Ground Moving Target Tracking and Refocusing Using Shadow in Video-SAR

Xiaqing Yang,Yao Hu,Shunjun Wei,Chen Wang,Jun Shi,Yuanyuan Zhou,Xiaoling Zhang

doi:10.3390/rs12183083

Xiaqing Yang, Yao Hu + Show 5 more

Open Access

https://doi.org/10.3390/rs12183083

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Abstract

Stable and efficient ground moving target tracking and refocusing is a hard task in synthetic aperture radar (SAR) data processing. Since shadows in video-SAR indicate the actual positions of moving targets at different moments without any displacement, shadow-based methods provide a new approach for ground moving target processing. This paper constructs a novel framework to refocus ground moving targets by using shadows in video-SAR. To this end, an automatic-registered SAR video is first obtained using the video-SAR back-projection (v-BP) algorithm. The shadows of multiple moving targets are then tracked using a learning-based tracker, and the moving targets are ultimately refocused via a proposed moving target back-projection (m-BP) algorithm. With this framework, we can perform detecting, tracking, imaging for multiple moving targets integratedly, which significantly improves the ability of moving-target surveillance for SAR systems. Furthermore, a detailed explanation of the shadow of a moving target is presented herein. We find that the shadow of ground moving targets is affected by a target’s size, radar pitch angle, carrier frequency, synthetic aperture time, etc. With an elaborate system design, we can obtain a clear shadow of moving targets even in X or C band. By numerical experiments, we find that a deep network, such as SiamFc, can easily track shadows and precisely estimate the trajectories that meet the accuracy requirement of the trajectories for m-BP.

Highlights

Synthetic Aperture Radars (SAR) that are mounted on aircrafts, satellites or other platforms are usually used to obtain images of regions of interest for all-weather all-time high-resolution reconnaissance [1,2,3]
To analyze the signal characteristics of moving target, we model the geometry of an synthetic aperture radar (SAR) system for observing a ground moving target as shown in Figure 1, in which x denotes azimuth direction, i.e., the direction that the platform moves, y and z denote range and height directions, respectively
For SiamFc, the tracking time of each frame is less than 0.01 s for a single target. moving target back-projection (m-BP) has the same efficiency as the standard BP

Summary

Introduction

Synthetic Aperture Radars (SAR) that are mounted on aircrafts, satellites or other platforms are usually used to obtain images of regions of interest for all-weather all-time high-resolution reconnaissance [1,2,3]. Ground moving target imaging is still a challenging task due to the unknown target’s trajectory. In early moving target imaging problems, a Moving Target Indicator (MTI) radar is utilized to detect moving targets and estimate the motion parameters under a relatively high signal-to-clutter ratio condition. The keystone transform [18] is popular for its capability of eliminating an arbitrary linear range migration, which might blur the moving target in the SAR image [19]

Methods

Discussion

Conclusion