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Abstract

Over the past several years, a definition for a modern International Terrestrial Gravity Reference System (ITGRS) has been developed by the IAG Joint Working Group 2.1.1. Now a resolution will be proposed to IAG to adopt the ITGRS. The ITGRS is based on the instantaneous acceleration of free-fall, expressed in the International System of Units (SI). Consequently, the International Terrestrial Gravity Reference Frame (ITGRF) will be its realization and will be based on measurements with absolute gravimeters at an accuracy level of a few microGal (1 µGal = 10^-8 m/s²). Conventional models for the correction of time dependent effects in these measurements are proposed which are compatible with previous standards. An adequate infrastructure then allows for replacement of IGSN71 which no longer meet the today’s requirements. The details of the concept are outlined and summarized, specifically the proposal to include constant components of temporal gravity corrections as part of the system definition and the importance of instrument comparisons at different levels to ensure a common reference level and the traceability to the SI. Reference stations to monitor the stability of absolute gravimeters will play a key role in the ITGRF. Colocation with space geodetic techniques will provide a link to the International Terrestrial Reference Frame and to GGOS. Establishing compatible first order gravity networks and sharing information on absolute gravity observations will provide access to users but will require support and collaboration with national authorities worldwide.