Investigações preliminares sobre a influência do clima espacial no posicionamento relativo com GNSS

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise de séries temporais de multicaminho em estações de monitoramento contínuo

Data from reference stations are widely used in GNSS (Global Navigation Satellite System) positioning, and can be used in relative positioning or network-based positioning concept. Positioning accuracy will be directly influenced by errors in signals collected in these stations. In this paper, it is aimed at evaluating these data quality using temporal series of multipath index MP1 and MP2. A statistical study of temporal series with 7 years of daily observations related to 7 stations from RBMC (Rede Brasileira de Monitoramento Contínuo) was accomplished. In order to investigate trends and seasonality a linear regression model, correlograms, and Fourier periodograms were used. We also used a harmonic adjust to identify peaks on temporal series. At last, the possible causes of seasonality found in some stations were discussed. It was also possible to identify peaks in MP values of March and October months (mainly in stations located near geomagnetic equator).

Extended ionospheric amplitude scintillation model for GPS receivers

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

AVALIAÇÃO ROBUSTA DA MODELAGEM NEUTROSFÉRICA SOBRE O TERRITÓRIO BRASILEIRO BASEADA EM MODELOS DE PREVISÃO NUMÉRICA DE TEMPO DA AMÉRICA DO SUL

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Tackling ionospheric scintillation threat to GNSS in Latin America

Scintillations are rapid fluctuations in the phase and amplitude of transionospheric radio signals which are caused by small-scale plasma density irregularities in the ionosphere. In the case of the Global Navigation Satellite System (GNSS) receivers, scintillation can cause cycle slips, degrade the positioning accuracy and, when severe enough, can even lead to a complete loss of signal lock. Thus, the required levels of availability, accuracy, integrity and reliability for the GNSS applications may not be met during scintillation occurrence; this poses a major threat to a large number of modern-day GNSS-based applications. The whole of Latin America, Brazil in particular, is located in one of the regions most affected by scintillations. These effects will be exacerbated during solar maxima, the next predicted for 2013. This paper presents initial results from a research work aimed to tackle ionospheric scintillation effects for GNSS users in Latin America. This research is a part of the CIGALA (Concept for Ionospheric Scintillation Mitigation for Professional GNSS in Latin America) project, co-funded by the EC Seventh Framework Program and supervised by the GNSS Supervisory Authority (GSA), which aims to develop and test ionospheric scintillation countermeasures to be implemented in multi-frequency, multi-constellation GNSS receivers.

Tomografia da ionosfera a partir do GNSS e técnicas algébricas: estudo de caso para a região brasileira

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Orientação semi-automática de uma sequência de pares de imagens frontais por fototriangulação a partir de fotocoordenadas extraídas pelo SIFT

Pós-graduação em Ciências Cartográficas - FCT

Desempenho do RTK em rede sob efeito da cintilação ionosférica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A dense GNSS meteorological network for observing deep convection in the Amazon

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

O entroncamento das políticas agrárias no Maranhão: encontros e desencontros institucionais na Microrregião Geográfica de Itapecuru Mirim

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Modelagem fotogramétrica e calibração de um sistema de visão omnidirecional

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Localização automática de pontos de controle em imagens aéreas baseada em cenas terrestres verticais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Orientação e ortorretificação de imagens terrestres nadirais

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Modelos geoidais híbridos para o Estado de São Paulo: desenvolvimento e avaliação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Using cubic splines to mitigate systematic errors in GPS relative positioning

Systematic errors can have a significant effect on GPS observable. In medium and long baselines the major systematic error source are the ionosphere and troposphere refraction and the GPS satellites orbit errors. But, in short baselines, the multipath is more relevant. These errors degrade the accuracy of the positioning accomplished by GPS. So, this is a critical problem for high precision GPS positioning applications. Recently, a method has been suggested to mitigate these errors: the semiparametric model and the penalised least squares technique. It uses a natural cubic spline to model the errors as a function which varies smoothly in time. The systematic errors functions, ambiguities and station coordinates, are estimated simultaneously. As a result, the ambiguities and the station coordinates are estimated with better reliability and accuracy than the conventional least square method.