed in this paper. After the TF ridge extraction, CFAR detection is performed to test each sample of the ridges, and a binary integration is run to determine whether the entire TF ridge is of a ship. To verify the effectiveness of the proposed algorithm, experimental data collected by the Ocean State Monitoring and Analyzing Radar, type SD (OSMAR-SD) were used, with the ship records from an automatic identification system (AIS) used as ground truth data. The processing results showed that the joint TF-CFAR method outperformed CFAR in detecting non-stationary and weak signals and those within the first-order sea clutters, whereas CFAR outperformed TF-CFAR in identifying multiple signals with similar frequencies. Notably, the intersection of the matched detection sets by TF-CFAR and CFAR alone was not immense, which takes up approximately 68% of the matched number by CFAR and 25% of that by TF-CFAR; however, the number in the union detection sets was much (>30%) greater than the result of either method. Therefore, joint detection with TF-CFAR and CFAR can further increase the detection probability and greatly improve detection performance under complicated situations, such as non-stationarity, low signal-to-noise ratio (SNR), and within the first-order sea clutters.

Highlights

Maritime surveillance is an important task for coastal nations in coastal conservancy, security, fishery, and managing their exclusive economic zones (EEZs) [1,2] where the location and motion information of the ships are especially valuable
High frequency surface wave radar (HFSWR) uses high frequency (3–30 MHz) vertical polarized electromagnetic wave, which can propagate along this surface with small attenuation, and, has the capability of remote sensing of moving targets at sea
The ship signals are detected in the frequency domain and the TF domain by constant false alarm rate (CFAR)

Summary

Introduction

Maritime surveillance is an important task for coastal nations in coastal conservancy, security, fishery, and managing their exclusive economic zones (EEZs) [1,2] where the location and motion information of the ships are especially valuable. 400 HF radar sites in operation for ocean observation globally. Europe, Japan, and Australia have built nearly complete HF radar observation networks [3], which provide real-time sea surface state parameters such as current velocity, wind speed, and wave heights. Part of these radar systems have been used for ship detection. To increase maritime domain awareness, SeaSonde HF radar coastal ocean current and wave-monitoring networks have been used for vessel detection in New York

Results

Discussion

Conclusion