Estimativa e análise de índices de irregularidades da ionosfera utilizando dados GPS de redes ativas

Observable GNSS (Global Navigation Satellite System) are affected by systematic errors due to free electrons present in the ionosphere. The error associated with the ionosphere depends on the Total Electron Content (TEC), which is influenced by several variables: solar cycle, season, local time, geomagnetic activity and geographic location. The GPS (Global Positioning System), GLONASS (Global Orbiting Navigation Satellite System) and Galileo dual frequency receivers allow the calculation of the error that affects the GNSS observables and the TEC. Using the rate of change of TEC (ROT - Rate of TEC) indices that indicate irregularities of the ionosphere can be determined, allowing inferences about its behavior. Currently it is possible to perform such studies in Brazil, due to the several Active Networks available, such as RBMC/RIBaC (Rede Brasileira de Monitoramento Contínuo/Rede INCRA de Bases Comunitárias) and GNSS Active Network of São Paulo. The proposed research aimed at estimating and analysing of indexes of irregularities of the ionosphere, besides supplying the geosciences of information about the behavior of the ionosphere.

Solução rápida das ambigüidades GPS para aplicações no posicionamento relativo de linhas de base curtas

Pós-graduação em Ciências Cartográficas - FCT

Método dos mínimos quadrados com penalidades: aplicação no posicionamento relativo GPS

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nivelamento através do GPS: avaliação e proposição de estratégias

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

Implicações do uso de recptores GPS de navegação sem conhecimento de suas limitações e configurações básicas

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Determinação de órbitas com o GPS através de mínimos quadrados recursivo com rotações de Givens

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

Avaliação do posicionamento plano-altimétrico com receptor gps em diferentes tipos de uso do solo

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

First results from an airborne GPS radio occultation system for atmospheric profiling

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Extended ionospheric amplitude scintillation model for GPS receivers

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Análise multiescala de séries temporais do efeito da cintilação ionosférica nos sinais de satélite GPS a partir de wavelets não decimadas

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

Inverse Modeling of GPS Multipath for Snow Depth Estimation-Part I: Formulation and Simulations

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Sistema GPS: uma órbita em evolução - número de satélites e periodicidade

The objective of this project was to monitor the satellites of the Global Positioning System (GPS) from a fixed point on Earth and to verify the rate of recurrence respect to their rotation and displacement. A topographic GPS signal receiver connected to a personal computer was used to recorded, for five days, the displacement of the satellites. This work was based on the fact that many literature references state that satellites complete one orbit around the Earth every 12 hours, then, it is assumed that the satellite would be seen twice in a day from the same fixed point on Earth.Although, this does not occur, as thise time interval correspond to 12 hours sidereal time and not solar time. In addition, this study was carried out in order toconfirm and update the information related to the number of satellites in operation today, found to be 31. In that sense, some references concerning the space segment of this system were defined in details.

Assessment of modernized GPS L5 SNR for ground-based multipath reflectometry applications

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Posicionamento por ponto preciso com solução de ambiguidades inteiras no contexto de rede GPS

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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

This 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 modulation owing to small displacements, random noise, receiver clock short time instabilities, and multipath. The results showed that it is possible to detect displacements of centimeters in the phase data of a single satellite and millimeters in the difference between the phases of two satellites. After applying a periodic nonsinusoidal displacement of 10 m to the antenna, it is clearly recovered in the difference of the residuals. The time domain spectrum obtained by the fast Fourier transform (FFT) exhibited a defined peak of the third harmonic much more than the random noise using the proposed third-degree polynomial model. DOI: 10.1061/(ASCE)SU.1943-5428.0000070. (C) 2012 American Society of Civil Engineers.