Performance Analysis of Dihedral Corner Reflectors for Slope Movements: A Case Study From Aniangzhai Landslide in China.

Using synthetic aperture radar (SAR) and interferometric SAR (InSAR) technology, artificial corner reflectors (CRs) are popular coherent targets for monitoring ground instability with subcentimeter accuracy in nonurban areas. In this letter, we investigate the performance of a newly designed small dihedral CR for monitoring postfailure creep at the Aniangzhai landslide in Danba County, China. The new double geometry CRs consist of two sets of semicircular metal plates, each 30-40 cm in radius and perpendicular to each other. Six such CRs are installed for CR-InSAR analysis using both TerraSAR-X (TSX) high-resolution spotlight (HS) data and medium-resolution Sentinel-1 (S1) SAR images. The CRs are first identified in SAR images using a probability model by taking into three factors. These are: 1) inverse of amplitude dispersion; 2) intensity increment after the installation; and 3) an upper empirical bound derived from the ensemble average of pixel intensities in postdeployment SAR images. Experimental results show that the CRs improve the background intensity in TSX images by around 30 dB, with signal-to-clutter ratio (SCR) exceeding 25 dB. Furthermore, the radar crass section (RCS) of CRs in both TSX and S1 images remains relatively stable, ranging from 15 to 23 dB, making them suitable for CR-InSAR analysis using double-difference phase observations.