Persistent Scatterer Interferometry Approach Research Articles

Fully Integrated Temporary Persistent Scatterer Interferometry

The persistent scatterer interferometry (PSI) is a powerful remote sensing technique to monitor displacements of the Earth’s surface. It is based on identifying and analyzing phase-stable scatterers undergoing marginal decorrelation over time. Most PSI approaches constrain the analysis to scatterers which are coherent over the whole considered time series (PS) and neglect scatterers which are only temporary persistent (TPS). Here, we propose a method to fully integrate TPS into an existing PSI approach which is characterized by an iterative parameter estimation with subsequent phase unwrapping. We build on a previously published method to identify TPS and estimate their coherent lifetime based on amplitude statistics. A phase-based likelihood ratio test is proposed to iteratively refine the appearing/fading dates of TPS during the parameter estimation. Finally, we jointly unwrap the phase observations of PS and TPS to receive displacement time series. The temporal datum of TPS is re-defined if their lifetime does not cover the selected master scene. Experimental results based on Sentinel-1 data in the Vietnamese city of Ca Mau show that the change date refinement significantly increases the average coherence and number of identified TPS. The densification of the observation point network by incorporating TPS helps to better detect and understand displacement phenomenons. The displacement time series of TPS are beneficial to analyze nonlinear motion in connection with urban development, like initial settlement of newly constructed buildings.

An innovative extraction methodology of active deformation areas based on sentinel-1 SAR dataset: the catalonia case study

ABSTRACT Persistent scatterer interferometry (PSI) has been proved to be an advanced Interferometric Synthetic Aperture Radar (InSAR) technique used to measure and monitor terrain deformation. Two of the critical problems with InSAR have been the effect of the refractive atmosphere and decorrelation on the interferometric phases due to long spatial-temporal baseline. The low density of persistent scatterers (PS) in non-urban areas affected by spatial-temporal decoherence more seriously has inspired the development of alternative approaches. Sentinel-1 (S1) has improved the data acquisition throughout, and compared to previous sensors, increased considerably the differential interferometric SAR (DInSAR) and PSI deformation monitoring potential. This paper describes an innovative methodology to process S1 SAR data. Different with PSI, its most original part includes two key processing stages: high and low frequency splitting from wrapped phases, prior to atmospheric filtering, and final direct integration to generate the complete deformation with time series containing linear and nonlinear components. The proposed method has two fundamental advantages compared with traditional PSI approach: the final monitoring results with excellent coverage of coherent points and the generation of active maps even for the areas with serious deformation in short term to break through the inherent limitation of PSI. The effectiveness of the proposed tools is illustrated using a case study located in Catalonia (Spain). This methodology has supposed a definitive step towards the implementation of DInSAR based techniques to support decision makers against geohazards. In this work, the deformation procedures happened in three different areas of the Catalonia (Spain) are presented and analysed. The maximum accumulated subsidence of over – 60 cm induced by mining activity can be detected by proposed methodology with nice coverage from January 2017 to January 2019. These reported cases illustrate how DInSAR based techniques can provide detailed terrain deformation for geohazard activity with complex topographical conditions. The active deformation areas map can be generated in fast aimed at geohazard risk early warning and management.

Ordu-Giresun Havalimanı'nın sürekli saçıcılar interferometrisi (PSI) ile deformasyon analizi

Nowadays, many countries cannot meet the land demands caused by rapid urbanization. This problem is even greater especially for coastal cities and land filling projects have been produced in order to eliminate this problem. In Turkey, there are also many applications similar to this type of projects. One of the most important of these projects is Ordu-Giresun Airport, which was built on the Eastern Black Sea coast close to the Ordu-Giresun provincial border. The foundation of the land, which was built with filling on the sea, is sensitive to settlement and geologically active. This can have adverse effects especially in areas with high population. Ensuring operational security at airports built on such areas is vital in terms of public security and surface deformation should be monitored at regional scale to ensure this security. In this study, the surface deformation of Ordu-Giresun Airport, which was founded in 2011 and became operational in 2015, was determined. For this purpose, Sentinel-1A/B images were obtained in a descending trajectory in geometry covering the same areas, and time series were analyzed with the Persistent Scatterer Interferometry (PSI) technique. Time series were created by using SNAP and Stanford Method Permanent Distributions (StaMPS) package programs offered to the user free of charge with the PSI approach. As a result, it was determined that the deformation at Ordu-Giresun Airport between August 2017 and February 2019 was approximately rates from -14 to 9 mm. In future studies, it is planned to monitor the deformation of the airport in a wider time interval and in two different orbits.

Implementation of Non-Linear Non-Parametric Persistent Scatterer Interferometry and Its Robustness for Displacement Monitoring.

To derive surface displacement, interferometric stacking with synthetic aperture radar (SAR) data is commonly used, and this technique is now in the implementation phase in the real world. Persistent scatterer interferometry (PSI) is one of the most universal approaches among in- terferometric stacking techniques, and non-linear non-parametric PSI (NN-PSI) was proposed to overcome the drawbacks of PSI approaches. The estimation of the non-linear displacements was successfully conducted using NN-PSI. However, the estimation of NN-PSI is not always stable with certain displacements because wider range of the velocity spectrum is used in NN-PSI than the conventional approaches; therefore, a calculation procedure and parameter optimization are needed to consider. In this paper, optimized parameters and procedures of NN-PSI are proposed, and real data processing with Sentinel-1 in the Kanto region in Japan was conducted. We confirmed that the displacement estimation was comparable to the measurement of the permanent global positioning system (GPS) stations, and the root mean square error between the GPS measurement and NN-PSI estimation was less than 3 mm in two years. The displacement over 2 ambiguity, which the conventional PSI approach wrongly reconstructed, was also quantitatively validated and successfully estimated by NN-PSI. As a result of the real data processing, periodical displacements were also reconstructed through NN-PSI. We concluded that the NN-PSI approach with the proposed parameters and method enabled the estimation of several types of surface displacements that conventional PSI approaches could not reconstruct.

Analysis and Classification of Natural and Human-Induced Ground Deformations at Regional Scale (Campania, Italy) Detected by Satellite Synthetic-Aperture Radar Interferometry Archive Datasets

The high levels of geo-hydrological, seismic, and volcanic hazards in the Campania region prompted full data collection from C-band satellites ERS-1/2, ENVISAT, and RADARSAT within regional (TELLUS) and national (PST-A) projects. The quantitative analysis, interpretation, and classification of natural and human-induced slow-rate ground deformations across a span of two decades (1992–2010) was performed at regional scale (Campania, Italy) by using interferometric archive datasets, based on the Persistent Scatterer Interferometry approach. As radar satellite sensors have a side-looking view, the post-processing of the interferometric datasets allows for the evaluation of two spatial components (vertical and E-W horizontal ones) of ground deformation, while the N-S horizontal component cannot be detected. The ground deformation components have been analyzed across 89.5% of the Campania territory within a variety of environmental, topographical, and geological conditions. The main part (57%) of the regional territory was characterized during 1992–2010 by stable areas, where SAR signals do not have recorded significant horizontal and vertical components of ground deformation with an average annual rate greater than +1 mm/yr or lower than −1 mm/yr. Within the deforming areas, the coastal plains are characterized by widespread and continuous strong subsidence signals due to sediment compaction locally enhanced by human activity, while the inner plain sectors show mainly scattered spots with locally high subsidence in correspondence of urban areas, sinkholes, and groundwater withdrawals. The volcanic sectors show interplaying horizontal and vertical trends due to volcano-tectonic processes, while in the hilly and mountain inner sectors the ground deformation is mainly controlled by large-scale tectonic activity and by local landslide activity. The groundwater-related deformation is the dominant cause of human-caused ground deformation. The results confirm the importance of using Persistent Scatterer Interferometry data for a comprehensive understanding of rates and patterns of recent ground deformation at regional scale also within tectonically active areas as in Campania region.

MONITORING LANDSLIDES IN THE MUSSOORIE REGION, UTTARAKHAND USING MULTI-TEMPORAL SAR INTERFEROMETRY WITH SENTINEL-1 IMAGES

Abstract. Occurrence of landslide events are common in the lesser Himalayan region which lie in a tectonically active zone with unstable slopes. The Mussoorie region is situated in the lesser Himalayas and is one of most visited tourist sites of the Uttarakhand state. The region is facing social and economic crisis due to the damage caused by multiple landslide events, which requires continuous monitoring for better planning and rescue operations. This study shows the time series analysis of landslide events occurring in the Mussoorie region using the Persistent Scatterer Interferometry (PSI) technique on Sentinel-1 synthetic aperture radar (SAR) images. The processing steps required to process the Sentinel-1 data stacks using both differential SAR interferometry (DInSAR) and PSI are presented. 13 Sentinel-1A C-band interferometric wide swath (IW) images covering a time period of one year are used for PSI processing, resulting in the generation of 12 differential interferograms. The PSI approach extracted 5593 measurement points in the study area. The one dimensional line of sight (1D LOS) time series displacement estimates obtained from PSI processing show a maximum velocity of −55.7 mm year−1 in the radar line of sight (LOS) direction, indicating subsidence. The displacement map further used to characterize the landslide susceptible zones show higher displacement magnitude for areas near Jabarkhet, Bhataghat, Bansagad and Raipur range. Use of more Sentinel-1 images and better DInSAR processing algorithms can improve the displacement estimation and pattern detection.

Combination of Persistent Scatterer Interferometry and Single-Baseline Polarimetric Coherence Optimisation to Estimate Deformation Rates with Application to Tehran Basin

This study reports on the monitoring of land subsidence in a rural area located in the southwest of the Tehran basin, Iran, by combining a persistent scatterer interferometry (PSI) method with a single-baseline polarimetric coherence optimisation. Owing to vegetation coverage in this rural area, coherence level experiences a decline and the performance and coverage of conventional interferometry to estimate deformation rate reduces concomitantly. Since the launch of satellites with polarimetric information, the polarimetric InSAR (PolInSAR) technique, which is vector interferometry with different polarimetric channels, has been introduced to optimise the coherence level. One of the most common criteria to select PS pixels is coherence and maximising the coherence can lead to an increased number of selected PS pixels and enhanced PSI performance. The single-baseline polarimetric coherence optimisation method assumes equal polarisation states at the end of each baseline. In order to apply this technique in our study, two different multi-look windows for coherence calculation and also two TerraSAR-X data sets with different numbers of images are used to assess their effect on the polarimetric PSI. Combination of the single-baseline coherence optimisation method with PSI shows significant improvements (more than 50%) in terms of the number of selected PS pixels in the case study even using a data set with a small number of images. A 15 times 15 multi-look window selects a greater number of PS pixels compared to a 9 times 9 multi-look window, although this entails reducing spatial resolution. The most effective PSI approach in terms of the density of the selected PS turned out to be polarimetric PSI using a data set with a large number of images and a selection of a 15 times 15 multi-look window. Validation of the PSI methods using a large number of images with 9 times 9 and 15 times 15 multi-look windows via levelling measurements confirms the accuracy and reliability of the results obtained.

Single-Look SAR Tomography as an Add-On to PSI for Improved Deformation Analysis in Urban Areas

Persistent scatterer interferometry (PSI) is in operational use for spaceborne synthetic aperture radar (SAR)-based deformation analysis. A limitation inherently associated with PSI is that, by definition, a persistent scatterer (PS) is a single dominant scatterer. Therefore, pixels containing signal contributions from multiple scatterers, as in the case of a layover, are typically rejected in the PSI processing, which in turn limits deformation retrieval. SAR tomography has the ability to resolve layovers. This paper investigates the added value that can be achieved by operationally combining SAR tomography with a PSI approach toward the objective of improving deformation sampling in layover-affected urban areas. Different tomographic phase models are implemented and compared as regards their suitability in resolving layovers. Single-look beamforming-based tomographic inversion and a generalized likelihood ratio test (GLRT)-based detection strategy are used to detect single and double scatterers. The quantity of the detected scatterers is weighed against their quality as defined in terms of the phase deviation between the single-look complex (SLC) measurements and the tomographic model fit. The gain in deformation sampling that can be derived with tomography relative to a PSI-based analysis is quantitatively assessed, and alongside the quality of the scatterers obtained with tomography is compared with the quality of the PSs identified with a PSI approach. The experiments are performed on an interferometric stack of 50 TerraSAR-X stripmap images. The results obtained show that, although there is a tradeoff between the quantity and the quality of the detected scatterers, the tested SAR tomography approach leads to an improvement in deformation sampling in layover-affected areas.

PERSISTENT SCATTERER INTERFEROMETRY USING SENTINEL-1 DATA

This paper is focused on deformation monitoring using a Persistent Scatterer Interferometry technique and the interferometric SAR data acquired by the Sentinel-1 satellite of the European Space Agency. The first part of the paper describes the procedure used to process and analyze Sentinel-1 interferometric SAR data. Two main approaches are described. The first one is a simplified Persistent Scatterer Interferometry approach that exploits two key properties of the Sentinel-1 data: the high coherence of the 12-day interferograms and the reduced orbital tube. The second approach is a full Persistent Scatterer Interferometry approach, where a more sophisticate data treatment is employed. The second part of the paper illustrates the results obtained with the two processing approaches. Two case studies are described. The first one concerns landslide detection and monitoring. In this case, the simplified Persistent Scatterer Interferometry approach was used. The second one regards the deformation monitoring of an urban area. In this case, a full Persistent Scatterer Interferometry approach was used.

PERSISTENT SCATTERER INTERFEROMETRY USING SENTINEL-1 DATA

Abstract. This paper is focused on deformation monitoring using a Persistent Scatterer Interferometry technique and the interferometric SAR data acquired by the Sentinel-1 satellite of the European Space Agency. The first part of the paper describes the procedure used to process and analyze Sentinel-1 interferometric SAR data. Two main approaches are described. The first one is a simplified Persistent Scatterer Interferometry approach that exploits two key properties of the Sentinel-1 data: the high coherence of the 12-day interferograms and the reduced orbital tube. The second approach is a full Persistent Scatterer Interferometry approach, where a more sophisticate data treatment is employed. The second part of the paper illustrates the results obtained with the two processing approaches. Two case studies are described. The first one concerns landslide detection and monitoring. In this case, the simplified Persistent Scatterer Interferometry approach was used. The second one regards the deformation monitoring of an urban area. In this case, a full Persistent Scatterer Interferometry approach was used.

Deformation Monitoring Using Persistent Scatterer Interferometry and Sentinel-1 SAR Data

During the last decades, Persistent Scatterer Interferometry (PSI) has demonstrated to be a powerful tool able to measure and monitor deformations. This technique makes use of large stacks of interferometric SAR images to derive the deformation maps and deformation time series. In this paper, Sentinel-1 images are used to derive the deformation monitoring over the Catalonia region (Spain). These images brings new improvements due to its wide coverage and high revisiting time, which allows us to make a wide area processing.The first part of the paper describes the data processing implemented by the authors to analyze Sentinel-1 data and the PSI approach used in this ongoing research. The second part of the paper illustrates the results derived over an area of 6750 km2 using Sentinel-1 images.

Short Baseline TerraSAR-X PSI for Monitoring Subsidence of Highways and Railways, Case Study with Corner Reflectors

Abstract. Ground subsidence is one of the key factors causing damages to transportation facilities, e.g., transportation network (TN) consists of highways and railways. For better exploration of TN subsidence, we propose to use the high resolution TerraSAR-X (TSX) persistent scatterer interferometry (PSI) approach to extract regional scale (RS) subsidence related to the TN. The primary procedures involve interferometric pair selection, interferogram generation, persistent scatterer (PS) detection, PS networking, phase parameterization and subsidence estimation. Xiqing district of southwest Tianjin (China) is selected as the study area, in which multiple highways and one railway line are located. 15 TSX images collected over this area between March, 2009 and June, 2010 are utilized to extract subsidence by the TSX PSI approach. The subsidence rate (SR) map shows that remarkably uneven subsidence occurs along and around the TN, and the SR ranges between –69 and –1.3 mm/yr. For validation purpose, the SR of the TN derived by PSI is compared with leveling data collected for the benchmarks deployed along the selected highways. The mean and root mean square error (RMSE) of discrepancies between two data sets are 0.1 and ±3.2 mm/yr, respectively. The numerical analysis indicates that the high resolution TSX PSI is able to reveal comprehensive and detailed subsidence related to the TN with a millimeter level accuracy.

Advanced interpretation of land subsidence by validating multi-interferometric SAR data: the case study of the Anthemountas basin (Northern Greece)

Abstract. The potential of repeat-pass space borne SAR (Synthetic Aperture Radar) interferometry has been exploited to investigate spatial patterns of land subsidence in the Anthemountas basin, in the northern part of Greece. The PSI (Persistent Scatterer Interferometry) approach, based on the processing of long series of SAR acquisitions, has been applied to forty-two images acquired in 1995–2001 by ERS1/2 satellites. Interferometric results have been analysed at a basin scale as support for land motion mapping and at a local scale for the characterisation of ground motion events affecting the village of Perea in the Thermaikos municipality and the "Macedonia" international airport. PSI results revealed a moderate subsidence phenomenon along the wider coastal zone of Anthemountas basin corresponding to intense groundwater extraction. Highest values, exceeding −20 mm yr−1, were measured in the airport area where the thickest sequence of compressible Quaternary sediments occurs. Intense subsidence has been detected also in the Perea village (maximum deformation of −10 to −15 mm yr−1), where a series of fractures, causing damages to both buildings and infrastructure, occurred in 2005–2006.