The Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG), taking care of providing a precise geodetic infrastructure for monitoring the System Earth, promotes the standardization of height systems worldwide. The GGOS Focus Area "Unified Height System” (GGOS-FA-UHS, formerly Theme 1) was established at the 2010 GGOS Planning Meeting (February 1 - 3, Miami, Florida, USA) to lead and coordinate these efforts. Starting point were the results delivered by the IAG Inter-Commission Project 1.2 "Vertical Reference Frames" (IAG ICP1.2 VRF), which was operative from 2003 to 2011.
During the term 2011-2015, the GGOS Focus Area Unified Height System (GGOS-FA-UHS) was chaired by Michael Sideris (University of Calgary, Canada) and Johannes Ihde (Bundesamt für Kartographie und Geodäsie, Germany). The main result is the compilation of the IAG resolution for the "Definition and realization of an International Height Reference System (IHRS)" approved during the 2015 General Assembly of the International Union of Geodesy and Geophysics (IUGG) in Prague, Czech Republic. Present efforts concentrate on the implementation of the IHRS. In the term 2015-2019, it was possible to define a global reference network for the International Height Reference Frame (IHRF) and to evaluate different strategies for the determination of potential values as IHRS/IHRF reference coordinates. A main outcome is the IAG Resolution No. 3, 2019 for the Establishment of the International Height Reference Frame (IHRF) adopted at the 2019 IUGG General Assembly in Montreal, Canada. (read more).
Since 2015, this Area is chaired by Laura Sánchez, Deutsches Geodätisches Forschungsinstitut, Technische Universität München, Germany.