Connecting the Local Vertical Data in South America to the IHRF

Abstract

Since 2015, the scientific community has been working on unifying the global vertical datum, following the resolution for the definition and realization of an International Height Reference System. One of the main goals of the task is to determine the vertical offset between the local vertical datum and the global one. This paper aims to estimate the vertical offset in seven countries (Argentina, Brazil, Chile, Colombia, Ecuador, Venezuela, and Uruguay) in South America. For this purpose, geoid (and quasi-geoid) models were computed based on the Geodetic Boundary Value Problem Solution. The technique of removing and restoring the gravity field’s long wavelengths was applied. Terrestrial gravity data and satellite gravity anomalies (in the ocean) were combined with a global geopotential model and a digital terrain model to estimate the geopotential values and compute geoid undulations. GNSS/leveling data were used to infer the geoid (quasi-geoid) models and four global geopotential models. Regarding the vertical offset, GNSS/leveling data and the geoid undulations were used in the computation. A parametric model was used to minimize random and systematic errors in the calculation process. The resultsshowed that the vertical offset varies from 0.293 m (Talcahuano tide gauge - Chile) to 1.689 m (Santana tide gauge - Brazil).