Evaluation of recent combined global geopotential models in Brazil

Abstract

The aim of this paper is to present a quantitative analysis of the adequacy of the main currently existing combined Global Geopotential Models (GGMs) for modeling normal-geoid heights throughout Brazil. As major advances have been reached since mid-2016 in the combined GGMs elaboration and development, the main objective of this analysis is to verify if, in fact, the most recent models present superior or equivalent performance to the most performant previous models. The analysis was based on comparisons between normal-geoid height values obtained fromGNSS/leveling solutions and values calculated from GGMs XGM2016, GOCO05C, EIGEN-6C4 and EGM2008, according to different geopotential functionals - geoid height and height anomaly - and in different degrees of development, always through the relative method. This procedure was applied to 997 stations which carry information of both ellipsoidal and normal-orthometric heights, located all over Brazil. As a main result, it was observed the superior performance of the recent combined GGMs, GOCO05C and XGM2016, when compared to the older models, EIGEN-6C4 and EGM2008, when all of them are developed up to degree 720, the maximum degree of the recent models; and a approximate equality of results when all of the models are used in their individual maximum degrees.

Use of GNSS and a refined GGM (XGM2019e) for determining normal heights in the Imbituba Brazilian Vertical Datum and in the International Height Reference System

“…It is noteworthy that, this research was carried out in 2017, when normal-orthometric heights were in use. According to IBGE (2019), the differences between previous and current HPAN heights in the study region vary almost entirely between -0.01 m and 0.01 m. Therefore, the results obtained by Nicacio, Dalazoana, and Freitas (2018) remain valid after REALT-2018. As GGM XGM2016 (Pail et al 2018) had the best performance and has been updated to XGM2019 (Zingerle et al 2020), this has been selected for the development of this research.…”

“…During the process of choosing the GGM, the study developed by Nicacio, Dalazoana, and Freitas (2018) was taken as reference, which verified the employability of some of the most recent GGMs for the extraction of normal-orthometric heights in Brazilian territory. It is noteworthy that, this research was carried out in 2017, when normal-orthometric heights were in use.…”

O Estabelecimento do IHRF no Brasil: Situação Atual e Perspectivas Futuras

“…O EGM2008 (PAVLIS et al, 2012) foi o primeiro modelo a ter coeficientes harmônicos esféricos com grau e ordem elevados (grau 2190 e ordem 2159), sendo a referência para o cálculo dos recentes modelos EIGEN-6C4 (FÖRSTE et al, 2014), GECO (GILARDONI; REGUZZONI; SAMPIETRO, 2016), XGM2019 (ZINGERLE et al, 2019) e SGG-UGM-2 (LIANG et al, 2020). A confiabilidade dos modelos é comumente avaliada comparando as funcionais geodésicas (ondulação geoidal ou anomalia de altitude) com estações GNSS sobre nivelamento (veja: GUIMARÃES et al, 2012;NICACIO;FREITAS, 2018). Gruber e Willberg (2019), demonstraram que os recentes MGGs possuem uma acurácia da ordem de 2 cm para regiões com topografia suave e bem desenvolvidas em termos de densificação gravimétrica.…”

Physical Connection Between BVRF Segments Based on Leveling Associated With Gravimetry

“…Solution 5: Same as Solution 4 but considering GGM XGM2016, with harmonic expansion up until degree and order 719. This model was adopted following suggestions by Nicacio, Dalazoana and De Freitas (2018) relating to the relative good behavior of this model in the region and the new approach used for its computation by considering its regional error behavior and data availability.…”