High-accuracy digital elevation model generation and ship monitoring from synthetic aperture radar images: innovative techniques and experimental results.

In this Thesis several state-of-the-art and innovative techniques for Digital Elevation Model (DEM) generation from Synthetic Aperture Radar (SAR) images are deeply analyzed, with a special focus on the methods which allow the improvement of the accuracy of the DEM product, which is directly related to the geolocation accuracy of geocoded images and is considered as an enabling factor for a large series of civilian and Defence applications. Furthermore, some of the proposed techniques, which are based both on phase and amplitude information, are experimented on real data, i.e. COSMO-SkyMed (CSK) data, assessing the achievable performances compared with the state-of-the-art, and pointing out and quantitatively highlighting the acquisition and processing strategies which would allow to maximize the quality of the results. Moreover, a critical analysis is performed about the main errors affecting the applied techniques, as well as the limitations of the orbital configurations, identifying several complementary techniques which would allow to overcome or mitigate the observed drawbacks. An innovative procedure for on-demand DEM production from CSK SAR data is elaborated and proposed, as well as an auto-validation technique which would enable the validation of the produced DEM also where vertical ground truths are not available. Based on the obtained results and on the consequent critical analysis, several interferometric specifications for new generation SAR satellites are identified. Finally, a literature review is proposed about the main state-of-the-art ship monitoring techniques, considered as one of the main fields of application which takes benefit from SAR data, based on single/multi-platform multi-channel SAR data, with a focus on TanDEM-X (TDX). In particular, in Chapter 1 the main concepts concerning SAR operating principles are introduced and the main characteristics and performances of CSK and TDX satellite systems are described; in Chapter 2 a review is proposed about the state-of-the-art SAR interferometric techniques for DEM generation, analyzing all the relevant processing steps and deepening the study of the main solutions recently proposed in the literature to increase the accuracy of the interferometric processing; in Chapter 3 complementary and innovative techniques respect to the interferometric processing are analyzed to mitigate disadvantages and to improve performances; in Chapter 4 experimental results are presented, obtained in the generation of high accuracy DEM by applying to a dataset of CSK images properly selected state-of-the-art interferometric techniques and innovative methods to improve DEM accuracy, exploring relevant limitations, and pointing out innovative acquisition and processing strategies. In Chapter 5, the basic principles of Ground Moving Target Indication (GMTI) are described, focusing on Displaced Phase Center Antenna (DPCA) and Along-Track Interferometry (ATI) techniques

Synthetic Aperture Radar für Monitoring in städtischen Gebieten und im Bergbau

Considering it is hazardous to the environment and people, monitoring land movements at urban area become more and more significant. On the other hand, studying of land movements in non-urban area is also important. Synthetic aperture radar using interferometric technique, which is known as InSAR, is capable of providing a quite denser measurement over large areas. More specifically, Interferometric SAR (InSAR), Differential InSAR (DInSAR), Persistent Scatterers InSAR (PSI) techniques are developing to meet people¡¯s requirements of detecting land movements. Due to the different features of urban and non-urban area, the application of InSAR for land movements monitoring may come cross different challenges. D¨¹sseldorf was used as the urban test site by processing 20 TerraSAR-X images using PSI. Levelling results provided by the State Capital of D¨¹sseldorf validated the PSInSAR result, when two time series showed similar progress with very few discrepancies. Xishan mining region was chosen as the non-urban test site in this project, because of clear advantages. Such as well served mining schedule and literature and rapid movements with big phase gradients. In the experiments carried out in Xishan mine, InSAR fulfilled the aim of mining parameters derivation. GPS surveying was collated for the coordinates of corner reflectors, which can validate and improve the accuracy of geocoding (better than 5 m).Die Überwachung von Setzungen in städtischen Gebieten wird immer wichtiger, da es sich um eine potenzielle Bedrohung für die Umwelt und den Menschen handelt. Die Untersuchung von Landsenkungen in nicht-städtischen Bereichen sind ebenfalls sehr wichtig. Mit interferometrischen Auswertungen von Synthetic Aperture Radar Messungen (InSAR) ist man in der Lage große Bereiche hochauflösend zu beobachten. SAR Systeme können während des Tages, der Nacht und unter allen Wetterbedingungen arbeiten. Heutzutage gibt es zunehmendes Interesse an der Anwendung von SAR für das Monitoring von Veränderungen der Erdoberfläche. Hierzu wurden speziell die Techniken des Interferometrischen SAR (InSAR), Differential InSAR (DInSAR) und Persistent Scatterers InSAR (PSI) entwickelt. Aufgrund der unterschiedlichen Merkmale von urbanen und nichturbanen Gebieten, kann die Anwendung von InSAR für das Monitoring von Bewegungen unterschiedliche Herausforderungen stellen. Die Stadt Düsseldorf wurde als Testfeld für die Verarbeitung von 20 TerraSAR-X Bilder mit PSI ausgewählt. Die Ergebnisse aus dem Nivellement der Landeshauptstadt Düsseldorf wurden für die Validierung der PSInSAR Ergebnisse genutzt. Zwei Zeitreihen zeigen einen ähnlichen Verlauf mit sehr geringen Abweichungen. Die Bergbauregion Xishan wurde als nichturbanes Testgebiete in diesem Projekt ausgewählt, weil es die Möglichkeit bietet an Informationen über den Bergbau, die Zeitpläne und Literatur zu kommen und es dort schnelle Oberflächenbewegungen mit großen Phasengradienten gibt. Die durchgeführten Experimente im Xishan Gebiet zeigen, dass man mit der InSAR Auswertung auch Bergbauparameter ableiten kann. Für die Koordinatenbestimmung der Corner Reflektoren wurden GPS Messungen durchgeführt, die auch zur Verbesserung der Satellitenbasislinien dienen und die Genauigkeit der Geokodierung (kleiner 5 m) verbessern

Fortgeschrittene InSAR Methodologie zum Studium vom Bodensenkung und Rissbildung aufgrund von Grundwasserentnahmen im Tal von Mexiko

Radar remote sensing techniques are well suited for deformation studies. The Mexico City subsidence,for example, has been mapped using both the conventional and multi-temporal methods; however, no complete characterization and detailed temporal analysis of the land settlement in the entire Valley of Mexico, covering the lakebed of the five ancient lakes (Chalco, Xochimilco, Texcoco, Xaltocan and Zumpango) has been performed until now. In this work, we mapped and analysed the subsidence and associated earth fissuring in the Valley by exploiting, for the first time, the Small Baseline method from StaMPS. The inversion methodology was studied in detail and interpreted, and the algorithm was adjusted to select a spatial reference on the basis of the surface geology information. This extended algorithm was assessed by comparing the results obtained with existing ones particularly over the southern Valley. Furthermore, unwrapping and quality of the times series were analysed using maps of system misclosure. Our results indicate that the proposed algorithm adapts adequately to the study area. Detailed ERS and ENVISAT conventional and multi-temporal InSAR analysis for the 1999-2000 and 2002-2010 periods, respectively, were performed on northern Valley of Mexico. Both urban and rural areas are experiencing subsidence, and rapid rates were found in densely populated areas or where sizeable volumes of water are used for crop irrigation. Time series were used to evaluate the impact of the subsidence on important infrastructure such as the Tunel Emisor Oriente. As second main aspect, the flexibility of the proposed InSAR algorithm to identify points undergoing non-linear deformation was exploited to develop a methodology that contributes to the location of soil fractures and to the understanding of their dynamics. Fissure-prone zones identified by this method, effectively coincided with existing records of ground failures. The fracture trigger mechanisms are furthermore discussed and evaluated where notable acceleration or deceleration is found. The proposed soil fracture identification approach provided useful and valuable information for improving the vulnerability maps in the area.Radarfernerkundungstechniken sind gut geeignet um Deformationsprozesse zu studieren. Beispielsweise wurden die Setzungen in Mexico City mit konventionellen und multitemporalen Methoden erfasst; allerdings wurde bis jetzt keine komplette Charakterisierung und detaillierte zeitliche Analyse der Landbesiedelung im gesamten Tal von Mexiko, die das Seebett von fünf ehemaligen Seen (Chalco, Xochimilco, Texcoco, Xaltocan und Zumpango) beinhaltet, durchgeführt. In dieser Arbeit wurde die Bodensenkungen und die dazugehörigen Boden-Brüche im Tal von Mexiko mit Hilfe der Small Baseline Methode von StaMPS kartiert und analysiert. Die dazugehörige Inversionsmethode wurde im Detail studiert und interpretiert und dieser Algorithmus auf Basis der geologischen Information so angepasst, dass die Ergebnisse als räumliche Referenz dienen können. Dieser erweiterte Algorithmus wurde durch den Vergleich mit existierenden Ergebnissen aus dem südlichen Tal validiert. Das „Unwrapping“ und die Qualität der Zeitreihen wurden mit statistischen Verfahren bewertet. Detaillierte Analysen von ERS- und ENVISAT-Daten mit konventionellem und multitemporalem InSAR für die Zeiträume von 1999-2000 und von 2002-2010 wurden im Norden des Talbereiches von Mexico durchgeführt. Sowohl die städtischen als auch die ländlichen Bereiche erfahren Bodensenkungen. Große Setzungsraten wurden besonders in dicht bevölkerten Gebieten gefunden oder in Bereichen mit beträchtlicher Wasserentnahme zur Feldbewässerung. Die Zeitreihen wurden verwendet um die Auswirkungen der GW-Entnahme auf wichtige Infrastrukturprojekte zu bewerten,z.B. den Tunel Emisor Oriente. Als weiterer Schwerpunkt wurde die Flexibilität des verwendeten InSAR Algorithmus genutzt, um nichtlineare Verformung zu identifizieren und eine Methode zur Lokalisierung von Boden-Bruchzonen zu entwickeln und um ihre Dynamik zu verstehen. Die Lage der mit dieser Methode identifizierten Bruchzonen stimmt mit existierenden Aufzeichnungen von Bruchaktivitäten überein. Die Bruchauslösemechanismen werden an den Stellen diskutiert und bewertet, an denen deutliche Beschleunigungen oder Verzögerungen erkannt wurden. Der vorgestellte Ansatz zur Identifikation der Brüche stellt nützliche und wertvolle Informationen für die Verbesserung der Schadenskarten in diesem Gebiet dar

Radar interferometry for monitoring land subsidence and coastal change in the Nile Delta, Egypt

Land subsidence and coastal erosion are worldwide problems, particularly in densely populated deltas. The Nile Delta is no exception. Currently, it is undergoing land subsidence and is simultaneously experiencing retreat of its coastline. The impacts of these long-term interrelated geomorphic problems are heightened by the economic, social and historical importance of the delta to Egypt. Unfortunately, the current measures of the rates of subsidence and coastal erosion in the delta are rough estimates at best. Sustainable development of the delta requires accurate and detailed spatial and temporal measures of subsidence and coastal retreat rates. Radar interferometry is a unique remote sensing approach that can be used to map topography with 1 m vertical accuracy and measure surface deformation with 1 mm level accuracy. Radar interferometry has been employed in this dissertation to measure urban subsidence and coastal change in the Nile Delta. Synthetic Aperture Radar (SAR) data of 5.66 cm wavelength acquired by the European Radar Satellites (ERS-1 and ERS- 2) spanning eight years (1993-2000) have been used in this investigation. The ERS data have been selected because the spatial and temporal coverage, as well as the short wavelength, are appropriate to measure the slow rate of subsidence in the delta. The ERS tandem coherence images are also appropriate for coastal change detection. The magnitude and pattern of subsidence are detected and measured using Permanent Scatterer interferometry. The measured rates of subsidence in greater Cairo, Mansura, and Mahala are 7, 9, and 5 mm yr-1, respectively. Areas of erosion and accretion in the eastern side of the delta are detected using the ERS tandem coherence and the ERS amplitude images. The average measured rates of erosion and accretion are -9.57 and +5.44 m yr-1, respectively. These measured rates pose an urgent need of regular monitoring of subsidence and coastline retreat in the delta. This study highlighted the feasibility of applying Permanent Scatterer interferometry in inappropriate environment for conventional SAR interferometry. The study addressed possibilities and limitations for successful use of SAR interferometry within the densely vegetated delta and introduced alternative strategies for further improvement of SAR interferometric measurements in the delta

Point target interferometry as applied to the characterization of localized deformation features

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 23, 2010).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dr. Brent Rosenblad, Dissertation Supervisor.Vita.Ph. D. University of Missouri--Columbia 2008.Monitoring of ground deformation is a critical component of geotechnical engineering practice. This study investigated the application of synthetic aperture radar interferometry (InSAR), using point target analysis (IPTA) for characterizing localized deformation features that are often associated with geotechnical engineering activities. In contrast to discrete point in-situ deformation measurement techniques, InSAR can be used to obtain a broader view of deformation processes at a site. Satellite data available for the time period of construction of the Los Angeles Metro Rail Red Line was utilized to characterize the technique in terms of dependence of the feasibility in its application on SAR image acquisition parameters. Additionally, a statistical assessment of the sensitivity of deformation rates and the associated standard errors to the size of the dataset analyzed was performed by analyzing randomly generated subsets of data. While the spatial and temporal signatures corresponding to tunneling during the construction of the Red Line were successfully detected, it was found that a minimum of twenty SAR acquisitions were required in order to constrain the deformation history of the study area. From the sensitivity analysis, it was found that the variability of the derived estimates of deformation parameters varied inversely as a function of the size of the dataset used for analysis.Includes bibliographical references

The 2-Look TOPS Mode: Design and Demonstration with TerraSAR-X

Burst-mode acquisition schemes achieve wide coverage at the expense of a degraded azimuth resolution, reducing therefore the performance on the retrieval of ground displacements in the azimuth direction, when interferometric acquisitions are combined. Moreover the azimuth varying line-of-sight can induce discontinuities in the interferometric phase when local azimuth displacements are present, e.g., due to ground deformation. In this contribution we propose the interferometric 2-look TOPS mode, a sustaining innovation, which records bursts of radar echoes of two separated slices of the Doppler spectrum. The spectral separation allows to exploit spectral diversity techniques, achieving sensitivities to azimuth displacements better than with StripMap, and eliminating discontinuities in the interferometric phase. Moreover some limitations of the TOPS mode to compensate ionospheric perturbations, in terms of data gaps or restricted sensitivity to azimuth shifts, are overcome. The design of 2-look TOPS acquisitions will be provided, taking the TerraSAR-X system as reference to derive achievable performances. The methodology for the retrieval of the azimuth displacement is exposed for the case of using pairs of images, as well as for the calculation of mean azimuth velocities when working with stacks. We include results with experimental TerraSAR-X acquisitions demonstrating its applicability for both scenarios

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