Persistent Scatterer Interferometry (PSI) is a powerful remote sensing technique able to measure and monitor displacements of the Earth’s surface over time. Specifically, PSI is a radar-based technique that belongs to the group of differential interferometric Synthetic Aperture Radar (SAR). This paper provides a review of such PSI technique. It firstly recalls the basic principles of SAR interferometry, differential SAR interferometry and PSI. Then, a review of the main PSI algorithms proposed in the literature is provided, describing the main approaches and the most important works devoted to single aspects of PSI. A central part of this paper is devoted to the discussion of different characteristics and technical aspects of PSI, e.g. SAR data availability, maximum deformation rates, deformation time series, thermal expansion component of PSI observations, etc. The paper then goes through the most important PSI validation activities, which have provided valuable inputs for the PSI development and its acceptability at scientific, technical and commercial level. This is followed by a description of the main PSI applications developed in the last fifteen years. The paper concludes with a discussion of the main open PSI problems and the associated future research lines.

https://zenodo.org/record/45568/files/Persistent_Scatterer_Interferometry.pdf

Persistent Scatterer Interferometry: A review

Preface 1. Introduction 2. Electromagnetic waves in free space 3. Interaction of electromagnetic radiation with matter 4. Interaction of electromagnetic radiation with the Earth's atmosphere 5. Photographic systems 6. Electro-optical systems 7. Passive microwave systems 8. Ranging systems 9. Scattering systems 10. Platforms for remote sensing 11. Data processing Appendix 1. The Global Positioning System Appendix 2. Data Bibliography Answers and hints to numerical problems Index.

Physical Principles of Remote Sensing

Investigating landslides and unstable slopes with satellite Multi Temporal Interferometry: Current issues and future perspectives

Landslides represent major natural hazards, which cause every year significant loss of lives and damages to buildings, properties and lifelines. In the last decades, a significant increase in landslide frequency took place, in concomitance to climate change and the expansion of urbanized areas. Remote sensing techniques represent a powerful tool for landslide investigation: applications are traditionally divided into three main classes, although this subdivision has some limitations and borders are sometimes fuzzy. The first class comprehends techniques for landslide recognition, i.e., the mapping of past or active slope failures. The second regards landslide monitoring, which entails both ground deformation measurement and the analysis of any other changes along time (e.g., land use, vegetation cover). The third class groups methods for landslide hazard analysis and forecasting. The aim of this paper is to give an overview on the applications of remote-sensing techniques for the three categories of landslide investigations, focusing on the achievements of the last decade, being that previous studies have already been exhaustively reviewed in the existing literature. At the end of the paper, a new classification of remote-sensing techniques that may be pertinently adopted for investigating specific typologies of soil and rock slope failures is proposed.

/pdf/remote-sensing-for-landslide-investigations-an-overview-of-27qvaxk6oy.pdf

Remote Sensing for Landslide Investigations: An Overview of Recent Achievements and Perspectives

This paper provides a review of ground-based SAR (GBSAR) interferometry for deformation measurement. In the first part of the paper the fundamentals of this technique are provided. Then the main data processing and analysis stages needed to estimate deformations starting from the GBSAR observations are described. This section introduces the two types of GBSAR acquisition modes, i.e., continuous and discontinuous GBSAR, and reviews the different GBSAR processing and analysis methods published in the literature. This is followed by a discussion of the specific technical aspects of GBSAR deformation measurement. A section then summarizes the pros and cons of GBSAR for deformation monitoring. The last part of the paper includes two reviews: one concerning the GBSAR systems described in the literature, including non-strictly SAR systems and a second one addresses the main GBSAR applications.

A review of ground-based SAR interferometry for deformation measurement

This letter focuses on the thermal expansion component of persistent scatterer (PS) interferometry (PSI), which is a result of temperature differences in the imaged area between synthetic aperture radar (SAR) acquisitions. This letter is based on very high resolution X-band StripMap SAR data captured by the TerraSAR-X spaceborne sensor. The X-band SAR interferometric phases are highly influenced by the thermal dilation of the imaged objects. This phenomenon can have a strong impact on the PSI products, particularly on the deformation velocity maps, if not properly handled during the PSI analysis. In this letter, we propose a strategy to deal with the thermal dilation phase component, which involves further developing the standard two-parameter PSI model (deformation velocity and residual topographic error) with a third unknown parameter called the thermal dilation parameter, which is estimated for each PS. The map obtained from plotting this parameter for all PSs of a given area is hereafter called thermal map. This letter describes the proposed model and outlines the issue of parameter estimability. In addition, the potential of exploiting the thermal maps is analyzed by illustrating two examples of the Barcelona (Spain) metropolitan area. Thermal maps provide two types of information: The first one is the coefficient of thermal expansion of the observed objects, while the second one, which is related to the pattern of the thermal dilation parameter, gives information about the static structure of these objects. Two important aspects that influence the exploitation of thermal maps are discussed in the last section of this letter: the line-of-sight nature of the derived estimates and the achievable precision in the estimation of the coefficient of thermal expansion.

The Thermal Expansion Component of Persistent Scatterer Interferometry Observations

This paper is focused on spaceborne Differential Interferometric SAR (DInSAR) for land deformation measurement and monitoring. In the last two decades several DInSAR data analysis procedures have been proposed. The objective of this paper is to describe the DInSAR data processing and analysis tools developed at the Institute of Geomatics in almost ten years of research activities. Four main DInSAR analysis procedures are described, which range from the standard DInSAR analysis based on a single interferogram to more advanced Persistent Scatterer Interferometry (PSI) approaches. These different procedures guarantee a sufficient flexibility in DInSAR data processing. In order to provide a technical insight into these analysis procedures, a whole section discusses their main data processing and analysis steps, especially those needed in PSI analyses. A specific section is devoted to the core of our PSI analysis tools: the so-called 2+1D phase unwrapping procedure, which couples a 2D phase unwrapping, performed interferogram-wise, with a kind of 1D phase unwrapping along time, performed pixel-wise. In the last part of the paper, some examples of DInSAR results are discussed, which were derived by standard DInSAR or PSI analyses. Most of these results were derived from X-band SAR data coming from the TerraSAR-X and CosmoSkyMed sensors.

Spaceborne Differential SAR Interferometry: Data Analysis Tools for Deformation Measurement

Persistent Scatterer Interferometry (PSI) is a remote sensing technique to measure and monitor land deformation from a stack of interferometric SAR images. Its main products are the deformation maps (maps of the average displacement rates), the deformation time series and the maps of the so-called residual topographic errors. In this paper, we describe a new product derived from X-band PSI: the thermal deformation maps. This paper briefly describes the thermal component of the PSI phase observations and outlines the approach to estimate the thermal maps. The last part of the paper discusses three examples of thermal maps derived from a stack of 28 StripMap TerraSAR-X images that cover the metropolitan area of Barcelona (Spain).

A new product from persistent scatterer interferometry: The thermal dilation maps

The paper describes a relatively new terrestrial remote sensing technique for deformation monitoring: ground-based SAR interferometry (GBSAR). It provides an introductory overview of this technique, making a short review of the most relevant GBSAR studies published in the literature. Then the basics of GBSAR interferometry for deformation measurement are outlined. Deriving deformation estimates from the GBSAR images is often not a straightforward process: a brief description of the GBSAR data processing chain developed by the authors is provided. Finally, the paper concisely discusses the main advantages and limitations of the technique.

Deformation Monitoring Using Ground-Based SAR Data

The PanGeo service has been designed with the original project aims, user requirements and technical requirements in mind. The PanGeo service will create an attributed, spatially referenced vector polygon dataset outlining all areas of ground instability for 52 European towns. INSPIRE compliant attributes will provide the reason for the instability, its area and the geologists confidence in their interpretation. The supporting Geohazard Description Document will be available as both a standalone document and the relevant section will be hyperlinked to the Ground Stability Layer polygon displayed in the portal. Along with providing a geological background to the PanGeo town the Geohazard Description will give detailed geological interpretation and evidence for the area of instability and provide information on how the instability was recognised and mapped. 
The PanGeo interpretation will be carried out by the National Geological Survey for the country for which the town resides. The inputs to the interpretation are; satellite radar derived data on ground motion, ground motions observed with other surveying techniques, geological data and models and ancillary data. The satellite radar derived ground motion data will be delivered to the geological surveys by the PSIPs within in the PanGeo Production Pack.
Two types of ground instability will be recognised; observed and potential. Observed instabilities are those observed on ground motion data or through geological field campaigns. Potential instabilities are those areas that the geologist believes may be subject to instabilities given their knowledge of the area or the results of geological modelling. One of eighteen geohazards is assigned to each area of ground instability; geohazards are grouped into four categories for display on the portal.
Once the Geological Survey has completed the GSL and GHD they will be validated by the British Geological Survey before being made available to the PanGeo portal. In the first instance the GSL will be submitted to an online validating tool which will carry out automated topological data checks of the vector data and attributes. Once passed the GSL is sent to BGS who will carry out manual checks of the GSL and GHD to ensure they meet the specifications.
Once validated the Geological Survey will make the GSL and GDH available on their IT servers for harvesting by the PanGeo portal. The display of the GSL on the portal will depend on the viewing scale; at the European scale PanGeo towns will be highlighted, at the regional scale a graphic showing the number of hazards affecting an area will be displayed. At the local scale the GSL polygons will be displayed according to the geohazard category, the boundary line will distinguish potential and observed hazards. The user can also choose to integrate the GSL with the Urban Atlas; the GSL polygons will highlight those Urban Atlas land cover types affected by hazards

Maria Cuevas

Papers

The Thermal Expansion Component of Persistent Scatterer Interferometry Observations

Spaceborne Differential SAR Interferometry: Data Analysis Tools for Deformation Measurement

A new product from persistent scatterer interferometry: The thermal dilation maps

Deformation Monitoring Using Ground-Based SAR Data

PANGEO : enabling access to geological information in support of GMES : deliverable 3.5 production manual. Version 1