Automatic identification of the number and values of decision thresholds in the log-ratio image for change detection in SAR images

In this letter, we propose an extension of an automatic and unsupervised change-detection method for synthetic aperture radar images we presented earlier. By analyzing a properly defined cost function, the proposed method allows the automatic detection of the number (zero, one, or two) and the values of the decision thresholds associated with changes (if any) in the log-ratio image. This cost function is the minimum value of the criterion function adopted to select the decision threshold in the log-ratio image according to a modified double-thresholding Kittler-Illingworth algorithm (implemented under the generalized Gaussian assumption for changed and unchanged classes). Experimental results carried out both on real and simulated multitemporal synthetic aperture radar images proved the effectiveness of the proposed automatic method in detecting both the number of changes to be identified (the situation of no changes is also explicitly identified) and the related threshold values.