title: A Robust and Multi-Weighted Approach to Estimating Topographically Correlated Tropospheric Delays in Radar Interferograms.
abstract: Spatial and temporal variations in the vertical stratification of the troposphere introduce significant propagation delays in interferometric synthetic aperture radar (InSAR) observations. Observations of small amplitude surface deformations and regional subsidence rates are plagued by tropospheric delays, and strongly correlated with topographic height variations. Phase-based tropospheric correction techniques assuming a linear relationship between interferometric phase and topography have been exploited and developed, with mixed success. Producing robust estimates of tropospheric phase delay however plays a critical role in increasing the accuracy of InSAR measurements. Meanwhile, few phase-based correction methods account for the spatially variable tropospheric delay over lager study regions. Here, we present a robust and multi-weighted approach to estimate the correlation between phase and topography that is relatively insensitive to confounding processes such as regional subsidence over larger regions as well as under varying tropospheric conditions. An expanded form of robust least squares is introduced to estimate the spatially variable correlation between phase and topography by splitting the interferograms into multiple blocks. Within each block, correlation is robustly estimated from the band-filtered phase and topography. Phase-elevation ratios are multiply- weighted and extrapolated to each persistent scatter (PS) pixel. We applied the proposed method to Envisat ASAR images over the Southern California area, USA, and found that our method mitigated the atmospheric noise better than the conventional phase-based method. The corrected ground surface deformation agreed better with those measured from GPS.
authors.affiliation: School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan 430079, China. byz@whu.edu.cn.
authors.forename: Bangyan
authors.initials: B
authors.lastname: Zhu
authors.affiliation: School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan 430079, China. jcli@sgg.whu.edu.cn.
authors.forename: Jiancheng
authors.initials: J
authors.lastname: Li
authors.affiliation: Nanjing Institute of Surveying, Mapping and Geotechnical Investigation, Nanjing 210019, China. zby7edgar@126.com.
authors.forename: Zhengwei
authors.initials: Z
authors.lastname: Chu
authors.affiliation: State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China. weitang@whu.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Tang
authors.affiliation: School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan 430079, China. binwangsgg@whu.edu.cn.
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.affiliation: School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan 430079, China. dwli@sgg.whu.edu.cn.
authors.forename: Dawei
authors.initials: D
authors.lastname: Li
keywords: InSAR; least squares; persistent scatterer interferometry; robust estimation; tropospheric delay