María Cuevas-González

An Approach to Persistent Scatterer Interferometry

This paper describes a new approach to Persistent Scatterer Interferometry (PSI) data processing and analysis, which is implemented in the PSI chain of the Geomatics (PSIG) Division of CTTC. This approach includes three main processing blocks. In the first one, a set of correctly unwrapped and temporally ordered phases are derived, which are computed on Persistent Scatterers (PSs) that cover homogeneously the area of interest. The key element of this block is given by the so-called Cousin PSs (CPSs), which are PSs characterized by a moderate spatial phase variation that ensures a correct phase unwrapping. This block makes use of flexible tools to check the consistency of phase unwrapping and guarantee a uniform CPS coverage. In the second block, the above phases are used to estimate the atmospheric phase screen. The third block is used to derive the PS deformation velocity and time series. Its key tool is a new 2+1D phase unwrapping algorithm. The procedure offers different tools to globally control the quality of the processing steps. The PSIG procedure has been successfully tested over urban, rural and vegetated areas using X-band PSI data. Its performance is illustrated using 28 TerraSAR-X StripMap images over the metropolitan area of Barcelona.

A Noninterferometric Procedure for Deformation Measurement Using GB-SAR Imagery

Deformation monitoring using ground-based synthetic aperture radar (GB-SAR) data usually exploits the interferometric phases. In this letter, a new noninterferometric procedure is proposed, which exploits the geometric content of GB-SAR amplitude imagery and estimates deformation through image matching. This letter describes, step by step, this procedure. In order to achieve acceptable deformation measurement performances, the technique needs special targets, which have to guarantee a good image matching quality. If the available natural targets are insufficient, artificial corner reflectors are required. The new approach overcomes some of the main limitations of GB-SAR interferometry; it yields aliasing-free deformation estimates, is insensitive to atmospheric effects, and provides 2-D displacement measurements while interferometry only has a mono-dimensional measurement capability. Several experiments focusing on the performances of the new procedure are described. The procedure is validated using different scenarios. On a real-size landslide scenario, a mean absolute error over 12 corner reflectors of 0.59 cm is achieved, i.e., 1/85th of the pixel size. These encouraging results can be of interest for several deformation monitoring applications.

Sentinel-1 Data Analysis for Landslide Detection and Mapping: First Experiences in Italy and Spain

Open image in new window The differential interferometric SAR (DInSAR) technique is a powerful tool to detect and monitor ground deformation. In this paper we address an important DInSAR application, which is the detection and mapping of landslides. The potential of DInSAR to detect and monitor landslides has been extensively documented in the literature, mainly using the C-band data from the European Remote Sensing (ERS-1 and -2), Envisat and Radarsat missions. A significant improvement in landslide monitoring is expected by the SAR data of the two satellites Sentinel-1A and -1B of the European Space Agency. This paper describes the authors’ first experience using Sentinel-1 for landslide monitoring. The paper describes the data processing and analysis strategy, and then illustrates some deformation measurement results obtained over Italy and Spain.

Monitoring soil creep landsliding in an urban area using persistent scatterer interferometry (El Papiol, Catalonia, Spain)

Soil creep is characterised by slow displacement, with depths of a few meters and loosely defined limits. Buildings and infrastructure located on slopes affected by such landslides may suffer significant damages if their foundations are poorly dimensioned. The presence of soil creep in urban areas makes it necessary to develop landslide activity maps, derive hazard maps, and implement risk management plans. Even though both geological and geomorphological analyses can provide basic information, it is often necessary to use additional techniques to obtain information about ground displacements. This paper proposes a method to derive a soil creep activity map using a multi-approach analysis based on geological, geomorphological, and persistent scatterer interferometry (PSI) data. PSI is a satellite-based technique to estimate land displacement velocity. The work described in this paper was carried out in the town of El Papiol, in the metropolitan area of Barcelona (Spain). This is an urban area that has been heavily affected by soil creep over the past decades. The results achieved show that PSI data substantially improve the information provided by the geological and geomorphological analyses and make it possible to accurately define the landslide area and estimate its activity.

The PSIG procedure to Persistent Scatterer Interferometry (PSI) using X-band and C-band Sentinel-1 data

A new approach to Persistent Scatterer Interferometry (PSI) data processing and analysis implemented in the PSI chain of the Geomatics (PSIG) Division of CTTC is used in this work. The flexibility of the PSIG procedure allowed evaluating two different processing chains of the PSIG procedure. A full PSIG procedure was implemented in the TerraSAR-X dataset while a reduced PSIG procedure was applied to the nine Sentinel-1 images available at the time of processing. The performance of the PSIG procedure is illustrated using X-band and C-band Sentinel-1 data and several examples of deformation maps covering different types of deformation phenomena are shown.

The PSIG approach to persistent scatterer interferometry

This paper describes some of the key features of the Persistent Scatterer Interferometry chain of the Geomatics (PSIG) Division of CTTC. The paper firstly provides an overview of the entire PSI chain. It then focuses on the first part of the chain, which provides the input data for the estimation of the Atmospheric Phase Screen (APS). In this part, the so-called Cousin Persistent Scatterers (CPSs) are sought, which are Persistent Scatterers (PSs) characterized by a moderate spatial phase variation that ensures a correct phase unwrapping. The main output of this part of the chain is a set of correctly unwrapped and temporally ordered phases, which are computed on CPSs that cover homogeneously the area of interest. In order to do so a procedure to check the consistency of phase unwrapping is used. The paper describes the used algorithms and illustrates their performances using a set of TerraSAR-X StripMap images over the metropolitan area of Barcelona.

The PSIG chain: an approach to Persistent Scatterer Interferometry

The PSIG procedure is a new approach to Persistent Scatterer Interferometry (PSI), which is implemented in the in-house PSI chain of the Geomatics Division of the CTTC. The PSIG procedure has been successfully tested over urban, rural and vegetated areas using X-band SAR data. This paper briefly describes the main steps of the procedure, mainly focusing on the two key processing steps of the approach. The first one is a selection of Persistent Scatterers (PS) consisting in a candidate Cousin PS (CPS) selection based on a phase similitude criteria that allows a correct phase unwrapping and a phase unwrapping consistency check. The second key element is a 2+1D phase unwrapping algorithm, which consists in a 2D phase unwrapping followed by a 1D phase unwrapping that allows the detection and correction of unwrapping errors. The results of the CPS selection and the 2+1D phase unwrapping obtained using a stack of 28 TerraSAR-X StripMap images over the metropolitan area of Barcelona are shown.