remote sensing Article An Improved Multi-Sensor MTI Time-Series Fusion Method to Monitor the Subsidence of Beijing Subway Network during the Past 15 Years Li Duan 1,2,3, Huili Gong 1,2,3,*, Beibei Chen 1,2,3, Chaofan Zhou 1,2,3, Kunchao Lei 4, Mingliang Gao 1,2, Hairuo Yu 1,2,3, Qun Cao 1,2,3 and Jin Cao 1,2,3 1 Key Laboratory of the Ministry of Education Land Subsidence Mechanism and Prevention, Capital Normal University, Beijing 100048, China;
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[email protected] (J.C.) 2 College of Resources Environment and Tourism, Capital Normal University, Beijing 100048, China 3 Observation and Research Station of Groundwater and Land Subsidence in Beijing-Tianjin-Hebei Plain, MNR, Beijing 100048, China 4 Beijing Institute of Hydrogeology and Engineering Geology, Beijing 100195, China;
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[email protected]; Tel.: +86-10-6890-2339 Received: 19 May 2020; Accepted: 30 June 2020; Published: 2 July 2020 Abstract: Land subsidence threatens the stable operation of urban rail transit, including subways. Obtaining deformation information during the entire life-cycle of a subway becomes a necessary means to guarantee urban safety. Restricted by sensor life and cost, the single-sensor Multi-temporal Interferometric Synthetic Aperture Radar (MTI) technology has been unable to meet the needs of long-term sequence, high-resolution deformation monitoring, especially of linear objects.