Satellite Synthetic Aperture Radar Interferometry Research Articles

Entity Embeddings in Remote Sensing: Application to Deformation Monitoring for Infrastructure

There is a critical need for a global monitoring capability for Tailings Storage Facilities (TSFs), to help protect the surrounding communities and the environment. Satellite Synthetic Aperture Radar Interferometry (InSAR) shows much promise towards this ambition. However, extracting meaningful information and interpreting the deformation patterns from InSAR data can be a challenging task. One approach to address this challenge is through the use of data science techniques. In this study, the representation of InSAR metadata as Entity Embeddings within a Deep Learning framework (EE-DL) is investigated for modelling the spatio-temporal deformation response. Entity embeddings are commonly used in natural-language-processing tasks. They represent discrete objects, such as words, as continuous, low-dimensional vectors that can be manipulated mathematically. We demonstrate that EE-DL can be used to predict anomalous patterns in the InSAR time series. To evaluate the performance of the EE-DL approach in SAR interferometry, we conducted experiments over a mining test site (Cadia, Australia), which has been subject to a TSF failure. This study demonstrated that EE-DL can detect and predict the fine spatial movement patterns that eventually resulted in the failure. We also compared the results with deformation predictions from common baseline models, the Random Forest model and Gaussian Process Regression (GPR). Both EE-DL and GPR greatly outperform Random Forest. While GPR is also able to predict displacement patterns with millimetric accuracy, it detects a significantly lower number of anomalies compared to EE-DL. Overall, our study showed that EE-DL is a promising approach for building early-warning systems for critical infrastructures that use InSAR to predict ground deformations.

STRUCTURAL HEALTH MONITORING OF CURVED ROADWAY BRIDGES THROUGH SATELLITE RADAR INTERFEROMETRY AND COLLAPSE SIMULATION

AbstractThis paper presents the application of a Structural Health Monitoring (SHM) strategy for bridges affected by slow deformation phenomena to a curved roadway bridge undergoing slow landslide‐induced movements. The chosen multidisciplinary approach is based on the combination of remote sensing data through satellite Synthetic Aperture Radar Interferometry (InSAR) and structural analysis up to collapse investigated through the Applied Element Method (AEM). The results of the application to the considered case study demonstrate that the integration of the displacement information obtained through InSAR technique with the numerical analysis allows for improving the comprehension of the health state of the bridge undergoing slow movements and identifying potentially critical conditions for the structure.

Monitoring artificial canals with multiple SAR satellites: A case study of the Changge Canal of the South-to-North Water Diversion Project in China

Surface monitoring of artificial canals is essential to ensure safe operation. Traditional geodetic tools are commonly employed to monitor the canal of China’s South-to-North Water Diversion Project (SNWDP), which is time-consuming and high-cost. The advanced satellite Synthetic Aperture Radar Interferometry (InSAR) is an effective tool to detect subtle surface deformation, while its application for monitoring canals is short of fine deformation interpretation on a structure scale. In this study, we applied multiple SAR satellites to monitor a typical canal of the Middle Route of the SNWD Project (MRP), the Changge Canal, by extracting the historical deformation, inverting two-dimensional (2D) deformation, and analyzing distortions. The result suggests that the focused canal section is experiencing continuous deformation caused by near coal mining activity. Its vertical and horizontal distortions both reach ±1.5 mm/100 m. The InSAR applicability, including visibility and sensitivity, is applied to the structure-level interpretation of deformation. The InSAR MPs distribution highly depends on canal structures' aspect and surface coverings. The canal structures with high coherence and lower R-Index (i.e., foreshortening) are favorable for detecting InSAR MPs; meanwhile, a few MPs are detected for the structures with high coherence but high R-index. For the sensitivity of the deformation vector along the downslope, its dependency on the aspect opposes InSAR MPs distribution. The structure-level interpretation considering InSAR applicability helps deploy targeted maintenance and analyze deformation mechanisms. The procedure of fine InSAR monitoring applies to similar water diversion projects.

VALIDATION OF FULL-RESOLUTION DINSAR-DERIVED VERTICAL DISPLACEMENT IN CULTURAL HERITAGE MONITORING: INTEGRATION WITH GEODETIC LEVELLING MEASUREMENTS

Abstract. Towards revealing the potential of satellite Synthetic Aperture Radar (SAR) Interferometry (InSAR) for efficient detection and monitoring of Cultural Heritage (CH) encouraging resilient built CH, this study is devoted to the validation of InSAR-derived vertical displacements with a full-resolution perspective taking advantage of high-precision geodetic levelling measurements. Considering the Cathedral of Como, northern Italy, as the case study, two different Persistent Scatterer Interferometry (PSI) techniques have been applied to Cosmo-SkyMed high-resolution SAR images acquired in both ascending and descending orbit tacks within the time interval of 2010–2012. Besides using the simplified approach for obtaining the vertical displacement velocity from Line of Sight (LOS) velocity, a weighted, localized, multi-track Vertical Displacement Extraction (VDE) approach is proposed and evaluated, which uses the technical outcome of Differential InSAR (DInSAR) and spatial information. The results, using a proper PSI technique, showed that the accuracy level of extracted vertical displacement velocities in a full-resolution application is ca. 0.6 [mm/year] with a dense concentration of InSAR-Levelling absolute errors lower than 0.3 [mm/year] which are reliable and reasonable levels based on the employed validation framework in this study. Also, the weighted localized VDE can significantly decrease the InSAR-Levelling errors, adding to the reliability of the InSAR application for CH monitoring and condition assessment in practice.

Episodic Subglacial Drainage Cascades Below the Northeast Greenland Ice Stream

AbstractSubglacial hydrology can exert an important control on ice flow by affecting friction at the ice‐bedrock interface. Here, we report on a series of subglacial drainage events along the Northeast Greenland Ice Stream (NEGIS), initiating as far inland as 500 km from the margin of Zachariae Isstrøm. The drainage events exhibit local transient uplift, followed by prolonged subsidence, measured by differential satellite synthetic aperture radar interferometry (DInSAR). In downstream regions, drainage events are associated with temporary acceleration in ice flow. The high spatiotemporal resolution of the DInSAR measurements allows for a detailed mapping of the drainage propagation pathway. We show that multiple drainage cascades have occurred along the same pathway over the years 2020–2022. Finally, the propagation speed of subglacial water flow is found to vary greatly along NEGIS, suggesting that fundamental differences could exist in the subglacial environment.

A Review of Satellite Synthetic Aperture Radar Interferometry Applications in Permafrost Regions: Current status, challenges, and trends

With climate change and the increment of human activities, global permafrost is undergoing degradation, threatening the stability of engineering and the ecological environment of the permafrost region. With the advantages of all-day, all-weather, wide-coverage, and high-accuracy monitoring, synthetic aperture radar interferometry (InSAR) is becoming a substantial tool for permafrost monitoring, and many studies with InSAR in permafrost regions have been conducted in the recent 20 years. In this article, the basic principles of time–series InSAR are introduced first. Then, the development and applications of InSAR in permafrost, such as the coherence analysis of permafrost ground surface, the deformation of permafrost and infrastructure, and active layer thickness (ALT) retrieval, are given. Next, the existing problems, including temporal decorrelation, atmospheric delay, deformation models, and the effect of soil moisture and phase unwrapping (PU), are discussed.

Application of an improved multi-temporal InSAR method and forward geophysical model to document subsidence and rebound of the Chinese Loess Plateau following land reclamation in the Yan'an New District

Land reclamation in the Yan'an New District (YND) on the Chinese Loess Plateau is one of the largest earthworks projects in the world, involving the excavation of loess from ridges and the deposition of the material in adjacent valleys, flattening an area of more than 78 km2. It can take multiple years for the landscape to adjust to the new topography after the earthworks are completed, with subsidence in the fill areas and uplift in the areas of excavation. Understanding the pattern and extent of this differential vertical movement has great importance for ensuring the structural integrity of any infrastructure built on the site. We therefore studied the spatial deformation field of the YND from January 2015 to December 2018 using satellite synthetic aperture radar interferometry (InSAR) technology. Persistent scatterers (PS) and distributed scatterers (DS) were combined in a two-tier network to overcome problems with temporal decorrelation of the InSAR phase signals. The derived deformation field was validated with in-situ ground leveling and GNSS measurements, and interpreted using a forward geophysical model. The results indicate that our approach provides a more detailed understanding of the deformation than conventional PSI and SBAS methods. Subsidence of up to 87 mm/yr occurred over about 4.4 km2 of the fill region, and uplift of up to 26 mm/yr in the excavated areas. There is a strong linear relationship between these displacements and prior topographic elevation change. The primary cause of subsidence in fill areas is compaction of remoulded loess. Instantaneous elastic and gradual poroelastic deformation are the main causes of uplift in excavated areas.

ASSESSING THE EFFECT OF ALOS-2 DATA UTILIZATION ON THE ACCURACY OF ESTIMATION VERTICAL AND HORIZONTAL DEFORMATION COMPONENTS IN THE AREA OF HARD COAL MINING EXPLOITATION IN POLAND BY USING DIFFERENTIAL SYNTHETIC APERTURE RADAR INTERFEROMETRY

Abstract. Mining-induced deformations are characterized by high deformation rates. These deformations consist of both vertical and horizontal components, which should not be neglected during the monitoring of such areas. Unfortunately, Differential Satellite Synthetic Aperture Radar Interferometry (DInSAR) can only measure deformations in the line of sight (LOS) direction towards the satellite. Combining data from ascending and descending geometry allows reconstruction of the vertical and east-west deformation components. Theoretically, at least information from one ascending and one descending geometry is enough to reconstruct the vertical and east-west deformation components; however, for the area of interest three various Sentinel-1 datasets (one ascending and two descending) are available and have been used in the study. Furthermore, considering the availability of other SAR missions with slightly different geometries, the objective of this study was to evaluate the effect of ALOS-2 use on the accuracy of estimating the east-west and vertical cumulative deformation component estimated for a time span of approximately one year. Unfortunately, we have access to only five ALOS-2 scenes within the area of interest. However, the comparison of the decomposed results with GNSS measurements shows that the application of additional ALOS-2 data, even five scenes, allows the root mean square error (RMSE) to be decreased for the vertical and horizontal deformation component from 0.038m to 0.032m and from 0.031m to 0.018m, respectively. This means that the application of ALOS-2 data has a positive value on the accuracy of decomposed vertical and horizontal deformation components.

Satellite-based interferometric monitoring of deformation characteristics and their relationship with internal hydrothermal structures of an earthflow in Zhimei, Yushu, Qinghai-Tibet Plateau

Under the influence of climate change, permafrost landforms are sensitive to seasonal heave and contraction, thus exacerbating surface instability and fostering landslides as a consequence. In the pastureland of Zhimei on the Qinghai-Tibet Plateau (QTP), a typical earthflow has drawn significant attention through social media. However, detailed knowledge of the deformation characteristics, internal hydrothermal regime, and structure is still scarce. In this study, we aim to enhance traditional satellite synthetic aperture radar interferometry to divide ground deformation into the seasonal oscillation and slope deformation components and identify the magnitude and spatial distribution of unstable slopes in frozen regions. Then, the use of unmanned aerial vehicles (UAVs) was combined with geophysical monitoring techniques to recognise the deformation dynamics from the pre- to post-failure stages. Sentinel-1 images, covering almost five years, highlighted that obvious creep behaviour dominated at the pre-failure stage, while a seasonal deformation pattern characterised by a piecewise distribution associated with the hydrothermal regime was observed at the post-failure stage. Fast retrogressive erosion on the head scarps at the post-failure stage was clearly identified by multidifferential digital surface models from the UAV observations. To better understand the internal structure, both electrical resistivity tomography and ground-penetrating radar were combined to determine the seasonal frozen thickness, underlying thawing materials, and vertical cracks, which controlled the kinematic evolution from the initial creep to the narrow and long oversaturated flow that represented the terminal portion of the landslide. Finally, by comparing in situ monitoring data with field investigations, the main driving factors controlling the movement mechanism are discussed. Our results highlight the specific kinematic behaviour of an earthflow and can provide a reference for slope destabilisation on the QTP under the influence of climate change.

Monitoring Large-Scale Hydraulic Engineering Using Sentinel-1 InSAR: A Case Study of China's South-to-North Water Diversion Middle Route Project

The Middle Route of South-to-North Water Diversion (SNWD) Project,known as one of the greatest hydraulic projects of China, undertakes most of domestic and industrial water use in the Beijing&#x2013;Tianjin area, as well as a part of ecological water use. The whole canal should be monitored to ensure a continuous water supply for water-receiving areas. Compared with traditional ground-based monitoring tools limited by the low distribution density, intensive labor force, and huge cost, the satellite synthetic aperture radar interferometry (InSAR) with wide coverage, high-frequency revisiting, and low cost is more suitable for monitoring large-scale infrastructures. In this study, we employed the Sentinel-1 data to monitor the canal of the Middle Route of the SNWD Project within Henan Province. The deformation rates along the canal were obtained by using persistent scatterer InSAR, from which a total of 20 deformed canal sections and seven suspected deformed canal sections were identified. Among them, the Shahe aqueduct is overall stable except for the Shahe Beam Aqueduct and Lushanpo Landing Aqueduct. The Yuzhou-Changge canal passes through a subsidence funnel with a maximum deformation rate of about &#x2013;20 mm&#x002F;year. The InSAR-derived deformation coincides well with the <i>in-situ</i> leveling measurements over the Yuzhou-Changge canal. Their correlation is 0.95 and the root mean square error of their differences is 2.41 mm&#x002F;year. The results demonstrate the effectiveness of satellite InSAR for monitoring large-scale hydraulic engineering. It can be combined with ground leveling to achieve overall investigations and detailed monitoring, largely improving the efficiency and cost of the current ground monitoring system.

Multi-scale deformation monitoring with Sentinel-1 InSAR analyses along the Middle Route of the South-North Water Diversion Project in China

As the longest water transfer route in the world, the South-North Water Diversion Project (SNWDP) plays a key role in mitigating the serious water shortage problem in the arid north China, and thus the routine stability monitoring of this mega infrastructure becomes a critical issue to ensure continuous fresh water supply. Compared with traditional geodetic tools such as leveling and GNSS that can only measure deformation at discrete points along the canal, modern satellite Synthetic Aperture Radar Interferometry (InSAR) that can capture subtle ground deformation over wide areas is much more suitable to accomplish this challenging task. In this study, we carried out multi-scale InSAR analyses with multi-track Sentinel-1 data stacks to monitor deformation along the Middle Route canal of SNWDP. A coarse-resolution InSAR analysis was first carried out to map regional land subsidence in north China, and the result suggested that the Middle Route canal bypassed the huge subsidence funnel in the southeast part of Hebei province and exhibited overall stability. Afterwards, the results of relatively high-resolution InSAR analyses performed within the 5 km buffering zones along the entire canal revealed that a few sections were affected by significant embankment deformation or land subsidence. In particular, the high-filled canal sections are more prone to deform, such as the cases in Ye County and Jiaozuo City in Henan province. The validation of InSAR deformation measurements with synchronous leveling in Jiaozuo City indicated that a measurement accuracy of 6 mm was achieved. Another big problem identified is the severe uneven land subsidence along the Tianjin Branch Route, which may pose great threats upon the long-term safety of local water transfer operation, and must be handled properly to avoid further degradation.

Regional Recognition and Classification of Active Loess Landslides Using Two-Dimensional Deformation Derived from Sentinel-1 Interferometric Radar Data

Identification and classification of landslides is a preliminary and crucial work for landslide risk assessment and hazard mitigation. The exploitation of surface deformation velocity derived from satellite synthetic aperture radar interferometry (InSAR) is a consolidated and suitable procedure for the recognition of active landslides over wide areas. However, the calculated displacement velocity from InSAR is one-dimensional motion along the satellite line of sight (LOS), representing a major hurdle for landslide type and failure mechanism classification. In this paper, different velocity datasets derived from both ascending and descending Sentinel-1 data are employed to analyze the surface ground movement of the Huangshui region (Northwestern China). With global warming, precipitation in the Huangshui region, geologically belonging to the loess basin in the eastern edge of Qing-Tibet Plateau, has been increasing, often triggering a large number of landslides, posing a potential threat to local citizens and natural and anthropic environments. After processing both SAR data geometries, the surface motion was decomposed to obtain the two-dimensional displacements (vertical and horizontal E–W). Thus, a classification criterion of the loess landslide types and failure mode is proposed, according to the analysis of deformation direction, velocities, texture, and topographic characteristics. With the support of high-resolution images acquired by remote sensing and unmanned aerial vehicle (UAV), 14 translational slides, seven rotational slides, and 10 loess flows were recognized in the study area. The derived results may provide solid support for stakeholders to comprehend the hazard of unstable slopes and to undertake specific precautions for moderate and slow slope movements.

A-DInSAR Performance for Updating Landslide Inventory in Mountain Areas: An Example from Lombardy Region (Italy)

This work focuses on the capabilities and limitations of the Advanced Satellite SAR (Synthetic Aperture Radar) Interferometry (A-DInSAR) in wooded and mountainous regions, with the aim to get insights on the performances for studying slow-moving landslides. The considered critical issues are related to the SAR acquisition geometries (angle of incidence of the satellite line of sight , ascending and descending geometries) and to the physical and morphological features of the slopes (land use, aspect and slope angles), which influence the measuring points coverage. 26 areas in Lombardy Region (Italy), affected by known slope instability phenomena, have been analyzed through A-DInSAR technique, using COSMO-SkyMed images. The results allowed to outline general considerations about the effectiveness of A-DInSAR analysis of a single dataset (descending or ascending dataset), selected accordingly to the aspect of the slopes. Moreover, we aimed to quantitatively describe the capability to update the state of activity of several previously mapped landslides using satellite SAR Interferometry results. Although in a wooded and mountainous region, where the chances of retrieving radar targets for satellite SAR analysis are generally low, the A-DInSAR results have allowed to detect landslides’ reactivations or new landslides and to update the inventory for about 70% of the investigated areas.

Multi-Temporal Investigation of the Boulder Clay Glacier and Northern Foothills (Victoria Land, Antarctica) by Integrated Surveying Techniques

The paper aims to detect the main changes that occurred in the area surrounding the Mario Zucchelli Station (MZS) through analysis of multi-temporal remote sensing integrated by geophysical measurements. Specific attention was directed at realizing an integrated geomorphological study of the Boulder Clay Glacier, a partially debris-covered glacier belonging to the Northern Foothills (Victoria Land, Antarctica). This area was recently chosen as the location for the construction of a new semi-permanent gravel runway for MZS logistical airfreight operations. Photogrammetric analysis was performed by comparing three historical aerial photogrammetric surveys (carried out in 1956, 1985, and 1993) and Very High Resolution (VHR) GeoEye-1 satellite stereo-image coverage acquired in 2012. The comparison of geo-referenced orthophoto-mosaics allowed the main changes occurring in some particular areas along the coast nearby MZS to be established. Concerning the study of the Boulder Clay Glacier, it has to be considered that glaciers and moraines are not steady-state systems by definition. Several remote sensing and geophysical investigations were carried out with the main aim of determining the general assessment of this glacier: Ground Penetrating Radar (GPR); Geodetic Global Positioning System (GPS) network; multi-temporal satellite Synthetic Aperture Radar (SAR) interferometry. The analysis of Boulder Clay Glacier moraine pointed out a deformation of less than 74 mm y−1 in a time span of 56 years, value that agrees with velocity and deformation data observed by GPS and InSAR methods. The presence of unexpected brine ponds at the ice/bedrock interface and the deformation pattern observed in the central part of the moraine has to be monitored and studied, especially under the long-term maintenance of the future runway.

Seasonal dynamics of a permafrost landscape, Adventdalen, Svalbard, investigated by InSAR

Nordenskiöld Land in Central Spitsbergen, Svalbard is characterized as a high latitude, high relief periglacial landscape with permafrost occurring both in mountains and lowlands. Freezing and thawing of the active layer causes seasonal frost heave and thaw subsidence, while permafrost-related mass-wasting processes induce downslope ground displacements on valley sides. Displacement rate varies spatially and temporally depending on environmental factors. In our study, we apply Satellite Synthetic Aperture Radar Interferometry (InSAR) to investigate the magnitude, spatial distribution and timing of seasonal ground displacements in and around Adventdalen using TerraSAR-X StripMap Mode (2009–2017) and Sentinel-1 Interferometric Wide Swath Mode (2015–2017) SAR images. First, we show that InSAR results from both sensors highlight consistent patterns and provide a comprehensive overview of the distribution of displacement rates. Secondly, two-dimensional (2D) TerraSAR-X InSAR results from combined ascending and descending geometries document the spatial variability of the vertical and east-west horizontal displacement rates for an average of nine thawing seasons. The remote sensing results are compared to a simplified geomorphological map enabling the identification of specific magnitudes and orientations of displacements for 14 selected geomorphological units. Finally, June to December 2017 6-day sampling interval Sentinel-1 time series was retrieved and compared to active layer ground temperatures from two boreholes. The timing of the subsidence and heave detected by InSAR matches the thawing and freeze-back periods measured by in-situ sensors. Our results highlight the value of InSAR to obtain landscape scale knowledge about the seasonal dynamics of complex periglacial environments.

Fusion of GNSS and Satellite Radar Interferometry: Determination of 3D Fine-Scale Map of Present-Day Surface Displacements in Italy as Expressions of Geodynamic Processes

We present a detailed map of ground movement in Italy derived from the combination of the Global Navigation Satellite System (GNSS) and Satellite Synthetic Aperture Radar (SAR) interferometry. These techniques are two of the most used space geodetic techniques to study Earth surface deformation. The above techniques provide displacements with respect to different components of the ground point position; GNSSs use the geocentric International Terrestrial Reference System 1989 (ITRS89), whereas the satellite SAR interferometry components are identified by the Lines of Sight (LOSs) between a satellite and ground points. Moreover, SAR interferometry is a differential technique, and for that reason, displacements have no absolute reference datum. We performed datum alignment of InSAR products using precise velocity fields derived from GNSS permanent stations. The result is a coherent ground velocity field with detailed boundaries of velocity patterns that provide new information about the complex geodynamics involved on the Italian peninsula and about local movements.

Integration of GNSS and Satellite InSAR Data: Derivation of Fine-Scale Vertical Surface Motion Maps of Po Plain, Northern Apennines, and Southern Alps, Italy

Global Navigation Satellite System (GNSS) and satellite synthetic aperture radar (SAR) interferometry represent the most important space geodetic techniques usually exploited to measure millimetric ground deformation on earth surface at both local and wide-area scale. SAR images processed with persistent scatterers interferometry (PSI) multitemporal approach lack of an absolute reference datum. In this paper, SAR images are calibrated with data derived from permanent GNSS stations, in order to obtain absolute and more accurate displacement values. The method used to correct PSI with GNSS is based on existing methodologies commonly applied in the geodetic practice of combining crustal and local deformation studies with geospatial statistical analysis. The spatial distribution of vertical terrain deformations and their temporal changes are coherently measured, leading to a fine-scale surface velocity map in the central-eastern Po Plain, Northern Apennines, and Southern Alps in Italy. The results reveal significant subsidence rates on the north-western Adriatic coast including the Po Delta and the lagoon of Venice, as well as on Bologna and Ferrara cities in agreement with long-term displacement motion values provided by geological data and other previous works performed at local scale. This paper demonstrates the importance and effectiveness in creating a single, unique surface motion map by merging different data sets in which geodesy plays a relevant role in the datum alignment of PSI products before the stacking of the SAR maps.

Detection of Building and Infrastructure Instabilities by Automatic Spatiotemporal Analysis of Satellite SAR Interferometry Measurements

Satellite synthetic aperture radar (SAR) interferometry (InSAR) is a powerful technology to monitor slow ground surface movements. However, the extraction and interpretation of information from big sets of InSAR measurements is a complex and demanding task. In this paper, a new method is presented for automatically detecting potential instability risks affecting buildings and infrastructures, by searching for anomalies in the persistent scatterer (PS) deformations, either in the spatial or in the temporal dimensions. In the spatial dimension, in order to reduce the dataset size and improve data reliability, we utilize a hierarchical clustering method to obtain convergence points that are more trustworthy. Then, we detect deformations characterized by large values and spatial inhomogeneity. In the temporal dimension, we use a signal processing method to decompose the input into two main components: regular periodic deformations and piecewise linear deformations. After removing the periodic component, the velocity variation in each identified temporal partition is analyzed to detect anomalous velocity trends and accelerations. The method has been tested on different sites in China, based on InSAR measurements from COSMO-SkyMed data. The results, verified with in-field surveys, confirm the potential of the method for the automatic detection of deformation anomalies that could cause building or infrastructure stability problems.

Satellite SAR interferometry for the improved assessment of the state of activity of landslides: A case study from the Cordilleras of Peru

In Peru landslides have been causing damages and casualties annually due to the high mountain relief and distinct seasonal precipitation distribution. Satellite Synthetic Aperture Radar (SAR) interferometry represents one possibility for mapping surface deformation at fine spatial resolution over large areas in order to characterize aspects of terrain motion and potentially hazardous processes. We present land surface motion maps derived from satellite SAR interferometry (InSAR) for a part of the Santa River Basin between the Cordilleras Blanca and Negra around the city of Carhuaz in Peru. Using both Persistent Scatterer Interferometry (PSI) and differential SAR Interferograms (DInSAR) from ALOS-1 PALSAR-1, ENVISAT ASAR, ALOS-2 PALSAR-2 and Sentinel-1 we mapped 42 landslides extending over 17,190,141 m2 within three classes of activity (i.e. 0–2 cm/a, 2–10 cm/a and >10 cm/a). A geomorphological inventory of landslides was prepared from optical satellite imagery and field experience and compared to the InSAR-based slope-instability inventory. The two approaches provide slightly different information about landslide spatial and temporal activity patterns, but altogether they can be combined for the assessment of the state of activity of landslides and possibly the development of hazard maps, which are not systematically available in this region. We conclude that ALOS PALSAR (1 and 2) and Sentinel-1 data have a high potential to derive high-quality surface deformation information of landslides in many mountainous regions worldwide due to their global and frequent acquisition strategies.

Imaging Multi-Age Construction Settlement Behaviour by Advanced SAR Interferometry

This paper focuses on the application of Advanced Satellite Synthetic Aperture Radar Interferometry (A-DInSAR) to subsidence-related issues, with particular reference to ground settlements due to external loads. Beyond the stratigraphic setting and the geotechnical properties of the subsoil, other relevant boundary conditions strongly influence the reliability of remotely sensed data for quantitative analyses and risk mitigation purposes. Because most of the Persistent Scatterer Interferometry (PSI) measurement points (Persistent Scatterers, PSs) lie on structures and infrastructures, the foundation type and the age of a construction are key factors for a proper interpretation of the time series of ground displacements. To exemplify a methodological approach to evaluate these issues, this paper refers to an analysis carried out in the coastal/deltaic plain west of Rome (Rome and Fiumicino municipalities) affected by subsidence and related damages to structures. This region is characterized by a complex geological setting (alternation of recent deposits with low and high compressibilities) and has been subjected to different urbanisation phases starting in the late 1800s, with a strong acceleration in the last few decades. The results of A-DInSAR analyses conducted from 1992 to 2015 have been interpreted in light of high-resolution geological/geotechnical models, the age of the construction, and the types of foundations of the buildings on which the PSs are located. Collection, interpretation, and processing of geo-thematic data were fundamental to obtain high-resolution models; change detection analyses of the land cover allowed us to classify structures/infrastructures in terms of the construction period. Additional information was collected to define the types of foundations, i.e., shallow versus deep foundations. As a result, we found that only by filtering and partitioning the A-DInSAR datasets on the basis of the above-mentioned boundary conditions can the related time series be considered a proxy of the consolidation process governing the subsidence related to external loads as confirmed by a comparison with results from a physically based back analysis based on Terzaghi’s theory. Therefore, if properly managed, the A-DInSAR data represents a powerful tool for capturing the evolutionary stage of the process for a single building and has potential for forecasting the behaviour of the terrain–foundation–structure combination.