Using D-InSAR and offset tracking technique to monitor mining subsidence

Differential synthetic aperture radar interferometry (D-InSAR) technology is a popular method to monitor ground deformation. Two-pass D-InSAR and sub-pixel offset tracking approaches are presented to analyze the mining subsidence, which is located in Yuxian, Hebei province, China. The availability of 20 commissioned TerraSAR-X (TSX) Spotlight SAR images were acquired from 9th June 2015 to 4th January 2016. To avoid decorrelation between SAR acquisitions, every 11-day TSX Spotlight pair was processed so that 19 SAR image pairs were formed. While differential interferograms were obtained based on SRTM DEM, interference fringes are too much denser or de-coherence in the main mining area and result in phase unwrapping error or the wrong deformation. Although the phase unwrapping in rapid sedimentation rate's areas would be failed, we can obtain the mining direction by means of time series settlement image analyzing. D-InSAR technology has the limitation that high-gradient deformation zone cannot be unwrapped truly because high-gradient deformation zone will result in phrase overlap or decorrelation. To improve the accuracy of these areas, the pixel offset tracking technology is used. Comparing with the leveling results, the unequal settlement can reach up to 1m. In this experiment, two images in 3th August, 2015 and 4th January, 2016 were applied to calculate through sub-pixel offset tracking technology. The subsidence result is up to 1.96m in the main coal mining area.