Abstract
In July 2018, IBGE launched the new heights of the Brazilian Geodetic System (BGS), the normal height, which has associated gravity. These new heights are replacing the old normal-orthometric ones, in which there was only the non-parallelism correction. The IBGE informs that the values farther from the origin, have less accuracy. This lower accuracy may interfere in the future, the connection of the local tide gauges to IHRF (International Reference Frame Height). Thus, this paper proposes the integration of the local tide gauge of Cananeia-SP to the IHRF. In order to validate the methodology, the normal, Helmert, and rigorous orthometric heights using two distinct references: the Imbituba-SC tide gauge, as the origin of the BGS and the Cananeia-SP tide gauge, as a local tide gauge to be integrated into the IHRF. Calculating the three heights through these two origins, we analyzed the discrepancies in comparison to the heights calculated by IBGE. Numerical tests indicate that there was an improvement in terms of a mean and standard deviation when using the Cananeia gauge as origin in the calculation of normal, Helmert, and rigorous heights. In the congruence analysis, the calculations indicate that the highest standard deviation is presented when using IBGE normal heights. Thus, we have a new origin that is reliable and functional, can be integrated with the IHRF, where the Helmert and rigorous orthometric heights have the best statistical results.
Highlights
A question normally discussed in physical geodesy surveys and related areas is: A purely physical height system can be accurately performed? This question arises since a purely physical height system must necessarily be related to the Earth’s gravitational field (Kingdon, 2012)
Statistical analyses were performed between the normal, Helmert, and rigorous heights obtained by the Imbituba and Cananeia tide gauges and the normal heights available in the BDG by IBGE
(1) The first analysis was to verify the discrepancy between the normal heights of IBGE and those calculated from Imbituba and Cananeia
Summary
A question normally discussed in physical geodesy surveys and related areas is: A purely physical height system can be accurately performed? This question arises since a purely physical height system must necessarily be related to the Earth’s gravitational field (Kingdon, 2012). Once the geopotential number was calculated, the IBGE could be tested for the performance of a classical height system (Helmert orthometric) which is the calculated measure of the difference between the geoid heights (NGrav), derived from a gravimetric geoidal model, concerning the geoid heights (NLev), derived from the level reference leveling (GNSS/ leveling). These measures are called congruence and are a metric for assessing the quality of the classic height system. We would have the analysis of which height best adapts to the Brazilian territory
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