Post-failure evolution analysis of a rainfall-triggered landslide by multi-temporal interferometry SAR approaches integrated with geotechnical analysis

Persistent Scatterers Interferometry (PSI) represents one of the most powerful techniques for Earth's surface deformation processes' monitoring, especially for long-term evolution phenomena. In this work, a dataset of 34 TerraSAR-X StripMap images (October 2013–October 2014) has been processed by two PSI techniques - Coherent Pixel Technique-Temporal Sublook Coherence (CPT-TSC) and Small Baseline Subset (SBAS) - in order to study the evolution of a slow-moving landslide which occurred on February 23, 2012 in the Papanice hamlet (Crotone municipality, southern Italy) and induced by a significant rainfall event (185 mm in three days). The mass movement caused structural damage (buildings' collapse), and destruction of utility lines (gas, water and electricity) and roads. The results showed analogous displacement rates (30–40 mm/yr along the Line of Sight – LOS-of the satellite) with respect to the pre-failure phase (2008–2010) analyzed in previous works. Both approaches allowed detect the landslide-affected area, however the higher density of targets identified by means of CPT-TSC enabled to analyze in detail the slope behavior in order to design possible mitigation interventions. For this aim, a slope stability analysis has been carried out, considering the comparison between groundwater oscillations and time-series of displacement. Hence, the crucial role of the interaction between rainfall and groundwater level has been inferred for the landslide triggering. In conclusion, we showed that the integration of geotechnical and remote sensing approaches can be seen as the best practice to support stakeholders to design remedial works.Peer ReviewedPostprint (author's final draft

Mass-Market Receiver for Static Positioning: Tests and Statistical Analyses

Nowadays, there are several low cost GPS receivers able to provide both pseudorange and carrier phase measurements in the L1band, that allow to have good realtime performances in outdoor condition. The present paper describes a set of dedicated tests in order to evaluate the positioning accuracy in static conditions. The quality of the pseudorange and the carrier phase measurements let hope for interesting results. The use of such kind of receiver could be extended to a large number of professional applications, like engineering fields: survey, georeferencing, monitoring, cadastral mapping and cadastral road. In this work, the receivers performance is verified considering a single frequency solution trying to fix the phase ambiguity, when possible. Different solutions are defined: code, float and fix solutions. In order to solve the phase ambiguities different methods are considered. Each test performed is statistically analyzed, highlighting the effects of different factors on precision and accurac

Consolidation and assessment of a technique to provide fast and precise point positioning (Fast-PPP)

Tesi per compendi de publicacions. La consulta íntegra de la tesi, inclosos els articles no comunicats públicament per drets d'autor, es pot realitzar prèvia petició a l'Arxiu de la UPCPremi extraordinari doctorat UPC curs 2015-2016, àmbit de CiènciesThe research of this paper-based dissertation is focused on the Fast Precise Point Positioning (Fast-PPP) technique. The novelty relies on using an accurate ionosphere model, in combination with the standard precise satellite clock and orbit products, to reduce the convergence time of state-of-the-art high-accuracy navigation techniques from approximately one hour to few minutes. My first contribution to the Fast-PPP technique as a Ph.D. student has been the design and implementation of a novel user navigation filter, based on the raw treatment of undifferenced multi-frequency code and carrier-phase Global Navigation Satellite System (GNSS) measurements. The innovative strategy of the filter avoids applying the usual ionospheric-free combination to the GNSS observables, exploiting the full capacity of new multi-frequency signals and increasing the robustness of Fast-PPP in challenging environments where the sky visibility is reduced. It has been optimised to take advantage of the corrections required to compensate the delays (i.e., errors) affecting the GNSS signals. The Fast-PPP corrections, and most important, their corrections uncertainties (i.e., the confidence bounds) are added as additional equations in the navigation filter to obtain Precise Point Positioning (PPP) in few minutes. A second contribution performed with the new user filter, has been the consolidation of the precise ionospheric modelling of Fast-PPP and its extension from a regional to a global scale. The correct use of the confidence bounds has been found of great importance when navigating in the low-latitude areas of the equator, where the ionosphere is difficult to be accurately modelled. Even in such scenario, a great consistency has been achieved between the actual positioning errors with respect to the formal errors, as demonstrated using similar figures of merit used in civil aviation, as the Stanford plot. A third contribution within this dissertation has been the characterisation of the accuracy of different ionospheric models currently used in GNSS. The assessment uses actual, unambiguous and undifferenced carrier-phase measurements, thanks to the centimetre-level modelling capability within the Fast-PPP technique. Not only the errors of the ionosphere models have been quantified in absolute and relative terms, but also, their effect on navigation.La investigació d'aquesta Tesi Doctoral per compendi d'articles es centra en la tècnica de ràpid Posicionament de Punt Precís (Fast-PPP). La novetat radica en l'ús d'un model ionosfèric precís que, combinat amb productes estàndard de rellotge i de l'òrbita de satèl·lit, redueix el temps de convergència de les actuals tècniques de navegació precisa d'aproximadament una hora a pocs minuts. La meva primera contribució a la tècnica Fast-PPP com a estudiant de Doctorat ha estat el disseny i la implementació d'un filtre de navegació d'usuari innovador, basat en el tractament de múltiples freqüències de mesures de codi i fase sense diferenciar (absolutes). La estratègia del filltre de navegació evita l'aplicació de l'habitual combinació lineal lliure de ionosfera per a aquests observables. Així, s'explota la capacitat completa dels senyals multi-freqüència en el nous Sistemes Globals de Navegació per Satèl·lit (GNSS) i s'augmenta la robustesa del Fast-PPP en entorns difícils, on es redueix la visibilitat del cel. S'ha optimitzat per tal de prendre avantatge de les correccions necessàries per a compensar els retards (és a dir, els errors) que afecten els senyals GNSS. Les correccions de Fast-PPP i més important, les seves incerteses (és a dir, els intervals de confiança) s'afegeixen com a equacions addicionals al filltre per aconseguir Posicionat de Punt Precís (PPP) en pocs minuts. La segona contribució ha estat la consolidació del modelat ionosfèric precís de Fast-PPP i la seva extensió d'un abast regional a una escala global. La correcta determinació i ús dels intervals de confiança de les correccions Fast-PPP ha esdevingut de gran importància a l'hora de navegar en zones de baixa latitud a l'equador, on la ionosfera és més difícil de modelar amb precisió. Fins i tot en aquest escenari, s'ha aconseguit una gran consistència entre els errors de posicionament reals i els nivells de protecció dels usuaris de Fast-PPP, tal com s'ha demostrat amb figures de mèrit similars a les utilitzades en l'aviació civil (els diagrames de Stanford). La tercera contribució d'aquesta Tesi Doctoral ha estat la caracterització de l'exactitud dels models ionosfèrics utilitzats actualment en GNSS. L'avaluació utilitza mesures de fase, sense ambigüitats i sense diferenciar, gràcies a la capacitat de modelatge centimètric emprat a la tècnica de Fast-PPP. No només els errors dels models de la ionosfera han estat quantificats en termes absoluts i relatius, sinó també, el seu efecte sobre la navegacióLa investigación de esta Tesis Doctoral, por compendio de artículos, se centra en la técnica de rápido Posicionamiento de Punto Preciso (Fast-PPP). La novedad, radica en el uso de un modelo ionosférico preciso que, combinado con productos estándard de reloj y órbita de satélite, reduce el tiempo de convergencia de las actuales técnicas de navegación precisa de una hora a pocos minutos.Mi primera contribución a la técnica Fast-PPP como estudiante de Doctorado ha sido el diseño y la implementación de un filtro de navegación de usuario innovador, basado en el tratamiento de múltiples frecuencias de medidas de código y fase sin diferenciar (absolutas). La estrategia del filtro de navegación evita la aplicación de la habitual combinación lineal libre de ionosfera para dichos observables. Así, se explota la capacidad de la señal multi-frecuencia en los nuevos Sistemas Globales de Navegación por Satélite (GNSS) y se aumenta la robustez del Fast-PPP en entornos difíciles, donde se reduce la visibilidad del cielo. Se ha optimizado para tomar ventaja de las correcciones necesarias para compensar los retardos (es decir, los errores) que afectan las señales GNSS. Las correcciones de Fast-PPP y más importante, sus incertidumbres (es decir, los intervalos de confianza) se añaden como ecuaciones adicionales al filtro para conseguir Posicionamiento de Punto Preciso (PPP) en pocos minutos. La segunda contribución ha estado la consolidación del modelado ionosférico preciso de Fast-PPP y la extensión de su cobertura regional a una escala global. La correcta determinación y uso de los intervalos de confianza de las correcciones Fast-PPP ha sido de gran importancia a la hora de navegar en zonas de latitudes ecuatoriales, donde la ionosfera es más difícil de modelar con precisión. Incluso en dicho escenario, se ha conseguido una gran consistencia entre los errores de posicionamiento reales y los niveles de protección de los usuarios de Fast-PPP, tal como se ha demostrado con figuras de mérito similares a las utilizadas en la aviación civil (los diagramas de Stanford).La tercera contribución de esta Tesis Doctoral ha sido la caracterización de la exactitud de los modelos ionosféricos utilizados actualmente en GNSS. El método usa medidas de fase, sin ambigüedad y sin diferenciar, gracias a la capacidad de modelado centimétrico empleado en la técnica de Fast-PPP. No solo los errores de los modelos de la ionosfera han sido cuantificados en términos absolutos y relativos, sino también, su efecto sobre la navegación.Award-winningPostprint (published version

Supporting energy regulation by monitoring land motion on a regional and national scale: a case study of Scotland

The advent of new satellite and data processing techniques have meant that routine, operational and reliable surveys of land motion on a regional and national scale are now possible. In this paper, we apply a novel satellite remote sensing technique, the Intermittent Small Baseline Subset method, to data from a new satellite mission, Sentinel-1, and demonstrate that a wide area map of ground deformation can be generated that supports the regulation of a range of energy related activities. The area for the demonstration is mainland Scotland (75,000 km2) and the land motion map required the processing of some 627 images acquired from March 2015 to April 2017. The results show that land motion is encountered almost everywhere across Scotland, dominated by subsidence over peatland areas. However, many other phenomena are also encountered including landslides and deformation associated with mining and civil engineering activities. Considering specifically Petroleum Exploration and Development Licence areas offered under the 14th Onshore Licensing Round in the UK, examples of the types of land motion are shown, including an example related to soil restoration by a wind farm. It is demonstrated that, in Scotland at least, almost all licence areas contain deformation of one form or another and, furthermore, the causes of that subsidence are dynamic and likely to be changing from year-to-year. Therefore, maps like this are likely to be of enormous use in a regulatory framework to scope out pre-existing problems in a licence area and to ensure that the correct monitoring framework is put in place once activities begin. They can also provide evidence of good practice and give assurance against litigation by third parties

Integrity Monitoring Using ARAIM Algorithm in Urban Environment

Aviation is one of the earliest application of the Global Navigation Satellite System (GNSS). Since the early days of the Global Positioning System (GPS), satellite navigation has been an essential part of the aviation industry. Being a particular mean of transport, which usually involves a large number of human lives, civil aviation always requires a high level of reliability from the navigation system. Such requirement brings about the concept of integrity, which concerns about the consistency and reliability of a navigation system, is defined as the capability of the system to provide timely warning when it should not be used for navigation. The concept of integrity allows the standardization of guidance systems' performance, with the utmost purpose of keeping safety for every flight. The concept of integrity has gained interests in other GNSS applications as well, especially in those that also require high reliability from the navigation solution, such as Intelligent Transport System (ITS), railways. This leads to the necessity to adapt the integrity monitoring techniques, in particular the Receiver Autonomous Integrity Monitoring (RAIM) algorithms, to use in working conditions other than the typical airport areas, such as urban environment. As a matter of fact, adaptation of RAIM algorithms to urban environment requires a throughout analysis of the environmental difference of the working condition as well as the requirement of the intended applications. This thesis focuses on developing a Kalman filter-based Advanced RAIM (ARAIM) algorithm for urban environment, which is an adaptation of the conventional ARAIM algorithm for civil aviation. ARAIM algorithm is considered the next generation of RAIM, aiming at providing higher integrity performance for more stringent phase of flight. The first step is to survey the necessary changes to adapt ARAIM algorithm to urban scenario. Experimental study highlights the prerequisite of finding a noise model to represents the signal noise level in urban area. After a suitable noise model was found after a comparative study, the KF-based ARAIM algorithm was developed. This method evaluates the separation of state correction using different subsets of measurement to detect abnormalities as well as potential faulty satellites for exclusion. The proposed method was also validated using simulation and real data. Performance analysis results show that the proposed algorithm can effectively follows the changes of signal quality which is expected to occur frequently when moving in urban environment, confirming its suitability for integrity monitoring in urban environment

Design of Rotorcraft Performance-Based Navigation Routes and Procedures: Current Challenges and Prospects

Helicopters play a relevant role in society due to their extraordinary versatility. However, they are particularly vulnerable to adverse weather conditions as the majority of operations are carried out under visual flight rules. This is partly due to the shortage of tailored helicopter instrument flight procedures and routes. The emergence of the performance-based navigation concept supported by the latest satellite navigation technologies has opened up new possibilities for rotorcraft operations in the last few years. This paper presents an extensive overview of the state of the art in the design of performance-based navigation routes for helicopters from two main standpoints: instrument flight procedures and route spacing. Apart from summarizing recent and current major initiatives to implement helicopter low-level routes and flight procedures, this paper provides an outlook on the latest advances and ongoing efforts by the International Civil Aviation Organization in the field of helicopter procedure and route design to ensure flyability, obstacle clearance, strategical separation, and segregation of traffic flows. In addition, several gaps in the current design criteria are identified and suggestions for future research and development are outlined

A user-oriented methodology for DInSAR time series analysis and interpretation: landslides and subsidence case studies

Recent advances in multi-temporal Differential Synthetic Aperture Radar (SAR) Interferometry (DInSAR) have greatly improved our capability to monitor geological processes. Ground motion studies using DInSAR require both the availability of good quality input data and rigorous approaches to exploit the retrieved Time Series (TS) at their full potential. In this work we present a methodology for DInSAR TS analysis, with particular focus on landslides and subsidence phenomena. The proposed methodology consists of three main steps: (1) pre-processing, i.e., assessment of a SAR Dataset Quality Index (SDQI) (2) post-processing, i.e., application of empirical/stochastic methods to improve the TS quality, and (3) trend analysis, i.e., comparative implementation of methodologies for automatic TS analysis. Tests were carried out on TS datasets retrieved from processing of SAR imagery acquired by different radar sensors (i.e., ERS-1/2 SAR, RADARSAT-1, ENVISAT ASAR, ALOS PALSAR, TerraSAR-X, COSMO-SkyMed) using advanced DInSAR techniques (i.e., SqueeSAR™, PSInSAR™, SPN and SBAS). The obtained values of SDQI are discussed against the technical parameters of each data stack (e.g., radar band, number of SAR scenes, temporal coverage, revisiting time), the retrieved coverage of the DInSAR results, and the constraints related to the characterization of the investigated geological processes. Empirical and stochastic approaches were used to demonstrate how the quality of the TS can be improved after the SAR processing, and examples are discussed to mitigate phase unwrapping errors, and remove regional trends, noise and anomalies. Performance assessment of recently developed methods of trend analysis (i.e., PS-Time, Deviation Index and velocity TS) was conducted on two selected study areas in Northern Italy affected by land subsidence and landslides. Results show that the automatic detection of motion trends enhances the interpretation of DInSAR data, since it provides an objective picture of the deformation behaviour recorded through TS and therefore contributes to the understanding of the on-going geological processes

Galileo: the added value for integrity in harsh environments

A global navigation satellite system (GNSS)-based navigation is a challenging task in a signal-degraded environments where GNSS signals are distorted by multipath and attenuated by fading effects: the navigation solution may be inaccurate or unavailable. A possible approach to improve accuracy and availability is the joint use of measurements from different GNSSs and quality check algorithms; this approach is investigated here using live GPS and Galileo signals. A modified receiver autonomous integrity monitoring (RAIM) algorithm, including geometry and separability checks, is proposed to detect and exclude erroneous measurements: the multi-constellation approach provides redundant measurements, and RAIM exploits them to exclude distorted observations. The synergy between combined GPS/Galileo navigation and RAIM is analyzed using live data; the performance is compared to the accuracy and availability of a GPS-only solution. The tests performed demonstrate that the methods developed are effective techniques for GNSS-based navigation in signal-degraded environments. The joint use of the multi-constellation approach and of modified RAIM algorithms improves the performance of the navigation system in terms of both accuracy and availability.JRC.G.5-Security technology assessmen

Delineating ground deformation over the Tengiz oil field, Kazakhstan, using the Intermittent SBAS (ISBAS) DInSAR algorithm

Changes in subsurface pore pressures and stresses due to the extraction of hydrocarbons often cause deformation over oil and gas fields. This can have significant consequences, including ground subsidence, induced seismicity and well failures. Geodynamic monitoring is an important requirement in recognising potential threats in sufficient time for remedial measures to be implemented. Differential interferometric synthetic aperture radar (DInSAR) is increasingly utilised for monitoring ground deformation over oil and gas reservoirs, achieving greater spatial coverage than traditional field-based surveying techniques. However, ground deformation over oil and gas fields can extend regionally into the surrounding rural landscape, where many conventional DInSAR techniques are of limited use due to the dynamic nature of the land cover. The Intermittent Small Baseline Subset (ISBAS) method is an advanced DInSAR technique, which considers the intermittent nature of coherence over dynamic land cover types to obtain markedly more ground motion measurements in non-urban regions. In this study, the ISBAS technique is used to delineate deformation over the super-giant Tengiz oil field in rural Kazakhstan. Analysis of ENVISAT data for 2004–2009 reveals a well-defined bowl subsiding with a maximum rate of −15.7 mm/year, corroborated by independent DInSAR studies and traditional levelling data. Subsequent application of ISBAS to Sentinel-1 data reveals significant evolution of deformation over the field in 2016–2017, with subsidence increasing dramatically to a maximum of -79.3 mm/year. The increased density of measurements obtained using the ISBAS technique enables accurate and comprehensive delineation and characterisation of ground deformation in this rural landscape, without the need for corner reflectors. This enhanced information could ultimately aid reservoir characterisation and management, and improve understanding of the risk posed by ground subsidence and fault reactivation

Analysis and comparison of the performance of satellite navigation procedures from flight test data at Zurich Airport

Prognosen sagen mittel- und langfristig eine steigende Anzahl von Flugbewegungen voraus, was zu einer Überlastung der bereits stark ausgelasteten Flugsicherungssektoren und Flughäfen in Regionen wie Mitteleuropa führt. Ein Lösungsvorschlag für dieses Problem ist die Einführung von Globalen Navigationssatellitensystemen (GNSS) als primäre Navigationsmittel, die einen flexibleren und effizienteren Betrieb ermöglichen, insbesondere für die Führung von Flugzeugen bei Präzisionsanflügen. Augmentierungssysteme für die Satellitennavigation wie das Ground Based Augmentation System (GBAS) oder das Satellite Based Augmentation System (SBAS) können die Anforderungen an die Navigationsleistung für solch kritische Phasen des Fluges erfüllen, vor allem die Integrität und die Genauigkeit für die sichere Führung des Flugzeugs. Daher konzentrieren sich die Forschungsfragen dieser Arbeit auf die Integritätsleistung in Bezug auf die Protection Levels von GBAS und SBAS und die Genauigkeit der Positionslösung von GBAS, SBAS und Standalone Signalen des Globalen Positionsbestimmungssystem (GPS). Forecasts predict an increased number of air traffic movements in the mid- and long-term, which results in intermediate congestions of already busy air traffic control sectors and airports in regions such as central Europe. A proposed solution to this consequence is the introduction of Global Navigation Satellite Systems (GNSS) as primary means of navigation, allowing more flexible and efficient operations, especially for the guidance of aircraft on precision approaches. Augmentation systems for satellite navigation such as the Ground Based Augmentation System (GBAS) or the Satellite Based Augmentation System (SBAS) can provide the navigation performance requirements for such critical phases of the flight, mainly the integrity and the accuracy for the safe guidance of the aircraft. Therefore, this bachelor's thesis focuses on the integrity performance in terms of protection levels of GBAS and SBAS and the accuracy performance of the position solution of GBAS, SBAS and unaugmented Global Positioning System (GPS) signals