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

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

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

On the influence of sub-pixel position correction for PS localization accuracy and time series quality

Persistent Scatterer Interferometry (PSI) is a time series remote sensing technique to estimate displacements of geo-objects from the interferometric phases of selected Persistent Scatterers (PS). The relative position of a scatterer within a resolution cell causes an additional phase contribution in the observed phase, which needs to be accounted for in PSI processing. Here we analyze the influence of this sub-pixel position correction on point localization and displacement quality. Apart from a theoretical evaluation, we perform experiments with TerraSAR-X, Radarsat-2, and Sentinel-1, demonstrating various levels of improvement. We show that the influence of the sub-pixel correction is significant for the geolocation of the scatterer (meter-level improvement), modest for the elevation estimation (centimeter-level improvement), and limited for the displacement estimation (submillimeter-level). For displacement velocities, we find variations of a few tenths of a millimeter per year. The effect of sub-pixel correction is most dominant for large orbital baselines and short time series.</p

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

World-wide InSAR sensitivity index for landslide deformation tracking

Landslides are a major geohazard in hilly and mountainous environments. In-situ inspection of downslope motion is costly, sometimes dangerous and, requires prior knowledge of the existence of a landslide. Remote sensing from space is a way to detect and characterize landslides systematically at large scale. Interferometric Synthetic Aperture Radar (InSAR) has shown to be a valuable resource of deformation information, but it requires expert knowledge and considerable computational efforts. Moreover, the successful application of InSAR for landslides requires a favorable acquisition geometry relative to the landslide deformation pattern. Consequently, there is a need for a widely applicable tool to assess the potential of InSAR at a particular location a priori. Here we present a novel, generic approach to assess the potential of InSAR-based deformation tracking, providing a standardised and automated method applicable on any slope. We define the detection potential as the sensitivity of InSAR to detect downslope displacement combined with the presence of coherently scattering surfaces. We show that deformation can be detected on at least 91% of the global landslide-prone slopes, and provide an open source Google Earth Engine tool for the quick assessment of the availability of potential coherent scatterers. This tool enables any person interested in applying InSAR to routinely assess the potential for monitoring landslide deformation in their region of interest

Data assimilation of PS-InSAR movement measurements applied to the bergermeer gas field

This paper reports a study on the use of satellite radar data to constrain the subsurface model parameters of the Bergermeer gas field. Using PSI (Persistent Scatterer InSAR) technology, ascending and descending data were applied in line-of-sight geometry, i.e., without first unravelling the horizontal and vertical components of the signal. The model parameters were constrained using an ensemble smoother with multiple data assimilation. A good match could be obtained with realistic values of the reservoir compaction coefficient and of the subsurface basement elastic modulus. For the aquifer parts that were depleted according to the reservoir simulation, the northern part indeed gave a reasonable value for the compaction coefficient. For the southern part the resulting compaction coefficient was around zero, indicating that the pressure depletion in this part of the aquifer was overestimated and that it was actually not connected to the reservoir. The study shows that it is feasible to use PSI surface movement data to obtain information about the reservoir and that the use of line-of-sight movements from both ascending and descending satellite passes adds an additional dimension to the data and an improved quality of the assimilation results