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IBGE releases today (28) the 2nd edition of the Methodological Report on the hgeoHNOR2020 Model to Convert Geometric Altitudes into Normal Altitudes
Like the previous edition, the second edition of the methodological report of hgeoHNOR2020 shows the conceptual bases that guided the development of the model, based on the change in the typology of high-precision altitudes of the Brazilian Geodetic System (SGB) in 2018. At that time, the Geodetic Database (BDG) began to release physical altitudes of normal type for all the SGB´s altimetric stations - the so-called Level References or RRNN - rather than the old normal-orthometric altitudes.
The hgeoHNOR2020 report also shows the details of its development and assessment - based on GNSS-leveling connection stations called SAT-RN -, as well as the calculation service available on the IBGE portal that streamlines the use of the model by the technical-scientific community. Additional details about the model are also shown, based on the contents of the queries on its use submitted to the IBGE´s Coordination of Geodesy after its release.
The launching of the hgeoHNOR2020 model in 2021 was a key and unprecedented step to refine the results of the conversion of altitudes obtained through satellite systems like GPS. Known as geometric or ellipsoidal altitudes, they do not represent properly the drainage of massas by gravity, like the water flow in large irrigation channels or in coastal plains, and they should necessarily be converted into the so-called physical altitudes, as they are unequivocally related to the field of the terrestrial gravity. They have been obtained by the IBGE in Brazil since 1945 as a result of the measurements of geometric leveling among the RRNN of the High-Precision Altimetric Network (RAAP).
The hgeoHNOR2020 model provides the factor to obtain physical altitudes from geometric altitudes, consistently with the normal altitudes of the IBGE´s RRNN, resulting from the Re-Adjustment of the Altimetric Network with Geo-Potential Numbers (REALT-2018), bringing significant benefits to the activities in which the vertical positioning is made through satellite systems.
Directorate of Geosciences
November 28, 2023