Layover Analysis in Synthetic Aperture Imagery

Layover is an artifact observed in synthetic aperture radar (SAR) images. This artifact manifests as geometric distortions or positioning errors due to unknown or inaccurate ground topography information. Layover artifact results in erroneous distance between reconstructed scatterers, particularly in elevated regions. We develop a quantitative analysis of positioning errors due to incorrect height information in backprojection based (BP) SAR image formation. Our analysis is based on microlocal techniques and provides an explicit algebraic relationship between the two-dimensional positioning error and height error. Our analysis is applicable to arbitrary imaging geometries including bistatic configuration, arbitrary antenna trajectories, wide apertures, and large scenes. While we focus primarily on BP based image formation, the results are also applicable to range-Doppler type image formation methods. Our results can be used to interpret and identify layover regions in SAR images and extract valuable information from layover artifacts.