Javier Duro

Generation of Advanced ERS and Envisat Interferometric SAR Products Using the Stable Point Network Technique

The advanced differential interferometric SAR techniques (A-DINSAR), based on time series of SAR images, are powerful geodetic tools for land deformation monitoring. This paper, which is focused on a particular A-DINSAR technique, named Stable Point Network, concisely outlines its characteristics and describes its products: average deformation maps, deformation time series, and the maps of the residual topographic error used to precisely geocode the A-DINSAR products. Furthermore, it illustrates the performance of the technique on a test area located in Barcelona, Spain. From this experiment, interesting features are highlighted: the capability to cover wide areas and at the same time measuring thin infrastructures, such as the main dike of the port; the good agreement between the deformation velocities and the reference values coming from leveling campaigns; the high sensitivity of the A-DINSAR estimations, which can measure millimeter-level periodical deformations due to thermal dilation, and the precise geocoding of the A-DINSAR products.

ASAR ERS interferometric phase continuity

For ten years, a long history of data was acquired by the SAR sensors on the satellite ERS-1 and ERS-2 offering a wide range of interferometric applications. In 2002, the more advanced satellite ENVISAT was launched. The SAR on board on ENVISAT (ASAR) can continue the success of the remote sensing mission of the ERS satellites and preserve or even increase the value of the archived ERS data. The subject of this study is to demonstrate the continuity of the interferometric measurements by the combination of the SAR scene of the different sensors to interferograms (cross interferometry).

Generation of deformation maps at low resolution using differential interferometric SAR data

In this paper, an advanced technique for the generation of deformation maps using SAR data is presented. The input data is a set of low resolution Differential Interferograms (multi-looked data) and their associated coherence images. An important advantage of this algorithm is that it can work with a reduced number of SAR images with a diversity of spatial baselines. The algorithm takes advantage of those pixels presenting a good coherence level in the whole set of interferograms, avoiding the rest affected by temporal decorrelation. All pixels accomplishing the selection criteria are related using a Delaunay triangulation. The subsidence velocity map over the scene is obtained adjusting an interferometric phase model, which also considers the error on the DEM used to remove the topography from the interferogram set, to the pixel phase increments. If the density of quality pixels is high enough over the scene, an interpolation of the areas with no information can be performed to obtain a complete deformation map of the zone. Otherwise, the information can be presented only on those zones with enough pixel density. This algorithm has been tested with ERS data from an area of Catalonia (Spain) and validated with precise levelling measurements.

Thermal dilation monitoring of complex urban infrastructure using high resolution SAR data

Monitoring the deformation of urban infrastructure is crucial for improving safety and reducing economic loss. Ground deformation (caused by construction, groundwater extraction etc.) can be measured with millimeter accuracy using advanced stacking techniques in differential SAR interferometry. However, deformation might also occur due to thermal dilation of complex urban objects such as buildings and bridges, resulting in structural stress and thus, a need for monitoring. High resolution SAR missions e.g. TerraSAR-X provide a unique opportunity to measure such small seasonal displacements. This paper investigates different techniques such as Persistent Scatterer Interferometry (PSI), Distributed Scatterer Interferometry (DSI), Stable Point Network (SPN) and Small Baseline Subset Algorithm (SBAS) for thermal dilation monitoring of complex urban infrastructure using X-band SAR data.

Combined X- and L-band PSI analyses for assessment of land subsidence in Jakarta

Jakarta is the capital of Indonesia and is home to approximately 10 million people on the coast of the Java Sea. The subsidence due to groundwater extraction, increased development, natural consolidation of soil and tectonics in Jakarta has been known since the early part of the 20th century. Evidence of land subsidence exists through monitoring with GPS, level surveys and preliminary InSAR investigations [1]. World Bank studies conservatively estimate land subsidence in Jakarta occurring at an average rate of 5 cm per year, and in some areas, over 1 meter was already observed. Recent studies of land subsidence found that while typical subsidence rates were 7.5-10 cm a year, in localized areas of North Jakarta subsidence in the range 15-25 cm a year was occurring, which if sustained, would result in them sinking to 4 to 5 meters below sea level by 2025. Land subsidence will require major interventions, including increased pumping, dikes and most likely introducing major infrastructure investment for sea defence [1]. With the increasing prevalence of Earth Observation (EO), the World Bank and the European Space Agency (ESA) have set up a partnership that aims at highlighting the potential of EO information to support the monitoring and management of World Bank projects. It in this framework that was defined the EOWorld projects [2]. Altamira Information, company specialized in ground motion monitoring, has managed one of those projects, focusing on the assessment of land subsidence in Jakarta.

KaRIn - the Ka-band radar interferometer on SWOT: Measurement principle, processing and data specificities

The principal instrument of the SWOT (Surface Water and Ocean Topography) altimetry mission is KaRIn, a Ka-band interferometric SAR system operating on near-nadir swaths on both sides of the satellite track. This article briefly describes the measurement principle, the processing steps and the specificities of the interferometric SAR data of KaRIn as compared to conventional spaceborne SAR systems.

Comparative analyses of multifrequency PSI ground deformation measurements

In recent years many new developments have been made in the field of SAR image analysis. The diversity of available SAR imagery allows a wider range of applications to be covered in the domain of risk management and hazard mapping. The work that we propose is based on the analysis of differences in ground deformation measurements extracted from the processing of data stacks acquired at different frequencies. The aim of the project is the definition of criteria that could assist in the selection of the most appropriate SAR mission according to the type of regions of interest. Key factors are geographic localization and land cover. The study is organized in two main parts. First, the impact of sensitivity to motion, land cover characteristics, spatial resolution and atmospheric artifacts is investigated at different wavelengths. Second, the PS density achieved and the capacity to detect and monitor fast and slow motions over urban and rural areas with different frequencies is analyzed. The presented InSAR analyses have been performed using the Stable Point Network (SPN) PSI software developed by Altamira Information.

KaRIn on SWOT: Modeling and simulation of near-nadir Ka-band interferometric SAR images

The principal instrument of the wide-swath altimetry mission SWOT is KaRIn, a Ka-band interferometric SAR system operating on near-nadir swaths on both sides of the satellite track. Due to the short wavelength and particular observation geometry, there are very limited reports on the backscattering from natural surfaces. Simulators that cover both radiometric and geometric aspects are therefore developed in the framework of the CNES phase 0 and A studies of SWOT. This article presents the modeling and simulation approaches that have been adopted, and shows some preliminary simulation results.

An assessment of TanDEM-X GlobalDEM over rural and urban areas

Digital Elevation Model (DEM) is a key input for the development of risk management systems. Main limitation of the current available DEM is the low level of resolution. DEMs such as STRM 90m or ASTER are globally available free of charge, but offer limited use, for example, to flood modelers in most geographic areas. TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement), the first bistatic SAR can fulfil this gap. The mission objective is the generation of a consistent global digital elevation model with an unprecedented accuracy according to the HRTI-3 (High Resolution Terrain Information) specifications. The mission opens a new era in risk assessment. In the framework of ALTAMIRA INFORMATION research activities, the DIAPASON (Differential Interferometric Automated Process Applied to Survey Of Nature) processing chain has been successfully adapted to TanDEM-X CoSSC (Coregistered Slant Range Single Look Complex) data processing. In this study the capability of CoSSC data for DEM generation is investigated. Within the on-going FP7 RASOR project (Rapid Analysis and Spatialisation and Of Risk), the generated DEM are compared with Intermediate DEM derived from the TanDEM-X first global coverage. The results are presented and discussed.

Multi-hazard Risk Analysis using the FP7 RASOR Platform

Climate change challenges our understanding of risk by modifying hazards and their interactions. Sudden increases in population and rapid urbanization are changing exposure to risk around the globe, making impacts harder to predict. Despite the availability of operational mapping products, there is no single tool to integrate diverse data and products across hazards, update exposure data quickly and make scenario-based predictions to support both short and long-term risk-related decisions. RASOR (Rapid Analysis and Spatialization Of Risk) will develop a platform to perform multi-hazard risk analysis for the full cycle of disaster management, including targeted support to critical infrastructure monitoring and climate change impact assessment. A scenario-driven query system simulates future scenarios based on existing or assumed conditions and compares them with historical scenarios. RASOR will thus offer a single work environment that generates new risk information across hazards, across data types (satellite EO, in-situ), across user communities (global, local, climate, civil protection, insurance, etc.) and across the world. Five case study areas are considered within the project, located in Haiti, Indonesia, Netherlands, Italy and Greece. Initially available over those demonstration areas, RASOR will ultimately offer global services to support in-depth risk assessment and full-cycle risk management.