{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,2,21]],"date-time":"2025-02-21T16:14:40Z","timestamp":1740154480015,"version":"3.37.3"},"reference-count":44,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2020,8,24]],"date-time":"2020-08-24T00:00:00Z","timestamp":1598227200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"the National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41671417"],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"the Beijing Outstanding Young Scientist Program","award":["BJJWZYJH01201910028032"]},{"name":"Capacity Building for Sci-Tech Innovation Fundamental Scientific Research Funds","award":["01119530050175"]},{"name":"Beijing Natural Science","award":["8202008"]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"Identifying Persistent Scatterers (PSs) is one of the key processing steps of the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique. The number, density, and reliability of identified PSs directly affect the monitoring accuracy of land subsidence, especially in higher density urban environments. As a result of the side-looking viewing geometry of SAR, the layover effect poses a major challenge to the PS identification. This research proposes joint modeling of the PS-InSAR technique and RELAX algorithm for SAR tomography (PS-InSAR+RELAX) to detect single and double scatterers and to improve the identification and reliability of PSs. It has been demonstrated that RELAX improves separation of the scatterers when compared to two other spectral analysis methods for SAR tomography, Beam-Forming (BF) and Singular Value Decomposition (SVD). RELAX exhibits the least noise when the number of baseline changes from 15 to 30, and it can separate the scatterers at a lower Normal-Slant-Range (NSR) height than the two other methods. As RELAX can better identify, separate, and then filter out layover scatterers, the number and density of PSs identified by PS-InSAR+RELAX is reduced and visually simplified, suggesting that the method can effectively reduce the influence of the layover effect on the PS identification. Also, the PSs identified by PS-InSAR+RELAX are more coherent than those identified by the traditional PS-InSAR technique. The proposed technique has been applied to Sentinel-1A data acquired from 2014 to 2016, to monitor land subsidence in the city of Beijing, China. When evaluated against the leveling measurements, PS-InSAR+RELAX performs better than the traditional PS-InSAR technique, with the correlation coefficients (r) of r = 0.98 and r = 0.95, respectively.<\/jats:p>","DOI":"10.3390\/rs12172730","type":"journal-article","created":{"date-parts":[[2020,8,24]],"date-time":"2020-08-24T14:37:32Z","timestamp":1598279852000},"page":"2730","source":"Crossref","is-referenced-by-count":5,"title":["Integrating RELAX with PS-InSAR Technique to Improve Identification of Persistent Scatterers for Land Subsidence Monitoring"],"prefix":"10.3390","volume":"12","author":[{"given":"Di","family":"Zhou","sequence":"first","affiliation":[{"name":"College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China"},{"name":"State Key Laboratory Incubation Base of Urban Environmental Processes and Digital Simulation, Beijing 100048, China"},{"name":"Key Laboratory of 3-Dimensional Information Acquisition and Application, Ministry of Education, Beijing 100048, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1573-1925","authenticated-orcid":false,"given":"Anita","family":"Simic-Milas","sequence":"additional","affiliation":[{"name":"School of Earth, Environment and Society, Bowling Green State University, Bowling Green, OH 43403, USA"}]},{"given":"Jie","family":"Yu","sequence":"additional","affiliation":[{"name":"College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China"},{"name":"State Key Laboratory Incubation Base of Urban Environmental Processes and Digital Simulation, Beijing 100048, China"},{"name":"Key Laboratory of 3-Dimensional Information Acquisition and Application, Ministry of Education, Beijing 100048, China"},{"name":"Beijing Laboratory of Water Resources Security, Beijing Municipal Education Commission, Beijing 100048, China"}]},{"given":"Lin","family":"Zhu","sequence":"additional","affiliation":[{"name":"College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China"},{"name":"State Key Laboratory Incubation Base of Urban Environmental Processes and Digital Simulation, Beijing 100048, China"},{"name":"Beijing Laboratory of Water Resources Security, Beijing Municipal Education Commission, Beijing 100048, China"}]},{"given":"Beibei","family":"Chen","sequence":"additional","affiliation":[{"name":"College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China"},{"name":"State Key Laboratory Incubation Base of Urban Environmental Processes and Digital Simulation, Beijing 100048, China"},{"name":"Beijing Laboratory of Water Resources Security, Beijing Municipal Education Commission, Beijing 100048, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4246-026X","authenticated-orcid":false,"given":"Nijiati","family":"Muhetaer","sequence":"additional","affiliation":[{"name":"State Key Laboratory Incubation Base of Urban Environmental Processes and Digital Simulation, Beijing 100048, China"},{"name":"Beijing Laboratory of Water Resources Security, Beijing Municipal Education Commission, Beijing 100048, China"}]}],"member":"1968","published-online":{"date-parts":[[2020,8,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"94","DOI":"10.1016\/j.rse.2013.08.038","article-title":"Land subsidence in central Mexico detected by ALOS InSAR time-series","volume":"140","author":"Chaussard","year":"2014","journal-title":"Remote Sens. Environ."},{"key":"ref_2","first-page":"1421","article-title":"Urban Infrastructure Health Monitoring with Spaceborne Multi-temporal Synthetic Aperture Radar Interferometry","volume":"46","author":"Lin","year":"2017","journal-title":"Acta Geod. Cartogr. Sin."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2737","DOI":"10.1364\/JOSAA.24.002737","article-title":"Phase unwrapping in three dimensions with application to InSAR time series","volume":"24","author":"Hooper","year":"2007","journal-title":"JOSAA"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"78","DOI":"10.1016\/j.isprsjprs.2015.10.011","article-title":"Persistent Scatterer Interferometry: A review","volume":"115","author":"Crosetto","year":"2016","journal-title":"ISPSR J. Photogramm. Remote Sens."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1109\/36.898661","article-title":"Permanent scatterers in SAR interferometry","volume":"39","author":"Ferretti","year":"2001","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1029\/2004GL021737","article-title":"A new Method for Measuring Deformation on Volcanoes and Other Natural Terrains Deformation Using InSAR Persistent Scatterers","volume":"31","author":"Hooper","year":"2004","journal-title":"Geophys. Res. Lett."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2202","DOI":"10.1109\/36.868878","article-title":"Nonlinear Subsidence Rate Estimation Using Permanent Scatterers in Differential SAR Interferometry","volume":"38","author":"Ferretti","year":"2002","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"2243","DOI":"10.1109\/TGRS.2003.814657","article-title":"Linear and nonlinear terrain deformation maps from a reduced set of interferometric SAR images","volume":"41","author":"Mora","year":"2003","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2375","DOI":"10.1109\/TGRS.2002.803792","article-title":"A new algorithm for surface deformation monitoring based on small baseline differential SAR interferograms","volume":"40","author":"Berardino","year":"2002","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"3460","DOI":"10.1109\/TGRS.2011.2124465","article-title":"A newalgorithm for processing interferometric data-stacks: SqueeSAR","volume":"49","author":"Ferretti","year":"2011","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"5454","DOI":"10.1109\/TGRS.2013.2289370","article-title":"A distributed scatterer interferometry approach for precision monitoring of known surface deformation phenomena","volume":"52","author":"Goel","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"6662","DOI":"10.3390\/rs6076662","article-title":"An approach to persistent scatterer interferometry","volume":"6","author":"Crosetto","year":"2014","journal-title":"Remote Sens."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1016\/j.rse.2016.11.002","article-title":"Post-failure evolution analysis of a rainfall-triggered landslide by multi-temporal interferometry SAR approaches integrated with geotechnical analysis","volume":"188","author":"Confuorto","year":"2017","journal-title":"Remote Sens. Environ."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"530","DOI":"10.3390\/rs70100530","article-title":"PSI Deformation Map Retrieval by Means of Temporal Sublook Coherence on Reduced Sets of SAR Images","volume":"7","author":"Iglesias","year":"2015","journal-title":"Remote Sens."},{"key":"ref_15","first-page":"123","article-title":"Compressive Sensing in High-resolution 3D SAR Tomography of Urban Scenarios","volume":"4","author":"Liao","year":"2015","journal-title":"J. Radars"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1109\/MSP.2014.2312073","article-title":"Tomographic Processing of Interferometric SAR Data: Developments, applications, and future research perspectives","volume":"31","author":"Fornaro","year":"2014","journal-title":"IEEE Signal Process. Mag."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Chen, F.L., Wu, Y.H., and Zhang, Y.M. (2017). Motion and Structural Instability Monitoring of Ming Dynasty City Walls by Two-Step Tomo-PSInSAR Approach in Nanjing City, China. Remote Sens., 9.","DOI":"10.3390\/rs9040371"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"717","DOI":"10.1080\/2150704X.2019.1601276","article-title":"Optimization of PSInSAR networks with application to TomoSAR for full detection of single and double persistent scatterers","volume":"10","author":"Ma","year":"2019","journal-title":"Remote Sens. Lett."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2284","DOI":"10.1109\/TGRS.2008.2011632","article-title":"Detection of single scatterers in multidimensional SAR imaging","volume":"47","author":"De","year":"2009","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Zhang, M., and Burbey, T.J. (2016). Inverse modeling using PS-InSAR data for improved land subsidence simulation in Las Vegas Valley, Nevada. Hydrol. Process.","DOI":"10.1002\/hyp.10945"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"507","DOI":"10.1109\/TGRS.2003.809934","article-title":"Three\u2013Dimensional Focusing with Multipass SAR Data","volume":"41","author":"Fornaro","year":"2003","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"3497","DOI":"10.1109\/TGRS.2006.881748","article-title":"Imaging of Single and Double Scatterers in Urban Areas via SAR Tomography","volume":"44","author":"Fornaro","year":"2006","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_23","first-page":"302","article-title":"Improved RELAX Algorithm for SAR Tomography","volume":"25","author":"Ren","year":"2010","journal-title":"J. Data Acquis. Proc."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1783","DOI":"10.1109\/29.60109","article-title":"Performance study of conditional and unconditional direction-of-arrival estimation","volume":"38","author":"Stoica","year":"1990","journal-title":"IEEE Trans. Acoust. Speech. Signal Proc."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"702","DOI":"10.1109\/TGRS.2005.843567","article-title":"Three-dimensional multipass SAR focusing: Experiments with long-term spaceborne data","volume":"43","author":"Fornaro","year":"2005","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_26","first-page":"3194","article-title":"Joint multibaseline SAR interferometry","volume":"20","author":"Fornaro","year":"2005","journal-title":"EURASIP J. Appl. Signal Process."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1007\/BF01827811","article-title":"An Efficient Algorithm for Two-dimensional Frequency Estimation","volume":"7","author":"Li","year":"1996","journal-title":"Multidimens. Syst. Signal Proc."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"3567","DOI":"10.1109\/TGRS.2012.2183002","article-title":"Detection of Double Scatterers in SAR Tomography","volume":"50","author":"Pauciullo","year":"2012","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1086","DOI":"10.1109\/JSTARS.2015.2494376","article-title":"GLRT Based on Support Estimation for Multiple Scatterers Detection in SAR Tomography","volume":"9","author":"Budillon","year":"2016","journal-title":"IEEE J. Appl. Earth Observ. Remote Sens."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"D\u0103ni\u0219or, C., Fornaro, G., and Pauciullo, A. (2018). Super-Resolution Multi-Look Detection in SAR Tomography. Remote Sens., 10.","DOI":"10.3390\/rs10121894"},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Zhou, C.D., Gong, H.L., Zhang, Y.Q., Warner, T., and Wang, C. (2018). Spatiotemporal Evolution of Land Subsidence in the Beijing Plain 2003\u20132015 Using Persistent Scatterer Interferometry (PSI) with Multi-Source SAR Data. Remote Sens., 10.","DOI":"10.3390\/rs10040552"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Zhang, Y.H., Wu, H.A., Kang, Y.H., and Zhu, C.G. (2016). Ground Subsidence in the Beijing-Tianjin-Hebei Region from 1992 to2014 Revealed by Multiple SAR Stacks. Remote Sens., 8.","DOI":"10.3390\/rs8080675"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1917","DOI":"10.1109\/TGRS.2002.803848","article-title":"Burst-Mode and ScanSAR Interferometry","volume":"40","author":"Holzner","year":"2002","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"9239","DOI":"10.1002\/2015GL066003","article-title":"The 2014-2015 eruption of Fogo volcano: Geodetic modeling of Sentinel-1 TOPS interferometry","volume":"42","author":"Bagnardi","year":"2015","journal-title":"Geophys. Res. Lett."},{"key":"ref_35","first-page":"109","article-title":"WorldView-2 high-resolution satellite successfully launched","volume":"4","author":"Shang","year":"2009","journal-title":"Remote Sens. Land Res."},{"key":"ref_36","first-page":"1","article-title":"Basic Principles, Key Techniques and Applications of Tomographic SAR Imaging","volume":"40","author":"Lin","year":"2015","journal-title":"J. Geomatics."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"234","DOI":"10.1029\/2011EO280002","article-title":"Open Radar Interferometry Software for Mapping Surface Deformation","volume":"92","author":"Sandwell","year":"2011","journal-title":"Eos Trans. AGU"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Farr, T., Rosen, P., Caro, E., Crippen, R., Duren, R., Hensley, S., and Alsdorf, D. (2007). The shuttle radar topography mission. Rev. Geophys., 45.","DOI":"10.1029\/2005RG000183"},{"key":"ref_39","first-page":"1","article-title":"Recent advances in SAR interferometry time series analysis for measuring crustal deformation","volume":"514","author":"Hooper","year":"2011","journal-title":"Tectonophysics"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1016\/j.rse.2015.08.035","article-title":"Statistical comparison of InSAR tropospheric correction techniques","volume":"170","author":"Bekaert","year":"2015","journal-title":"Remote Sens. Environ."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"553","DOI":"10.1002\/qj.828","article-title":"The ERA-Interim reanalysis: Configuration and performance of the data assimilation system","volume":"137","author":"Dee","year":"2011","journal-title":"Q. J. R. Meteorol. Soc."},{"key":"ref_42","first-page":"8","article-title":"Accuracy Analysis and Evaluation of InSAR Land Subsidence Monitoring","volume":"30","author":"Wang","year":"2015","journal-title":"Remote Sens. Inf."},{"key":"ref_43","first-page":"1","article-title":"A Nearest Neighbor Index Clustering Algorithm for Ecological Regionalization Based on Multi-layer Grid Model","volume":"13","author":"Yuan","year":"2011","journal-title":"Geo-Inf. Sci."},{"key":"ref_44","first-page":"73","article-title":"Application of spaceborne interferometric synthetic aperture radar to geohazard monitoring","volume":"9","author":"Yun","year":"2020","journal-title":"J. Radars"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/12\/17\/2730\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,1,7]],"date-time":"2025-01-07T03:56:40Z","timestamp":1736222200000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/12\/17\/2730"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,8,24]]},"references-count":44,"journal-issue":{"issue":"17","published-online":{"date-parts":[[2020,9]]}},"alternative-id":["rs12172730"],"URL":"https:\/\/doi.org\/10.3390\/rs12172730","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2020,8,24]]}}}