Ana Paula Camargo Larocca

A Methodology for Monitoring Vertical Dynamic Sub-Centimeter Displacments with GPS

This article describes a methodology to monitor dynamic vertical sub-centimeter displacement, of a GPS antenna. The dynamic movement of an antenna is determined by choosing the appropriate reference satellite for measurement differencing and by applying a FFT filter on the double-difference phase residuals. The validity of the method depends on the time variations of the GPS residuals and errors, such as, receiver noise, atmospheric contribution, multipath effects, and the antenna movement. This research is under development and results for simulated motion are presented here.

Use of a Single L1 GPS Receiver for Monitoring Structures: First Results of the Detection of Millimetric Dynamic Oscillations

AbstractThis paper presents preliminary results to determine small displacements of a global positioning system (GPS) antenna fastened to a structure using only one L1 GPS receiver. Vibrations, periodic or not, are common in large structures, such as bridges, footbridges, tall buildings, and towers under dynamic loads. The behavior in time and frequency leads to structural analysis studies. The hypothesis of this article is that any large structure that presents vibrations in the centimeter-to-millimeter range can be monitored by phase measurements of a single L1 receiver with a high data rate, as long as the direction of the displacement is pointing to a particular satellite. Within this scenario, the carrier phase will be modulated by antenna displacement. During a period of a few dozen seconds, the relative displacement to the satellite, the satellite clock, and the atmospheric phase delays can be assumed as a polynomial time function. The residuals from a polynomial adjustment contain the phase modula...

Flooding and inundation collaborative mapping – use of the Crowdmap/Ushahidi platform in the city of Sao Paulo, Brazil

The trend of using volunteered and collaborative data in the context of natural disasters has been increasing. This fact, together with floods and inundations, which occur in the city of Sao Paulo, makes it possible to explore the volunteered and collaborative way of generating and transmitting geographic data dynamically. This can be done by using technologies affordable to the population, such as the Internet, the global positioning system and other monitoring systems embedded in mobiles. This article aims to present the proposal of a conceptual scheme for a dynamic and collaborative mapping system of flooding points, whose data source comes from people equipped with mobile devices that allow identify their locations. The results correspond to the conceptual scheme of the system as well as the prototype ‘Flooding Points’ – a map available on the web showing the flooding points in the city, which were provided at the time of the event by ordinary people. The prototype was developed by using the free and open source Crowdmap/Ushahidi platform. The system was assessed by a questionnaire answered by the users, who gave their opinion about its feasibility, as well as the adjustments which must be made for the populations effective use. It was found that the application of system for subjects of inundation and flooding is complex in relation for other types of events due to its temporal dynamics characteristics. The results of the questionnaire, applied to evaluate the system, demonstrated the public utility of the application and the interest of the population for a dynamic system that enables the exchange of information on the problem of inundation and flooding in near real time in the city of Sao Paulo.

First Steps Using Two GPS Satellites for Monitoring the Dynamic Behavior of a Small Concrete Highway Bridge

AbstractThis work presents the results of global positioning system (GPS) data processing using the phase residuals method (PRM)—L1 carrier phase from two satellites—to monitor the dynamic behavior of a small concrete bridge. The bridge tested, the Jaguari Bridge, is a small, curvd, reinforced concrete bridge. The bridge over the Jaguari River is a reinforced concrete bridge built in 1999, located on Fernao Dias Highway (BR 381), positioned at Kilometer 946, Minas Gerais, Brazil. The small concrete bridge was chosen for this study because its construction type is found in great numbers throughout Brazil. In parallel, there was a significant increase of pathologies in these structures as a result of lack of maintenance procedures. The detection of small vibrations of spans, for example, which is a good indicator of the health of a structure, can be monitored by GPS. The challenge in this case is trying to detect with GPS the dynamic displacement that has an amplitude close to 5 mm. Application of the PRM o...

Mapeamento dinâmico e colaborativo de alagamentos na cidade de São Paulo

A tendencia de utilizacao de dados voluntarios e colaborativos em contextos de desastres naturais e crescente. Esse fato aliado aos cenarios de alagamentos que ocorrem na cidade de Sao Paulo traz a possibilidade de exploracao sobre o modo voluntario e colaborativo de geracao e transmissao da informacao geografica de forma dinâmica. E estas sao proporcionadas por tecnologias acessiveis a populacao, como o GPS (Global Positioning System) embarcado em celulares e a internet. O presente artigo tem como objetivo a proposta de um esquema conceitual para um sistema dinâmico e colaborativo de mapeamento dos pontos alagados, cuja fonte dos dados advem das pessoas equipadas com aparelhos celulares que permitem a sua localizacao. Os resultados apresentados correspondem aos esquemas conceituais do sistema, bem como ao prototipo “Pontos de Alagamento” - mapa disponibilizado via web com os pontos de alagamento da cidade, fornecidos no momento da ocorrencia do evento por pessoas comuns. O prototipo foi desenvolvido por meio da plataforma livre e de codigo aberto – Crowdmap/Ushahidi. O sistema foi avaliado atraves de um questionario respondido por usuarios, os quais opinaram sobre a viabilidade do mesmo, bem como os ajustes que devem ser realizados para o uso efetivo da populacao.

USO DE RECEPTORES GPS DE 100 HZ NA DETECÇÃO DE DEFLEXÕES VERTICAIS MILIMÉTRICAS DE PONTES DE CONCRETO DE PEQUENO PORTE

As ultimas quatro decadas foram importantes para o desenvolvimento da malha rodoviaria brasileira. O pais recebeu incentivos financeiros para a sua expansao e diversas solucoes estruturais para pontes e viadutos foram criadas. Em paralelo a este desenvolvimento, houve nos ultimos anos um crescimento significativo dessas estruturas em estagio avancado de deterioracao devido a ausencia de programas de manutencao preventiva. Dessa maneira, este trabalho propoe o uso de receptores GPS num plano de monitoramento de curta duracao para acompanhar o comportamento estrutural de uma ponte rodoviaria curva de concreto armado ja em servico. E apresenta os primeiros resultados da pesquisa com a portadora L1 do sistema GPS e dados gravados com taxa de 100 Hz, no monitoramento do vao central de ponte de concreto de pequeno porte situada sobre o Rio Jaguari, na cidade de Extrema, divisa entre os Estados de Minas Gerais e Sao Paulo. O desafio reside no fato de que estruturas como estas - pontes de concreto de pequeno e medio porte - respondem pela grande maioria das obras de arte da malha rodoviaria brasileira e por serem estruturas rigidas, apresentam deflexoes verticais pequenas, de ate 5mm. O experimento foi realizado por meio de sessoes de observacoes com receptores GPS sobre a ponte, no vao instrumentado por equipamentos convencionais para posterior confrontacao de resultados entre os receptores GPS e os metodos classicos de monitoramento. A ferramenta de filtragem Continuos Wavelet Transform (CWT) foi utilizada para analisar as frequencias de resposta da ponte a partir dos residuos da dupla diferenca de fase da portadora L1. A analise do espectro de energia da CWT gerado a partir dos dados coletados com os receptores GPS indicou alta concentracao de energia nas mesmas faixas de frequencia - de resposta do tabuleiro da ponte - apontadas pela Modelagem por Elementos Finitos e pela prova de carga dinâmica.

COMPATIBILIZAÇÃO DE REFERENCIAIS DE COORDENADAS E VELOCIDADES COM ESTIMATIVA DE PRECISÃO

As transformacoes de coordenadas e velocidades entre as realizacoes do ITRS (International Terrestrial Reference System), bem como a atualizacao de coordenadas, tornar-se-ao tarefas rotineiras em levantamentos geodesicos devido ao emprego de sistemas de referencia dinâmicos e ao movimento das placas tectonicas. Neste estudo foram realizadas compatibilizacoes de sistemas de referencia (ITRF2000, ITRF2005 e ITRF2008) das coordenadas e velocidades com suas respectivas estimativas de precisao, via propagacao de variância, de 11 estacoes distribuidas nas placas tectonicas Norte e Sul Americanas e da Eurasia. Foi verificado com base nas coordenadas nos ITRF2008, epoca 2005 e ITRF2005, epoca 2000, obtidas pelo IERS (International Earth Rotation and Reference System Service), que 54,55% das discrepâncias planimetricas sao centimetricas e 45,45% decimetricas. Comparando as coordenadas no ITRF2008, epoca 2005,0 e no ITRF2000, epoca 1997,0 verificou-se discrepâncias planimetricas da ordem do decimetro para todas as estacoes. Confrontando as coordenadas ITRF2000, epoca 1997,0 obtidas pelo IERS com as calculadas com base nas transformacoes entre sistemas de referencia e atualizacoes verifica-se discrepâncias planimetricas da ordem do milimetro em 72,73% dos casos e da ordem do centimetro em 27,27%. As analises realizadas confirmam a necessidade de atualizar e compatibilizar o referencial das coordenadas e velocidades para aumentar a acuracia do posicionamento.

THE USE OF THREE-DIMENSIONAL VISUALIZATION TOOLS TO DETECT DEFICIENCIES IN GEOMETRIC ROADWAY DESIGNS

The use of three-dimensional (3D) visualization technologies in the field of transportation sciences has contributed not only to the assessment of the impact of a road project on its surroundings but also to the development and study of elements of the geometric design itself. The present study aimed to assess the effectiveness of the use of 3D visualization tools in the detection of poor compatibility between the horizontal and vertical alignments of a road project. The assessment was performed by conducting tests with groups of participants who were students from a civil engineering course with no experience in the development of geometric roadway designs. These participants each assessed two road stretches: one stretch with unflawed coordination between the vertical and horizontal alignments of the road and another stretch in which this coordination had been intentionally distorted. It was used an application software for roadway geometric designs that allowed the creation of a video of the trajectory of the targeted road. Subsequently, the participants answered a questionnaire that aided the interpretation of the results regarding the design deficiencies in road layouts perceived from the 3D visualization of the roadways.

L1 GPS as Tool for Monitoring the Dynamic Behavior of Large Bridges

In 1973 the JPO (Joint Program Office) subjected to United States Air Force received the missionof Department of Defense for implanting, developing, testing and use a spatial positioningsystem for military applications and able to calculated coordinates and guide missilesaccording to the project “Star Wars”.The Global Positioning System is fruit of those studies which became able to use the L bandof carrier phase (frequency microwaves around 1 up to 3 Ghz and wave length close to 23 cm)for calculating the spatial trilateration. Therefore, in 1978 began the launch of the first NAV‐STAR (Navigation Satellite with Time and Ranging) satellites – the begging of GPS as is knowntoday. Due to the high cost of project and as the MIT confirmed by itself the excellence on civilapplications (geodesy, topography, navigation, digital modeling, simulators), the AmericanCongress, with the acquiescence of the U.S. President, pressed the Pentagon to open theNAVSTAR system for civil use and other countries. However, only from the 90s is that theGPS became popular. This was a result of technological advance in the micro-computers fieldallowing the trackers manufacturers to produce the GPS receivers that processed in thereceiver, the codes of the received signals.In this context, from the end of the 80´s, the technology of Global Positioning System, untilthen, used to conduct surveys of areas, deploy geodetic networks, manage resources, trackfleets of vehicles, ships, achieve the control of displacements of structures under static load,etc. began to be used to characterize the dynamic displacement of large structures, earthquakesand so, it was being considered as a tool to extract the values of frequency and amplitude of

Structures oscillations monitoring with global positioning system and adaptive filtering techniques

Purpose – This paper aims to detect small dynamic displacements by analysis of L1 Global Positioning System carrier frequency using an improved method for collecting data and filtering techniques on monitoring large structures. It is proposed to analyze the phase residuals directly from the raw phase observable data collected in a short baseline during a limited time span, in lieu of obtaining the residual data file from regular GPS processing programs.Design/methodology/approach – The approach of this paper is an update on the method based on the interferometer idea for analyzing the Global Positioning Systems signals applying adaptive filtering techniques on the phase residuals computed through the double difference adjusted by the 3rd order polynomial. The method is based on the frequency domain analysis of the phase residuals resulted from the L1 double difference static data processing of only two satellites.Findings – This research improves the ability to characterize the dynamic behavior of large s...