Local Effects in the Brazilian Vertical Datum

Abstract

Nowadays, determining the topography of Mean Sea Level (Sea Surface Topography — SST) at the tide gauge station and its temporal variation is one of the most important aspects of defining a vertical Datum. Different approaches are used for this purpose: Oceanographic approach; Satellite altimetry associated with geostrophic levelling; Gravity associated with satellite positioning; Geodetic boundary-value problem approach (GBVP). In this sense, time series for observing tide gauge geocentric position permits to fix its geometric position and to detect local dynamic effects on the crust and in the SST. The main purpose of Work Group III in SIRGAS project (Geocentric System for the Americas) is to establish the link of all vertical reference systems in South America. In general, each national vertical network in that region was established under three particular conditions: local vertical datum; height system without physical meaning; and different spirit levelling standards. The unification of South American vertical datums, is a fundamental step to understand the observed off set among the networks in the region. The achieved results of two multiparametric on the brazilian vertical datum and their analysis are presented in this paper.KeywordsVertical DatumGeoidMSL and SSTGeopotential numberSIRGAS Project.