Monitoring Mining Activities Using Sentinel-1A InSAR Coherence in Open-Pit Coal Mines

Lili Wang,Baili Chen,Liao Yang,Xiaolin Sun,Weisheng Wang

doi:10.3390/rs13214485

Abstract

Long-term continuous monitoring of the mining activities in open-pit coal mines is conducive to planning and management of the mining operations. Additionally, this faciliatates assessment on their environmental impact and supervises illegal mining behaviors. Interferometric Synthetic Aperture Radar (InSAR) technology can be effectively applied in the monitoring of open-pit mines where vegetation is sparse and land cover is dominated by bare rock. The main objective of this study is to monitor the mining activities of four open-pit coal mines in the Wucaiwan mining area in China from 2018 to 2020, namely No. 1, No. 2 (containing two mining areas), and No. 3. We use the normalized differential activity index (NDAI) based on the coherence coefficient as an indicator of the mine activity due to its robustness to temporal and spatial decorrelation. After analyzing and removing the decorrelation caused by rain and snow weather, 70 NDAI images in 12-day intervals are obtained from Sentinel-1A InSAR coherence images. Then, the annually-averaged NDAI images are applied to an RGB composite technique (red for 2018, green for 2019, blue for 2020) to express the interannual variation of the mining activities. Points of interest are then selected for NDAI time series analysis. The RGB composite results indicated that No. 1 and 3 open-pit coal mines were continuously mined during the three years; whereas, the two mining areas of No. 2 were mainly active in 2018. The 12-day NDAI time-series graphs of No. 2 open-pit coal mine also indicate that the coal piles located in the coal transferring area of the first mining area were not completely removed until April 2019. It is also seen that the second mining area was decommissioned in November 2018 and became rehabilitated in July 2019. Results were validated using the Sentinel-2A images and related background information confirming the efficiency of the proposed approach for monitoring the mining activity in open-pit mines.

Highlights

Open-pit coal mining activity often causes large-scale and high-intensity ecological disturbances, resulting in substantial impacts such as surface damage, air pollution, soil erosion, and degradation of ecosystem functions [1]
Compared with the coherence values that phasize surface stability, normalized difference activity index (NDAI) is used to represent the degree of surface activity, which is suitable for monitoring active mining areas
The decorrelation noise due to emphasize surface stability, NDAI is used to represent the degree of surface activity, which is suitable for monitoring active mining areas

Summary

Introduction

Open-pit coal mining activity often causes large-scale and high-intensity ecological disturbances, resulting in substantial impacts such as surface damage, air pollution, soil erosion, and degradation of ecosystem functions [1]. Open-pit coal mining is the domi-nant production method in the Wucaiwan mine located in the western part of the Zhundong coalfield at Xinjiang, China. Since the development of this coalfield in 2006, coal mining and coal-chemical industry have significantly affected the surrounding eco-logical environment [2]. Illegal mining can cause extra environmental issue as they often ignore regulated mining methods [4]. Continuous monitoring of open-pit coal mining activities is an utmost necessity and enables efficient planning and managing of mining operations by accessing their impact on the environment and enforcing relevant regulations

Objectives

Methods

Discussion

Conclusion