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.
Highlights
The High Precision Altimetric Network (HPAN) belongs to the Brazilian Geodetic System (BGS) and is maintained by the Brazilian Institute of Geography and Statistics (IBGE)
Considering the uncertainties of the H N values estimated by the Constrained LSM (CLSM), which vary from 0.000 m to 0.037m (Figure 5), it can be seen that the stations and points farthest from the reference station (RN-IBGE 2223S) have less accurate results
The results show good accuracy of the estimated normal height values
Summary
The High Precision Altimetric Network (HPAN) belongs to the Brazilian Geodetic System (BGS) and is maintained by the Brazilian Institute of Geography and Statistics (IBGE). This network covers the entire Brazilian territory, having nowadays two vertical datums, Imbituba and Santana, and continuous data collection via geometric leveling technique, where new stations are implanted. To incorporate new stations into the HPAN, all stations in the network adjustment are used to estimate and/or update their heights using the Least Squares Method (LSM). Like the HPAN, a Gravimetric Network (GN), which belongs to the BGS, has been continually updated, with the acquisition of new gravimetric data. The IBGE published new heights, called normal heights, for the HPAN stations in 2018 (IBGE 2018), where gravimetric observations were included in the functional model for the network adjustment, following the recommendations of the International Association of Geodesy (IAG)
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