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Interferogram

For generating an interferogram, two co-registered SAR images covering the same area are multiplied in a complex fashion. The result of this complex multiplication is the average of the two SAR images and the difference of their corresponding phase values. The interference pattern, also called fringe, is stored in a range of (-, ].

Interferograms show differences in phase. This phase difference is the result of a path length difference that can be caused by elevation differences, motion, or deformation. Hence, we can use interferograms to derive accurate elevation maps, monitor small motions, and detect tiny deformations.

The phase of the above interferogram shows the topography of the imaged mountain. We can convert phase into elevation if the two satellites separated by baseline of a certain length (less than 1100 meters for the ERS satellite).