Subsidence monitoring in coal area using time-series InSAR combining persistent scatterers and distributed scatterers

https://doi.org/10.1016/j.jag.2015.02.007Get rights and content

Highlights

  • Both classification and statistical characteristics are applied for DS identification.

  • Two-scale network on PSs and DSs is proposed to improve the computational efficiency.

  • Spatial density of measurement points increases greatly especially in natural area.

Abstract

In coal mining areas, ground subsidence persistently happens, which produces serious environmental issues and affects the development of cities. To monitor the ground deformation due to coal mining, a modified time-series InSAR technique combining persistent scatterers (PSs) and distributed scatterers (DSs) is presented in this paper. In particular, DSs are efficiently identified using classified information and statistical characteristics. Furthermore, a two-scale network is introduced into traditional PSI to deal with PSs and DSs in a multi-layer framework by taking the advantage of the robust of PSs and the widely distribution of DSs. The proposed method is performed to investigate the subsidence of Huainan City, Anhui province (China), during 2012–2013 using 14 scenes of Radarsat-2 images. Experimental results show that the proposed method can ease the estimation complexity and significantly increase the spatial density of measurement points, which can provide more detailed deformation information. Result shows that there are obvious subsidence areas detected in the test site with subsidence velocity larger than 5 cm/year. The proposed method brings practical applications for non-urban area deformation monitoring.

Introduction

With the rapid development, the demand for mining underground energy resource becomes more and more enormous in China. The exploitation of underground coal often causes persistent land subsidence, which would lead to huge threats to infrastructure and safety in the coal area (Jung et al., 2007, Baek et al., 2008). Subsidence monitoring and surveys in coal areas are urgently needed, which can provide knowledge for the hazard warning system. Traditional leveling and GPS data are able to produce reliable measurement of ground subsidence (Demoulin et al., 2005). However, these field surveys are time-consuming and cannot provide deformation map with high spatial sampling density.

Synthetic aperture radar (SAR) interferometry (InSAR) is a powerful technology, which can obtain high precise elevation and surface deformation along the line of sight (LOS) using phase information from different SAR images. DInSAR technique has been applied to monitor the surface movement in coal mining areas (Ng et al., 2009, Ge et al., 2007). However, conventional DInSAR usually suffers from temporal, geometrical and atmospheric decorrelation (Zebker et al., 1997, Zebker and Villasenor, 1992). To overcome these limitations, several advanced techniques have been proposed, such as Persistent Scatterer Interferometry (PSI) (Ferretti et al., 2001, Hooper et al., 2004), small baseline subset algorithm (SBAS) (Berardino et al., 2002), coherent pixels technique (CT) (Mora et al., 2003), and partially coherent targets technique (P-CTs) (Prati et al., 2010, Tao et al., 2012). These techniques have been applied in several studies to retrieve ground movement due to underground mining (Ng et al., 2010, Perski et al., 2009, Jiang et al., 2012, Zakharov et al., 2013, Guéguen et al., 2009). However, these methods have some limitations in mapping the mining-induced subsidence due to low density of PSs or coherent points and their inhomogeneous distribution. In recent years, distributed scatterers interferometry (DSI) (Guarnieri and Tebaldini, 2008, Ferretti et al., 2011, Goel and Adam, 2014, Wang et al., 2012) has been proposed to monitor the surface deformation of large scale suburb areas. Most coal areas are located in suburbs areas, in where man-made objects are too sparse to obtain enough measure points for PSI. But the bare soil areas, land covered by sparse vegetable or debris areas (referring them as DSs) are widely distributed, which can be selected as measure points for subsidence monitoring.

In this work, we present an approach to obtain ground subsidence due to mining in Huainan City, China using time-series InSAR technique combining PSs and DSs by taking the advantage of the robust of PSs and the widely distribution of DSs. To increase the spatial density of measure points, a new processing method using both classified information and statistical characteristics is proposed to identify DSs. To decrease the computationally difficulty and control error propagation, a two-scale network is introduced in the processing of PSs and DSs, which deals with PSs and DSs in a multi-layer schema from high phase quality to low. Linear deformation rate and DEM error of PSs are first retrieved using conventional PSI (Ferretti et al., 2001), and then the deformation parameters of DSs are obtained under the constrain of the result of the PSs. A series of Radarsat-2HH polarization images collected in Huainan are used to verify the effectiveness of the proposed method. A dense ground surface deformation map is obtained. Experimental results show the potential application of the proposed method to retrieve ground movement in coal mining areas.

Section snippets

Proposed method

The block diagram of the proposed method is shown in Fig. 1. After all the SAR images are co-registered, the DSs are selected first by combining classified information and statistical characteristics. For simplicity, PSs are identified based on their coherence stability in the stack of the interferograms. Then, a two-scale network is constructed at PSs and DSs. Finally, linear deformation and nonlinear deformation components are retrieved using conventional PSI. It should be noticed that in the

Study area and data processing

Huainan, located in the Yangtze River Delta hinterland central of Anhui province, is rich in coal resource, accounted for 19% of the national vision of stocks of coal stock. There are total 14 pairs of key state-owned coal mines in Huainan. These mines are mostly located in central Huainan. Coal mining in Huainan is of great importance for local economic development. However, this anthropogenic activity has caused series land subsidence, which result in many series of environmental problems and

Conclusions

This paper has presented an approach to retrieve ground deformation over nonurban areas using time-series InSAR combining PSs and DSs. DSs can be efficiently identified by the new strategy using classified information and statistical characteristics. A two-scale network on PSs and DSs has been constructed, which may make parameter estimation easier and more efficient.

The approach has been applied to monitor the subsidence in coal mining areas of Huainan City, China from September 2012 to

Acknowledgments

This work was supported in part by the National Natural Science Foundation of China under Grants 41271425 and 41331176.

We would like to thank the anonymous reviewers for carefully reading the manuscript and providing valuable comments and suggestions.

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