Applying stereo SAR to remove height-dependent layover effects from video SAR imagery

Abstract

This paper describes a correction technique using stereo SAR (Synthetic Aperture Radar) that improves the image quality of video SAR. The video SAR mode provides a persistent view of a scene centered at the Motion Compensation Point (MCP). The radar platform follows a circular flight path. The effect of height-dependent layover in video SAR imagery is that objects higher than the image plane appear translated towards the along-track direction in the image plane. A Digital Elevation Map (DEM) provides the height of the MCP. A height error in the MCP results in a SAR image that is not centered at the MCP. An objective is to form a sequence of SAR images centering the MCP for each image. This paper details a correlation method performed on a pair of SAR images in order to estimate the layover. Using multiple pairs of images taken from video SAR imagery improves the reliability of the layover estimate. Synthetic target imagery with targets at non-zero heights demonstrates the method. The paper presents 2011-2013 flight data collected by General Atomics Aeronautical Systems, Inc. (GA-ASI) implementing the video SAR mode with correction for layover. The flight data demonstrates good video quality with the MCP centered in each video frame.