Integration of LIDAR and IFSAR for mapping

LiDAR and IfSAR data is now widely used for a number of applications, particularly those needing a digital elevation model. The data is often complementary to other data such as aerial imagery and high resolution satellite data. This paper will review the current data sources and the products and then look at the ways in which the data can be integrated for particular applications. The main platforms for LiDAR are either helicopter or fixed wing aircraft, often operating at low altitudes, a digital camera is frequently included on the platform, there is an interest in using other sensors such as 3 line cameras of hyperspectral scanners. IfSAR is used from satellite platforms, or from aircraft, the latter are more compatible with LiDAR for integration. The paper will examine the advantages and disadvantages of LiDAR and IfSAR for DEM generation and discuss the issues which still need to be dealt with. Examples of applications will be given and particularly those involving the integration of different types of data. Examples will be given from various sources and future trends examined

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

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

Volcano monitoring with bistatic TanDEM-X SAR interferometry

Das Ziel der Dissertation ist die Untersuchung der Nutzbarkeit der Daten der TanDEM-X-Satellitenmission in der Vulkanforschung. Dabei wird die Topographie vor, während und nach einem vulkanologischen Ereignis abgebildet. Anhand einer differentiellen Analyse der abgeleiteten DEMs können topographische und volumetrische Änderungen quantifiziert werden. Als Untersuchungsgebiete dienen der Merapi in Indonesien, der Volcán de Colima in Mexico und der Tolbachik in Kamtschatka, Russland

InSAR Deformation Analysis with Distributed Scatterers: A Review Complemented by New Advances

Interferometric Synthetic Aperture Radar (InSAR) is a powerful remote sensing technique able to measure deformation of the earth’s surface over large areas. InSAR deformation analysis uses two main categories of backscatter: Persistent Scatterers (PS) and Distributed Scatterers (DS). While PS are characterized by a high signal-to-noise ratio and predominantly occur as single pixels, DS possess a medium or low signal-to-noise ratio and can only be exploited if they form homogeneous groups of pixels that are large enough to allow for statistical analysis. Although DS have been used by InSAR since its beginnings for different purposes, new methods developed during the last decade have advanced the field significantly. Preprocessing of DS with spatio-temporal filtering allows today the use of DS in PS algorithms as if they were PS, thereby enlarging spatial coverage and stabilizing algorithms. This review explores the relations between different lines of research and discusses open questions regarding DS preprocessing for deformation analysis. The review is complemented with an experiment that demonstrates that significantly improved results can be achieved for preprocessed DS during parameter estimation if their statistical properties are used

Integration of Synthetic Aperture Radar Interferometry (InSAR) and Geographical Information Systems (GIS) for monitoring mining induced surface deformations

Surface subsidence induced by mining is a source of risk to people, equipment and environment. It may also disrupt mining schedules and increase the cost of mine safety. To provide accurate assessment of the surface subsidence and its level of impact on mine production and environment, it is necessary to develop and introduce comprehensive subsidence monitoring systems. Current techniques for monitoring of surface deformation are usually based on classical survey principles. In general these techniques have disadvantages that limit their applicability: they follow point-by-point data collection techniques, they are relatively time-consuming and costly, they usually cover only a small area, they are not applicable for the monitoring of inaccessible areas and they are not able to collect data continuously.As a complementary or alternative technique, the thesis discusses the applicability of SAR interferometry for monitoring mining induced deformations. InSAR is a remote sensing technique that makes use of Synthetic Aperture Radar (SAR) observations to acquire change in terrain topography. In spite of the widespread application of the technique for monitoring large-scale deformations of the Earth crust, specific modifications are necessary for utilising the technology within a mining context. Limitations, such as difficulty to resolve deformation for a high gradient slope, difficulty to retrieve subsidence for localised highly dynamic ground movements and the unavailability of SAR images with the desired specifications restrict the potential to monitor high rate, localised mine subsidence on day-to-day basis.The secondary aim of the thesis is to present integration of InSAR and GIS in order to propose an optimum methodology for processing of InSAR data to determine mine subsidence. The presented research also involves detailed analysis of InSAR limitations. This in consequence has led to suggestions on how to improve current InSAR capability with respect to the mining needs.The thesis introduces a set of new GIS-based tools and methodologies that are integrated into a conventional InSAR processing technique, to further improve and facilitate application of InSAR in mining. The developed tools and techniques cover the three main stages of data processing (pre-processing, processing and postprocessing). The researcher tried to address InSAR.’s limitations associated with mining related applications and also to provide practical solutions to resolve these issues

Investigation of developments in interferometric synthetic aperture radar until 1994

Bibliography: p. 149-155.This thesis examines the topic of Synthetic Aperture Radar Interferometry in a historical perspective, tracing its development from its beginnings in the 1960s up until May 1994. Applications are listed and airborne and spaceborne implementations reviewed. The underlying theory of interferometry is explained, including a discussion of error sources, and a simulation for point targets is documented to illustrate the interferometric processing steps. The application of the SASAR VHF SAR system to interferometric operation is examined analytically

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

DInSAR for a Regional Inventory of Active Rock Glaciers in the Dry Andes Mountains of Argentina and Chile with Sentinel-1 Data

The Dry Andes region of Argentina and Chile is characterized by a highly developed periglacial environment. In these arid or semi-arid regions, rock glaciers represent one of the main pieces of evidence of mountain creeping permafrost and water reserves in a solid state. However, their distribution, degree of activity, and response to global warming are not yet well understood. In this context, this work aims to show the potential of the Sentinel-1-based interferometric technique (DInSAR) to map active rock glaciers at a regional level. In particular, the paper presents an active rock glacier inventory for the study area, which covers approximately 40,000 km2, ranging from latitude 30°210S to 33°210S. A total of 2116 active rock glaciers have been detected, and their elevations show a high correlation with the west-east direction. This result was obtained by using only 16 interferometric pairs. Compared to other remote sensing classification techniques, the interferometric technique offers a means to measure surface displacement (active rock glacier). This results in a reliable classification of the degree of activity compared to other methods, based on geomorphological, geomorphometric, and/or ecological criteria. This work presents evidence of this aspect by comparing the obtained results with existing optical data-based inventories. We conclude that the combination of both types of sensors (radar and optical) is an appropriate procedure for active rock glacier inventories, as both mapping methodologies are complementary.Fil: Villarroel, Cristian Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geología; ArgentinaFil: Tamburini Beliveau, Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Rosario; ArgentinaFil: Forte, Ana Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Monserrat, Oriol. Agencia Espacial Europea; EspañaFil: Morvillo, Mónica Cristina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentin

Characterizing slope instability kinematics by integrating multi-sensor satellite remote sensing observations

Over the past few decades, the occurrence and intensity of geological hazards, such as landslides, have substantially risen due to various factors, including global climate change, seismic events, rapid urbanization and other anthropogenic activities. Landslide disasters pose a significant risk in both urban and rural areas, resulting in fatalities, infrastructure damages, and economic losses. Nevertheless, conventional ground-based monitoring techniques are often costly, time-consuming, and require considerable resources. Moreover, some landslide incidents occur in remote or hazardous locations, making ground-based observation and field investigation challenging or even impossible. Fortunately, the advancements in spaceborne remote sensing technology have led to the availability of large-scale and high-quality imagery, which can be utilized for various landslide-related applications, including identification, monitoring, analysis, and prediction. This efficient and cost-effective technology allows for remote monitoring and assessment of landslide risks and can significantly contribute to disaster management and mitigation efforts. Consequently, spaceborne remote sensing techniques have become vital for geohazard management in many countries, benefiting society by providing reliable downstream services. However, substantial effort is required to ensure that such benefits are provided. For establishing long-term data archives and reliable analyses, it is essential to maintain consistent and continued use of multi-sensor spaceborne remote sensing techniques. This will enable a more thorough understanding of the physical mechanisms responsible for slope instabilities, leading to better decision-making and development of effective mitigation strategies. Ultimately, this can reduce the impact of landslide hazards on the general public. The present dissertation contributes to this effort from the following perspectives: 1. To obtain a comprehensive understanding of spaceborne remote sensing techniques for landslide monitoring, we integrated multi-sensor methods to monitor the entire life cycle of landslide dynamics. We aimed to comprehend the landslide evolution under complex cascading events by utilizing various spaceborne remote sensing techniques, e.g., the precursory deformation before catastrophic failure, co-failure procedures, and post-failure evolution of slope instability. 2. To address the discrepancies between spaceborne optical and radar imagery, we present a methodology that models four-dimensional (4D) post-failure landslide kinematics using a decaying mathematical model. This approach enables us to represent the stress relaxation for the landslide body dynamics after failure. By employing this methodology, we can overcome the weaknesses of the individual sensor in spaceborne optical and radar imaging. 3. We assessed the effectiveness of a newly designed small dihedral corner reflector for landslide monitoring. The reflector is compatible with both ascending and descending satellite orbits, while it is also suitable for applications with both high-resolution and medium-resolution satellite imagery. Furthermore, although its echoes are not as strong as those of conventional reflectors, the cost of the newly designed reflectors is reduced, with more manageable installation and maintenance. To overcome this limitation, we propose a specific selection strategy based on a probability model to identify the reflectors in satellite images