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Abstract
Due to the side-looking imaging geometry of the current synthetic aperture radar (SAR) sensors, only ground deformation along the radar’s line-of-sight (LOS) and azimuth directions can be potentially obtained from a single amplitude pair (SAP) of SAR using offset tracking (OT) procedures. This significantly hinders the accurate assessment of mining-related hazards and better understanding of the mining subsidence mechanism. In this paper, we propose a method for completely retrieving three-dimensional (3-D) mining-induced displacements with OT-derived observations of LOS deformation from a single amplitude pair of SAR (referred to as OT-SAP hereinafter). The OT-SAP method first constructs two extra constraints at each pixel of the mining area based on the proportional relationship between the horizontal motion of the mining area and the gradients of the vertical subsidence in the east and north directions. The full 3-D mining-induced displacements are then solved by coupling the two constructed extra constraints with the OT-derived observations of the LOS deformation. The Daliuta coal mining area in China was selected to test the proposed OT-SAP method. The results show that the maximum 3-D displacements of this mining area were about 4.3 m, 1.1 m, and 1.3 m in the vertical, east, and north directions, respectively, from 21 November 2012 to 6 February 2013. The accuracies of the retrieved displacements in the vertical and horizontal directions are about 0.201 m and 0.214 m, respectively, which are much smaller than the mining-induced displacements in this mining area and can satisfy the basic requirements of mining deformation monitoring.
Highlights
It is crucial to measure the full three-dimensional (3-D) surface displacements caused by underground extraction, to allow for better understanding of the mechanism of mining subsidence and to accurately assess mining-related hazards.The capability of interferometric synthetic aperture radar (InSAR) techniques to monitor the surface deformation associated with the Earth and/or anthropic activities has been presented in many studies (e.g., [1,2,3,4,5,6,7,8,9,10,11])
The real data experiment based on the Daliuta coal mining subsidence, but sharply magnified to the estimated 2-D
In addition to the errors of the LOS deformation estimated 3-D displacements demonstrated that the accuracies of the estimated displacements in observations, ground fissures may be another factor causing the large discrepancies over the three the vertical and horizontal directions were about 0.201 m and 0.214 m, respectively
Summary
It is crucial to measure the full three-dimensional (3-D) surface displacements caused by underground extraction, to allow for better understanding of the mechanism of mining subsidence and to accurately assess mining-related hazards (e.g., landslides and damage to surface infrastructure).The capability of interferometric synthetic aperture radar (InSAR) techniques to monitor the surface deformation associated with the Earth and/or anthropic activities has been presented in many studies (e.g., [1,2,3,4,5,6,7,8,9,10,11]). Over the past few decades, several InSAR-based approaches have been developed for measuring the 3-D surface displacements associated with geophysical activities such as earthquakes and volcanic eruptions These approaches can be roughly divided into three categories: (i) differential InSAR (DInSAR)-based methods (e.g., [12,13,14,15]); (ii) offset tracking (OT)-based methods (e.g., [16,17,18,19,20,21,22,23]); and (iii) multi-aperture InSAR (MAI)-based methods (e.g., [24,25]). One of the significant limitations of all of these methods is that nearly synchronous SAR images from at least two different imaging geometries (e.g., ascending and descending orbits) are needed This problem was partially solved in [27,28] when looking at rapidly deforming glaciers, but two problems arise if these methods are applied to retrieve 3-D mining-related displacements. If only asynchronous SAR images from two different imaging geometries are available, large errors are most likely to be contained in the estimated 3-D displacements, due to the high nonlinearity of mining-related deformation [29,30]
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