Instituto Brasileiro de Geografia e Estatística

The IBGE will release, at 10 am on November 28th, the 2nd edition of the Methodological Report on the hgeoHNOR2020 Model for Conversion of Geometric Altitudes into Normal Altitudes.

This second edition of the methodological report on hgeoHNOR2020, similarly to the previous one, presents conceptual bases, details on the elaboration and evaluation, and the calculation service made available on the IBGE website to facilitate the use of this model by the scientific community. There are also additional details about the model, considering the content of the consultation submitted to the IBGE Department of Geodesy after the release.

The release of the hgeoHNOR2020 model, in 2021, represents a fundamental and unprecedented step taken by the IBGE towards the refining of results of altitude conversions by means of satellite systems such as the GPS. Known as geometric or ellipsoid altitudes, they do not properly represent the flow of mass by gravity, for example, the flow of water in large irrigation channels or coastal tableland, and have to be converted into physical altitudes, related to the Earth’s gravitational field. In Brazil, they have been obtained by the IBGE, since 1945, as the result of geometric levelling measurements in the References of the High precision Altimetric Network (RAAP), and made available in the Geodetic Database (BGD).

The hgeoHNOR2020 model provides the factor for the obtention of physical altitudes using geometric altitudes, accordingly to the IBGE normal reference level (RRNN) altitudes, which result from the Adjustment of the Altimetric Network with Geopotential Figures (REALT-2018).

Directorate of Geosciences
October 27, 2023