ABSTRACT
This chapter describes the SAR geometry, ortho-rectification, and slope-correction, all of which are essential in making the SAR images more applicable in Geographic Information System (GIS). The SAR observation is performed in squint direction, and the image is distorted both in geometry and radiometry by five processes: foreshortening, range and azimuth shift, layover, radiometric modulation associated with slope, and shadowing. Under the ortho-rectification process, the iterative calculation is required to determine the pixel position in correspondence to the given height but this sometimes fails due to layover or shadowing issues. Instead, we introduce a simple and robust method that combines a simulated SAR image (generated from a digital elevation model, or DEM) and the SAR image for a further correction step. The geometric accuracy of the ortho-rectification is measured as high as 11.9 m (of RMSE) for ALOS/PALSAR.
