Artigos de Revista
Info
SARClust
Interferometric Synthetic Aperture Radar (InSAR) has proved its efficiency for displacementmonitoring in urban areas. However, the large volume of data generated by this technology turnsthe retrieval of information useful for structure monitoring into a big data problem. In this study, anew tool (SARClust) to analyze InSAR displacement time series is proposed. The tool performs theclustering of persistent scatterers (PSs) based on dissimilarities between their displacement time seriesevaluated through dynamic time warping. This strategy leads to the formation of clusters containingPSs with similar displacements, which can be analyzed together, reducing data dimensionality, andfacilitating the identification of displacement patterns potentially related to structural damage. Aproof of concept was performed for downtown Lisbon, Portugal, where ten distinct displacementpatterns were identified. A relationship between clusters presenting centimeter-level displacementsand buildings located on steep slopes was observed. The results were validated through visualinspections and comparison with another tool for time series analysis. Agreement was found inboth cases. The innovation in this study is the attention brought to SARClust
Ano: 2023
Número Páginas:
19p..
Autor(es): Fonseca, A. M.; Lemos, J. V.; Amado, C; D. Perissin; Falcão, A. P.; Roque, D.
Revista: Sustainability
Editor: MDPI
Volume:
15.
Keywords: Dynamic time warping; Hierarchical clustering; RADAR interpretation; InSAR; Structure monitoring
Info
Analysis of periodicities in long-term displacement time series in concrete dams
The hydrostatic-season-time (HST) model is a widely used method in the safety assessment of dams and for the estimation of reversible and irreversible deformations due to different load scenarios. After implementing an optimal HST-model to observational data, the residual time series can still expose some underlying periodicities. In our contribution, the underlying periodicities and their contribution to residual minimisation are further analysed by the LombScargle normalised periodogram frequency method. The extended HST-model, obtained by adding additional sinusoidal terms for the statistically most significant frequencies, presents a slight statistical improvement on the optimal HST-model. Statistically significant frequencies may not be justified or correlated to some physical process of the dam, but they make it possible to identify a pattern in the analysed period. The analyses are performed for the radial direction of long-term displacement time series measured at the topmost reading station of an inverted pendulum system in the central cantilever of the Alqueva concrete arch dam
Ano: 2019
Autor(es): Gamse, S.; Henriques, M. J.; Oberguggenberger, M.; Mata, J.
Revista: Journal Structural Control and Health Monitoring
Editor: John Wiley & Sons, Ltd.
Keywords: multiple linear regression; LombScargle normalised periodogram; hydrostatic-season-time model; false alarm probability; concrete arch dam
Info
Points clouds and orthomosaics from photographs
The three authors of this paper work at the Applied Geodetic Division of the National Laboratory for Civil Engineering (LNEC), in Lisbon, Portugal. LNEC is a state owned research and development institution founded in 1946. It works in the various domains of civil engineering (structures, hydraulic, geotechnics, environment, materials, among others), giving it a unique multidisciplinary perspective in this field. The main goals of the LNEC are to carry out innovative research and development and to contribute to the best practices in civil engineering. The Applied Geodetic Division nowadays develops works in two domains: the geodetic surveying of large dams and other engineering structures for monitoring purposes, and the processing of digital images with applications in several domains, which includes the study of the evolution of pathologies in engineering works. Originally the processing of digital images made use mostly of the chromatic information included in the images (from satellite images to close range photographs). But recently it has evolved to extract information of the geometry of the objects by the generation of point clouds. This use of close range photographs (from distances of decimetres to a few meters), which started in the summer of 2014, looks very promising and we, the authors, are identifying possible areas where the use of point clouds and orthomosaics that can be of interest to our colleagues of LNEC, civil engineers mostly. This paper presents the first examples where point clouds and orthomosaics, generated from close range photographs, can help civil engineers on their studies. The photogrammetic products were all generated using the free open-source software Micmac (Multi-Image Correspondances, Méthodes Automatiques de Corrélation) from IGN (Institut National de lInformation Géographique et Forestière, France).
Ano: 2016
Número Páginas:
8p.
Autor(es): Henriques, M. J.; Roque, D.; Braz, N.
Revista: Coordinates Magazine
Editor: Coordinates Media Private Limited
Volume:
vol. 12 - Issue 9.
Keywords: Civil engineering; Structure; Monitoring; Point cloud; Orthomosaic
Info
Surveillance par drone des digues à talus
Les ports et autres infrastructures construits sur des côtes exposées à de fortes houles ont besoin dêtre protégés. Une telle protection peut être obtenue par des digues ou brise-lames. Les digues à talus ont en général une meilleure résilience pendant les événements les plus agressifs. Un endommagement des digues affaiblit la structure et peut entraîner la perte de la capacité de protection, ce qui peut avoir des conséquences environnementales et économiques très graves. Pour cette raison, les brise-lames doivent être soumis à une surveillance régulière pour la détection des anomalies. Cet article présente quelques exemples de l'utilisation de drones dans la surveillance de la sécurité de ces structures, et décrit en particulier deux vols menés avec des drones et quelques possibilités d'extraction de données pour obtenir des informations d'intérêt pour les responsables de la sécurité.
Ano: 2016
Número Páginas:
5p.
Autor(es): Henriques, M. J.
Revista: XYZ
Editor: Association Francaise de Topographie
Volume:
148.
Keywords: Digue; Drone; Oscultation
Info
Using simplified bathymetry and SAR imagery in the validation of a hydraulic model for the Tagus River floodplain
This work presents several approaches in the validation of the hydrodynamic model Tuflow on the simulation of flood extents and water levels, based on satellite SAR imagery. A methodology that uses a simplified bathymetry in the river main course is employed, which proves to be reliable and accurate for high-flow events. This was made possible as the digital terrain model was acquired in a dry period, accounting for large dry areas in the river bed, avoiding in this way the need of expensive river bathymetry surveys. Also, two methods are applied to the SAR imagery to extract the flood boundaries: visual interpretation followed by manual delimitation and an object-based algorithm approach. The hydraulic model is tested on a reach of the Tagus River, Portugal, where the largest flood inundation areas occur, using a historical flood event to verify its robustness and reliability. The accuracy of model prediction is done through comparisons of water levels at a hydrometric station and the determination of commission and omission errors of flood extent, between the reference SAR image and the predicted inundation. It was concluded that the methodology followed in this work is well suited for the hydraulic model validation.
Ano: 2016
Número Páginas:
5p.
Autor(es): Araújo, M. A. V. C.; R. Pestana; M. Matias; Roque, D.; Teixeira, A.; Heleno, S.
Revista: Journal of Coastal Research
Editor: Coastal Education & Research Foundation
Volume:
75.
Keywords: Tuflow; Commission and omission errors; SAR imagery; Simplified bathymetry
Info
Port infrastructure control (Madeira Island, Portugal) through a hybrid monitoring system (GNSS and Accelerometers)
This article describes the implementation of a monitoring system on the breakwater at the Funchal Port (Madeira Island, Portugal) for the purpose of understanding its dynamic behavior and the temporal evolution of structural health. The monitoring system focuses on the breakwater superstructure and aims to identify the evolution of damage on the breakwater and analyze the impact of cruise ships docking and undocking. The system includes the measurement of displacements through geodetic techniques using global navigation satellite systems and the measurement of vibrations using accelerometers. Ten observation campaigns were performed over almost 3 years. As the measured displacements during this period were less than 7.5 mm it can be concluded that, despite some visible cracks, the breakwater superstructure did not suffer significant structural changes. It was shown from the measured acceleration records that some of the main modal parameters could be identified, namely the main natural frequencies of the superstructure. Through an analysis of the natural frequencies progression over time, it will be possible to identify deterioration effects on the foundation and/or the superstructure. The comparison of natural frequencies identified could be useful to evaluate the impact of these events on structural health.
Ano: 2015
Número Páginas:
617-629pp.
Autor(es): Pereira, Mário; Teodoro, A.; Lima, J. N.; Oliveira, S.; Gomes, F.V.
Revista: Journal Marine Georesources & Geotechnology
Editor: Taylor & Francis Group
Volume:
Volume 34, 2016 - Issue 7.
Keywords: Port; Docking/undocking; Breakwater; Accelerometers; GNSS
Info
Fusão de deslocamentos medidos com o GNSS e acelerações
A fusão de dados provenientes de diferentes tipos de instrumentos pode dar uma informação mais completa para a monitorização do comportamento de estruturas de engenharia civil, em particular nas pontes de grande vão. O objectivo da fusão de deslocamentos medidos com o GNSS e de acelerações, é tirar partido da precisão conseguida com o GNSS, em baixas frequências, e da grande sensibilidade dos acelerómetros, em altas frequências, e obter uma única série temporal de deslocamentos, longa e de grande resolução. Através dum filtro de Kalman será possível integrar deslocamentos medidos, com uma frequência de amostragem de, por exemplo, 1 Hz, e acelerações medidas, com uma frequência de amostragem de, por exemplo, 100 Hz, de modo a obter uma série temporal de deslocamentos de longa duração e com uma resolução de 100 Hz. Nesta comunicação apresentam-se os resultados preliminares dum ensaio realizado num modelo estrutural simples correspondente a um edifício de três pisos, instrumentado com antenas GNSS da Topcon e acelerómetros da Kinemetrics, modelo Episensor ES-U2, e da Nanometrics, modelo Titan SMA, tendo em vista a futura aplicação desta metodologia em pontes de grande vão.
Ano: 2013
Número Páginas:
10.
Autor(es): Lima, J. N.; Oliveira, S.; Henriques, M.
Revista: 3 ASCP, Actas do 3º Congresso da Associação Portuguesa para a Segurança e Conservação de Pontes
Editor: Associação Portuguesa para a Segurança e Conservação de Pontes
Keywords: Fusão; Acelerómetros; Monitorização; Pontes; Gnss
Info
SMOOTHING GNSS TIME SERIES WITH ASYMMETRIC MOVING AVERAGES
There is an increasing trend to apply GNSS continuous observation of short baselines to the monitoring of engineering works, such as bridges and dams, for their structural analysis and safety control. In the case of large dams, one important application of the GNSS continuous observation is the establishment of early warning systems that demand accurate, frequently updated information and where the analysis of the baseline time series, in order to separate signal from noise is mandatory. The paper presents a study on the performance of linear filters of the asymmetric moving average (AMA) type to smooth baseline time series. The transfer function of the AMA is adopted as a smoothing criterion to define an adequate order for the AMA, in face of the spectral density function of the baseline time series. One series of measurements of a short test baseline (325 m), materialized in the campus of the National Laboratory for Civil Engineering, is used as an example of the proposed strategy.
Ano: 2012
Número Páginas:
6.
Autor(es): Lima, J. N.; Casaca, J. M.
Revista: Journal of Civil Engineering and Architecture
Editor: David Publishing Company
Volume:
Volume 6, Number 6.
Keywords: Spectral density; Signal; Noise; Moving average; Gnss
Info
Bayesian Estimation in Dam Monitoring Networks
Summary: A Bayesian estimator with informative prior distributions (a multi-normal and an inverted gamma distribution), adequate to displacement estimation at dam monitoring net-works, is presented. The hyper-parameters of the prior distributions are obtained by Bayesian empirical methods with non-informative priors. The performances of the Bayes estimator and the classical generalized lest squares estimator are compared using two measurements of the horizontal monitoring network of a concrete gravity dam: the Penha Garcia dam (Portugal). In order to test the robustness of the two estimators, gross errors are added to one of the measured horizontal directions: the Bayes estimator proves to be significantly more robust than the generalized least squares estimator.
Ano: 2011
Número Páginas:
7.
Autor(es): Casaca, J. M.; Mateus, P. B.; Coelho, J. I.
Revista: Journal of Civil Engineering and Architecture
Editor: David Publishing Company
Volume:
Vol. 5, Nº 2.
Keywords: Parametric elicitation; Hyper-parameter; Bayes estimator
Info
Persistent Scatterers Interferometry detects and measures ground subsidence in Lisbon
Results from the application of Persistent Scatterers Interferometry in Lisbon Metropolitan Area revealed two previously unknown subsiding urban areas: one (Laranjeiras) is located in the center of Lisbon; another (Vialonga) is to be found toward the North, in an industrial region crossed by Lisbon's main highway and railway lines. The two subsiding sectors are bordered by sharp velocity gradients, and the subsidence pattern appears partially delimited by mapped geologic faults. Surface geology and urbanization alone are unable to explain the phenomena. In the Vialonga area, the historical record of water pore pressure shows a clear decline of the levels (up to 65 m in 27 years), providing evidence of over-exploitation of groundwater resources. Limited information from wells drilled inside and outside the subsidence area points to a spatial correlation between the subsidence and the water pressure levels, and suggests that faults could be acting as hydraulic barriers in the aquifer system. The surface subsidence detected is probably caused by compaction of a clay-rich Oligocene-aged aquitard, led by over-exploitation of adjacent aquifers. The same Oligocene aquitard layer is present in the Laranjeiras area, immediately bellow a multi-layered sandclaylimestone Miocene aquifer, but further work is needed to diagnose the possibility of over-exploitation of groundwater here. In this work we were able to independently confirm the PSI results, by comparing autonomous PSI results processed for the same geographical areas, and by comparing PSI with leveling and continuous GPS derived subsidence velocities, whose close match provided further ground validation of the space-borne PSI technique.
Ano: 2011
Autor(es): Heleno, S.; Oliveira, L. G. S.; Henriques, M. J.; Falcão, A. P.; Lima, J. N.; Cooksley, G.; Ferretti, A.; Fonseca, A. M.; Lobo Ferreira, J. P. C.; Fonseca, J.
Revista: Remote Sensing of Environment
Volume:
doi:10.1016/j.rse.2011.04.021.
Keywords: Gps; Leveling; Groundwater; Surface subsidence; Metropolitan lisbon; Psi interferometry
|
Comunicações
Info
Deciphering magma plumbing system at Fogo volcano using geodetic (InSAR, GNSS and gravimetric) data
Fogo volcano is one of the most active volcanoes in the Atlantic, with 27 eruptions since the Portuguese settlement in the early 15th century. Located nearby the center of a 9 km-wide truncated caldera, Chã das Caldeiras, Fogo is a stratovolcano capped by a 500 m-wide summit crater that rises ~1 km above the caldera floor. It has been interpreted as a recent structure formed at the top of an older volcanic edifice that would have collapsed about ~117 or at ~73 ka. Evidences of this collapse can be seen on land as illustrated by the horseshoe shape of Chã das Caldeiras and the tsunami deposit recognized on the neighboring Santiago island and offshore, with landslide debris deposit; even though its origin is still debated. Eruptive activity at Fogo includes both explosive and effusive phases with alkaline products ranging from basic to intermediate compositions. Eruptive fissures that fed lava flows are mostly distributed along three rift zones that are north, southwest and southeast oriented. The recurrence time for eruption is ranging from 1 to 94 years, with a 20 year interval for the three last eruptions. The last eruption started on November 23, 2014, ending February 7, 2015. The 2014-2015 fissure was 700 m long and included up to seven vents where lava was emitted and where strombolian and vulcanian explosions took also place. This eruption as well as the 1951 and 1995 ones have produced extensive lava flows that threatened the local populations resulting in 2014-2015, in the total destruction of two villages, Portela and Bangaeira. Interferometric analysis of the 1995 and 2014-2015 eruptions at Fogo volcano using C-band SAR data have allowed to characterize the feeder dykes of the two eruptions without any evidence of shallow magma reservoir. Recent petro-geochemical analyses suggested the existence of a transient magma chamber, located <1.5 km below sea level, where magma would have been stored ~50 days prior to the onset of the eruption. To unravel the existence of this transient reservoir and the related volcanic plumbing system at Fogo and also investigate the processes leading to the eastward flank movement, we have considered X-band SAR satellite and field-based GNSS data. We used COSMO-SkyMed SAR data acquired from July 2013 to the end of the eruption in both ascending and descending configurations to investigate surface deformation during the pre and co-eruptive period. The tropical atmospheric conditions, the highly non coherent material composing Fogo volcano and the extensive lava field make challenging the interferometric analysis in this volcanic environment. Therefore, InSAR analysis was completed by GNSS measurements. The surface deformation was analyzed for the 20 years using a compilation of GNSS campaign data performed in 1998, 1999, 2000, 2014-2015 (eruptive period) and 2017, suggesting a horizontal displacement rate up to 2 mm/yr with respect to Nubia plate. The acquired gravimetric data (~90 points) since 2014 combined with the new computed Digital Terrain Model is used here to provide complementary observation on the magma plumbing system of the volcano. This is a contribution to Project FIRE (PTDC/GEOGEO/1123/2014) funded by FCT (Portugal). The GNSS solutions were computed using resources provided by C4G Collaboratory for Geosciences (POCI-01-0145-FEDER-022151).
Ano: 2018
Número Páginas:
2p.
Autor(es): Fernandes, R.; Dumont, S.; Roque, D.; Martins, B.; Falcão, A. P.; Bos, M.; Heleno, S.
Editor: American Geophysical Union
Keywords: Fogo volcano
Info
Projeto ELEVAR Estudo localizado de estruturas verticais com aeronaves robotizadas
N/A
Ano: 2018
Autor(es): Henriques, M. J.; Gonçalves, J.
Editor: Ordem dos Engenheiros
Keywords: Drone; Monitorização
Info
Projeto ELEVAR Estudo localizado de estruturas verticais com aeronaves robotizadas
O projeto "ELEVAR Estudo Localizado de Estruturas Verticais com Aeronaves Robotizadas", financiado pelo programa COMPETE, tem como objetivo o desenvolvimento de um multicóptero destinado à realização autónoma de levantamentos de superfícies verticais, nomeadamente de paramentos de barragens, pilares de pontes, fachadas de edifícios e de monumentos. Esta aeronave irá capturar imagens para uma posterior avaliação de anomalias e navegar através de câmaras, sensores e algoritmos dedicados sem o auxílio de sistemas GNSS. O sistema está a ser desenvolvido por um consórcio, liderado pela empresa TEKEVER ASDS, e integrando o Laboratório Nacional de Engenharia Civil e o Instituto de Sistemas e Robótica do Instituto Superior Técnico. Na primavera de 2018 começaram os testes envolvendo um protótipo sendo que a presente comunicação se destina a apresentar o projeto e os resultados alcançados no primeiro ano de atividade.
Ano: 2018
Autor(es): Henriques, M. J.; Pinto, T.; Dornellas, D.; Gonçalves, J.; Ribeiro, R.; Bernardino, A.; Santos-Victor, J.
Editor: Ordem dos Engenheiros
Keywords: estrutura; monitorização; drone; UAV
Info
Structural safety control of the Baixo Sabor dam based on an automated data acquisition system
This paper presents the main characteristics of the automated structural monitoring system of Baixo Sabor dam and addresses a proposal for the definition of triggers for the physical quantities measured through the use of an automated data acquisition system (ADAS). The defined triggers for the physical quantities will be linked to an Internal Early Warning Control System of the dam, allowing the early identification and notification of potential abnormal situations to the entities responsible for the dam safety. In operation since August 2016, the ADAS of the Baixo Sabor dam defined by EDP allows the measurement of several quantities used for the safety control, analysis and interpretation of the dam behaviour, such as: horizontal and vertical displacements, movements of joints, strains, uplift pressures, foundation displacements, seepage, concrete and air temperatures, and reservoir water level, among others. The measurements, obtained through the use of the ADAS developed and installed by Prointega Ingeneria, are sent to the gestBarragens system, which is the LNEC and EDP data processing and management system used for monitoring, diagnosis and safety control of dams.
Ano: 2018
Número Páginas:
11.
Autor(es): Cunha, J.; Mata, J.; Ortiz,G.
Editor: Commission Internationale des Grands Barrages
Keywords: Triggers; Automated monitoring system; Concrete dam; Baixo Sabor dam
Info
Concrete block tracking in breakwater models
The protection of harbours in coastal areas, that are exposed to the action of the sea waves, is made by breakwaters. During the phase of design of new breakwaters or the rehabilitation of existing ones, the evaluation of effectiveness of the shape and of the protective elements to save the harbour, 3D scale models are built inside wave basins or wave flumes. In the testing phase, water waves are generated, and the resulting impact on the breakwater model is periodically evaluated to study the hydraulic and structural behaviour under predefined sea-wave conditions. This study proposes a methodology to estimate displacements of concrete blocks of the outer layer, also called protection layer, of rouble-mound breakwater models. These blocks are placed in the areas where it is expected that action of the waves is stronger. The combination between the 3D information of a point cloud survey and the visual information of a digital image is a key factor for estimate the spatial location of the geometric centre of the blocks. The location of a block centre point, at different instants, gives its spatial displacement. The equipment used for data acquisition tests were a Kinect V2 sensor and a digital camera, with which were obtained the main data sets for this work: RGB imagery and 3D Point Clouds. The data collected by this allowed the generation of point clouds (X, Y and Z) and orthomosaics, both fundamental for the determination of displacements of the blocks. Indeed, displacements detection results from the determination of the spatial coordinates of the several locations of the Geometric Centre of each block, which is in fact the main outcome of this study. It is expected to serve as a contribution to the laboratory teams working at the Harbours and Maritime Structures Division of the Department of Hydraulics and Environment.
Ano: 2017
Número Páginas:
12p.
Autor(es): Soares, F.; Henriques, M. J.; Rocha, C.
Editor: FIG
Keywords: Least squares; Point cloud; 3D Monitoring; Breakwater
Info
Evaluation of breakwater damages from multitemporal InSAR techniques
Maritime structures such as breakwaters have a large economic importance as they protect the harbours, the ships and their contents from sea waves. Rubble-mound breakwaters are one of the most used types of these structures and they are composed by rocks forming a trapezoidal cross-section covered with rock or concrete blocks whose goal is to dissipate sea wave energy. The breakwaters are often exposed to severe meteorological conditions, especially during storms, which may move the blocks from their original position, reducing the protection capability of the structure. An early detection of those changes is of the utmost importance as it may minimize costs both for the breakwater reconstruction and for the consequences of not having it working properly. Structural health monitoring of breakwaters is often performed through visual inspections. Due to the shape of the structure, the size and dimensions of the protective blocks, and the fact that it is surrounded by the sea, in situ measurements are difficult to perform. Photographic surveys using unmanned aerial vehicles are sometimes hard to accomplish due to the strong winds that are observed at the coast. Multitemporal InSAR techniques can overcome the hindrances of the mentioned methods and provide a useful way to identify the damages. In this study, damage assessment is performed for a breakwater located at Ericeira town, Portugal, using multitemporal InSAR techniques. This breakwater was built in the 1970s and it is exposed to northwestern Atlantic Ocean waves which are very energetic and led to severe damages several times. From 2008 to 2010 the structure was reconstructed and expanded in order to increase its protection capability. A dataset of 70 SAR images acquired between 2011 and 2015 by the sensor on board COSMO-SkyMed 4 was used to evaluate changes occurred at the breakwater during this time interval. Displacement and amplitude time-series as well as coherence matrixes are analysed for damage assessment using the SARPROZ© software. Time-series analysis shows a good agreement between changes at displacement and amplitude data and the occurrence of storms at the Portuguese coast. Spatial patterns are found that enable the identification of the most fragile areas of the breakwater which may need maintenance interventions in the near future.
Ano: 2017
Autor(es): Roque, D.; D. Perissin; Falcão, A. P.; Marujo, N.; Henriques, M. J.; Lemos, J. V.; Fonseca, A. M.
Editor: European Space Agency
Keywords: Displacement measurement; Breakwater; SAR interferometry
Info
Monitoring of rubble-mound breakwaters using UAV technology
Breakwaters are protective and sheltering structures which aim to provide either protection from waves and currents for people and goods at the coast or sheltering conditions for ships and boats moored at the port, thus ensuring that port operations are performed in safe conditions. For that reason, occurrence of damages on such structures usually implies significant economic losses, such as harbour inoperability. In Portugal where severe sea states due occur, rubble mound breakwaters (RMB) are the most common type of these breakwater structures. The most conventional structure of a RMB consists in a core of a mix of fine and coarse material covered by one or two layers of natural rock or/and artificial concrete blocks that forms the so-called armour layer. In order to predict damages that may occur in RMBs and evaluate its importance in terms of structural safety and functionality, it is of utmost importance to follow a monitoring program on such structures. The main goal of such monitoring is to detect changes, movements and instabilities in the position of the armour layer blocks, since those mechanisms may lead to a weakening or even a breakage of the structure. Results on the monitoring will enable authorities to plan and prioritize repairs and minimize future short and long-term costs. Traditionally, the monitoring of the RMB is made with visual, systematic, observations, but this technique is both time-consuming and depends heavily on the experience of the observer and, additionally, a limited amount of quantitative information is obtained, although a relevant qualitative evaluation is achieved. Photogrammetric techniques, using photos acquired by cameras mounted in UAV (drones) have already proved to be the most suitable technique to complement traditional monitoring, as they provide quantitative, with required accuracy, measurements on the surveyed area, they enable observation of specific areas and new perspectives difficult for human observers, and at present they are not too expensive to implement. This paper joins, as authors, two groups of experts: one with experience in flights with different UAV models and another one with experience in systematic monitoring surveys of breakwaters and maritime structures. This paper includes, as example, the results of studies conducted in three rubble mound breakwaters and presents conclusions according to the views of each group of experts.
Ano: 2017
Número Páginas:
8p.
Autor(es): Henriques, M. J.; Lemos, R.; Capitão, R.; Fortes, C. J. E. M.
Editor: LNEC
Keywords: Drone; Point cloud; Orthomosaic; Photogrammetry; Breakwater; Monitoring; UAV
Info
Monitoring the behaviour of MEO Arena roof
The roof structure of MEO Arena (previously known as Atlantico multipurpose Pavilion) is a pioneering example of large glued laminated timber (glulam) structures. At the time of its construction (1995) for the EXPO98 world exhibition, this was the first large glulam structure ever built in Portugal, it had the longest single span glulam arch (122m) in the world and it was the first large timber structure designed according with an early version of Eurocode 5 (European Standard ENV 1995-1-1(1994): Design of timber structures). This timber roof structure, shaped like the shell of a horseshoe crab and covered with an oxidized zinc sheet, stands more than 40m above the arena and is independent from the concrete building underneath. LNEC was requested to carry out systematic inspections and monitoring of the roof structure after its construction and the follow up of its performance still continues. In this scope, the geodetic monitoring set on a regular basis (twice a year) allows the assessment of three dimensional displacements of selected points of the timber arches. The analysis of this data has allowed to distinguish normal variations throughout the year from those resulting from the initial settling and climatic adjustment of the structure and will allow identify any abnormal movements that may be due to accidental or exceptional circumstances. The good knowledge of the structure behaviour has also been an important basis to a pioneer study of the behaviour of the zinc roof cover based on multitemporal InSAR techniques. In this paper, we describe the geodetic monitoring system and an analysis of the behaviour of the glulam structure as well as of the roof cover based on the geodetic and InSAR data.
Ano: 2017
Número Páginas:
8p.
Autor(es): Henriques, M. J.; Cruz, H.; Roque, D.; Fonseca, A. M.
Editor: LNEC
Keywords: Pavilion; Structure; Geodesy; Monitoring; InSAR
Info
Monitornig the behavior of MEO ARENA roof
N/A
Ano: 2017
Número Páginas:
8p.
Autor(es): Henriques, M. J.; Roque, D.; Cruz, H.; Fonseca, A. M.
Editor: LNEC
Keywords: Pavilhão; Monitorização
Info
Nuvens de pontos e imagens numéricas. O objeto de estudo no computador
N/A
Ano: 2017
Autor(es): Henriques, M. J.; Roque, D.; Fonseca, A. M.
Editor: Ordem dos Engenheiros
Keywords: Estrutura; Nuvem de Pontos
|
Livros
Info
História Breve do Calendário
O calendário Gregoriano não é mais do que uma reforma do calendário Juliano, devido a Júlio César, que adaptou os formalismos romanos a uma antiga estrutura solar de origem egípcia. Este ensaio descreve a história do calendário Gregoriano e dos calendários da bacia do Mediterrâneo e do Oriente Próximo, com ele mais ou menos aparentados.
Ano: 2009
Número Páginas:
61pp.
Autor(es): Casaca, J. M.
Editor: LNEC
Keywords: Calendários
|
|
Teses de Doutoramento
Info
Displacement measurement through InSAR geodesy for structural health monitoring
Interferometric synthetic aperture RADAR is an applied geodesy technique, which enables displacement measurement through satellite images. A literature review of the technique principles and of previous studies regarding its application to structural health monitoring allowed the identification of a few bottlenecks to the operational usage of this cost-effective technology for monitoring purposes.Three research lines were defined. First, a data mining strategy was developed to extract structural behaviour information from displacement time series from thousands of points on the region of interest, with tens of observation epochs each. Second, displacements from this technique were integrated into a previously existing monitoring system and were used to expand it to a larger number of points on the structure and to its surroundings. Third, an experimental infrastructure was deployed in order to perform several tests for displacement validation and uncertainty assessment. The infrastructure included a new model of artificial reflector to the satellite signals, purposefully developed in the scope of this study.The developed methods enabled the successful monitoring of different types of civil and geotechnical structures. Slope behaviour around water reservoirs was assessed during both the reservoir first impoundment and regular operation. Differential displacements were detected on building-blocks at a cultural heritage urban area and concrete arch dam responses to temperature loads were identified. The experimental work showed the achieved displacements agreed with those of other geodetic techniques and uncertainties around 2 mm were obtained for the measurements.In conclusion, interferometric synthetic aperture RADAR is a promising technique, able to provide useful information for structure monitoring, such as aiding in the planning of in situ monitoring activities and in identifying space-time patterns in structural behaviour. Thanks to its spatial coverage, observation period of a few days and achieved displacement uncertainty, it is advantageous to complement existing monitoring systems with data from this technique.
Ano: 2020
Autor(es): Roque, D.
Keywords: Uncertainty analysis; Data mining; Interferometric synthetic aperture RADAR; Geodesy; Structure monitoring systems
|
Dissertações de Mestrado
Info
Simulador de cenários sísmicos em ambiente WebSIG
O Simulador de Cenários Sísmicos, LNECloss, é uma ferramenta computacional que permite avaliar perdas em consequência de um cenário sísmico especificado [LESSLOSS, 2007]. Esta ferramenta automática compreende vários módulos, como sejam, a modelação da acção sísmica no substrato rochoso e à superfície, a avaliação dos danos no edificado e a avaliação das perdas económicas e humanas. O Simulador foi integrado como aplicação externa num Sistema de Informação Geográfica (SIG) [Sousa, 2006]. Foram identificadas algumas necessidades de desenvolvimento no Simulador, que compreendem, por um lado, o alargamento do seu domínio geográfico para além do território de Portugal Continental, nomeadamente para o Arquipélago dos Açores, que possui uma taxa de ocorrência de sismos muito elevada e, por outro, a sua disponibilização através da Web, com um carácter autónomo, ou seja, que não necessite de alguma plataforma de informação geográfica tendo no entanto as suas capacidades no que respeita ao mapeamento e à síntese gráfica e tabular dos efeitos de um cenário sísmico. De entre as características deste simulador WebSIG, saliente-se uma interface gráfica de fácil operação, permitindo a sua utilização por agentes da protecção civil, no que respeita ao planeamento e à gestão da emergência na eventualidade de ocorrência de um sismo.
Ano: 2009
Autor(es): Afonso, N.
Keywords: Websig; Serviços web; Simulador; Risco sísmico; Cenário sísmico; Arquipélago dos açores
|
Relatórios
Info
ImEngine
Neste relatório apresenta-se, de forma sucinta, a atividade de investigação realizada no âmbito do projeto ImEngine no período 2014-2023. Os resultados da atividade são analisados e avaliados, em face dos objetivos inicialmente previstos.
Ano: 2023
Autor(es): Roque, D.; Henriques, M. J.; Fonseca, A. M.
Keywords: Drone; Inspeção visual; ImEngine; IVisA; Deteção de alterações; Reconhecimento de padrões; Processamento digital de imagens; Imagem numérica
Info
INFRASAR
Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto INFRASAR no período 2014-2023. Os resultados da atividade são analisados e avaliados, em face dos objetivos inicialmente previstos.
Ano: 2023
Autor(es): Roque, D.; Fonseca, A. M.
Keywords: Deteção de deslocamentos; Difusores permanentes; INFRASAR; PSInSAR; Interferometria SAR
Info
MEGA
Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto MEGA no período 2015-2023. Os resultados da atividade são analisados e avaliados, em face dos objetivos inicialmente previstos.
Ano: 2023
Autor(es): Lima, J. N.
Keywords: Séries temporais; GNSS; Análise Bayesiana; MEGA
Info
MOSAIC.pt Levantamento fotogramétrico com drone da praia da Cova Gala em 2020
Este relatório apresenta os procedimentos do levantamento fotogramétrico, realizado com um drone, assim como as ações complementares, destinados a obter informação de carácter geométrico da praia da Cova Gala em 2020. Este documento inclui ainda uma análise da qualidade dos produtos gerados e uma comparação com o levantamento realizado em 2019, cerca de um ano antes.
Ano: 2021
Autor(es): Henriques, M. J.
Keywords: Drone; Fotogrametria; Levantamento; Praia da Cova Gala
Info
Base das Lajes - Resultados do nivelamento geométrico de precisão realizado em outubro de 2020, nos pontos de monitorização da qualidade das águas subterrâneas
Este relatório apresenta os resultados da campanha de nivelamento geométrico das bocas de furos de captação de água na proximidade da Base das Lajes, realizada pelo Núcleo de Geodesia Aplicada do Departamento de Barragens de Betão do LNEC, em outubro de 2020. Os resultados são as cotas, num referencial local, das bocas dos furos de captação de água.
Ano: 2020
Autor(es): Candeias, H.; Fonseca, A. M.
Keywords: Furos de captação de água; Nivelamento geométrico; Base das Lajes
Info
MOSAIC.PT Levantamentos fotogramétricos com drone das praias de Cova-Gala, Vieira e São Pedro de Moel em 2019
Este relatório apresenta os procedimentos dos levantamentos fotogramétricos, realizados com um drone, assim como as ações complementares, efetuadas em 2019, destinados a obter informação de carácter geométrico das praias de Cova - Gala, Vieira e São Pedro de Moel.
Ano: 2020
Autor(es): Henriques, M. J.
Keywords: Drone; Fotogrametria; Levantamento; Praia
Info
ImEngine Imagens Numéricas: Aplicações à engenharia - Relatório de progresso 2014-2017 do projeto do P2I/LNEC
Neste relatório apresenta-se, de forma sucinta, a atividade de investigação realizada no âmbito do projeto ImEngine no período 2014-2017. Os resultados da atividade são analisados e avaliados, em face dos objetivos inicialmente previstos, sendo proposta uma extensão do projeto, e respetiva revisão do plano de atividades, para os próximos dois anos.
Ano: 2018
Autor(es): Fonseca, A. M.; Henriques, M. J.; Roque, D.
Keywords: Drone; Inspeção visual; ImEngine; IVisA; Deteção de alterações; Reconhecimento de padrões; Processamento digital de imagens; Imagem numérica
Info
INFRASAR Interferometria SAR com difusores permanentes (PSINSAR) aplicada à deteção de deslocamentos em geodinâmica e infraestruturas - Relatório de progresso 2014-2017 do projeto do P2I/LNEC
Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto INFRASAR no período 2014-2017. Os resultados da atividade são analisados e avaliados, em face dos objetivos inicialmente previstos, sendo proposta uma extensão do projeto e revisão do plano de atividades para os próximos dois anos.
Ano: 2018
Autor(es): Fonseca, A. M.; Roque, D.
Keywords: Deteção de deslocamentos; INFRASAR; Difusores permanentes; PSINSAR; RADAR; Interferometria; Processamento digital de imagens
Info
MEGA Métodos estocásticos em geodesia aplicada - Relatório de progresso 2015-2017 do projeto do P2I/LNEC
Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto MEGA no triénio 2015-2017. Os resultados da atividade são analisados e avaliados, em face dos objetivos inicialmente previstos, sendo proposta uma revisão do plano de atividades para os próximos dois anos.
Ano: 2018
Autor(es): Casaca, J. M.; Lima, J. N.
Keywords: Séries temporais; GNSS; Análise bayesiana
Info
Determinação de deslocamentos com geodesia InSAR para o controlo de segurança de estruturas - Plano de tese de doutoramento da bolseira Dora Roque
O relatório apresenta uma proposta de plano de estudos para a tese de doutoramento da bolseira Dora Roque, a realizar no Núcleo de Geodesia Aplicada do Departamento de Barragens de Betão do Laboratório Nacional de Engenharia Civil. O objetivo principal do estudo é contribuir para a operacionalização da geodesia InSAR na determinação de deslocamentos para o controlo de segurança de estruturas.
Ano: 2016
Autor(es): Roque, D.; Fonseca, A. M.; Lemos, J. V.; Falcão, A. P.
Keywords: Sistemas de observação; Geodesia InSAR; Plano de tese
|
Informações Científicas e Técnicas
Info
A distribuição do desvio padrão empírico
O trabalho aborda simultaneamente a distribuição do desvio padrão da amostra aleatória normal e a distribuição do desvio padrão do modelo de Gauss-Markov, designados genericamente por desvio padrão empírico. Após mostrar que o desvio padrão empírico é um estimador excêntrico que subestima o desvio padrão da amostra ou do modelo, conforme o caso, são apresentadas correções de excentricidade. É também tratada a estimação do desvio padrão da amostra e do modelo em cenário Bayesiano, com diferentes distribuições anteriores. O trabalho é rematado por casos de estudo baseados na simulação de amostras normais e por um exemplo concreto relacionado com o controlo da precisão de um distanciómetro eletromagnético.
Ano: 2015
Autor(es): Casaca, J. M.
Keywords: Desvio padrão
Info
A resolução de problemas mal colocados na observação geodésica de barragens
O presente trabalho apresenta uma metodologia genérica para a regularização de problemas inversos lineares mal colocados e a sua aplicação às redes altimétricas e planimétricas usadas na monitorização de deslocamentos de pontos notáveis de grandes barragens por métodos da Geodesia Aplicada. A metodologia é ilustrada por intermédio de três casos de estudo.
Ano: 2013
Número Páginas:
39pp.
Autor(es): Casaca, J. M.
Editor: LNEC
Keywords: Observação geodésica; Observação de barragem
Info
The Beta-Binomial Model
This paper deals with the beta-binomial model, which is an important stochastic model within the scope of the Bayesian statistical inference. After a short review of the binomial and beta distributions, the paper presents the closed formulae for the posterior probability density function of the binomial trial parameter and for the prior predictive and for the posterior predictive probabilities of the successes in binomial experiments. A description of the Bayesian methodology to test different hyper-parameters for the conjugate prior probability density functions of the beta family is also presented. Finally, the beta-binomial model is illustrated with a study case related to the quality control of the geodetic observation of large dams.
Ano: 2013
Número Páginas:
24pp.
Autor(es): Casaca, J. M.
Editor: LNEC
Keywords: Binomial distribution; Beta distribution; Bernoulli trial parameter; Bayes factor
Info
Análise de regressão multivariada - Uma perspetiva Bayesiana
O presente trabalho, além de uma revisão sintética da abordagem frequencista, trata da abordagem Bayesiana da análise de regressão linear multivariada. É apresentada uma compilação de procedimentos e fórmulas para a estimação dos coeficientes da regressão, sob três cenários de informação anterior. Finalmente, o trabalho ocupa-se dos problemas da predição de respostas e da comparação de modelos de regressão.
Ano: 2012
Número Páginas:
47pp.
Autor(es): Casaca, J. M.
Editor: LNEC
Keywords: Estatística bayesiana; Análise de regressão; Análise multivariada
Info
The Gamma, Multi-gamma, Digamma and Trigamma Functions
The work presents the theoretical definitions of the gamma, multi-gamma, digamma and trigamma functions as well as operational approximations to compute their values. A more precise alternative, due to Robert Windschitl, to the traditional approximation of the gamma function by the Stirlings series, is reported. The work is completed with a study case, related to the geodetic monitoring of large dams, that illustrates the previous concepts and definitions.
Ano: 2012
Número Páginas:
20pp.
Autor(es): Casaca, J. M.
Editor: LNEC
Keywords: Trigamma-function; Digamma-function; Multi-gamma function; Gamma functions; Windschitl approximation; Stirlings approximation
Info
Introdução à análise Bayesiana
O trabalho descreve os princípios da análise Bayesiana, usando como caso de estudo a amostra aleatória normal identicamente distribuída. Após um curto preâmbulo histórico, são resumidos, na Secção 2, os conceitos mais importantes da análise frequencista. Nas secções seguintes, são abordados os temas Bayesianos mais importantes, tais como a estimação, pontual e regional (Secção 5), e o teste de hipóteses sobre os parâmetros da distribuição da amostra (Secção 6). As distribuições anteriores de Laplace, Jeffreys e conjugada normal-gama invertida são apresentadas na Secção 4. O problema da eliciação paramétrica das distribuições anteriores conjugadas é tratado na Secção 7. Palavras Chave: distribuições anteriores e posteriores, divergência de Kullback-Leibler, eliciação paramétrica, factor de Bayes, fórmula de Bayes, verosimilhança.
Ano: 2011
Número Páginas:
78pp.
Autor(es): Casaca, J. M.
Editor: LNEC
Keywords: Análise bayesiana
Info
Estratégia para a Calibragem dos Distanciómetros Electromagnéticos Utilizados na Observação Geodésica de Barragens
Este trabalho define uma estratégia, apoiada o mais possível nas disponibilidades do LNEC, para a calibragem dos distanciómetros electromagnéticos (DEM) usados pelo Núcleo de Geodesia Aplicada na observação geodésica de barragens.
Ano: 2002
Número Páginas:
38.
Autor(es): Henriques, M. J.
Editor: LNEC
Keywords: Base de teste; Dem; Distanciómetros; Calibragem
|
|
Outros
Info
Integration of image processing tools for monitoring breakwaters models
N/A
Ano: 2016
Autor(es): Soares, F.; Henriques, M. J.; Braz, N.
Editor: ESA
Keywords: Quebra-mar; Monitorizaçao
|