3-pass and 2-pass Differential Interferometry and Result Comparison

We concentrate on areas with abandoned open brown coal mines, or undermined areas. We made analyzes of terrain deformation in the area of the Slatinice above-level dump that is monitored because of potential terrain deformations. Further we concentrated on the Jirkov-Most route and railway that slides and is also monitoring and levelled very precisely. Especially its part called the Ervenice corridor.

The 3-pass method for differential interferometry was performed in the GAMMA software. Perpendicular baseline of the topo pair is 160m. This baseline for the deformation pair is 4m. Then their relation is 0,025. It is the best configuration for all scenes we kept at disposition.

The phase of differential interferograms is in [-pi,pi), and thus the phase ambiguity occurs. Therefore, we are not able to recognize jump deformations larger than 2.8 cm. For subsidence confirmation, we demand as continuous phase as possible with a sufficient number of neighboring pixels and lines. The suspect areas of subsidence must be sufficiently coherent. For incoherent areas there occurs decorrelation and thus loss of data. Areas were not much coherent. Data were often decorrelated. In this article we used the 2-pass method to compare results of both methods. The differential interferogram for the 2- pass method was filtered and then unwrapped. Due to filtering we achieved much better coherence. Unwrapped phase of that differential interferogram can also be used for a terrain-deformation detection more profitably.