Contribuição para o estabelecimento do IHRF no estado de São Paulo
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Data
2019-02-25
Autores
Ribeiro, Leticia Cristina [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A definição e determinação da coordenada vertical de pontos da superfície terrestre é alvo de pesquisas atualmente. As técnicas de posicionamento Global Navigation Satellite System (GNSS) proporcionam o conhecimento das altitudes de forma rápida e fácil; porém, a componente fornecida por estas técnicas possui caráter geométrico, ou seja, a altitude corresponde à distância normal entre o ponto mensurado e o elipsoide de revolução. Esta altitude tem sua importância, porém não possui caráter físico. Em obras de engenharia, é fundamental o conhecimento da altitude física, pois é a do sentido de escoamento da água. Este fator físico corresponde ao geopotencial, que quando relacionado com dados gravimétricos resulta em uma altitude física que representa a distância entre a superfície equipotencial do ponto de interesse e a superfície equipotencial de referência. Em 2015, a International Association of Geodesy (IAG) publicou uma resolução de fundamental importância na integração dos sistemas de altitudes entre os países, visando à formação de um Sistema Internacional de Referência Altimétrico, o International Height Reference System (IHRS). Dessa forma, para que as altitudes possam ser integradas ao IHRS é necessário calcular o valor do geopotencial. Os dados gravimétricos disponíveis no estado de São Paulo possibilitaram o cálculo do geopotencial, uma vez que o estado possui distribuição gravimétrica homogênea, que é uma das sugestões de condições para determinar o valor do potencial. Assim, levando em consideração a importância da integração das altitudes brasileiras com um sistema global, foi calculado o número geopotencial para as estações PPTE e NEIA do estado de São Paulo. Nestes cálculos foram aplicados os Modelos Globais do Geopotencial (MGGs) EIGEN-6C4, GECO, GOCO05c e XGM2016 para grau e ordem n=m=200 e aplicado os métodos da Colocação por Mínimos Quadrados (CMQ), Integral de Stokes via Fast Fourier Transform (FFT) e Integral de Hotine. Os resultados obtidos foram consistentes entre os modelos e os métodos aplicados. A estação NEIA apresentou resultados menos precisos do que a estação PPTE o que pode ser explicado pelo uso dos dados gravimétricos de um modelo global marinho.
Knowledge the vertical coordinate of points of the terrestrial surface is currently under investigation. Global Navigation Satellite System (GNSS) techniques provide the heights quickly and easily; however, the component provided by these techniques has a geometric character, that is, the height corresponds to the normal distance between the measured point and the revolution ellipsoid. This height has its importance, but it does not have physical meaning. In engineering works, it is fundamental to know the physical height, because it is the one that the direction of water flow obeys. This physical factor corresponds to the geopotential, which when related to gravimetric data results in a physical height. Represents the distance between the equipotential surface of the point of interest and the equipotential reference surface. In 2015, the International Association of Geodesy (IAG) published a resolution of fundamental importance in the integration of height systems between countries, aiming at the formation of a global altimetric system, the International Height Reference System (IHRS). Thus, in order for the heights to be integrated into the IHRS, it is necessary to calculate the potential value. Thus, considering the importance of integrating Brazilian heights with a global system, the geopotential number for the PPTE and NEIA stations in the state of São Paulo was calculated. In these calculations were applied the Global Geopotential Models (GGMs) EIGEN-6C4, GECO, GOCO05c and XGM2016 for degree and order n=m=200 and the methods of the Least Squares Collocation (LSC), Stokes Integral via Fast Fourier Transform (FFT) and Hotine Integral. The results obtained were consistent between the models and the methods applied. The NEIA station presented less precise results than the PPTE station, which can be explained by the use of the gravimetric data of a global marine model.
Knowledge the vertical coordinate of points of the terrestrial surface is currently under investigation. Global Navigation Satellite System (GNSS) techniques provide the heights quickly and easily; however, the component provided by these techniques has a geometric character, that is, the height corresponds to the normal distance between the measured point and the revolution ellipsoid. This height has its importance, but it does not have physical meaning. In engineering works, it is fundamental to know the physical height, because it is the one that the direction of water flow obeys. This physical factor corresponds to the geopotential, which when related to gravimetric data results in a physical height. Represents the distance between the equipotential surface of the point of interest and the equipotential reference surface. In 2015, the International Association of Geodesy (IAG) published a resolution of fundamental importance in the integration of height systems between countries, aiming at the formation of a global altimetric system, the International Height Reference System (IHRS). Thus, in order for the heights to be integrated into the IHRS, it is necessary to calculate the potential value. Thus, considering the importance of integrating Brazilian heights with a global system, the geopotential number for the PPTE and NEIA stations in the state of São Paulo was calculated. In these calculations were applied the Global Geopotential Models (GGMs) EIGEN-6C4, GECO, GOCO05c and XGM2016 for degree and order n=m=200 and the methods of the Least Squares Collocation (LSC), Stokes Integral via Fast Fourier Transform (FFT) and Hotine Integral. The results obtained were consistent between the models and the methods applied. The NEIA station presented less precise results than the PPTE station, which can be explained by the use of the gravimetric data of a global marine model.
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Palavras-chave
IHRS, Geopotencial, Altitude, Geopotential, Height