Abstract
The offset-tracking method (OTM) utilizing SAR image intensity can detect large deformations, which makes up for the inability of interferometric synthetic aperture radar (InSAR) technology in large mining deformation monitoring, and has been widely used. Through lots of simulation experiments, it was found that the accuracy of OTM is associated with deformation gradients and image noises in the cross-correlation window (CCW), so CCW sizes should be selected reasonably according to deformation gradients and noise levels. Based on the above conclusions, this paper proposes an adaptive CCW selection method based on deformation gradients and image noises for mining deformation monitoring, and this method considers influences of deformation gradients and image noises on deformations to select adaptive CCWs. In consideration of noise influences on offset-tracking results, smaller CCWs are selected for large deformation gradient areas, and larger CCWs are selected for small deformation gradient areas. For some special areas, special CCWs are selected for offset-tracking. The proposed method is implemented to simulation and real experiments, and the experiment results demonstrate that the proposed method with high reliability and effectiveness can significantly improve the accuracy of OTM in mining deformation monitoring.
Highlights
Published: 27 July 2021Underground mining usually induces severe ground subsidence [1,2,3,4]
We found that using small cross-correlation window (CCW) can ensure deformation accuracy, but it is difficult to suppress image noises; using large CCWs can better suppress image noises, but using large CCWs in larger deformation gradient areas will result in deformation compression and accurate deformations cannot be obtained
According to the conclusion of simulation experiments, this paper proposes an adaptive CCW selection method based on deformation gradients and image noises to improve the accuracy of offsettracking method (OTM), and applies this method to the simulation experiment and the real experiment
Summary
Underground mining usually induces severe ground subsidence [1,2,3,4]. In China, under the condition of longwall mining, simultaneous ground subsidence can reach several meters in a few days [5,6]. Accurate information on mining subsidence is crucial for studying the deformation characteristics of the overlying strata, for maintaining the safety of underground excavation, and for assessing the impacts on the local ecological environment imposed by mining activities. Interferometric Synthetic Aperture Radar (InSAR) has broad applications in mining deformation monitoring, but may face one problem: the inability to retrieve large-scale deformations in mining areas, owing to temporal and spatial decorrelation [8]. The master and slave images with sizes of n × m pixels in Figure 1a have been registered, and the patch A with size of n × m pixels in the master image and the patch B with size of n × m pixels at the same position in the slave image are patches to Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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