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Abstract:
The extensive use of GNSS positioning, combined with the importance of precise geoid heights for transformation between geodetic and orthometric heights, brings up the discussion of the influence of data uncertainties and the use of patameters on these estimates. In this sense, we first analyze the influence of the topographic density values and the data uncertainty on the computation of orthometric and geoid heights in 569 stations of the Brazilian Altimetric Network (stations whose values of geodetic and normal heights, gravity, and geopotential numbers are known), considering the Helmert and Mader methods. Second, we analyze the influence of different parameters (such as topographic density model, topographic models, geopotential models and Stokes kernel modifications) on the gravimetric geoid model determination through the remove-compute-restore technique, adopting the state of São Paulo, Brazil, as a study area. In the first analysis, the results indicate that orthometric heights are more sensitive to density values and to greater heights than to the Helmert and Mader methods applied. Also we verify that the normal and orthometric heights present significant differences for the analyzed stations, considering the high correlation between the heights, which provides small uncertainty values. In the second analysis, it was suggested that the Stokes kernel modification type and the Global Geopotential Model selection have a greater influence on the improvement of geoid models in the study area. However, the resolution of the Digital Terrain Models and the topographic density values have less impact on geoid models estimation.
