Identifying ground movement with interferograms.
DInSAR is used to extract ground deformation data when an insufficient number of SAR images are available over an area of interest to perform a full SqueeSAR™ analysis. Learn more about the DInSAR technique.
Interferograms and deformation maps can be easily imported and visualized in ArcGIS. Learn more about map visualization.
The two principle results of DInSAR analysis are:
- Interferograms
- Deformation maps
Below is a description of the individual maps:
An interferogram highlights areas of ground affected by displacement on a cyclic scale. By analyzing and comparing the phase components of two SAR images, interferograms show displacement that has occurred between the two time periods of acquisition. Interferograms are said to be ‘wrapped’ as displacement information is represented as ‘fringes’ on a cyclic scale.
As only two satellite images are used, temporal and spatial atmospheric noise contributions cannot be removed, as would be done in a full SqueeSAR™ analysis. Nevertheless, interferograms highlight areas affected by ground movement and, upon converting the phase difference to distance, an approximation of the extent of ground displacement that has occurred over the area and time period analyzed.
Example: interferogram
A displacement map highlights areas of ground affected by displacement on a continuous scale. Displacement maps are ‘unwrapped’ interferogram images (displacement is no longer represented on a cyclic scale). Unwrapping the ‘fringes’ of an interferogram allows a qualitative estimate of displacement to be calculated, enabling contour intervals and displacement values to be mapped. This process can only be performed if a high level of coherence exists between the two SAR images analyzed.
As only two satellite images are used, temporal and spatial atmospheric noise contributions cannot be removed, as would be done in a full SqueeSAR™ analysis. Nevertheless, displacement maps provide a quantitative estimation of ground movement that has occurred over the area and time period analyzed.
Example: displacement map