Parametric Study of the Errors Obtained from the Measurement of the Oscillating Movement of a Bridge Using Image Processing

The movement of a pedestrian bridge retrieved by means of image processing technique has been analysed in this paper. An optical target has been attached to the deck and its oscillation has been tracked with fast cameras. The movement of the bridge has also been measured with a radar interferometer and this result has been taken as the reference signal. Using these data, a parametric study of the errors introduced by the image-based methods has been performed. The influence of some variables in the measurement error such as the distance to the target, the image size, the type of camera or the movement amplitude has been analysed for four different distances, and two types of excitations. Results show that the relative error decreases with the amplitude and the target diameter and it increases with the target distance. Additionally, the maximum relative error obtained in most of the analysed cases is below 10 %.The authors acknowledge the support of the Generalitat Valenciana through the project PROMETEO II/2015/015 and GV/2015/116 and the University of Alicante through the project GRE13-10

Discontinuous GBSAR deformation monitoring

This paper is focused on deformation monitoring using the Ground-Based SAR (GBSAR) technique and a particular data acquisition configuration, which is called discontinuous GBSAR (D-GBSAR). In the most commonly used GBSAR configuration, the radar is left installed in situ, acquiring data periodically, e.g. every few minutes. Deformations are estimated by processing sets of GBSAR images acquired during several weeks or months, without moving the system. By contrast, in the D-GBSAR the radar is installed and dismounted at each measurement campaign, revisiting a given site periodically. This configuration is useful to monitor slow deformation phenomena. This paper outlines the D-GBSAR data analysis procedure implemented by the authors. This is followed by a discussion of some specific aspects of D-GBSAR monitoring. Two successful examples of D-GBSAR monitoring are discussed: one concerns an urban area, while the second one involves a rural area where the monitoring requires the use of artificial corner reflectors

DINSAR ANALYSIS REVEALS BULGING OF AZERBAIJAN MUD VOLCANO EDIFICES BEFORE AN ERUPTION

Mud volcanism consists in the surface extrusion of gases, saline waters and mud breccias, which produce conical edifices of various sizes with morphology similar to that of magmatic volcanoes. In this work, DInSAR technique has been used to investigate the ground deformation related to the activity of Azerbaijan mud volcanoes during the period October 2003-November 2005. This work focuses on two important deformation events at the Ayaz-Akhtarma and Khara-Zira mud volcanoes. The ground deformations at mud volcanoes are generally originated by fluid pressure and volume variations in the reservoir. The observed deformation pattern is characterized by pre-eruptive inflation that reaches a cumulative value of up to 20 cm at Ayaz-Akhtarma in about two years. Similar pre-eruptive bulging has been observed at magmatic volcanoes, where uplift is typically associated with magma intrusion. We conclude that mud and magmatic volcanoes display some similarities in the behavior of ground deformation during pre-eruptive stages

Using ground based radar interferometry during emergency: the case of A3 motorway (Calabria Region, Italy) threatened by a landslide

The rapid assessment of the evolution of the phenomena which occur during an emergency, along with an all weather and h24 monitoring capability, are probably the main characteristics of a system aimed at optimizing intervention in natural disasters, such as landslide collapses. A few techniques are able to provide all these features remotely, hence assuring safe conditions to operators. This paper reports on an application of the GB-InSAR (Ground-Based Interferometric Synthetic Aperture Radar) technique to monitor a landslide threatening an infrastructure, the A3 motorway in the Calabria Region (Southern Italy), in emergency conditions. Here, it is evaluated how well this technique is able to satisfy these requirements. On 30 January 2009, a mass movement never detected before and located near Santa Trada viaduct caused the closure of that sector of the A3 motorway. The prompt installation of a GB-InSAR permitted to follow and to understand the temporal evolution of the landslide until the end of the emergency and then safely reopen of the motorway. The main steps of the GB-InSAR interferometry data interpretation used in managing this emergency are described and discussed here. In detail, data collected through a continuous acquisition have permitted the division of the unstable area into three smaller zones characterized by different extents of displacement

Measuring thermal expansion using X-band Persistent Scatterer Interferometry

This paper is focused on the estimation of the thermal expansion of buildings and infrastructures using X-band Persistent Scatterer Interferometry (PSI) observations. For this purpose an extended PSI model is used, which allows separating the thermal expansion from the total observed deformation thus generating a new PSI product: the map of the thermal expansion parameter, named thermal map. The core of the paper is devoted to the exploitation of the information contained in the thermal maps: three examples are discussed in detail, which concern a viaduct, a set of industrial buildings and two skyscrapers. The thermal maps can be used to derive the thermal expansion coefficient of the observed objects and information on their static structure. In addition, the paper illustrates the distortions in the PSI deformation products that occur if the thermal expansion is not explicitly modelled. Finally, an inter-comparison exercise is described, where the thermal expansion coefficients estimated by PSI are compared with those derived by a Ku-band ground-based SAR campaign

The Interferometric Use of Radar Sensors for the Urban Monitoring of Structural Vibrations and Surface Displacements

In this paper, we propose a combined use of real aperture radar (RAR) and synthetic aperture radar (SAR) sensors, within an interferometric processing chain, to provide a new methodology for monitoring urban environment and historical buildings at different temporal and spatial scales. In particular, ground-based RAR measurements are performed to estimate the vibration displacements and the natural oscillation frequencies of structures, with the aim of supporting the understanding of the building dynamic response. These measurements are then juxtaposed with ground-based and space-borne SAR data to monitor surface deformation phenomena, and hence, point out potential risks within an urban environment. In this framework, differential interferometric SAR algorithms are implemented to generate short-term (monthly) surface displacement and long-term (annual) mean surface displacement velocity maps at local (hundreds m2) and regional (tens km2) scale, respectively. The proposed methodology, developed among the activities carried out within the national project Programma Operativo Nazionale MASSIMO (Monitoraggio in Area Sismica di SIstemi MOnumentali), is tested and discussed for the ancient structure of Saint Augustine compound, located in the historical center of Cosenza (Italy) and representing a typical example of the Italian Cultural Heritage

Dynamic monitoring of a mid-rise building by real-aperture radar interferometer: advantages and limitations

In this paper, remote and in situ techniques to estimate the dynamic response of a building to ambient vibration are reported: data acquired through a real-aperture radar (RAR) interferometer and conventional accelerometers are analyzed. A five-story reinforced concrete housing building, which was damaged during the May 11th 2011 Lorca (Spain) earthquake, is used as a case study. The building was monitored using both types of instruments. The dynamic properties of the building are estimated first taking acceleration measurements using a set of 10 high-precision accelerometers installed on the roof of the building. Further, the displacement–time histories, recorded with the RAR device pointing to a corner of the building, are analyzed. Then, the ability and shortcomings of RAR measurements to deal with the fundamental frequencies of vibration of the structure are investigated. The advantages and limitations of from-inside (accelerometric) and from-outside (RAR) measurements are highlighted and discussed. A relevant conclusion is that, after strong earthquakes, RAR may be an interesting and useful tool, as it allows surveying the structural response of mid-rise buildings remotely, without the need to enter the structures, which may be dangerous for inspectors or technicians in cases of severely damaged buildings. Given that the instrumented building suffered significant damage, the ability of these kinds of measurements to detect damage is also discussed.This research has been partially funded by the Ministry of Economy and Competitiveness (MINECO) of the Spanish Government and by the European Regional Development Fund (ERDF) of the European Union (EU) through projects with references CGL2015-65913-P (MINECO/ERDF, EU) and EFA158/16/POCRISC (INTERREG/POCTEFA. EU). R.E.A. holds a PhD fellowship from the Consejo Nacional de Ciencia y Tecnología (CONACyT) in México. L.A.P. is supported by a Ph.D. scholarship grant from the Institute for the Training and Development of Human Resources (IFARHU) and the Government of Panama’s National Secretariat of Science, Technology, and Innovation (SENACYT).Peer ReviewedPostprint (published version

Non-Contact Detection of Breathing Using a Microwave Sensor

In this paper the use of a continuous-wave microwave sensor as a non-contact tool for quantitative measurement of respiratory tidal volume has been evaluated by experimentation in seventeen healthy volunteers. The sensor working principle is reported and several causes that can affect its response are analyzed. A suitable data processing has been devised able to reject the majority of breath measurements taken under non suitable conditions. Furthermore, a relationship between microwave sensor measurements and volume inspired and expired at quiet breathing (tidal volume) has been found