5th Joint International Symposium on Deformation Monitoring

the 5th Joint International Symposium on Deformation Monitoring (JISDM 2022), is organized by the Universitat Politècnica de València, Spain and endorsed by the three leading scientific and professional organizations in the field: the International Federation of Surveyors (FIG), the International Association of Geodesy (IAG) and the International Society of Photogrammetry and Remote Sensing (ISPRS).

The Symposium aims to connect research in deformation monitoring, including all aspects from measurement, technical realization, analysis to interpretation with advanced practice. Bringing together leading experts from academia, industry and representatives from public authorities with promising young scientists, the Symposium has been established as a reference point for scientific discussion and interaction.

URI permanente para esta colecciónhttps://riunet.upv.es/handle/10251/191596

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Mostrando 1 - 20 de 101

Access status: Abierto ,
Including virtual target points from laser scanning into the point-wise rigorous deformation analysis at geo-monitoring applications
(Editorial Universitat Politècnica de València, 2023-01-27) Raffl, Lukas; Holst, Christoph; Bayerisches Staatsministerium für Umwelt und Verbraucherschutz
[EN] We present a method to include virtual target points from laser scanning into the point-based rigorous deformation analysis to derive precise 3D deformation vectors. This method overcomes the challenge of missing point identities in laser scans and is developed especially for geo-monitoring applications that demand an early identification of deformations at previously unknown positions. Our approach is based on virtual targets represented by local scan patches. Each patch is matched between overlapping stations and across different measurement epochs using the Iterative Closest Point Algorithm (ICP). Thus, similar to feature points, a number of homologous points is created and polar pseudo-observations are derived. This allows to integrate the observations into a free network adjustment and into a rigorous deformation analysis. We apply this method to the geo-monitoring of rock surfaces on Mt. Hochvogel where we use a scanning total station combining point-wise measurements to signalized targets and pseudo-observations derived from area-wise laser scans. In our application, numerous virtual target points could be created throughout the deformation object. The results show that the new method improves the accuracy and reliability of the subsequent rigorous deformation analysis and it, thus, allows for an early identification of deformations at geo-monitoring applications. Still there is some improvement in the selection of suitable patches needed, as the matching accuracy of the ICP strongly depends on the point distribution within the patches.
Access status: Abierto ,
Structural analysis of monitoring results of long-span roof structures
(Editorial Universitat Politècnica de València, 2023-01-27) Shults, Roman
[EN] The concept of analysis of geodetic monitoring results solely from a geometric point of view is recognized as an obsolete approach. A complex analysis of geodetic measurements (geometric approach) and the structure stress-strain analysis (mechanical approach) allows obtaining the whole picture of any engineering structure displacements. The detailed scheme of the structural analysis of geospatial monitoring results of the long-span roof structures has been given in the presented paper. The results of the geospatial monitoring of the large warehouse have been chosen as a study subject. The structure's roof consists of planar trusses, the main objects of external loads combined with dead loads. According to the complex analysis procedure, the trusses were analyzed using the method of joints with the determination of partial member forces. At the next step, these forces were leveraged in the following order member force–member deformation–node displacement. To obtain the actual displacements of the truss nodes, one has to account for the vertical displacements of the leaning points where the truss touched the column. That step is also being accomplished using the method of joints. Having the actual node displacements, one may compare them with geodetic monitoring results. The comparison results generally allow us to reveal the places with unacceptable displacements and estimate whether they are determined with the necessary accuracy. In this particular case, the final node's displacements were yielded as an output of combined analysis, both geometric and mechanical. That, in turn, lets to acquire the deformation process's genuine parameters. The study results have shown the high efficiency of the presented research methodology.
Access status: Abierto ,
Monitoring the production process of lightweight fibrous structures using terrestrial laser scanning
(Editorial Universitat Politècnica de València, 2023-01-27) Balangé, Laura; Harmening, Corinna; Duque Estrada, Rebeca; Menges, Achim; Neuner, Hans; Schwieger, Volker; Deutsche Forschungsgemeinschaft
[EN] The Cluster of Excellence Integrative Computational Design and Construction for Architecture at the University of Stuttgart brings together various disciplines to jointly develop amongst other things a better understanding of processes in the manufacturing and construction domain. One of the cluster’s aims is to create new solutions for the construction of lightweight fibrous structures using coreless winding of lightweight fiber composite systems. For this purpose, a precise geometry and an understanding of the fibers’ behavior during the production process are of major importance. The fibers’ production process is monitored by repeatedly scanning the fibers during different stages of the process using a terrestrial laser scanner. In order to determine the geometry of the fibers’ axes as well as their cross-sections, two different strategies are used. The first strategy focuses on the segmentation of several straight lines between two intersection points. For the comparison of the individual fabrication steps, the positions of the intersection points are contrasted. For the cross-sectional areas of the fibers, orthogonal planes of intersection are then defined and all points within a predefined area are projected onto this plane. Then the area is calculated using a convex hull. In the second strategy, the fibers‘ main axes are represented by best-fitting B-spline curves. The borders of the cross-sections of interest are also approximated by best-fitting B-spline curves, forming the basis for the final determination of the cross-sectional areas. In this case study two epochs are analyzed with a deformation of the size of around 1cm. For both epochs the cross-sections are calculated in cm steps.
Access status: Abierto ,
Soil Moisture Mapping Based on Temperature-Soil Moisture Dryness Index - a case study for the tailing dam in Brumadinho, Brazil
(Editorial Universitat Politècnica de València, 2023-01-27) Lan, Yu; Paffenholz, Jens-André
[EN] The tailing dam in Brumadinho of Brazil collapsed on 25th January 2019, it caused serious casualties and environmental pollution. The monitoring of the tailing dam stability has become an urgent problem. For monitoring, soil moisture is an important parameter, if the soil moisture is too high, it will cause soil liquefaction and then the stability of the tailing dam will decrease. In this study, Landsat 8 data is innovatively used to calculate the Temperature-Soil Moisture Dryness Index (TMDI) for the estimation of soil moisture of the collapsed tailing dam in Brumadinho. The data on 14th January 2019 and 30th January 2019 are used in order to better understand the soil moisture before and after the collapse of tailing dam. TMDI is calculated based on triangle space of Land Surface Temperature (LST) and Normalized Difference Latent Heat Index (NDLI). This new index TMDI is used for the assessment of the soil moisture and evapotranspiration (ET). The performance of TMDI and Temperature Vegetation Dryness Index (TVDI) are evaluated by the reference evapotranspiration (ET), which is calculated based on the Surface Energy Balance Algorithm for Land (SEBAL). Results of the correlation between TMDI, TVDI and SEBAL-derived ET indicate that TMDI is a better index for estimating soil moisture. The built-up region shows high negative correlation with SEBAL-derived ET. According to the spatial distribution of TMDI and TVDI, in the tailing dam, some parts of the dam body shows high soil moisture which may have the potential risk of soil liquefaction.
Access status: Abierto ,
On the quality checking of persistent scatterer interferometry by spatial- temporal modelling
(Editorial Universitat Politècnica de València, 2023-01-27) Omidalizarandi, Mohammad; Mohammadivojdan, Bahareh; Alkhatib, Hamza; Paffenholz, Jens-André; Neumann, Ingo
[EN] Today, rapid growth in infrastructure development and urbanization process increases the attention for accurate deformation monitoring on a relatively large-scale. Furthermore, such deformation monitoring is of great importance in the assessment and management of natural hazard processes like landslides, earthquakes, and floods. In this study, the Persistent Scatterer Interferometry (PSI) technique is applied using open-source synthetic aperture radar (SAR) data from the satellite Sentinel-1. It allows point-wise deformation monitoring based on time series analysis of specific points. It also enables performing spatio-temporal area-based deformation monitoring. Currently, these data do not have a sophisticated quality assurance process to judge the significance of deformations. To obtain different quality classes of the Persistent Scatterer (PS) data points, the first step is to classify them into buildings and ground types using LoD2 building models. Next, time series analysis of the PS points is performed to model systematic and random errors. It allows estimation of the offset and the deformation rate for each point. Finally, spatio-temporal modelling of neighbourhood relations of the PS points is carried out using local geometric patches which are approximated with a mathematical model, such as, e.g., hierarchical B-Splines. Subsequently, the quality of SAR data from temporal and spatial neighbourhood relations is checked. Having an appropriate spatio-temporal quality model of the PS data, a deformation analysis is performed for areas of interest in the city of Hamburg. In the end, the results of the deformation analysis are compared with the BodenBewegungsdienst Deutschland (Ground Motion Service Germany) provided by the Federal Institute for Geosciences and Natural Resources (BGR), Germany.
Access status: Abierto ,
Towards an automated machine learning and image processing supported procedure for crack monitoring
(Editorial Universitat Politècnica de València, 2023-01-27) Parente, Luigi; Castagnetti, Cristina; Falvo, Eugenia; Grassi, Francesca; Mancini, Francesco; Rossi, Paolo; Capra, Alessandro
[EN] Development of automated and remotely controlled procedures for accurate crack detection and analysis is an advantageous solution when compared to time-consuming and subjective crack examination conducted by operators. Recent studies have demonstrated that Machine Learning (ML) algorithms have sufficient potential for crack measurements. However, training of large amount of data is essential. When working on single sites with permanently installed fixed cameras adoption of ML solutions may be redundant. The purpose of this work is to assess the performance of a procedure for crack detection based on an easy to implement workflow supported by the use of ML and image processing algorithms. The datasets used in this work are composed of temporal sequence of single digital images. The workflow proposed includes three main modules covering acquisition, optimization and crack detection. Each module is automated and basic manual input by an operator is only required to train the classifier. The processing modules are implemented in modular open-source programs (e.g., ImageJ and Ilastik). Results obtained in controlled conditions led to a satisfactory level of detection (about 99% of the crack pattern detected). Experiments conducted on real-sites highlighted variable detection capabilities of the proposed approach (from 12 to 96%). The main limitation of the approach is the production of false-positive detection due to significant variation in illumination conditions. Further work is being conducted to define scalability of the approach and to verify deformation detection capabilities.
Access status: Abierto ,
BIM Approach Applied to Urban Tunneling Interferences
(Editorial Universitat Politècnica de València, 2023-01-27) Trani, Marco; Longo, Silvia; Conti, Monica
[EN] Interferences management induced on buildings during underground works -including the excavation of a metro tunnel- is a topic that must be carefully studied and analysed. The paper provides a proposal for the creation of a BIM model by which it is possible to control, over time, the influencing parameters, to visualize subsidence values and foreseen harmful events for building falling in the subsidence basin of an excavation machine. The method is based on the creation of a model which allows to graphically monitor the subsidence to which the buildings may be subjected through the attribution of predefined thresholds. In the same way, in the model, the parameters linked to the excavation machine itself are also checked. This control is useful to predict the formation of chimneys that could damage buildings structures and façades. To import all the data in the 3D model, specific scripts have been written using the software Dynamo, to semi-automatically connect an Excel file with a Revit model. This method will be then applied to a specific case study, a portion of the central section of the new M4 metro line in Milan, built with EPB type TBM machines. To provide indications of the measures to be adopted if the different thresholds are reached, guidelines for interference management are subsequently proposed. The conclusion of the paper shows how the model, together with the guidelines, with the necessary implementations and modifications, is to be considered valid for the management of the same topic in other works.
Access status: Abierto ,
Concept for the integration of BIM and GIS data for monitoring land deformation around an ongoing infrastructure project
(Editorial Universitat Politècnica de València, 2023-01-27) Glinka, Szymon; Owerko, Tomasz
[EN] The BIM (Building Information Modeling) technology, currently being introduced in many countries, and its integration with GIS (Geographic Information System) data within a single CDE (Common Data Environment) platform may allow a more in-depth monitoring of the investment and faster detection of irregularities related to its implementation. Considered separately, each of the above technologies allows different types of analysis, but the synergy effect created by their integration makes it possible to view the problem in a broader perspective and to make the optimal decision. This issue also concerns the analysis of deformations around the erected object, which can be described by GIS data. On the other hand, the object is currently most often represented by a 3D model in IFC format that has the relevant information. The main aspect of this work is to combine these two types of data and analyse such a solution in terms of investment management support. The final result of the work is a description of a BIM and GIS use case for deformation monitoring and the creation of a algorithm for this task including the exchanged information with reference to OpenBIM standards (data exchange format Industry Foundation Classes - IFC, Information Delivery Manual - IDM). The whole work was also considered with reference to risk management during the project.
Access status: Abierto ,
Point displacements during classical measurements – a practical approach to pseudo epochs between measurements
(Editorial Universitat Politècnica de València, 2023-01-27) Duchnowski, Robert; Wyszkowska, Patrycja; Uniwersytet Warminsko-Mazurski w Olsztynie
[EN] Various measurement techniques and data processing are applied to determine point displacements and deformation of geodetic networks or buildings. Considering classical measurements and analysis of the network deformation, we should realize that the measurements are not “immediate.” The question arises: what happens if a point (or some points) displaces between particular measurements within one epoch. In such a case, the observation set would consist of the observations before and after point displacement, and such hypothetical observation groups can be regarded as related to two (or more) pseudo epochs. The paper's main objective is to examine some estimation methods that would probably deal with such a problem, namely Msplit estimation (in two variants, the squared and the absolute Msplit estimation) and chosen robust methods, namely Huber’s method (example M-estimation) and the Hodges-Lehmann weighted estimation (basic R-estimation). The first approach can provide two (or more) variants of the network point coordinates (here, before and after point movements), providing information about two (or more) states of the network during measurements. In contrast, the robust methods can only decrease the influence of the outliers on the computed network point coordinates. Thus, estimation results would concern only one network state in such a case. The presented empirical analyses show that the better and more realistic results are obtained by applying Msplit estimation. Huber’s method can also provide acceptable results (describing the network state at the epoch beginning) only if the number of observations conducted after the point displacements is not too high.
Access status: Abierto ,
Monitoring Gravitational Deformations of the Wettzell 20 m Radio Telescope’s Main Reflector Using a Leica RTC360
(Editorial Universitat Politècnica de València, 2023-01-27) Weinhuber, Agnes; Neidhardt, Alexander; Holst, Christoph
[EN] Quasars are nowadays the basis to determine the world’s absolute orientation in space by radio interferometry (VLBI). The global network of baselines measured by the used radio telescopes, which vary greatly in size, is subject to various influences that have an impact on the International Terrestrial Reference Frame. Among others, those influences are imperfections of individual panels of the dishes, a possible elevation dependent deformation of the whole dish and a shift of the reference point due to gravitational influences. In this study, we monitor the elevation dependent deformation of the main reflector of the 20 m radio telescope of the Geodetic Observatory Wettzell by a Leica RTC360 laser scanner. For this task, we mount the terrestrial laser scanner overhead near the subreflector to capture the surface of the moving dish at each elevation angle. This study focusses on 1) introducing further redundancy in the measurement and processing strategy to gain a reliable and accurate result even the used scanner is a no high-end one. This furthermore leads to 2) investigations whether there are differences in the results between in related work used high-end scanners and the RTC360 and thus 3) whether the RTC360 proves to be capable to detect deformations at a radio telescope’s main reflector. Using these three foci, we show that deformations in the main reflector between elevations can be reliably determined areal and in focal length by redundant measurements with the RTC360. It is also shown that the results are less sensitive to axis errors compared to those obtained with high-end scanners. However, the compensations also show that the application scanner has certain systematics, which must be investigated in further steps.
Access status: Abierto ,
Monitoring of land subsidence in the city of Recife/Brazil using Sentinel-1 SAR interferometry
(Editorial Universitat Politècnica de València, 2023-01-27) Souza, Wendson; Ruiz-Armenteros, Antonio; Cabral, Jaime; Junta de Andalucía; Universidad de Jaén; European Space Agency
[EN] One of the main causes of land subsidence in the world is the exploitation of groundwater above the regeneration capacity of the aquifer systems. However, the rapid urban growth in estuarine areas can also contribute to the development of this phenomenon. An example of this occurs in the city of Recife, northeastern Brazil. The municipality is built on an estuarine plain composed of several rivers (Capibaribe, Beberibe, Tejipió), which formation results from the occupation of humid areas and mangroves. In recent decades, the excessive removal of water resources from the subsoil has caused the reduction of more than 100 meters of the deep aquifer piezometric level in some places. The presence of these factors in Recife may contribute to land subsidence. To detect this phenomenon, the Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) technique was used. The dataset consisted of 135 Sentinel-1A Interferometric Wide (IW) Single Look Complex (SLC) images from September 2016 to April 2021. The images were acquired in descending orbits and VV polarization. The results of the PSInSAR analysis reveal that in Recife there are several areas of land subsidence with a rate close to -15 mm/year. The main occurrence of soil settlement is observed in large recently built areas in the west zone, and small areas in the north zone. Minor cases occur in the southern zone due to the exploitation of groundwater. The identification of these land subsidence areas can help in the study of urban drainage to avoid flooding sites and in the adoption of mitigating measures for the suitable use of underground water resources.
Access status: Abierto ,
Current State of Multi-constellation and multi-frequency Precise Point Positioning
(Editorial Universitat Politècnica de València, 2023-01-27) Chacón, Fernando; Herrera, Antonio; de Lacy, M. Clara; Ministerio de Economía y Competitividad; Junta de Andalucía; Universidad de Jaén
[EN] Precise Point Positioning is a standalone method to estimate the coordinates of a single GNSS receiver based on undifferenced observations and modelling all the effects present during the observation session by precise products. The reference system of the coordinates estimated will be the same as the satellite orbits used in GNSS data processing. Due to its accuracy, PPP satisfies all most of applications where GPS observations are used. In recent years, the interoperability of new global navigation satellite systems (referred to as multi-GNSS) has driven the combination of observations coming from different satellite constellations. Multi-GNSS consists of the interoperability of at least two satellite constellations with some of their frequencies working in common. In this context, it has been essential to implement effective PPP algorithms to take advantage of the novelties presented by the different satellite navigation systems. As a consequence, some scientific software has been updated to support multi-frequency and multi-constellation GNSS data in PPP mode. Some of them are Bernese 5.2, RTKLIB, goGPS and PCUBE. The last one is being developed by the authors. This program implements two techniques for multi-GNSS data processing. One of them is based on a sequential filter and the other one is based on the Least Squares Approach. The purpose of this work is to study the capability and evaluation of multi-GNSS PPP performance along a whole day comparig the solutions estimated by different GNSS processing software. Special attention will be paid to the benefits introduced by new frequencies and services provided by the European System Galileo.
Access status: Abierto ,
Monitoring embankment dams from space using satellite radar interferometry: Case studies from RemoDams project
(Editorial Universitat Politècnica de València, 2023-01-27) Ruiz-Armenteros, Antonio; Delgado-Blasco, José Manuel; Bakon, Matus; Lamas-Fernández, Francisco; Marchamalo-Sacristán, Miguel; Gil-Cruz, Antonio J.; Gil-Cruz, Antonio; Papco, Juraj; González-Rodrigo, Beatriz; Lazecky, Milan; Perissin, Daniele; Sousa, Joaquim J.; Sousa, Joaquim; Ministry of Education, Youth and Sport of the Czech Republic; Slovak Grant Agency for Science; Fundação para a Ciência e a Tecnologia, Portugal; Junta de Andalucía; Agencia Estatal de Investigación; Universidad de Jaén
[EN] The monitoring procedures with different geotechnical/structural sensors and classical geodetic techniques including GNSS are the usual practices in most of the dams where these controls are established. Other geomatic techniques such as TLS, GB-SAR and multi-temporal InSAR (MT-InSAR), allow the determination of 3D displacements with the advantage of covering a large number of control points. In particular, MT-InSAR techniques enable the detection of displacements at a very low cost compared to other techniques, and without the need for field work or the installation of special equipment. In addition, they can provide a single source of information on the stability of the dam when monitoring programs are not carried out due to lack of funding, resources or other reasons. These techniques provide measurement uncertainties of the order of 1 mm/year, interpreting time series of interferometric phases of coherent reflectors present in the area, called Persistent Scatterers. In this work, we present the adaptation and application of MT-InSAR techniques to monitor embankment dams, obtaining vertical displacements, characterizing their consolidation rates, and allowing the identification of potential problems surrounding the reservoir that require further field investigation. This study is part of the ReMoDams project, a Spanish research initiative developed for monitoring dam structural stability from space using satellite radar interferometry.
Access status: Abierto ,
Experimental assessment of the accuracy of a Ground-Based Radar Interferometer in a fully controlled laboratory environment
(Editorial Universitat Politècnica de València, 2023-01-27) Piniotis, George; Gikas, Vassilis
[EN] Ground Based Radar Interferometry (GBRI) counts almost twenty years of maturity. Ever since its infancy, GBRI has been extensively used in structural health monitoring, thanks to its high sampling rate (up to 200 Hz) and remote, ultra-high displacement observation accuracy (claimed to be of the order of ± 0.01 mm in lab. conditions) at multi-point locations on a structure. Nevertheless, despite the fact that GBRI has already been extensively used for bridge monitoring projects, the published results of the comparisons derived between GBRI and other technologies (e.g., accelerometers, seismometers and Laser Doppler Vibrometers) are usually limited to real structures cases at operational conditions; and therefore, an exhaustive assessment of the inherent quality measures of GBRI observables is still missing. This paper presents the results obtained from an exhaustive investigation of the performance capabilities of a GBRI sensor (IBIS-S sensor, IDS Radar®), in terms of precision (repeatability) and accuracy (trueness) at fully controlled, lab conditions. Dynamic displacements of a sinusoidal form were produced using an automatically operated portable shake table and on-purpose built software. Testing scenarios cover a frequency range corresponding to structural modal frequencies (up to 20 Hz) and an amplitude range of 10-5 to 10-2 m. The measurements of a Laser Tracker sensor serve as a benchmark against which the results of the GBRI unit are assessed, in terms of displacement accuracy and frequency estimation correctness.
Access status: Abierto ,
Accuracy improvement of mobile laser scanning point clouds using graph-based trajectory optimization
(Editorial Universitat Politècnica de València, 2023-01-27) Esser, Felix; Moraga, José Angel; Klingbeil, Lasse; Kuhlmann, Heiner; Deutsche Forschungsgemeinschaft
[EN] The detection of deformations on man-made structures such as bridges and dams are an essential task in engineering geodesy. The classical method uncovering deformations is based on geodetic networks using measurements from total stations or GNSS receivers. Another new approach is the determination of deformations based on terrestrial laser scans leading to large-scale deformation results by point cloud comparisons. In the field of geodetic engineering, mobile laser scanning systems are increasingly used for high-resolution point cloud generation in short measurement times, which leads to the idea to use these for deformation analysis. A crucial part of this measurement strategy is the estimation of the trajectory (position and orientation) of the scanner, which allows a consistent registration of the single scan lines in a global coordinate system (georeferencing). The largest limitation to the accuracy of the resulting point cloud is the accuracy of the estimated trajectory. In most applications, the estimation of position and orientation are based on the fusion of GNSS (Global Navigation Satellite System) and IMU (Inertial Measurement Unit) measurements. Systematic errors, as they often appear in GNSS measurements, are directly transferred to the georeferenced point cloud and therefor limit the potential for deformation analysis. With this paper we address the questions, if the trajectory estimation can be improved by the integration of known landmarks into the trajectory estimation procedure. Using a point cloud generated with an initial GNSS/IMU based trajectory, landmark targets can be observed in the point cloud and integrated into an updated estimate, using a factor graph-based approach. For the evaluation of a potential accuracy increase due to landmark observations, we performed measurements, comparing GNSS/IMU based results with the ones where landmarks are additionally integrated. The experiments show, that the accuracy increases especially in the heading angle, which is reflected in lower residuals to observed reference coordinates, but also in the trajectory covariances of the estimation results.
Access status: Abierto ,
Selected aspects of geometrical analyses of surfaces measured using terrestrial laser scanning (TLS)
(Editorial Universitat Politècnica de València, 2023-01-27) Zaczek-Peplinska, Janina; Kowalska, Maria; Ryczko, Krystian; Sekular, Cezary
[EN] Modern measurement technologies are widely used for the monitoring and determination of surface deformations. One more frequently used measurement technology is terrestrial laser scanning (TLS), which provides quasi-continuous information about the tested surface in the form of a point cloud at a given resolution. At the same time, TLS is based on measuring the distance in a given direction, thanks to which we can obtain a high precision of measurement, often compared to tacheometric measurements. This paper presents a study on the determination of surface flatness parameters extracted from a point cloud. It takes into account the roughness characteristics of the different structures on the measured surfaces and analyzes them using the most popular algorithms for determining the distance of points from the reference surface. Additionally, the review presents the issue of expanding selected surfaces onto a plane to analyze their geometric parameters, and thus to determine the deformation. The applied solution can be used to monitor the deformation of objects such as tunnels and interiors of collectors or large-diameter downpipes, the shape of which is similar to a cylinder surface. Thanks to the expansion of the cylinder surface into a plane, it is possible to perform a comprehensive analysis of surface deformation, and not only selected fragments in the form of sections. The conducted analyses show the great potential of data obtained using terrestrial laser scanning, when an appropriate procedure and data processing method are applied. This paper focuses on two types of studies; the study of surface flatness and analysis of the deformation of cylindrical surfaces. These types of studies are extremely useful in assessing the technical condition of structures, especially in studying the deformation of structures built underground (tunnels, passages, warehouses), where the loads from the surrounding earth are significant.
Access status: Abierto ,
Static and Dynamic Monitoring of the Notre Dame de Paris Cathedral
(Editorial Universitat Politècnica de València, 2023-01-27) Le Corvec, Véronique; Lézin, Patrick; Cartiaux, François-Baptiste
[EN] During the fire which took place on 15th April 2019, the Cathedral of Notre Dame de Paris underwent extensive structural damages: most of the roof was destroyed, part of the stone vaulted ceiling collapsed, and the wooden framework of the north tower was partially burned. After the fire, a list of actions was carried on in order to secure the remaining structure, prevent any further damage and start the rehabilitation. Very early on, a monitoring system was used to assist the project manager in these tasks. With the progress of site works, the monitoring system was updated to provide more insightful information. The present paper focuses on the monitoring system deployed on the towers and the stone vaulted ceiling with the objective to produce a first assessment of the current state and follow the evolution during the reconstruction phase. The monitoring campaign was carried out from December 2020 to December 2021 with two distinct sets of sensors. The first objective was to characterize the current state and identify the dynamic behavior of the structure, for that purpose 48 directional accelerometers were installed on the two towers and the two vaults lane. Acceleration measurements and analytical methods lead to the identification of the fundamental modes of these structural elements. In a second time, to follow the evolution of the vaults, 56 inclinometers were positioned on the outer side of the vaults, constituting 15 inclinometer measuring chains. Set up to transmit data continuously with a 10 min frequency, measurements allow to notify settlements or uprisings and correlate these evolutions with external factors (weather conditions or rehabilitation works).
Access status: Abierto ,
Dynamic monitoring of civil infrastructures with geodetic sensors
(Editorial Universitat Politècnica de València, 2023-01-27) Schönberger, Caroline; Lienhart, Werner; Moser, Thomas
[EN] Geodetic sensors are conventionally used for the long-term monitoring of civil structures like bridges, buildings or water dams. With the recorded data the reaction of the structure to slow changing impacts like temperature changes can be observed. However, the reaction due to dynamic impacts like wind loads, traffic loads or earthquakes are usually assessed using non-geodetic sensors like accelerometers. This article discusses how advances in geodetic sensing technology opens up new possibilities. In laboratory tests and on a real footbridge, it is demonstrated that modern total stations and GNSS receivers are well suited for the dynamic monitoring of bridges. It is shown that even small amplitudes in the range of about 1 mm for GNSS and of about 0.2 mm for total stations depending on the distance to the object can be detected.
Access status: Abierto ,
Sensitivity analysis of control networks in terms of minimal detectable displacements
(Editorial Universitat Politècnica de València, 2023-01-27) Książek, Krzysztof; Lapiński, Sławomir
[EN] Sensitivity analysis is one aspect of the calculation process in displacement measurement. For this purpose, sensitivity measures are used in the form of minimal detectable displacements ( ), derived from the definition of minimal detectable bias ( ). Analyses were performed based on disturbing the parameter vector with the value (calculated from principal component analysis). Analyses were considered for displacements of the levelling network based on the global vector ( ). The calculations were conducted using the least squares adjustment with pseudo-random observations. The mean success rate ( ) was used to perform the detection analyses. The effectiveness of the global test agrees with the assumed power of the test. Local tests for a single point showed 48.6 % displacements of more than one point. It should be considered using another local test for the case of displacements of multiple points. This study concludes that in addition to the accuracy of the designed network points, the network configuration is also important in sensitivity analyses. The research shows that sensitivity analyses should be considered at the design stage of control networks, i.e. to determine at what level a given network is able to detect displacement.
Access status: Abierto ,
Deformation Analysis with Feature Voting
(Editorial Universitat Politècnica de València, 2023-01-27) Bar, Omer; Even-Tzur, Gilad
[EN] Deformation analysis of GNSS network is usually computed using precise coordinates of the monitoring network points. Coordinates change over time construct a velocity field, which is used to estimate fault model parameters. Estimation process of coordinates is affected by several factors such as measurement errors, datum definition and the measurements datum defect. Points defining the monitoring datum have position accuracies which can increase inaccuracies in velocity estimations and the datum defect could cause biases and instability in computing the velocity field. This research proposes an algorithm of estimating geometric fault parameters using feature voting – addressing changes over time in GNSS vectors. The algorithm selects best solution for specific data-sets using minimal squared-disclosure between data and a tested value set of the fault model parameters. We concentrate on geometric fault models which rely solely on geometry between fault-line and monitoring network points. Geometric fault models are ill-conditioned, combined with low-frequency nature data - numerical instability rises. Vectors were computed with scientific processing software (Bernese), with consistent processing parameters at all epochs. Additionally, several numerical processes were adopted to transform the low-frequency data into usable datasets. Test cases were based upon 8 northern sites in the Israel’s continuous operating permanent stations. Simulative data was created from a true solved epoch; then variety of epoch data-sets were introduced to the algorithm to compute pre-defined geometric fault model parameters. Test cases show that simulative data, without and with noises, introduced to the algorithm is suited for estimating model parameters properly.

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