ACCURATE GEOMETRIC CORRECTION OF ATSR IMAGES

An accurate geometric correction algorithm of raw ATSR images is propo sed in this paper, The proposed algorithm is divided into two modules: pre-correction and precision correction, In the pre-correction algori thm, the scanning geometry of the ATSR, ephemeris data and the Earth's shape and rotation were modeled mathematically, It corrected elliptic ally-distorted raw ATSR images and resulted in a mean collocation erro r of 1 pixel between the nadir and forward images. The proposed naviga tion model showed a better geolocation performance than ATSR image geo metric correction algorithms currently in operation, The geometric err ors in the pre-corrected images were reduced further by the precision correction algorithm, Coastlines were detected from the pre-corrected nadir and forward images and matched with map coastline data. The matc hed coastline pixels, GCP's, were combined with the pre-correction mod el to estimate the errors of the position, velocity and attitude of th e satellite, An extended Kalman filter was used for the optimal estima tion. The corrected images showed the collocation error of 0.4 pixel a nd the geolocation error of 0.7 pixel. The results were compared with those from a polynomial warping technique, It proved that the proposed precision correction algorithm gave better geometric correction perfo rmance than collocation algorithms based on a polynomial warping techn ique.