Moving Target Detection with Modified Logarithm Background Subtraction and Its Application to the GF-3 Spotlight Mode

Wenjie Shen,Yanping Wang,Wen Hong,Yun Lin,Bing Han

doi:10.3390/rs11101190

Abstract

Spaceborne spotlight SAR mode has drawn attention due to its high-resolution capability, however, the studies about moving target detection with this mode are less. The paper proposes an image sequence-based method entitled modified logarithm background subtraction to detect ground moving targets with Gaofen-3 Single Look Complex (SLC) spotlight SAR images. The original logarithm background subtraction method is designed by our team for airborne SAR. It uses the subaperture image sequence to generate a background image, then detects moving targets by using image sequence to subtract background. When we apply the original algorithm to the spaceborne spotlight SAR data, a high false alarm problem occurs. To tackle the high false alarm problem due to the target’s low signal-to-noise-ratio (SNR) in spaceborne cases, several improvements are made. First, to preserve most of the moving target signatures, a low threshold CFAR (constant false alarm rate) detector is used to get the coarse detection. Second, because the moving target signatures have higher density than false detections in the coarse detection, a modified DBSCAN (density-based spatial-clustering-of-applications-with-noise) clustering method is then adopted to reduce false alarms. Third, the Kalman tracker is used to exclude the residual false detections, due to the real moving target signature having dynamic behavior. The proposed method is validated by real data, the shown results also prove the feasibility of the proposed method for both Gaofen-3 and other spaceborne systems.

Highlights

Due to its wide coverage and all-day all weather capability, the idea of utilizing spaceborne SAR to detect ground moving targets has been a hot topic for a long time
The capability of ground moving target detection in current systems is typically provided by using a multichannel configuration
The purpose of this paper is to propose a subaperture image sequence-based method to detect moving targets in spaceborne SAR spotlight mode

Summary

Introduction

Due to its wide coverage and all-day all weather capability, the idea of utilizing spaceborne SAR to detect ground moving targets has been a hot topic for a long time. The capability of ground moving target detection in current systems is typically provided by using a multichannel configuration. The system has more than one channel aligned along track direction and, provides extra degrees of freedom to fulfill the moving target detection task. The idea of generating a background image is simple. The basic assumption is that certain pixel values change slowly along the azimuth viewing angle. The position of moving target signature changes relatively fast from image to image. For a certain pixel, a high value will occur when the moving target signature moves onto it. An alternative plan is to use the subaperture image sequence to generate the background image

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