SIRGAS WG III activities for promoting the modernization of height systems in South America, Central America and Caribe and their connections to IHRS

SILVIO R. DE FREITAS; WILLIAM A. MARTÍNEZ; MARÍA V. MACKERN; V. CIOCE; R. PEREZ RODINO

Copenhagen

Simposio; International Symposium. Gravity, Geoid and Height Systems; 2018

Asociación Internacional de Geodesia

Among the main objectives of SIRGAS (SIstema de Referencia Geocéntrico para las AméricaS) is the establishment of a unified height reference system for its country members withina global frame. The central purpose is to refer the geopotential numbers (or physical heights) when existing in all countries to the equipotential surface defined by the W0 value adopted by theIAG in July, 2015. Thus, a present challenge is the compatibilization (or integration) of the existing height systems into the International Height Reference System (IHRS). To advance in thisdirection, initial actions concentrated on the co-location of the national vertical datums with the geocentric reference frame SIRGAS (densification of the International Terrestrial Reference Frame? ITRF ? in Latin America) and the continental adjustment of the Vertical Reference Frame (VRF) in terms of geopotential numbers. To determine the relationship between the global and the localreference levels, we are evaluating different geodetic boundary value problem (GBVP) formulations in three different approaches: at the reference points (tide gauges) of the classical height datums, in the marine areas close to the tide gauges, and at (or between) fiducial stations of the geometrical reference frame SIRGAS. The kernel of the intended realization of the unified vertical reference system will be done by a continental set of very good (reproducible) benchmarks with ITRS/ITRF geometric coordinates as well as known global geopotential numbers and anomalous potential values. These stations should contribute to the establishment of the Global Geodetic Reference System and Frame (GGRS/GGRF). In this work, we report about several goals already obtained and promising ongoing activities like the connection of local VRF to the reference level of the global IHRS.