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31.5.2020 : 19:42 : +0200

Change Detection

Space-borne remote sensing and in particular SAR has a good potential for change detection and a good data availability and is therefore well suited for the assessment of damages after natural disasters and similar catastrophes. One major advantage of SAR as compared to optical imagery is its "all-weather" capability.

A typical processing sequence for multi-temporal SAR change detection includes radiometric calibration, co-registration of the images to a common geometry, multi-temporal and spatial filtering, rationing, and change classification, for example by simple thresholding, geocoding, and visualization of the result. Results can be either a SAR only product as shown below, a combination with other information layers like optical data, ground information and maps, or the change layer can be imported into a GIS for further analysis. Not only the backscattering information but also the coherence, as an indicator of random displacements of scatterers within the SAR resolution cell, and the interferometric phase, indicating coherent displacement of the combined scattering phase center can also be used in the context of hazard mapping.


Change map in UTM z48 projection, pixel spacing is 25m. The change layer (blue channel) is combined with the red and green channel of the Coherence Product. This is a good example of a rapid mapping product that gives a quick overview but also detailed information solely based on SAR. Of course the change layer, in this case the flood indicator, can also be combined with data of other sensors or topographic maps or imported into a GIS.