KEY TECHNOLOGY OF D-INSAR AT X-BAND FOR MONITORING LAND SUBSIDENCE IN MINING AREA AND ITS APPLICATION

In theory, land subsidence measurement results with high accuracy can be obtained by using the Differential Interferometry Synthetic Aperture Radar(D-InSAR) at X-band. In practice, however, the measuring accuracy of D-InSAR at X-band has been seriously affected by some factors, e.g., decorrelation and high deformation gradient. In this work, the monitoring capability of D-InSAR for coal-mining subsidence is evaluated by using SAR data acquired by TerrraSAR-X system. The SAR image registration method for low coherence image pairs, the denoising phase filter for high noise level interferogram and atmospheric effects mitigation method are the key technical aspects which directly influence the measurement results of D-InSAR at X-band. Thus, a robust image registration method, an improved phase filter method and an atmospheric effects mitigation method are proposed in this paper. The proposed image registration method successfully achieves InSAR coregistration, while the amplitude cross-correlation cannot properly coregister low coherence SAR image pairs. Moreover, the time complexity of the proposed image registration method is obviously slighter than that of the Singular Value Decomposition(SVD) method. The comparing experiment results and the unwrapping phase results show that the improved Goldstein filter is more effective than the original Goldstein filter in noise elimination. The atmospheric influence correction experiment results show that the land subsidence areas with atmospheric influence correction are more clarified than that of without atmospheric influence correction. In summary, the presented methods directly improved the measurement results of D-InSAR at X-band.

Quantifying glacial elevation changes in the central Qilian Mountains during the early 21^(st) century

Glaciers in the central Qilian Mountains provide important water resources for the arid Hexi corridor and Qaidam Basin;however,changes in these glaciers interact with climate change.Twenty-four bi-static image pairs of TerraSAR-X add-on for Digital Elevation Measurement(TanDEM-X)data,in addition to a Shuttle Radar Topography Mission-C/X band digital elevation model,and the technology of iterative differential synthetic aperture radar interferometry were used to carry out glacier elevation change analysis in the central Qilian Mountains in China during 2000–2014.Glacier elevation changed with an average rate of(−0.47±0.06)m yr^(−1),while changes in elevation of(−0.51±0.06)m yr^(−1) and(−0.44±0.06)m yr^(−1) were found in the northern(including the Zoulangnan,Tuolai,and Tuolainan mountains)and southern(including the Shulenan and Hark mountains)regions,respectively.Summer mean temperature has risen by 0.51℃(10 yr)^(−1)in the northern region and 0.48℃(10 yr)^(−1) in the southern region during 1989–2014;however,the change in amplitude of annual precipitation was 2.69 mm yr^(−1) in the northern region and 4.77 mm yr^(−1) in the southern region for the same period.These changes can be ascribed as major driving factors for the differences in the changes in glacial elevation in the northern and southern regions.Four types of glaciers existed in the region when considering the change in elevation of the glacial tongue and variation in the position of the glacial terminus:surging,advancing,intensively retreating,and slightly retreating glaciers.If elevation decreased more than 20 m on the part of glacier tongue,the glacier terminus position had commonly retreated more than 100 m.