Assessment of temporal variations of geoid, ellipsoidal and orthometric heights at proposed IHRF sites using space geodetic data

Abstract The determination of accurate geoid, ellipsoidal and orthometric heights is essential for applications related to surveying engineering, geodetic and geoscience research. The International Association of Geodesy (IAG) defined the International Height Reference System (IHRS) as the conventional gravity field-related global height system. The realization of the IHRS to establish an International Height Reference Frame (IHRF) and its temporal variations, is an ongoing geodetic task. The objective of this research is to assess temporal variations of geoid, ellipsoidal and orthometric heights at proposed IHRF sites using space geodetic data, namely Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO), Global Navigation Satellite Systems (GNSS), Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Doppler Orbitography and Radio-positioning Integrated by Satellite (DORIS) and hydrological model. GRACE/GRACE-FO-based and GLDAS-based Global Geopotential Models were utilized to determine temporal variations of geoid height (Δ N ) and time-dependent changes of ellipsoidal height (Δ h ) at proposed IHRF sites. Moreover, Δ h at proposed IHRF sites were also obtained from GNSS, VLBI, SLR and DORIS solutions. Temporal variations of orthometric height (Δ H ) at proposed IHRF sites were determined by combining Δ N and Δ h . Results reveal that Δ N , Δ h , and Δ H at proposed IHRF sites are not negligible as they can reach several centimetres in terms of seasonal variations and at the and 1 cm level annually. These Δ N , Δ h , and Δ H would be required for the modernization and unification of international/national vertical datums in addition to contemporary requirements for precise height measurements.