Abstract

Due to the challenge that the Amazon Basin imposes for traditional geodetic surveys, the Brazilian Fundamental Vertical Network (BFVN) is materialized in two independent parts: the southern segment is linked to the Imbituba tide gauge and the northern part is linked to the Santana tide gauge. The mouth of the Amazon River and its surrounding wetlands generate a large area without access for spirit levelling and conventional gravimetry. There is a minimum distance of about 330 km between the nearest bench marks of the two above mentioned vertical networks. Nowadays, satellite gravity missions such as CHAMP, GRACE and GOCE make it possible to explore new solutions based on Global Geopotential Models (GGMs) obtained from satellite data only. Digital Elevation Models (DEMs) allow an improvement in the spectral resolution of the GGMs based on Residual Terrain Modelling (RTM). Such an approach is an alternative to filling the information gaps in the GGMs by reducing omission errors. The spectral improvement of the GGMs allows us to integrate the vertical datums in a more realistic way, and with a reduction of terrestrial gravity dependency. In this study, two alternatives to the indirect connection of the BFVN are analyzed. A solution is based on a combination of GGM satellite-only data from the GOCE mission and the spectral contribution of the RTM. The other solution is based on the integration of information from GOCE GGM, EGM2008 and the RTM effect. The offset obtained shows that the Imbituba datum is located 1.32 and 1.43 m below the Santana datum for the solutions GGMGOCECRTM and GGMGOCECEGM2008CRTM respectively.