Detection of urban damage using interferometric SAR decorrelation

The authors attempted to use norm type correlation coefficient of single-look intensity data (intensity correlation) and complex correlation coefficient of single-look complex data (coherence) for the purpose of detecting the ground surface change due to urban damages. The test site was Kobe city area in Japan where a lot of buildings were collapsed by an earthquake in 1995. The test data were ERS-1 SAR data, three of which were observed before the earthquake and the other three were observed after the earthquake. According to the comparison of decorrelation patterns between the intensity correlation and the coherence, both of the correlation coefficients were found to behave almost similarly. The correlation patterns were related to the land cover types. The data pairs taken before and after the earthquakes indicated clear decorrelation at damaged city areas. For additional similarity, the long baseline distance data pairs showed large decorrelation on whole image and their correlation patterns were obscure. It is supposed from these correspondences that the major factor in the intensity decorrelation is still related to the interferometric decorrelation process, namely, the change of speckle patterns due to the change of urban surface patterns. The change of the cardinal effect is also suggested for additional factor in the intensity decorrelation. From this result, the coherency is important for detecting the damaged urban area using the correlation of SAR data.