Abstract
The monitoring of large-gradient deformation caused by coal mining is of great significance to the prevention and management of disasters in mining areas. The interferometric synthetic aperture radar (InSAR) method captures the small-gradient ground deformation on the edge of the subsidence basin accurately but is unreliable for capturing large-gradient deformation. The intensity-based pixel-tracking method (e.g., the normalized cross-correlation (NCC) method) can overcome the limitations of InSAR’s maximum detectable displacement gradient and incoherence. However, the pixel-tracking method is sensitive to template size. It is difficult to estimate ground subsidence accurately by the conventional pixel-tracking method with fixed template size. In this paper, the signal-to-noise ratio (SNR) is redefined and an improved locally adaptive template size method is proposed by identifying optimal template adaptively based on maximization of the redefined SNR. The constraint radius is used to constrain the search area in this improved method. The frequency of misrepresentation is reduced by finding the peak of the correlation coefficient surface within the search area. Both simulation data and real ground subsidence data are used to test this algorithm. The results show that this method can improve monitoring accuracy compared with the traditional pixel-tracking method for fixed template size.
Highlights
China is the world’s largest coal consumer and the largest coal producer
The root mean squared error (RMSE) and the mean absolute value of difference (MAVD) between the monitoring results and the GPS results were computed in both the strike and dip directions (Table 2)
The classic pixel-tracking method based on normalized crosscorrelation can overcome the limitations of the maximum detectable displacement gradient that interferometric synthetic aperture radar (InSAR) is subject to, but the accuracy of fixed template size method is severely affected by template size, especially in areas with a small area of subsidence and large subsidence gradient
Summary
China is the world’s largest coal consumer and the largest coal producer. With the rapid progress in Earth observation techniques in recent years, different interferometric synthetic aperture radar (D-InSAR) and time-series InSAR methods such as PS-InSAR [5,6,7,8], SBAS-InSAR [9,10,11,12,13,14,15,16], TCP-InSAR [17,18,19,20], and ITPA-InSAR [21, 22] have been proven to be effective methods with an accuracy of millimeters to centimeters for mapping ground deformation induced by various natural and anthropogenic causes Those methods are based on phase unwrapping and have significant limitations based on deformation gradient. The InSAR technique based on phase unwrapping can only obtain the deformation information of edge of the subsidence basin
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