Coherent Change Detection: Theoretical Description and Experimental Results
DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION EDINBURGH (AUSTRALIA)
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This report investigates techniques for detecting fine scale scene changes using repeat pass Synthetic Aperture Radar SAR imagery. As SAR is a coherent imaging system two forms of change detection may be considered, namely incoherent and coherent change detection. Incoherent change detection identifies changes in the mean backscatter power of a scene typically via an average intensity ratio change statistic. Coherent change detection on the other hand, identifies changes in both the amplitude and phase of the transduced imagery using the sample coherence change statistic. Coherent change detection thus has the potential to detect very subtle scene changes to the sub-resolution cell scattering structure that may be undetectable using incoherent techniques. The repeat pass SAR imagery however, must be acquired and processed interferometrically. This report examines the processing steps required to form a coherent image pair and describes an interferometric spotlight SAR processor for processing repeat pass collections acquired with DSTO Ingara X-band SAR. The detection performance of the commonly used average intensity ratio and sample coherence change statistics are provided as well as the performance of a recently proposed log likelihood change statistic. The three change statistics are applied to experimental repeat pass SAR data to demonstrate the relative performance of the change statistics.
- Optical Detection and Detectors