Persistent Scatterer Interferometry based on geodetic estimation theory

The Earth's surface is continuously deforming due to natural and anthropogenic processes, such as tectonics, landslides, oil and gas extraction, and groundwater level changes. Persistent Scatterer Interferometry is a technique that provides measurements of this surface motion based on satellite radar images. The technique uses the persistent radar reflection from certain objects on the Earth's surface to estimate their deformation time series. However, since the location of these objects is unknown, Persistent Scatterer Interferometry comprises both an estimation and a detection problem. In this contribution a Persistent Scatterer Interferometry algorithm is presented that resolves this estimation and detection problem based on geodetic estimation theory. The complete processing procedure, from the original radar images to the geolocated Persistent Scatterers, is described. Herein, the estimation of the unknown phase ambiguities, both in the time and space domain, forms a key component. The developed algorithm is characterized by a continuous update of the stochastic model of the phase observations after the estimation and removal of error sources, a direct testing of the estimated phase ambiguities, and the ability to apply local deformation models to improve the number of detected Persistent Scatterers and the reliability of the estimated time series.Geoscience and Remote SensingCivil Engineering and Geoscience

Satellietdeformatiemetingen Eemdijk: Technisch Report

Satellietradarinterferometrie (InSAR) maakt het mogelijk om voor bepaalde objecten op het aardoppervlak deformaties op mm niveau te meten. De techniek wordt onder andere toegepast voor het monitoren van de stabiliteit van verschillende typen infrastructuur, zoals wegen en spoorwegen. De voordelen van satellietradarinterferometrie zijn dat grote gebieden kunnen worden waargenomen, over lange tijd, met een meetfrequentie van enkele dagen tot enkele weken. Door de hoge meetprecisie kan de techniek potentieel bijdragen tot een vroege detectie van stabiliteitsproblemen in infrastructuur. Vanwege de grootte van het totale netwerk van waterkeringen in Nederland is toepassingvan de techniek op waterkeringen ook erg interessant. Momenteel wordt binnen het kader van het SAFELevee project door de Technische Universiteit Delft verder onderzoek gedaan naar de toepasbaarheid van de techniek. Een van de mogelijke toepassen is het gericht monitoren van speciale constructies, zoals damwanden.Het doel van dit door de Technische Universiteit Delft uitgevoerde project is om de bruikbaarheid van InSAR voor dijken met speciale constructies te analyseren enevalueren gebaseerd op metingen van de damwandproef bij Eemdijk. Om een aantal goede reflectiepunten van de radarsignalen te creëren, zullen hoekreflectoren op de dijk worden geplaatst. Ondanks dat de looptijd van de proef kort is in vergelijking met de meetfrequentie van de satellietdata, kunnen toch enkele metingen worden verkregen, die gebruikt kunnen worden voor het bepalen van de potentie van de techniek voor monitoring in de toekomst.Hydraulic Structures and Flood RiskMathematical Geodesy and Positionin

A generic approach to parameterize the turbulent energy of single-epoch atmospheric delays from InSAR time-series

The observed phase in time series of interferometric synthetic aperture radar (InSAR) products is a superposition of various components. Differential topography, line-of-sight displacements, and differential atmospheric delays are the main contributions and need to be disentangled to derive accurate digital elevation model (DEM), deformation, or atmospherical products from InSAR. However, isolating the atmospheric component has been proven difficult as it is spatiotemporally highly dynamic and a superposition of two atmospheric states. Here, we propose an approach to parameterize the stochastic properties of the single-epoch atmospheric delay field as a way to define the atmospheric signal. We found that the atmospheric signal of a time series of interferograms can be characterized by structure functions, which can be used to isolate the single-epoch structure functions. Due to the scaling properties of the atmospheric signal, it is then possible to construct a parametric function per SAR acquisition, using two isotropic and three anisotropic parameters. In particular, the isotropic parameters for the short-distance variation and long-distance variation in atmospheric delay can be used to characterize the atmospheric signal. For a test set of 151 Sentinel-1 acquisitions, this results in an atmospheric energy range of about 10 for short-distance scales and about 50 for long-distance scales. Our parameterization demonstrates that we can describe the spatiotemporal variability of InSAR atmospheric delays, which provides a measure for atmospheric noise for individual epochs in deformation time series based on distance and azimuth.Geoscience and Remote SensingMathematical Geodesy and Positionin

First analysis of C-band ECR transponders for InSAR geodesy

Well-identifiable reference benchmarks are important in SAR interferometry to enable linking between different measurement techniques, or to enable datum connection between the local InSAR datum and Terrestrial Reference Systems. As corner reflectors for C-band are rather large, weather sensitive, and difficult to maintain over time frames of several years, active electronic transponders are an alternative. However, low cost transponders have not been on the market until recently. Here we report results from field tests of a new type of transponder. We show that the phase precision is in the order of an equivalent displacement of 0.5 mm, and that the RCS of the transponder is equivalent to a trihedral corner reflector with a leg length of 1.03 m.Mathematical Geodesy and Positionin

Hybrid InSAR Processing for Rapidly Deforming Peatlands Aided by Contextual Information

We present a novel InSAR processing scheme which combines point scatterer (PS) and distributed scatter (DS) approaches in a hybrid framework along with contextual information about the environment under study. Data such as land parcel divisions, precipitation and temperature are integrated into the processing pipeline in order to produce accurate deformation time series estimates of the Dutch peatlands. In addition to these steps, a segmented processing scheme is introduced to manage irreversible losses of coherence in the interferogram stack. Initial results show a promising agreement with in-situ ground truth measurements gathered by extensometer readings of shallow surface deformation.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Mathematical Geodesy and Positionin

Bridging Loss-of-Lock in InSAR Time Series of Distributed Scatterers

We introduce the term loss-of-lock to describe a specific form of coherence loss that results in the breakage of a synthetic aperture radar interferometric (InSAR) time series. Loss-of-lock creates a specific pattern in the coherence matrix of a multilooked distributed scatterer (DS) by which it may be detected. Along with identification, we introduce a new DS processing methodology that is designed to mitigate the effects of loss-of-lock by introducing contextual data to assist in the time-series processing. This methodology is of particular relevance to regions that suffer from severe temporal decorrelation, such as northern peatlands. We apply our new method to two subsiding cultivated peatland regions in The Netherlands which previously proved impossible to monitor using DS InSAR techniques. Our results show a very good agreement with in situ validation data as well as spatial correlation between regions and the natural terrain.Mathematical Geodesy and Positionin

Preliminary Results of the Safelevee Project

Hydraulic Structures and Flood RiskMathematical Geodesy and Positionin

Augmented satellite inSAR for assessing short-term and long-term surface deformation due to shield tunnelling

In this work, we investigate if, when, and how satellite InSAR can be used for evaluating surface settlements that occur during shield tunnelling in soft soil areas. We evaluate the applicability of InSAR prior, during, and after tunnel construction. Special emphasis is placed on the influence of the InSAR phase ambiguities in relation to short-term settlements that may occur during tunnel construction. We demonstrate that a rough analytic settlement prediction can be sufficient to resolve the most probable phase ambiguity level, leading to an augmented implementation of InSAR. We use the shield tunnel of the in North/South Metro Line Amsterdam as a case study, where surface levelling data is available to assess and validate the results. We conclude that InSAR is a valuable complementary source of information as it provides data outside the area of the conventional surveying benchmarks and it reveals relevant information about settlement patterns before and after traditional construction monitoring periods.Hydraulic Structures and Flood RiskMathematical Geodesy and PositioningGeo-engineerin

On the Stochastic Model for InSAR Single Arc Point Scatterer Time Series

InSAR enables the estimation of displacements of (objects on) the earth's surface. To provide reliable estimates, both a stochastic and mathematical model are required. However, the intrinsic problem of InSAR is that both are unknown. Here we derive the Variance-Covariance Matrix (VCM) for double differenced phase observations for an arc, i.e., the phase difference between two points relative to a reference epoch. Using the Normalized Amplitude Dispersion we subdivide the time series in multiple partitions. The method results in a more realistic stochastic model, and consequently more realistic and reliable displacement parameters. The stochastic model also allows to make statements on the precision and reliability of the estimated parameters.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Mathematical Geodesy and Positionin

Doris 5 and Event-Triggered InSAR Processing

Mathematical Geodesy and Positionin