Abstract
In 2015, the International Association of Geodesy defined the International Height Reference System (IHRS) as the conventional gravity field-related global height system. The IHRS is a geopotential reference system co-rotating with the Earth. Coordinates of points or objects close to or on the Earth’s surface are given by geopotential numbers C(P) referring to an equipotential surface defined by the conventional value W0 = 62,636,853.4 m2 s−2, and geocentric Cartesian coordinates X referring to the International Terrestrial Reference System (ITRS). Current efforts concentrate on an accurate, consistent, and well-defined realisation of the IHRS to provide an international standard for the precise determination of physical coordinates worldwide. Accordingly, this study focuses on the strategy for the realisation of the IHRS; i.e. the establishment of the International Height Reference Frame (IHRF). Four main aspects are considered: (1) methods for the determination of IHRF physical coordinates; (2) standards and conventions needed to ensure consistency between the definition and the realisation of the reference system; (3) criteria for the IHRF reference network design and station selection; and (4) operational infrastructure to guarantee a reliable and long-term sustainability of the IHRF. A highlight of this work is the evaluation of different approaches for the determination and accuracy assessment of IHRF coordinates based on the existing resources, namely (1) global gravity models of high resolution, (2) precise regional gravity field modelling, and (3) vertical datum unification of the local height systems into the IHRF. After a detailed discussion of the advantages, current limitations, and possibilities of improvement in the coordinate determination using these options, we define a strategy for the establishment of the IHRF including data requirements, a set of minimum standards/conventions for the determination of potential coordinates, a first IHRF reference network configuration, and a proposal to create a component of the International Gravity Field Service (IGFS) dedicated to the maintenance and servicing of the IHRS/IHRF.
Highlights
A current main objective of Geodesy is the implementation of an integrated global geodetic reference system that simultaneously supports the consistent determination and monitoring of the Earth’s geometry, rotation, and gravity field changes with high accuracy worldwide (IAG 2017)
Given that a reference frame realises a reference system physically by a solid materialisation of points or observing instruments, and mathematically by the determination of coordinates referring to that reference system (Drewes 2009), this study considers four main aspects: (1) methods for the determination of International Height Reference Frame (IHRF) physical coordinates; (2) standards and conventions needed to ensure consistency between the definition and the realisation of the reference system; (3) station selection for the IHRF reference network; and (4) Operational infrastructure to guarantee a reliable and longterm sustainability of the International Height Reference System (IHRS)/IHRF
To assess the repeatability of the results provided by different approaches utilised in the solution of the geodetic boundary value problem (GBVP) and to identify a set of basic standards to ensure a minimum consistency between them, a computation experiment based on the same input data and different processing strategies was performed over two years (2017–2019)
Summary
A current main objective of Geodesy is the implementation of an integrated global geodetic reference system that simultaneously supports the consistent determination and monitoring of the Earth’s geometry, rotation, and gravity field changes with high accuracy worldwide (IAG 2017). This objective is in accordance with the resolution adopted by the United Nations General Assembly on a Global Geodetic Reference Frame (GGRF-UN) for Sustainable Development (A/RES/69/266) on February 26, 2015. These sections provide a description of current limitations and possibilities of improvement in the coordinate determination using each method The outcome of this analysis is presented in two parts: Sect. The paper finishes with an outlook about the activities to be faced in the near future
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