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Interferometric coherence products, also known as Coherent Change Detection (CCD) images, display the complex signal correlation between two radar collections. Because the coherence is dependent upon backscatter and phase similarity, it is highly sensitive to wavelength scale surface changes.
This means that Radarsat scenes collected from successive orbital cycles (occurring every 24 days) can be combined to detect surface changes that are significantly smaller than the Radarsat wavelength of 5.5cm in scale.
Surface changes such as the following are regularly observable in the coherence data but not in the backscatter: