A method of monitoring three-dimensional ground displacement in mining areas by integrating multiple InSAR methods

ABSTRACT

Underground mining often causes large-gradient vertical and horizontal displacement in ground surface, resulting in the losses of coherence and difficulties in phase unwrapping. This article presents an approach to determine three-dimensional ground displacements in mining areas with the large gradient or phase decorrelation by integrating multiple interferometric synthetic aperture radar (InSAR) methods. The core of the proposed method is that the offset-tracking method is employed to solve for the displacement with the large gradient or phase decorrelation. First, the displacements in the radar line-of-sight directions are obtained from two interferometric pairs with different viewing geometries by integrating the measurements of differential InSAR and offset tracking. Then, the displacements in the azimuthal directions are obtained from two interferometric pairs with different viewing geometries by integrating the measurements of multiple aperture interferometry and offset tracking. Finally, the three-dimensional ground displacement fields are inferred from these four independent, one-dimensional displacements using the least squares method and Helmert variance component estimation. We apply this method to obtain the three-dimensional ground displacement field in the Dongtan mine region. We compare the results with those of levelling and global positioning system surveys, and the root mean square errors of the results were 24 and 43 mm in the vertical direction and horizontal directions, respectively. The experimental results indicate that the proposed method can be used to estimate three-dimensional ground displacement fields in mining areas with large-gradient displacement and phase decorrelation.

Acknowledgements

We are grateful to the European Space Agency (ESA) for supplying the Envisat data and the Japan Aerospace Exploration Agency (JAXA) for supplying the ALOS data. We also want to express our sincere thanks to the Editor and the anonymous reviewers for their valuable comments and suggestions for this article. This work was supported by the National Natural Science Foundation of China: [Grant Numbers 41274007 and 41404003], the Taishan Scholars Program of Shandong Province: [Grant Number TSXZ201509], the Science and Technology Project of AQSIQ [Grant Number 2016QK176], and the Graduates Innovation Fund of Shandong University of Science and Technology: [Grant Numbers SDKDYC170206 and SDKDYC170208].

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China: [Grant Numbers 41274007 and 41404003]; Graduates Innovation Fund of Shandong University of Science and Technology: [Grant Numbers SDKDYC170206 and SDKDYC170208]; the Science and Technology Project of AQSIQ: [Grant Number 2016QK176]; and the Taishan Scholars Program of Shandong Province: [Grant Number TSXZ201509].