DIGITAL TECHNIQUES FOR NOISE REDUCTION IN APT NOAA SATELLITE IMAGES.

Comparative tests of different noise reduction filters have been performed using NOAA/APT (automatic picture transmission) meteorological satellite images. The best results, in terms of noise suppression and blur attenuation, have been obtained by two kinds of digital filtering techniques. The other techniques showed a nonuniform behavior, mainly in terms of noise pixel leaving. Both filters were used in the iterative mode: the weighted median filter presented a number of iterations to reach a stable condition of less than that of the 'extremal' filter. On the other hand, the mean computing time per iteration of the extremal filter is about 30% less than the weighted filter time.