Geodetic reference systems: Towards GGRS/GGRF

Abstract

One of the main challenges in Geodesy is the definition and realization of global Geodetic Reference Systems with geometric and physical characteristics. This is necessary to fulfill the demands of different knowledge areas where the observations related to Earth Observation Systems (EOS) must be integrated into reference frames with an accuracy of 10-9 or better. The development of satellite positioning systems has brought significant improvements in positional accuracy and made possible the replacement of local reference frames by global reference frames. Today, the geometric coordinates are well resolved with ITRS/ITRF (International Terrestrial Reference System/International Terrestrial Reference Frame). However, physical processes, like that related to mass distribution, are not attended by pure geometric reference systems. The resolution for the GGRS/GGRF (Global Geodetic Reference System/Global Geodetic Reference Frame) was approved with the aim to integrate the terrestrial reference system, the inertial reference system, a global reference system with physical meaning for the heights and the new global absolute gravity network. Efforts are been made to define and realize this height reference system. It is a complex task due to the classical characteristics of existing vertical reference systems, heterogeneity in terms of data accuracy and spatial distribution, especially those related to the Earth's gravity field. The need to establish standard procedures for the integration with a global height reference system and the precision needed for the establishment of the EOS are the big challenges for the future.