CHANGE DETECTION TECHNIQUES FOR ERS-1 SAR DATA

Several techniques for detecting temporal changes in satellite synthet ic aperture radar (SAR) imagery are compared using both theoretical pr edictions and spaceborne SAR data collected by the European first Remo te Sensing Satellite, ERS-1. In a first set of techniques, changes are detected based on differences in the magnitude of the signal intensit y between two dates. Ratioing of the multidate radar intensities is sh own to be better adapted to the statistical characteristics of SAR dat a than subtracting, and works best when the number of looks is large. In a second set of techniques, changes are detected based on estimates of the temporal decorrelation of speckle. This method works best with one-look complex amplitude data, but can also be used with intensity data provided that the number of looks is small. The two techniques, r atioing of the signal intensity and decorrelation of speckle, are comp ared using actual SAR data collected by ERS-1. The results illustrate the viability as well as the complementary character of these techniqu es for detecting changes in the structural and dielectric properties o f remotely sensed surfaces. Finally, change detection using the ratio method is applied to mosaics of repeat-pass SAR imagery to illustrate the potential of this method for monitoring applications at the region al scale.