This paper presents a technique for a fully automatic and operational geometric correction system capable of georeferencing satellite images with high accuracy. A simple Keplerian orbital satellite model is considered and mean orbital elements are given as input from ephemeris data. To correct the systematic errors caused by these simplifications, nonzero values for the spacecraft roll, pitch and yaw and failures in the satellite internal clock, an automatic global contour matching approach is proposed. It has three main steps: (i) estimation of the gradient energy map (edges) and detection of the cloudless (reliable) areas; (ii) initialization of the contour positions; (iii) obtaining the transformation parameters (affine model) by means of a global contour optimization approach. Three different algorithms are proposed for optimization. The performance of the overall technique is assessed using AVHRR and multisensor AVHRR-SeaWiFS imagery.
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