Practical SAR orthorectification

Abstract

SAR orthorectification procedures have been implemented at major processing facilities for several years, but only recently has workstation computer speed increased to a level where it is now practical for the SAR researcher to have their own orthorectification capability in-house. The present article presents the authors' efforts to implement such a program and the practical lessons learned in doing so. Orthorectification encompasses all the corrections needed to precisely align a SAR image with a map, accounting for actual topography. However, there are several other operations that are required in order to produce radiometrically corrected data during the orthorectification process: calculating layover and shadow masks, local incidence angle, and calibration to /spl sigma//sup 0/. Without calibration the image is far less useful in further processing, such as in land-cover classification and biophysical parameter estimation. Specifics of the authors' effort to apply this to ERS PRI data, and to JERS level 2.1 data are presented, including an assessment of how well it performed.