Sentinel-1 A-DInSAR approaches to map and monitor ground displacements

Persistent scatterer interferometry (PSI) is a group of advanced interferometric synthetic aperture radar (SAR) techniques used to measure and monitor terrain deformation. Sentinel-1 has improved the data acquisition throughout and, compared to previous sensors, increased considerably the differential interferometric SAR (DInSAR) and PSI deformation monitoring potential. The low density of persistent scatterer (PS) in non-urban areas is a critical issue in DInSAR and has inspired the development of alternative approaches and refinement of the PS chains. This paper proposes two different and complementary data-driven procedures to obtain terrain deformation maps. These approaches aim to exploit Sentinel-1 highly coherent interferograms and their short revisit time. The first approach, called direct integration (DI), aims at providing a very fast and straightforward approach to screen-wide areas and easily detects active areas. This approach fully exploits the coherent interferograms from consecutive images provided by Sentinel-1, resulting in a very high sampling density. However, it lacks robustness and its usability lays on the operator experience. The second method, called persistent scatterer interferometry geomatics (PSIG) short temporal baseline, provides a constrained application of the PSIG chain, the CTTC approach to the PSI. It uses short temporal baseline interferograms and does not assume any deformation model for point selection. It is also quite a straightforward approach, which improves the performances of the standard PSIG approach, increasing the PS density and providing robust measurements. The effectiveness of the approaches is illustrated through analyses performed on different test sites.This work has been partially funded by AGAUR, Generalitat de Catalunya, through a grant for the recruitment of early-stage research staff (Ref: FI_B 00741) and through the Consolidated Research Group RSE, “Remote Sensing” (Ref: 2017-SGR-00729). It has been also partially funded by the Spanish Ministry of Economy and Competitiveness through the DEMOS project “Deformation monitoring using Sentinel-1 data” (Ref: CGL2017-83704-P) and by AGAUR.Peer ReviewedPostprint (published version

Sentinel-1 data exploitation for terrain deformation monitoring

Persistent Scatterer interferometry (PSI) is a group of advanced differential interferometric Synthetic Aperture Radar (SAR) techniques used to measure and monitor terrain deformation. Sentinel-1 has improved the data acquisition throughout and, compared to previous sensors, increased considerably the Differential Interferometric SAR (DInSAR) and PSI deformation monitoring potential. The effect of the refractive atmosphere on the interferometric phase and phase unwrapping ambiguity are two critical issues of InSAR. The low density of Persistent Scatterer (PS) in non-urban areas, another critical issue, has inspired the development of alternative approaches and refinement of the PS chains. Along with the efforts to develop methods to mitigate the three above-mentioned problems, the work presented in this thesis also deals with the presence of a new signal in multilooked interferograms which cannot be explained by noise, atmospheric or earth surface topography changes. This paper describes a method for atmospheric phase screen estimation using rain station weather data and three different data driven procedures to obtain terrain deformation maps. These approaches aim to exploit Sentinel-1 highly coherent interferograms and their short revisit time. The first method called the splitting makes uses of the power spectrum of the interferograms to split the signals into high and low frequency, and following a mutually exclusive consecutive processing chain for the two sets. This approach has resulted in greater density of PSs with decreased phase unwrapping errors. The second approach, called Direct Integration (DI), aims at providing a very fast and straightforward approach to screen wide areas and easily detect active areas. This approach fully exploits the coherent interferograms from the consecutive images provided by Sentinel-1 resulting in a very high sampling density. However, it lacks robustness and its usability lays on the operator experience. The third method, called PSIG (Persistent Scatterer Interferometry Geomatics) short temporal baseline, provides a constrained application of the PSIG chain, the CTTC approach to the PSI. It uses short temporal baseline interferograms and do not assume any deformation model for point selection. It is also quite a straightforward approach and a perfect complement to the direct integration approach. It improves the performances of the standard PSIG approach, increasing the PS density and providing robust measurements. The effectiveness of the approaches is illustrated through analyses performed on different test sites.La técnica Persistent Scatterer Interferometry (PSI) es un grupo de técnicas avanzadas de radar de apertura sintética interferométrica diferencial (SAR) que se utiliza para medir y monitorear losmovimientos del terreno. Sentinel-1 ha mejorado sensiblemente la adquisición de datos y, en comparación con los sensores SAR anteriores, ha aumentado considerablemente el potencial uso de la interferometría diferencial SAR y del PSI para medir y monitorizar desplazamientos del terreno. El efecto de la atmósfera sobre la fase interferométrica y la naturaleza ambigua de esta son dos cuestiones críticas de InSAR. Además, la baja densidad de Persistent Scatterer (PSs) en áreas no urbanas, es otro tema crítico que ha inspirado el desarrollo de enfoques alternativos y el refinamiento de las cadenas PS existentes. Junto con los esfuerzos por desarrollar métodos para mitigar los tres problemas antes mencionados, el trabajo presentado en esta tesis también aborda la presencia de una nueva señal en interferogramas multilooked que no puede explicarse por cambios de ruido, atmosféricos o topográficos de la superficie terrestre. Esta tesis describe un método para la estimación de la fase atmosférica utilizando datos meteorológicos adquiridos in-situ y tres aproximaciones diferentes basadas en datos Sentinel-1 para obtener mapas de deformación del terreno. Estos enfoques tienen como objetivo explotar los interferogramas altamente coherentes proporcionados por Sentinel-1 gracias a su corto tiempo de revisita. El primer método llamado división hace uso de filtros en el dominico frecuencial de los interferogramas para dividir las señales en alta y baja frecuencia, y siguiendo una cadena de procesamiento consecutiva independiente para cada clase. Este enfoque ha dado como resultado una mejora substancial de PS minimizando los errores debidos al desenrollado de fase. El segundo enfoque, llamado Integración Directa (DI), tiene como objetivo proporcionar un enfoque muy rápido y sencillo para examinar áreas amplias y detectar fácilmente áreas activas. Este enfoque aprovecha al máximo los interferogramas coherentes de las imágenes consecutivas proporcionadas por Sentinel-1, lo que da como resultado una densidad de muestreo muy alta. Sin embargo, carece de robustez y su usabilidad depende de la experiencia del operador. El tercer método, llamado PSIG (Persistent Scatterer Interferometry Geomatics) de línea de base temporal corta, proporciona una aplicación restringida de la cadena PSIG, el enfoque CTTC para el PSI. Utiliza interferogramas de línea base temporales cortos y no asume ningún modelo de deformación para la selección de puntos. Su uso es complementario al enfoque de integración directa proporcionando robustez en las zonas. Mejora el rendimiento del enfoque estándar de PSIG, aumentando la densidad de PS y proporcionando mediciones robustas. La efectividad de los enfoques se ilustra a través de análisis realizados en diferentes sitios de prueba.Postprint (published version

The PSIG procedure to Persistent Scatterer Interferometry (PSI) using X-band and C-band Sentinel-1 data

A new approach to Persistent Scatterer Interferometry (PSI) data processing and analysis implemented in the PSI chain of the Geomatics (PSIG) Division of CTTC is used in this work. The flexibility of the PSIG procedure allowed evaluating two different processing chains of the PSIG procedure. A full PSIG procedure was implemented in the TerraSAR-X dataset while a reduced PSIG procedure was applied to the nine Sentinel-1 images available at the time of processing. The performance of the PSIG procedure is illustrated using X-band and C-band Sentinel-1 data and several examples of deformation maps covering different types of deformation phenomena are shown. \ua9 (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Ground movement classification using statistical tests over persistent scatterer interferometry time series

This study proposes modifications to an existing automatic classification method of Persistent Scatterers Interferometry (PSI) time series (TS) and a new procedure to classify ground movements into seven classes. We also represent a technique to detect TSs affected by phase unwrapping errors and a reclassification part to detect stable points, which are incorrectly classified as moving points using the original method. Around 60 km2 of Catalunya were classified using Sentinel-1 images and a PSI technique. The proposed method classified 78359 PS TS. This study provided the spatial distribution of ground movement classes and detected several time series anomalies.Peer ReviewedPostprint (published version

Pyrenees deformation monitoring using Sentinel-1 data and the Persistent Scatterer Interferometry technique

This study focuses on deformation mapping and monitoring using Sentinel-1 radar data and the DInSAR (Differential Interferometric Synthetic Aperture Radar) technique. In particular, a Persistent Scatterer Interferometry technique was used over 15000 ¿¿¿¿2 of the Pyrenees, located in Spain, Andorra and France. The main goal is to monitor deformations over a vegetated and mountainous region by exploiting the wide-area coverage, the high coherence and temporal sampling provided by the Sentinel-1satellites. All possible interferograms were generated using 150 images covering five years. The velocity map of the entire region is presented considering the characteristics of the study area, including vegetation and severe steep mountains. Two areas of deformation are shown, which are characterized by velocity values ranging between -20 to -40 mm/year.The work of S.M. Mirmazloumi has been funded by the Spanish State Research Agency, through a grant for a pre doctorate contract (Ref: PRE2018-083394). This work has been co-funded by the European Regional Development Fund through the Interreg V-A Spain, France and Andorra (POCTEFA 2014-2020), project EFA295/19Peer ReviewedPostprint (published version

Systematic exploitation of the persistent scatterer interferometry potential

This paper briefly addresses the problem of exploiting the potential of Persistent Scatterer Interferometry (PSI) data. This has always been an open issue with the previous SAR missions. With Sentinel-1 it is becoming even more important due to its high throughput. Current data processing capabilities allow us to process a fraction of the acquired data; and the data analysis and exploitation only cover a part of the PSI results. From one side the PSI processing tools require to be improved, while from the other side there is the need of increasing the capabilities to analyze and interpret the PSI results, thus exploiting their potential

ADATools: a set of tools for the analysis of terrain movement maps obtained with SAR Interferometry

The SAR Interferometry techniques, Persistent Scatterer Interferometry (PSI) among them, are nowadays known as important tools for monitoring Earth surface movements. Several regional and national Ground Motion Services based on PSI already exist. Moreover, since 2022 the European Ground Motion Service will be operational and will annually provide an updated displacement map over the whole Europe. This will suppose a big amount of ground displacement measurements along the European territory. For each measurement EGMS will provide the annual velocity and the time series of deformation covering the period 2014 to one year prior to each delivery. In this context, it will be more and more necessary having tools to ease the management, analysis, and interpretation, of those wide areas and huge amount of data. We present here a first step in this direction: the ADATools are a set of tools to automatically have secondary, and more operational, products derived from a PSI map. Starting from a fast extraction of the most significant Active Deformation Areas (ADA), with the ADAFinder tool, then we can have a preliminary classification of the most probable phenomena (landslides, subsidence, settlements, or sinkholes) that is behind the detected movement, with the ADAClassifier tool. Moreover, LOS2hv tool allows to derive the horizontal (east-west) and vertical components of the movement in case we have maps of ascending and descending geometries. Finally, it is presented a product that analyzes the local displacement gradients to generate potential damage maps in urban areas. The tools will be presented thorough some results obtained on an area of the Granada County with the use of Sentinel-1 data. All the results have been achieved within the framework of the Riskcoast Project (financed by the Interreg Sudoe Program through the European Regional Development Fund, ERDF).This work was mainly supported by the European Regional Development Fund (ERDF) through the project “RISKCOAST” (SOE3/P4/E0868) of the Interreg SUDOE Programme

Detection of ground movements in Montjuïc (Barcelona) using TerraSAR-X data

In this study, 28 StripMap TerraSAR-X images were processed using a Persistent Scatterer Interferometry technique in order to detect and analyze superficial deformation phenomena affecting the hill of Montjuic in Barcelona between December 2007 and November 2009. The results show significant displacement values in two main areas affected by different types of superficial displacements, specifically compaction in a former quarry refill and sliding processes. Displacement values of up to 12 mm/ year along the line of sight of the satellite were detected in the area near the Perez de Rozas baseball stadium whereas values of up to 7 mm/year were found in the vicinity of Costa i Llobera gardens. For each deformation area, high resolution deformation velocity data were analyzed and integrated with historical images and field data to interpret the detected phenomena

Interferometric SAR deformation timeseries: a quality index

Estimating unknown absolute phase from a wrapped observation is a challenging and ill-posed problem that possibly leads to misinterpretation of interferometric SAR (InSAR) deformation results. In this study, we introduce a quality index to cluster post-phase unwrapping multi-master InSAR timeseries outputs based on the estimated phase residuals and redundancy of network of interferograms. The index is supposed to indicate the reliability of a timeseries, including the identification of persistent scatterers (PSs) possibly affected by phase unwrapping jumps. The algorithm was tested on two Sentinel-1 interferometric datasets with 622,991 and 95,398 PSs, generated from the PSI processing chain PSIG of the geomatics division of CTTC. Promising result have been achieved-especially in identifying erroneous PSs with phase unwrapping jumps. Along with existing temporal phase consistency checking algorithms, the approach could provide rich information toward a better interpretation of the deformation timeseries results.This work has been funded by AGAUR, Generalitat de Catalunya, in the framework of Resolution EMC/ 2459/2019, FI-2020.Peer ReviewedPostprint (published version