Comparison between Range-Doppler and Rational-Function methods for SAR Terrain Geocoding

Abstract

Geocoding of Synthetic Aperture Radar (SAR) imagery is an essential preprocessing step in multi-source data integration, management and analysis for many geomatics applications. The Range-Doppler (RD) approach is a rigorous physical sensor model, which achieves the highest geometric accuracy and has been widely used in terrain-geocoding of satellite SAR data. However the main drawback is that it is not computationally efficient. The Rational-Function (RF) model has been successfully used for processing of optical images (push broom sensors IKONOS and QuickBird), and is of considerable interest in processing of SAR datasets as an alternative to the RD method because of its high computational efficiency and fitting accuracy (e.g. RADARSAT-2). Two SAR terrain-geocoding methods, based on the RD and the RF models, have been implemented at Canada Center for Mapping and Earth Observation (CCMEO). In this paper we briefly describe the well-known RD mathematical model and the RF mathematical model in more detail. The relative geometric accuracy for the two methods is analysed and compared. Finally, some major advantages of the RF method over the RD method are presented.