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A five-story reinforced concrete building severely damaged during the Mw 5.1, May 11th 2011, Lorca earthquake (Murcia, Spain), has been monitored with an interferometric radar and has been numerically modelled with the aim to study the evolution of the structural damage. An initial non-damaged and a final damaged configuration of the building after the earthquake have been modelled first. Radar measurements helped to calibrate the models. Four intermediate models, with damage configurations representing four steps of cumulative damage of the building facing the earthquake, have been built based on the information related to the building seismic damage included in a technical report. The objectives were to obtain calibrated numerical models, to perform a modal analysis, to calculate the capacity curve, and to study the evolution of the natural periods and the strength capacity of the building within each damage configuration representing the incremental damage process. Results show that a growth of 20% in the values of natural periods and reductions of 50% in the capacity lead the building over the severe damage state threshold. The interferometric radar is a suitable remote sensing technique to identify, in a rapid screening, the natural periods of mid and tall damaged buildings. This research has been partially funded by the Spanish Research Agency (AEI) of the Spanish Ministry of Science and Innovation (MICIN) through project with reference: PID2020-117374RB-I00/AEI/10.13039/501100011033, and by the European Regional Development Fund (ERDF) of the European Union (EU) through project with reference EFA158/16/POCRISC (INTERREG/POCTEFA. EU). Esteban Cabrera, sponsored by the University of Azuay (UDA), obtained a scholarship from the Ministry of Higher Education, Science and Technology, SENESCYT, Government of Ecuador, for doctoral studies in the Earthquake Engineering program at UPC-Barcelona-Tech. Yeudy F. Vargas-Alzate has been granted an Individual Fellowship (IF) in the research grants program of the Marie Sklodowska-Curie Actions (MSCA) of the European Union/European (H2020-MSCA-IF-2017) No 799553.

Monitoring the internal structure of the snowpack is crucial for managing snow-related hazards such as snow avalanches and snowmelt floods. Recently, the availability of low cost, low power and low-profile frequency-modulated continuous-wave (FMCW) radars at 24 GHz has grown thanks to its potential use the automotive sector. This paper proposes the use of a compact and low-cost FMCW radar as an instrument for improving the study of the snowpack, delivering Snow Density and Liquid Water Content in a fast way. The radar is intended to be used as a snowpit instrument, creating density and Liquid water content (LWC) snow profiles and trying to overcome the customary density cutters (slower and operator-dependent). The theoretical equations of the principle are presented and a preliminary validation by means of a laboratory test is done using dry snow mimicking material, providing encouraging results., NO ACK.

A performance assessment of the Cyclone Global Navigation Satellite System (CyGNSS) mission for biomass studies is presented in this paper over Congo and Amazon tropical rainforests. The functional correlation between CyGNSS-derived trailing edge width TE and Avitabile et. al. Above Ground Biomass (AGB) pan-tropical data is evaluated using ICESat-1/GLAS-derived Canopy Height (CH), SMAP-derived Vegetation Optical Depth (VOD), and Polarization Index (PI). The main objective is to investigate the sensitivity of CyGNSS to biomass over dense forest canopies. The potential advantage of CyGNSS as compared to classical monostatic radar missions could rely on the increasing signal attenuation by the upwelling vegetation cover that reduces the coherent scattering component. This term can only be collected in a bistatic radar geometry. Using empirically-derived polynomial fitting functions, preliminary results show that the use of TE allows to estimate AGB up to ~ 400 ton/ha and ~ 250 ton/ha over Congo and Amazon rainforests at low elevation angles ~ [20, 40] º. The analysis using the SMAP-derived microwave vegetation parameters shows that: a) VOD performs well even over rainforests, and b) PI could depend also on the CH levels., NO ACK.

An experimental assessment of the performance of Global Navigation Satellite Systems Reflectometry (GNSS-R) for biomass monitoring over tropical forests is presented. Several observables of the so-called Delay Doppler Maps (DDMs), as provided by the Cyclone Global Navigation Satellite Systems (CyGNSS) microsatellites constellation, are evaluated using the pan-tropical Above Ground Biomass (AGB) map provided by Avitabile et al. and Canopy Height (CH) data derived from the Geoscience Laser Altimeter System (GLAS) lidar-instrument on-board the National Aeronautics and Space Administration NASA’s Ice, Cloud, and land Elevation Satellite (ICESat). In so doing, different tropical forests types are studied. Preliminary results show that the spreading of the DDMs in the delay domain has a sensitivity up to a mean AGB ~ 325 ton/ha over Congo rainforests for elevation angles in the range e  ~ [20, 40] º., © 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

Understanding the effects of Earth’s surface topography on Global Navigation Satellite Systems Reflectometry (GNSS-R) spaceborne data is essential to correct experimental observations so as to provide accurate Soil Moisture Content (SMC) determination and biomass monitoring. A comprehensive set of observables obtained from Delay Doppler Maps (DDMs) generated on-board Cyclone Global Navigation Satellite Systems (CyGNSS) are evaluated as a function of several topographic parameters derived from a Digital Elevation Model (DEM). Preliminary results over the Himalayan mountains show a sudden change on the scattering mechanisms for a Terrain Ruggedness Index (TRI) ~ 15 at an elevation angle e ~ [45, 65] º. This change is interpreted as an effect of the Earth’s surface convexity.

This paper reports the design and preliminary test of a circular polarized patch array antenna operating in C band. The antenna was designed as part of a C band Active Corner reflector (ACR). The operating band is 5.405 GHz ± 50 MHz band, the same used by ESA Sentinel-1 SAR. The main requirements for the antenna system are: a simple design to assure an adequate phase stability, simple installation, and low cost, as requested for the proposed ACR., NO ACK.

This paper reports the results of two terrestrial surveys aimed at monitoring two Alpine glaciers located in Italy and Spain respectively, and carried out using a Ground Based SAR interferometer. Although the monitoring of glaciers based on this technique does not represent a novelty, these two case studies are peculiar, due to the characteristics of the Alpine glaciers among which the dominant role of the atmospheric phase screen (APS) on the radar signal propagation. These kind of glaciers, with their climate and geographical features, often demand a detailed analysis of the acquired data, at small temporal (less than an hour), and spatial (a few square meters) scale. The meteorological conditions, which affect the dynamics of the glaciers, deeply influenced the backscattering behavior, demanding a careful analysis of the amplitude of the radar signal, to characterize the surface, and of the interferometric phase, to evaluate the role of the APS. Only after the correction of the APS, a final accuracy of a few millimeters/day was attained in the daily velocity of the glacier in both cases.

Nowadays, ensuring the safeguard of natural, cultural and mixed UNESCO sites is increasingly difficult, due to not only ravages of time or anthropic actions but also to natural events. Even though it is widely recognized that UNESCO World Heritage Sites are threatened by geological risks, the level of attention placed on geohazards appears to be poor, especially if compared with the others potential threatening factors, such as wars, uncontrolled urban development or arsons. Promoting the detection and monitoring of geohazards should become a common practice, in order to preserve the Outstanding Universal Value of UNESCO properties over time. This study, therefore, shows a new satellite data analysis procedure to identify, in a fast, simple and repeatable way, the temporal and spatial evolution of the most critical and reliable ground deformation areas related to slow-kinematic geohazards (volcanic activity, slow-moving landslides or ground-subsidence). This approach has been tested in the Tuscan UNESCO sites (Central Italy). Thanks to the main characteristics of the recent Sentinel-1 data (short revisit time, systematic and free availability for all data users and worldwide coverage), this procedure can be easily exploited by the local risk management decision makers of each World Heritage Site, in order to define long-term geohazards monitoring activities and conservation strategies., NO ACKNOWLEDGEMENTS

This work presents an assessment on the correlation between CyGNSS-derived Global Navigation Satellite Systems Reflectometry (GNSS-R) bistatic reflectivity rl and SMAP-derived brightness temperature BT , over land surfaces. This parametric-study is performed as a function of Soil Moisture Content (SMC), vegetation opacity τ, and albedo ω. Several target areas are selected to evaluate potential differentiated geophysical effects on “active” (as many transmitters as navigation satellites are in view), and passive approaches. Although microwave radiometry has potentially a better sensitivity to SMC, the spatial resolution is poor ~ 40 km. On the other hand, GNSS-R bistatic coherent radar footprint is limited by half of the first Fresnel zone which provides about ~ 150 m of spatial resolution (depending on the geometry). The synergetic combination of both techniques could provide advantages with respect to active monostatic Synthetic Aperture Radar (SAR)., © 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

Ground Based SAR (GB-SAR) interferometry, is a consolidated remote sensing technique to monitor ground displacements. During the last decade it has gained interest for monitoring instable slopes in near real time. However, in the literature can be found a range of applications where the techniques can be potenially a valuable tool. One of these applications is the monitoring of glaciers. One of the main reason is that alpine glaciers are often located on steep flanks, steep slopes and narrow valleys, often making the use of other techniques not suitable. In this work are shown the results of two GB-SAR surveys aimed at monitoring two Alpine glaciers located in Italy and Spain respectively. The target of the surveys is different for each case, development of integrated monitoring systems in the Italian case and glacier dynamics in the Spanish case. However both cases are good examples of the main difficulties to be faced using GB-SAR for alpine glacier monitoring: the dominant role of the atmospheric phase screen (APS) on radar signal propagation. The meteorological conditions, which affect the dynamics of the glaciers, deeply influence the GB-SAR response behaviour, demanding a careful analysis of the amplitude of the radar signal, to characterize the surface, and of the interferometric phase, to evaluate the role of the APS. Only after the correction of the APS, a final accuracy of a few milimeters/day was attained in the daily velocity of the glacier in both cases.

Ambient vibration testing has become a useful tool to assess the operational conditions of any existing structure, and allows the engineers to maintain a continuous monitoring in order to check its structural health conditions. In this paper an experimental survey performed by means of an original interferometric technique applied on a real building damaged after the Mw 5.1, may 11th 2011, Lorca earthquake (southeast Spain) is presented and discussed. This interferometric technique, based on real aperture radar (RAR), allows an easy, non-invasive and contactless procedure to evaluate the dynamic response of a building excited by ambient vibration noise. Contemporaneously, a 3D computational model of the monitored structure has been developed and an equivalent non-linear static analysis has been performed. The capacity spectrum method and a specific fragility model were used in order to obtain a global damage index of the structure. A specific post process of the RAR output combined with the numerical analysis of the modelled structure should help to establish the damage condition of the building in the aforementioned specific post-earthquake scenario, in order to estimate the occupancy conditions. The results of the computational assessment are consistent with the observed damage and with the results of the experimental RAR survey. The consistency of the results allows considering the interferometric RAR technique as an interesting alternative, or, in any case, a complementary non-invasive prospecting tool to assess the structural health conditions in a post-earthquake scenario. This research has been partially funded by the Ministry of Economy and Competitiveness (Ministerio de Economía y Competitividad-MINECO) of the Spanish Government and by the European Regional Development Fund (FEDER) of the European Union (UE) through projects referenced as CGL2011-23621 and CGL2015-65913-P (MINECO/FEDER, UE). Mr. Esteban Cabrera, sponsored by the University of Azuay (UDA), obtained a scholarship from the Ministry of Higher Education, Science and Technology, SENESCYT, Government of Ecuador, for doctoral studies in the Earthquake Engineering program of the UPC-Barcelona Tech.

We present the 3-dimensional modelling of a glacier kinematics, obtained by coupling the results of two monitoring campaigns, simultaneously collecting data from two different and independent remote sensing devices, focused on the surface deformation of the Planpincieux glacier, on the Italian side of the Mont Blanc massif. The analysed period lasted 25 days and occurred in correspondence of the beginning of the Alpine cold season. The unstable weather conditions, affecting both the monitored surfaces and the signal propagation, demanded an accurate understanding of the atmospheric effect and the development of a specific correction procedure for radar data. The considered devices are a low-cost optical photography station (OPS) and a ground-based synthetic aperture radar (GB-SAR). The OPS is placed frontally to the glacier surface and measures the daily motion components orthogonal to the line of sight (LOS). The processing is performed through spatial cross-correlation between consecutive images, acquired at the same hours to limit shadow effects. The images are orthorectified on a 1 m-resolution digital surface model (DSM) of the glacier and a pixel-to-metric conversion is performed. The GB-SAR acquires data every 16 minutes. The GB-SAR location is decided aiming at maximising the parallel condition to the LOS and the estimated direction of the main flow. The main processing steps include i) a coherence-driven pixel-selection criterion to identify glacier areas, ii) 2D unwrapping algorithm, iii) atmosphere phase screen (APS) filtering with a newly 2D polynomial model, function of the elevation. The radar maps are also georeferenced on the DSM. Finally, from the 3 different components of the glacier surface motion it is possible to reconstruct the actual deformation vector. The results are mapped on the DSM. The proposed method allows to determine the evolution of the 3-dimensional kinematics of the observed surface; it can be applied in general to the gravitational processes.

In the last years, the Ground-Based SAR (GBSAR) technique has proved to be a reliable tool for deformation measurement and monitoring. Compared with other point-wise geodetic techniques it can provide “continuous” displacement measurements over areas of few squared kilometers, with a high spatial resolution and precision up to millimeter level. The process of estimating deformation from the GBSAR data is not always straightforward: it requires appropriate data processing and analysis tools. One of the main critical steps is the phase unwrapping, which can critically affect the deformation measurements and hence the interpretation of the deformation phenomenon at hand. This paper is addressed to a specific type of GBSAR data acquisition: the so-called discontinuous mode. The paper includes two main parts. In the first one we describe the procedure used at the CTTC to process and analyze discontinuous GBSAR data. The second part of the paper discusses the performances of the proposed procedure in a real case study: the deformation monitoring of the village of Barberà de la Conca, located in Southern Catalonia.

The capability of radar interferometry to monitor the vibration characteristics of different civil structures has been consolidating in the last decade and successful case studies have been issued by different research teams. In this paper the authors describe the development of a novel sensor working at a higher frequency with respect to system available from the market, and with a larger radiofrequency bandwidth, able to provide an improved range resolution. Measurement tests aimed at validating the observations carried out with the new sensors, and comparing the new prototype with a commercial instrument are discussed.

Ground Based SAR Interferometry: a Novel Tool for Geoscience

Galahad is an ongoing Specific Targeted Research Project developed within the EU 6th Framework Programme ¿ Priority 1.1.6.3. The objective is to retrieve, through the use of improved GB-SAR and TLS technologies, field parameters that can be used in prediction algorithms of landslides, avalanches and glaciers related hazards. The landslide study area is located in the ski resort of Formigal, central Pyrenees (province of Huesca, Spain). The excavation of a parking area in the summer of 2004 reactivated a complex paleolandslide creating new sliding surfaces. The movement extends over an area of 0.25 km2 and experienced displacements as large as 0.5 cm/day during the period 2004¿2005. Stabilization engineering solutions were carried out reducing maximum observed displacement to 0.2 cm/day at the end of 2005. Within Galahad performed activities consisted in the collection of data on the landslide useful for its detailed characterization and the execution of a series of site measurement campaigns with GB-SAR, TLS and Differential GPS (D-GPS). The monitoring activities started in May 2006 completing a series of four campaigns with Total Station and D-GPS, a continuous two month data acquisition with GB-SAR and several TLS scans during two different periods from three points of view over the landslide. In this paper data obtained by GB-SAR and TLS are compared with D-GPS data, and a good agreement has been found between data sets. The project is still in progress and new site measurement campaigns with GB-SAR, TLS and D-GPS in 2007 will provide further insight into landslide forecasting models., JRC.H.7-Land management and natural hazards