[G07-1] GGOS activities and focus on gravity

[G07-1-06] A first approximation to the International Height Reference Frame (IHRF)

^○Laura Sanchez¹, Heiner Denker², Denizar Blitzkow³, Roland Pail¹, Jianliang Huang⁴, Daniel Roman⁵, Matt Amos⁶, Johannes Ihde⁷, Riccardo Barzaghi⁸, Michael Sideris⁹, Ilya Oshchepkov¹⁰, Ana C. O. C. Matos³, Diego Pinon¹¹, David Avalos¹², Silvio R. C. Freitas¹³ (1.Technische Universitatet Muenchen, Germany, 2.Leibniz Universitaet Hannover, Germany, 3.Universidade de Sao Paulo, Brazil, 4.Natural Resources Canada, Canada, 5.National Geodetic Survey, NOAA, USA, 6.Land Information New Zealand, New Zealand, 7.Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum, Germany, 8.Politecnico di Milano, Italy, 9.University of Calgary, Canada, 10.Center of Geodesy, Cartography and SDI, Russia, 11. Instituto Geografico Nacional, Argentina, 12. Instituto Nacional de Estadistica y Geografia, Mexico, 13. Universidade Federal do Parana, Brazil)

invited

The International Height Reference System (IHRS) is defined as a geopotential reference system co-rotating with the Earth. Coordinates of points attached to the solid surface of the Earth are given by (1) geopotential numbers C(P) referring to the equipotential surface defined by the conventional W0 value 62636853.4 m2s-2 and, (2) geocentric Cartesian coordinates X referring to the International Terrestrial Reference System (ITRS). The determination of the coordinates C(P) and X(P) includes their variation with time. As W0 is a conventional constant value, C(P) basically depends on the potential value W(P). Thus, W(P) may be understood as a main coordinate of the IHRS. The present challenge is the realization of the IHRS; i.e., the establishment of the International Height Reference Frame (IHRF). This comprises, among others, (1) the selection of a global well-distributed set of stations as the IHRF core network, and (2) the development of strategies for the precise computation of the coordinates W(P) and X(P) at those core stations. While X(P) may be determined following the standards and conventions of the International Earth Rotation and Reference Systems Service, the estimation of the potential values W(P) is not a standardized procedure so far. Consequently, the establishment of the IHRF also includes the identification of harmonized standards for the consistent determination of W(P) and X(P), the precise modelling of the time-dependent changes of the coordinates, and the implementation of strategies for the collocation of IHRF reference stations with other reference frames (like the GGRF, the ITRF, geodetic observatories, time laboratories, etc.). This contribution presents the first approximation to the IHRF: it describes the preliminary IHRF core network and the criteria applied to select its reference stations. It also discusses and compares different approaches for the computation of the potential values W(P) at the IHRF core stations.