Target detection in SAR imagery by diffraction patterning

We report on an investigation into the detection of power and telephone cables in SAR imagery by the presence of diffraction patterning. Laboratory SAR imaging measurements on metal pipes suspended above a gravel surface produced downrange fringe patterns in both backscatter and interferometric phase. Modelling was carried out using an incremental diffraction algorithm, and the positioning and modulation characteristics of the fringes could be understood by the relative positioning of the targets above the gravel and the imaging geometries. Whereas previous studies have relied upon the direct return from the cables, this study has shown their presence might still be inferred from the persistent presence of ground fringes even when a direct return is absent. The effect could find an application in collision avoidance of power and telephone cables by low-flying aircraft, as well as in surveillance and monitoring.