Calibration of High-Resolution Synthetic Aperture Radar (SAR) Image Features by Ground-Based Experiments

Abstract

ABSTRACTResults of recent experiments reported in the literature with frequency-modulated continuous wave (FMCW) mode of synthetic aperture radar (SAR) imaging are enabling high-resolution, day and night remote sensing of ground terrain. Also, FMCW-based SAR techniques are accepted for ground-based SAR (GB-SAR) instrumentation for early warning of fragile slopes such as in coal mines, avalanche detection. Features of images generated by FMCW SAR sensors need to be calibrated for interpretation purposes as like other forms of microwave imaging. In this paper, we demonstrate a ground-based method to calibrate high-resolution FMCW SAR image features by experimenting with a long railSAR testbed. Signal processing algorithms are derived to support high-resolution SAR image formation according to the requirement of the experiment. Trihedral corner reflectors (CRs) of submeter dimensions are placed on terrains with different normalized radar cross-section (RCS) coefficient (σ0) to measure backscattering properties from targets and surrounding clutter from different heights and varied look angles. Calibration of the features of CRs is performed with respect to their physical dimensions by measuring the impulse response functions and spatial resolution in the SAR images. Target RCS and speckle properties derived from single-look and multilook processing of experimental data closely follows target and scene parameters such as radiometric and geometric measures of RCS of the CRs and σ0 of surroundings such as tar road and concrete road. By this experiment the features of high-resolution FMCW SAR images are measured and calibrated without flying the radar sensor on airborne platform.