Geodetic monitoring of complex shaped infrastructures using Ground-Based InSAR

In the context of climate change, alternatives to fossil energies need to be used as much as possible to produce electricity. Hydroelectric power generation through the utilisation of dams stands out as an exemplar of highly effective methodologies in this endeavour. Various monitoring sensors can be installed with different characteristics w.r.t. spatial resolution, temporal resolution and accuracy to assess their safe usage. Among the array of techniques available, it is noteworthy that ground-based synthetic aperture radar (GB-SAR) has not yet been widely adopted for this purpose. Despite its remarkable equilibrium between the aforementioned attributes, its sensitivity to atmospheric disruptions, specific acquisition geometry, and the requisite for phase unwrapping collectively contribute to constraining its usage. Several processing strategies are developed in this thesis to capitalise on all the opportunities of GB-SAR systems, such as continuous, flexible and autonomous observation combined with high resolutions and accuracy. The first challenge that needs to be solved is to accurately localise and estimate the azimuth of the GB-SAR to improve the geocoding of the image in the subsequent step. A ray tracing algorithm and tomographic techniques are used to recover these external parameters of the sensors. The introduction of corner reflectors for validation purposes confirms a significant error reduction. However, for the subsequent geocoding, challenges persist in scenarios involving vertical structures due to foreshortening and layover, which notably compromise the geocoding quality of the observed points. These issues arise when multiple points at varying elevations are encapsulated within a singular resolution cell, posing difficulties in pinpointing the precise location of the scattering point responsible for signal return. To surmount these hurdles, a Bayesian approach grounded in intensity models is formulated, offering a tool to enhance the accuracy of the geocoding process. The validation is assessed on a dam in the black forest in Germany, characterised by a very specific structure. The second part of this thesis is focused on the feasibility of using GB-SAR systems for long-term geodetic monitoring of large structures. A first assessment is made by testing large temporal baselines between acquisitions for epoch-wise monitoring. Due to large displacements, the phase unwrapping can not recover all the information. An improvement is made by adapting the geometry of the signal processing with the principal component analysis. The main case study consists of several campaigns from different stations at Enguri Dam in Georgia. The consistency of the estimated displacement map is assessed by comparing it to a numerical model calibrated on the plumblines data. It exhibits a strong agreement between the two results and comforts the usage of GB-SAR for epoch-wise monitoring, as it can measure several thousand points on the dam. It also exhibits the possibility of detecting local anomalies in the numerical model. Finally, the instrument has been installed for continuous monitoring for over two years at Enguri Dam. An adequate flowchart is developed to eliminate the drift happening with classical interferometric algorithms to achieve the accuracy required for geodetic monitoring. The analysis of the obtained time series confirms a very plausible result with classical parametric models of dam deformations. Moreover, the results of this processing strategy are also confronted with the numerical model and demonstrate a high consistency. The final comforting result is the comparison of the GB-SAR time series with the output from four GNSS stations installed on the dam crest. The developed algorithms and methods increase the capabilities of the GB-SAR for dam monitoring in different configurations. It can be a valuable and precious supplement to other classical sensors for long-term geodetic observation purposes as well as short-term monitoring in cases of particular dam operations

InSAR as a tool for monitoring hydropower projects: A review

This paper provides a review of using Interferometric Synthetic Aperture Radar (InSAR), a microwave remote sensing technique, for deformation monitoring of hydroelectric power projects, a critical infrastructure that requires consistent and reliable monitoring. Almost all major dams around the world were built for the generation of hydropower. InSAR can enhance dam safety by providing timely settlement measurements at high spatial-resolution. This paper provides a holistic view of different InSAR deformation monitoring techniques such as Differential Synthetic Aperture Radar Interferometry (DInSAR), Ground-Based Synthetic Aperture Radar (GBInSAR), Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR), Multi-Temporal Interferometric Synthetic Aperture Radar (MTInSAR), Quasi-Persistent Scatterer Interferometric Synthetic Aperture Radar (QPSInSAR) and Small BAseline Subset (SBAS). PSInSAR, GBInSAR, MTInSAR, and DInSAR techniques were quite commonly used for deformation studies. These studies demonstrate the advantage of InSAR-based techniques over other conventional methods, which are laborious, costly, and sometimes unachievable. InSAR technology is also favoured for its capability to provide monitoring data at all times of day or night, in all-weather conditions, and particularly for wide areas with mm-scale precision. However, the method also has some disadvantages, such as the maximum deformation rate that can be monitored, and the location for monitoring cannot be dictated. Through this review, we aim to popularize InSAR technology to monitor the deformation of dams, which can also be used as an early warning method to prevent any unprecedented catastrophe. This study also discusses some case studies from southern India to demonstrate the capabilities of InSAR to indirectly monitor dam health

Displacements Monitoring over Czechia by IT4S1 System for Automatised Interferometric Measurements Using Sentinel-1 Data

The Sentinel-1 satellite system continuously observes European countries at a relatively high revisit frequency of six days per orbital track. Given the Sentinel-1 configuration, most areas in Czechia are observed every 1–2 days by different tracks in a moderate resolution. This is attractive for various types of analyses by various research groups. The starting point for interferometric (InSAR) processing is an original data provided in a Single Look Complex (SLC) level. This work represents advantages of storing data augmented to a specifically corrected level of data, SLC-C. The presented database contains Czech nationwide Sentinel-1 data stored in burst units that have been pre-processed to the state of a consistent well-coregistered dataset of SLC-C. These are resampled SLC data with their phase values reduced by a topographic phase signature, ready for fast interferometric analyses (an interferogram is generated by a complex conjugate between two stored SLC-C files). The data can be used directly into multitemporal interferometry techniques, e.g., Persistent Scatterers (PS) or Small Baseline (SB) techniques applied here. A further development of the nationwide system utilising SLC-C data would lead into a dynamic state where every new pre-processed burst triggers a processing update to detect unexpected changes from InSAR time series and therefore provides a signal for early warning against a potential dangerous displacement, e.g., a landslide, instability of an engineering structure or a formation of a sinkhole. An update of the processing chain would also allow use of cross-polarised Sentinel-1 data, needed for polarimetric analyses. The current system is running at a national supercomputing centre IT4Innovations in interconnection to the Czech Copernicus Collaborative Ground Segment (CESNET), providing fast on-demand InSAR results over Czech territories. A full nationwide PS processing using data over Czechia was performed in 2017, discovering several areas of land deformation. Its downsampled version and basic findings are demonstrated within the article

GB-InSAR monitoring and observational method for landslide emergency management: the Montaguto earthflow (AV, Italy)

Abstract. On 10 March 2010, because of the heavy rainfall in the preceding days, the Montaguto landslide (Southern Italy) reactivated, affecting both state road 90 Delle Puglie and the Rome–Bari railway. A similar event occurred on May 2005 and on September 2009. As a result, the National Civil Protection Department (DPC) started an accurate monitoring and analysis program. A monitoring project using the GB-InSAR (ground-based interferometric synthetic aperture radar) system was emplaced to investigate the landslide kinematics, plan urgent safety measures for risk mitigation and design long-term stabilization work.Here, we present the GB-InSAR monitoring system results and its applications in the observational method (OM) approach. GB-InSAR is an established instrument for long-term campaigns aimed at early warning and monitoring during construction works. Our paper further develops these aspects in that it highlights how the OM based on the GB-InSAR technique can produce savings in terms of cost and time in engineering projects without compromising safety. This study focuses on the key role played by the monitoring activities during the design and planning activities, with special reference to the emergency phase

A hydrogeological approach in urban underground infrastructures

The competition for space in urban areas due to an exponential growth of population makes derground engineering plays a crucial role in the development of cities. Urban underground infrastructures deal with variables such as cost, duration, safety, and management; faces political, social, economic and environmental issues; and guarantees future sustainability, maintenance, and energy efficiency. To do so, all these concepts and variables must be kept in mind during the whole construction process: (I) project design, (II) project construction and (III) project exploitation. This thesis aims to demonstrate how the construction cycle deals with the various impacts produced by the interaction of underground constructions with groundwater at each stage of the process, with a view to providing improved processes. During the project design previous data is collected, new data is generated, created and processed, helping to understand the context and to design the infrastructure. There are very advanced tools to store and process hydrogeological data, but most of these tools are not common in infrastructure projects. Often most of the constructions only perform the minimum legal requirement to characterize the ground: a pumping test. Therefore, there is a need to provide the constructors with a set of methods and tools to allow them to increase the quality of their hydrogeological analysis, which will allow early detection problems associated with the groundwater. The interaction of underground constructions with groundwater generates impacts. These impacts can usually be minimized by using mitigation measures. The most common impacts caused by underground constructions are the groundwater barrier effect and the groundwater pressure distribution and limitation under the bottom slab. In the literature there are many examples and designs to mitigate both groundwater barrier effect and groundwater pressure distribution impacts. However, there is no design that integrates both solutions. This thesis presents an innovative groundwater by-pass design that enables the groundwater to flow through the structure and provide a homogenous distribution of the water pressure under the bottom slab. The new integrated design was applied to the largest underground infrastructure of Barcelona: La Sagrera railway station. A hydrogeological model was implemented to test the original and the integrated designs in three different scenarios. This new solution mitigates the groundwater barrier effect and optimizes the bottom slab, considerably reducing the costs and increasing safety during the construction phase. Monitoring is required when dewatering underground constructions in order to anticipate unexpected events and preserve nearby existing structures. The most accurate and spread monitoring method to measure displacements is levelling, a pointlike surveying technique that typically allows for tens of discrete in-situ sub-millimetric measurements per squared kilometer. Another emerging technique for mapping soil deformation is the Interferometric Synthetic Aperture Radar (InSAR), which is based on SAR images acquired from orbiting satellites or by ground-based stations (GB-SAR). This remote sensing technique can provide better spatial point density than levelling, more extensive spatial coverage and cheaper acquisitions. Both satellite and ground-based SAR systems have been used and tested in a variety of analyses. However, nobody has applied this technology as a monitoring tool during construction works yet. This thesis contributes to data storing and data analysis software that implies new and significant method developments for increasing the quality of the hydrogeological analysis; it provides new approaches to address the groundwater corrective measures definition during the design stage, and it develops and applies new methods of nfrastructure monitoring using ground-based and satellite SAR sensors during the construction stage.Degut al creixement exponencial de la població i tenint en compte que l'espai dins les àrees urbanes és finit és, necessari la construcció d'infraestructures subterrànies. Variables com el cost, la durada, la seguretat i la gestió; els problemes polítics, socials, econòmics i ambientals; garantir la sostenibilitat futura, el manteniment i l'eficiència energètica, han d'estar presents durant totes les fases del procés constructiu: (I) fase de disseny, (II) fase de construcció, i (III) fase d'explotació. Les construccions subterrànies interactuen amb el medi subterrani, el resultat de la interacció són uns impactes en la construcció i en el medi ambient. Tots aquests impactes són avaluats al llarg del procés constructiu per tal de ser corregits o minimitzats. L'objectiu principal d'aquesta tesi és conèixer com s'avaluen els diferents impactes a cadascuna de les fas es del procés constructiu per poder així proposar millores. Durant el disseny del projecte i per tal d'entendre el context i el disseny de la infraestructura es recullen dades històriques i es generen noves dades . L'ús de la majoria d'eines hidrogeològiques no és habitual en els projectes d'infraestructures ja que la majoria caracteritzen el terreny amb una prova de bombament. Per tant, és necessari proporcionar als constructors un conjunt de mètodes i d'eines que permetin augmentar la qualitat dels seus anàlisis, per augmentar així la detecció primerenca de problemes associats a les aigües subterrànies. Els impactes produïts per la interacció de les construccions subterrànies amb les aigües subterrànies es poden minimitzar mitjançant l'ús de mesures de mitigació. Els impactes més comuns causats per construccions subterrànies són l'efecte barrera i la distribució i limitació de subpressions sota la llosa de fons. A la literatura hi ha molts dissenys que permeten mitigar l'efecte barrera i millorar la distribució de les subpressions, però no hi ha cap disseny que integri les dues solucions. Aquesta tesi presenta un disseny innovador per bypassar les aigües subterrànies a través de l'estructura proporcionant una distribució homogènia de les subpressions sota la llosa de fons. Aquesta nova solució minimitza l'efecte barrera de les aigües subterrànies i optimitza la llosa de fons, reduint considerablement els costos i augmentant la seguretat durant la fase de construcció. Quan una construcció rebaixa el nivell freàtic cal auscultar els nivells i la deformació del terreny per tal d'anticipar esdeveniments inesperats i preservar les estructures properes existents. El mètode actual més utilitzat per mesurar desplaçaments és l'anivellament, que permet avaluar in situ desenes de punts discrets amb una precisi ó submil·limètrica. Una tècnica emergent és el Radar d'Obertura Sintètica Interferomètrica (InSAR), que es basa en imatges SAR adquirides des de satèl·lits en òrbita o bé des d'estacions al terra (GB-SAR). Aquesta tècnica de detecció remota proporciona una major cobertura espacial i més econòmica que els mètodes d'auscultació tradicionals. Tot i que la tecnologia SAR s'ha utilitzat i validat en una gran varietat d'anàlisis, ningú ha aplicat encara aquesta tecnologia com a eina d'auscultació durant la construcció d'infraestructures. Aquesta tesi contribueix a: (I) millorar l'emmagatzematge i processament de dades a través de nous desenvolupaments i mètodes que permeten augmentar la qualitat de l'anàlisi hidrogeològica; (II) oferir noves formes d'anàlisi per al disseny de mesures correctores durant l'etapa de disseny; i (III) desenvolupar i aplicar nous mètodes d'auscultació d'infraestructura a través de sensors SAR (terrestres i satèl·lit) durant la fase constructiva.La limitación de espacio en áreas urbanas junto al crecimiento exponencial de la población, hace necesaria la construcción de infraestructuras subterráneas. Nuevos conceptos en planificación urbana junto con los avances tecnológicos en la construcción hacen posible la ejecución de infraestructuras más grandes y de más eficiencia. No obstante, variables tales como el coste, la duración, la seguridad y la gestión; los problemas políticos, sociales, económicos y ambientales; y garantizar la sostenibilidad futura, el mantenimiento y la eficiencia energética, hacen de esta ejecución un problema complejo. Por ello, todas estas variables deben estar presentes durante todo el proceso constructivo: (I) diseño del proyecto, (II) construcción del proyecto y (III) explotación del proyecto. Esta tesis tiene como objetivo principal saber cómo el ciclo constructivo (diseño del proyecto, construcción y explotación de proyectos) procesa las problemáticas inducidas por la interacción de las nuevas infraestructuras subterráneas urbanas con las aguas subterráneas para luego mejorarlo. Durante el diseño del proyecto (fase I) se recogen los datos históricos, se generan nuevos datos (pozos, pruebas de campo, muestras químicas ...) y se procesa conjuntamente, lo que ayuda a entender el contexto y el diseño de la infraestructura. Existen herramientas muy avanzadas para almacenar y procesar información geológica, hidroquímica e hidrogeológica, aunque la mayoría de estas herramientas no son comunes en los proyectos de infraestructuras subterráneas ya que es común que la mayoría de las construcciones sólo se realice una prueba de bombeo para caracterizar el subsuelo. Por lo tanto, hay una necesidad de proporcionar un conjunto de métodos y de herramientas a los constructores para que puedan aumentar la calidad de su análisis (como pruebas de bombeo), para aumentar así la detección temprana de problemas asociados a las aguas subterráneas. La interacción de las construcciones subterráneas con las aguas subterráneas genera impactos. Estos impactos generalmente pueden minimizarse mediante el uso de medidas correctoras. Los impactos más comunes causados por las construcciones subterráneas son el efecto barrera (impacto en las aguas subterráneas) y la distribución y limitación de subpresiones bajo la losa de fondo (impacto en la construcción subterránea). En la literatura hay muchos ejemplos de diseños para mitigar tanto el efecto barrera y como para mejorar la distribución de las subpresiones bajo la losa de fondo. Sin embargo, no hay ningún diseño que integre ambas soluciones. Es ilógico diseñar una medida correctora sin tener en cuenta todos los factores que intervienen en el problema. Esta tesis presenta un diseño innovador de by-pass para las aguas subterráneas que permite el flujo de agua subterránea a través de la estructura a la vez que proporciona una distribución homogénea de las subpresiones bajo la losa de fondo. El nuevo diseño se ha aplicado en la infraestructura subterránea más grande de Barcelona: la futura estación de tren de La Sagrera. Se ha realizado un modelo hidrogeológico para probar los nuevos diseños en tres escenarios diferentes. Esta nueva solución mitiga el efecto barrera de las aguas subterráneas y optimiza la losa de fondo, lo que reduce considerablemente los costes y aumenta la seguridad durante la fase de construcción. Durante la construcción (fase II) se genera una gran cantidad de nuevos datos. Es necesario auscultar los niveles y la deformación del terreno cuando una construcción rebaja el freático con el fin de anticiparse a acontecimientos inesperados y a preservar las estructuras y / o edificios cercanos existentes. El método actual más usado para medir desplazamientos en el terreno es la nivelación, una técnica que permite evaluar in situ decenas de puntos discretos con una precisión sub-milimétrica. Una técnica emergente para medir la deformación del suelo es el Radar de Apertura Sintética Interferométrica (InSAR), que se basa en imágenes SAR adquiridas o bien desde satélites en órbita o bien desde estaciones en tierra (GB-SAR). Esta técnica de detección remota proporciona una mayor cobertura espacial y más barata que los métodos de auscultación tradicionales. Aunque la tecnología SAR se ha utilizado y validado en una gran variedad de análisis, nadie ha aplicado esta tecnología como una herramienta de auscultación durante la construcción de infraestructuras. Esta tesis contribuye a mejorar el almacenamiento y tratamiento de datos a través de nuevos desarrollos y métodos que permiten aumentar la calidad del análisis hidrogeológico; ofrece nuevas formas de análisis para el diseño de medidas correctoras durante la etapa de diseño; y desarrolla y aplica nuevos métodos de auscultación de infraestructura a través de sensores SAR (terrestres y satélite) durante la fase constructiv

The Interferometric Use of Radar Sensors for the Urban Monitoring of Structural Vibrations and Surface Displacements

In this paper, we propose a combined use of real aperture radar (RAR) and synthetic aperture radar (SAR) sensors, within an interferometric processing chain, to provide a new methodology for monitoring urban environment and historical buildings at different temporal and spatial scales. In particular, ground-based RAR measurements are performed to estimate the vibration displacements and the natural oscillation frequencies of structures, with the aim of supporting the understanding of the building dynamic response. These measurements are then juxtaposed with ground-based and space-borne SAR data to monitor surface deformation phenomena, and hence, point out potential risks within an urban environment. In this framework, differential interferometric SAR algorithms are implemented to generate short-term (monthly) surface displacement and long-term (annual) mean surface displacement velocity maps at local (hundreds m2) and regional (tens km2) scale, respectively. The proposed methodology, developed among the activities carried out within the national project Programma Operativo Nazionale MASSIMO (Monitoraggio in Area Sismica di SIstemi MOnumentali), is tested and discussed for the ancient structure of Saint Augustine compound, located in the historical center of Cosenza (Italy) and representing a typical example of the Italian Cultural Heritage

Ground-based synthetic aperture radar (GBSAR) interferometry for deformation monitoring

Ph. D ThesisGround-based synthetic aperture radar (GBSAR), together with interferometry, represents a powerful tool for deformation monitoring. GBSAR has inherent flexibility, allowing data to be collected with adjustable temporal resolutions through either continuous or discontinuous mode. The goal of this research is to develop a framework to effectively utilise GBSAR for deformation monitoring in both modes, with the emphasis on accuracy, robustness, and real-time capability. To achieve this goal, advanced Interferometric SAR (InSAR) processing algorithms have been proposed to address existing issues in conventional interferometry for GBSAR deformation monitoring. The proposed interferometric algorithms include a new non-local method for the accurate estimation of coherence and interferometric phase, a new approach to selecting coherent pixels with the aim of maximising the density of selected pixels and optimizing the reliability of time series analysis, and a rigorous model for the correction of atmospheric and repositioning errors. On the basis of these algorithms, two complete interferometric processing chains have been developed: one for continuous and the other for discontinuous GBSAR deformation monitoring. The continuous chain is able to process infinite incoming images in real time and extract the evolution of surface movements through temporally coherent pixels. The discontinuous chain integrates additional automatic coregistration of images and correction of repositioning errors between different campaigns. Successful deformation monitoring applications have been completed, including three continuous (a dune, a bridge, and a coastal cliff) and one discontinuous (a hillside), which have demonstrated the feasibility and effectiveness of the presented algorithms and chains for high-accuracy GBSAR interferometric measurement. Significant deformation signals were detected from the three continuous applications and no deformation from the discontinuous. The achieved results are justified quantitatively via a defined precision indicator for the time series estimation and validated qualitatively via a priori knowledge of these observing sites.China Scholarship Council (CSC), Newcastle Universit

MT-InSAR and Dam Modeling for the Comprehensive Monitoring of an Earth-Fill Dam: The Case of the Benínar Dam (Almería, Spain)

The Benínar Dam, located in Southeastern Spain, is an earth-fill dam that has experienced filtration issues since its construction in 1985. Despite the installation of various monitoring systems, the data collected are sparse and inadequate for the dam’s lifetime. The present research integrates Multi-Temporal Interferometric Synthetic Aperture Radar (MT-InSAR) and dam modeling to validate the monitoring of this dam, opening the way to enhanced integrated monitoring systems. MT-InSAR was proved to be a reliable and continuous monitoring system for dam deformation, surpassing previously installed systems in terms of precision. MT-InSAR allowed the almost-continuous monitoring of this dam since 1992, combining ERS, Envisat, and Sentinel-1A/B data. Line-of-sight (LOS) velocities of settlement in the crest of the dam evolved from maximums of −6 mm/year (1992–2000), −4 mm/year (2002–2010), and −2 mm/year (2015–2021) with median values of −2.6 and −3.0 mm/year in the first periods (ERS and Envisat) and −1.3 mm/year in the Sentinel 1-A/B period. These results are consistent with the maximum admissible modeled deformation from construction, confirming that settlement was more intense in the dam’s early stages and decreased over time. MT-InSAR was also used to integrate the monitoring of the dam basin, including critical slopes, quarries, and infrastructures, such as roads, tracks, and spillways. This study allows us to conclude that MT-InSAR and dam modeling are important elements for the integrated monitoring systems of embankment dams. This conclusion supports the complete integration of MT-InSAR and 3D modeling into the monitoring systems of embankment dams, as they are a key complement to traditional geotechnical monitoring and can overcome the main limitations of topographical monitoringReMoDams project ESP2017-89344-R (AEI/FEDER, UE) from the Spanish Ministry of Economy, Industry and CompetitivenessSIAGUA project PID2021-128123OB-C21PID2021-128123OB-C22MCIN/AEI/10.13039/ 501100011033/FEDER,UEPOAIUJA-2023/2024CEACTEMA from University of Jaén (Spain)RNM-282 research group from the Junta de Andalucía (Spain

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

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.Peer ReviewedPostprint (author's final draft