Change detection in SAR time-series based on the coefficient of variation

This paper discusses change detection in SAR time-series. Firstly, several statistical properties of the coefficient of variation highlight its pertinence for change detection. Then several criteria are proposed. The coefficient of variation is suggested to detect any kind of change. Then other criteria based on ratios of coefficients of variations are proposed to detect long events such as construction test sites, or point-event such as vehicles. These detection methods are evaluated first on theoretical statistical simulations to determine the scenarios where they can deliver the best results. Then detection performance is assessed on real data for different types of scenes and sensors (Sentinel-1, UAVSAR). In particular, a quantitative evaluation is performed with a comparison of our solutions with state-of-the-art methods

Urban deformation monitoring in Bangkok metropolitan (Thailand) using permanent scatterer and differential interferometry techniques

Extensive ground water extraction has been identified as the principle cause of land subsidence in Bangkok and its vicinity. To mitigate major damages from large subsidence magnitudes the phenomenon must be well understood in this area. Up-to-date and reliable subsidence information is indispensable to develop this understanding. Conventionally, surface leveling has served as the primary method for measuring subsidence in Bangkok. But this is costly and time consuming. Differential SAR interferometry (DInSAR) can be an alternative means to obtain measurements of the surface displacement providing better resolution and comparable accuracy while being less time consuming. However, spatial and temporal decorrelation and atmospheric signal contributions in repeat-pass SAR interferometry often hamper the accurate measurement of surface displacements in SAR interferograms. The recently developed Permanent Scatterer (PS) technique invented by POLIMI researchers [1],[2],[3], overcomes these difficulties by interpreting time-series of interferometric phases at coherent point scatterers. In this study, we apply both DInSAR and PS techniques using two time-series of 17 and 11 ERS-SAR acquisitions for two partly overlapping image frames. This study is the first attempt to apply the PS technique to derive urban displacement information in Bangkok. We investigate the feasibility and reliability of using this technique with relatively few acquisitions and in a tropical location for deformation estimation. Using a linear deformation model and network algorithm, we estimate spatially varying displacement rates for the metropolitan area. Our first PS estimation results agree well with available ground leveling measurements

PSInSAR Analysis in the Pisa Urban Area (Italy): A Case Study of Subsidence Related to Stratigraphical Factors and Urbanization

Permanent Scatterer Interferometry (PSI) has been used to detect and characterize the subsidence of the Pisa urban area, which extends for 33 km2 within the Arno coastal plain (Tuscany, Italy). Two SAR (Synthetic Aperture Radar) datasets, covering the time period from 1992 to 2010, were used to quantify the ground subsidence and its temporal evolution. A geotechnical borehole database was also used to make a correspondence with the detected displacements. Finally, the results of the SAR data analysis were contrasted with the urban development of the eastern part of the city in the time period from 1978 to 2013. ERS 1/2 (European Remote-Sensing Satellite) and Envisat SAR data, processed with the PSInSAR (Permanent Scatterer InSAR) algorithm, show that the investigated area is divided in two main sectors: the southwestern part, with null or very small subsidence rates (<2 mm/year), and the eastern portion which shows a general lowering with maximum deformation rates of 5 mm/year. This second area includes deformation rates higher than 15 mm/year, corresponding to small groups of buildings. The case studies in the eastern sector of the urban area have demonstrated the direct correlation between the age of construction of buildings and the registered subsidence rates, showing the importance of urbanization as an accelerating factor for the ground consolidation process

Analysis of permanent scatterers properties by land cover type in Ida-Virumaa

http://tartu.ester.ee/record=b2693107~S1*es

ANALYSIS OF X-BAND VERY HIGH RESOLUTION PERSISTENT SCATTERER INTERFEROMETRY DATA OVER URBAN AREAS

Persistent Scatterer Interferometry (PSI) is a satellite-based Synthetic Aperture Radar (SAR) remote sensing technique used to measure and monitor land deformation from a stack of interferometric SAR images. This work concerns X-band PSI and, in particular, PSI based on very high resolution (VHR) StripMap CosmoSkyMed and TerraSAR-X SAR imagery. In fact, it mainly focuses on the technical aspects of deformation measurement and monitoring over urban areas. A key technical aspect analysed in this paper is the thermal expansion component of PSI observations, which is a result of temperature differences in the imaged area between SAR acquisitions. This component of PSI observations is particularly important in the urban environment. This is an interesting feature of PSI, which can be surely used to illustrate the high sensitivity of X-band PSI to very subtle displacements. Thermal expansion can have a strong impact on the PSI products, especially on the deformation velocity maps and deformation time series, if not properly handled during the PSI data processing and analysis, and a comprehensive discussion of this aspect will be provided in this paper. The importance of thermal expansion is related to the fact that the PSI analyses are often performed using limited stacks of images, which may cover a limited time period, e.g. several months only. These two factors (limited number of images and short period) make the impact of a non-modelled thermal expansion particularly critical. This issue will be illustrated considering different case studies based on TerraSAR-X and CosmoSkyMed PSI data. Besides, an extended PSI model which alleviates this problem will be described and case studies from the Barcelona metropolitan area will demonstrate the effectiveness of the proposed strategy

Analyse flächenhafter Senkungserscheinungen in sedimentären Gebieten mit den neuen Techniken der Radarfernerkundung : am Beispiel der Niederrheinischen Bucht

Die vorliegende Arbeit versucht das am DLR zu Forschungszwecken entwickelte Permanent Scatterer Verfahren zum ersten Mal in einem eher ländlichen Gebiet anzuwenden. Im Arbeitsgebiet in der südlichen Niederrheinischen Bucht kam es in Folge von Sümpfungsmaßnahmen zu Absenkungen der Erdoberfläche. Gegenstand der Untersuchungen dieser Arbeit waren zum einen die Anwendung der neuen Permanent Scatterer Technik im Untersuchungsgebiet und deren Verifizierung und Validierung, um zu neuen objektiven Informationsquellen hinsichtlich der Bewegungsbeobachtung zu gelangen. Zum anderen wurde versucht, zu einer verbesserten Wahrnehmung von Bodenbewegungsphänomenen mit den gewonnenen fernerkundlichen Daten beizutragen, um als Interpretationshilfe der Bewegungsmechanismen dienen zu können. Die geschätzten linearen Absenkungsraten an den PS wurden mit den aus den Nivellementmessungen des Landesvermessungsamtes NRW (LVermA NRW) ermittelten Deformationsdaten verglichen. Der Vergleich von Nivellement- und PS-Messungen an Punkten, Profillinien und in der Fläche erbrachte, dass die relative Schätzung der Bewegungsraten an den PS eine gute Übereinstimmung mit dem Datensatz aus den Nivellements ergibt. Die Genauigkeit beider Verfahren (Nivellement und Permanent Scatterer) und die zeitliche Auflösung der Daten führen zu einer Bewertung des PS Verfahrens. Die Schlussfolgerung aus dieser Bewertung ist, dass das PS System erfolgreich zur großräumigen Beobachtung von Absenkungserscheinungen auch in eher ländlichen Gebieten geeignet ist. Die vorliegende Untersuchung zeigt eine Möglichkeit der erweiterten Wahrnehmung mittels Fernerkundung von Bewegungen an der Erdoberfläche auf. Diese Arbeit kann damit weitere Modelluntersuchungen unterstützen und helfen die komplexen Bewegungsabläufe in den Senkungsgebieten der Niederrheinischen Bucht zu entschlüsseln. Das Ziel der Arbeit, den Zugewinn objektiver Informationen hinsichtlich Bodenbewegungsbeobachtungen und das Schaffen von geeigneten Randbedingungen im Bezug auf die Diskussion und Interpretation der Bewegungsmechanismen, wurde damit erreicht.Investigation of extensive subsidence in a sedimentary region by means of new techniques of the radarinterferometry – in the region of the Lower Rhine Embayment The present work applies the research system of the Permanent Scatterer method developed by the German Aerospace Center to a rural area for the first time. Withdrawal procedures have led to subsidence at the earth surface in the area under investigation, the brown coal area in the Lower Rhine Embayment. The objective of this thesis is to apply the Permanent Scatterer technique to the test site and to verify and validate the measuring. Furthermore, there was the effort to come to interpretation approaches of the deformation mechanism by means of the radar interferometry. The results of the PS analysis, the estimated deformation rates at the point targets (the Permanent Scatterers), were compared with levelling data of the land surveying office. The comparison and the accuracy of the data sets (levelling and Permanent Scatterer) and the resolution in time with the ground truth data and the remote sensing data led to an evaluation of the new Permanent Scatterer technique. The PS system is an outstanding tool to observe deformation within large areas even in rural regions. The present work shows a possibility of an improved cognition of deformations on the earth surface by means of remote sensing. These studies can encourage further model analysis and help to map the complex deformation sequences in the subsidence area of the Lower Rhine Embayment. Therewith, the aim of this thesis, the gain of objective information concerning ground deformation observations and the creation of adequate boundary conditions regarding the discussion and the interpretation of the deformation mechanisms, was successfully achieved

URBAN MONITORING BASED ON SENTINEL-1 DATA USING PERMANENT SCATTERER INTERFEROMETRY AND SAR TOMOGRAPHY

A lot of research and development has been devoted to the exploitation of satellite SAR images for deformation measurement and monitoring purposes since Differential Interferometric Synthetic Apertura Radar (InSAR) was first described in 1989. In this work, we consider two main classes of advanced DInSAR techniques: Persistent Scatterer Interferometry and Tomographic SAR. Both techniques make use of multiple SAR images acquired over the same site and advanced procedures to separate the deformation component from the other phase components, such as the residual topographic component, the atmospheric component, the thermal expansion component and the phase noise. TomoSAR offers the advantage of detecting either single scatterers presenting stable proprieties over time (Persistent Scatterers) and multiple scatterers interfering within the same range-azimuth resolution cell, a significant improvement for urban areas monitoring. This paper addresses a preliminary inter-comparison of the results of both techniques, for a test site located in the metropolitan area of Barcelona (Spain), where interferometric Sentinel-1 data were analysed

Impact of high resolution radar imagery on reservoir monitoring

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