Local gravimetric geoid model in the city of Porto Alegre, Brazil
20/09/2016 | 17:00 | Session 3: Local/regional geoid determination methods and models
Author(s): Elen De Lima, Sergio Florencio de Souza and Roosevelt De Lara Jr
Elen De Lima, Sergio Florencio de Souza and Roosevelt De Lara Jr
GNSS has revolutionized geodetic positioning methods by replacing classical techniques and by offering new applications since the first system (GPS) became operational. It is changing the concepts and methodologies for the dissemination of time, monitoring of deformations, implementation of three-dimensional geodetic networks, and leveling. Despite scientific and technological advances, the determination of orthometric heights, needed to solve various everyday problems, was subject to the practical difficulties, with classical levelling remaining the preferred method. Currently, GNSS has been used successfully in two important applications related to this issue: improving the geoid and satellite leveling. In this article, we present and discuss the methodologies for the determination and evaluation of a geoid model for the city of Porto Alegre and its surroundings. For this purpose, a campaign was undertaken to increase the density and distribution of gravimetric data. The mathematical model used was the Stokes integral, with long wavelength components computed through the EGM2008 geopotential model (complete to order and degree 360). We found that the error obtained in this work after fitting the data with GNSS and classical levelling measurements was about (7 cm). The methodology used in this work can be applied in other parts of Brazil to improve the precision geoidal heights compatible with that of classical levelling.