ADJUSTMENT OF A REGIONAL ALTIMETRIC NETWORK, IN BRAZIL, TO ESTIMATE NORMAL HEIGHTS AND GEOPOTENTIAL NUMBERS

Abstract

: In 2018, the Brazilian Institute of Geography and Statistics (IBGE) defined the normal height values and geopotential numbers for the High Precision Altimetric Network (HPAN), creating the need for developing procedures able to adapt works correlated with the Brazilian Geodetic System (BGS). In that context, and considering the state and municipal altimetric networks, it is necessary to estimate normal heights. To this end, this paper proposes to estimate normal height values and geopotential numbers for the Altimetric Network of the Federal District (AN-DF). Computational procedures involving the Least Squares Method were established and applied in a geometric levelling survey, which includes 200 stations distributed throughout the study area. The obtained results allowed estimating the normal heights of the network stations with accuracy up to 0.032m. However, because significant differences were found in the adjusted and known values of some used HPAN stations, we recommend a rigorous analysis of these stations before using them. In any case considering that the geometric levelling and the applied procedures were carried out correctly, it is suggested that the values estimated for all stations of the AN-DF in this work may be used. This work presents procedures adopted for adjusting, using the geometric leveling, and estimating the normal heights and geopotential numbers for stations and points that are part of the Altimetric Network of the Federal District, Brazil. The results show good accuracy of the estimated normal height values. Spatially, the accuracy increased (ranging from 0.000 m to 0.032 m) as the number of stations used as reference to compute the normal heights also increased.