Geospatial warning systems
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Project > Methodologies > Satellite Imaging
Differential Radar Interferometry (DInSAR)
Differential interferometry (DInSAR) applied to a digital elevation models (DEM) proves to be a powerful tool to detect surface displacements on the order of a few centimetres.
Differential Radar Interferometry (DInSAR) was applied on Nisyros to study
the regional deformation of the area in conjunction with the GPS observations
existing from the area.
The two-pass differential interferometry method (or DEM-elimination method)
was applied. This method employs two SAR images, producing one interferogram.
To perform the differential, another interferogram has to be synthesized.
The main steps of the interferometric processing include:
The above processing generates two InSAR geo-coded images for the production of a differential interferogram for deformation estimates. The differential interferogram (change map) and the coherence imagery is analyzed.
[Fig.23 subset] one fringe cycle = 28 mm displacement
Fig. 23 The produced interferometric image from the first
interferometric pair, covering the period 22 May 1995 to 22 January 1996, coinciding
with the beginning of the seismic unrest period in Nisyros Island (Fig. 17).
One interferometric fringe, equivalent to 28 mm of ground deformation along
the slant direction, was recognized and evaluated. Most of the island is covered
by a circular shaped fringe, which extends from the NW part, covers the southern
island and dies out (due to poor coherence) on the NE part of Nisyros. A second
fringe located on the SW extremity of the island can also be recognized. National
Kapodistrian University of Athens (NKUA)
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