The new unconstrained static gravity field HUST-Grace2026s is recently developed at Huazhong University of Science and Technology. During retrieving our model, the reprocessed GRACE L1b RL03 data and GRACE-FO RL04 data are used, and the newly de-aliasing product AOD1B RL07 is applied in the time span from 2002-04 to 2025-03. In addition, a hybrid processing chain is applied to improve the quality of final solutions. Further details are presented in Zhou et al. (2024) and Zheng et al. (2026).
The MK_HREF2022 quasi-geoid model is a height reference surface for North Macedonia, referred to the GRS80 ellipsoid. It was computed by the Agency for Real Estate Cadastre of the Republic of North Macedonia, in cooperation with the Norwegian Mapping Authority (Kartverket), and it is given in the form of a regular grid, with resolution of 0.01° × 0.01°, within the limits of 40.8° < latitude < 42.4° and 20.4° < longitude < 23.1°. The model is based on a set of relatively new gravity data measured in 2014 (along the high accuracy levelling lines and in the frame of the regional gravimetric survey), in total 2470 points in mean-tide system. Stokes/Molodensky equations and the Fast Fourier transform technique were applied in the calculations, with use of the global geopotential model EGM2008. The computed quasi-geoid surface was fitted to 77 high quality GNSS/levelling points, fairly distributed throughout the territory of the country. The resulting height reference surface allows the conversion between ellipsoidal heights (ETRS89, epoch 1989.0) and heights in the official national height system (NVT1, datum Trieste 1875.0, normal orthometric heights). The inner accuracy of the calculated quasi-geoid model is 4.0 cm, while the outer accuracy (based on 1035 control GNSS/levelling measurements along levelling lines) is up to 10 cm. MK_HREF2022 is the official quasi-geoid model for North Macedonia since November 28, 2025.
The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
QgeoidCOL2023 is a gravimetric quasi-geoid model for Colombia, computed by the Deutsches Geodätisches Forschungsinstitut (DGFI), Technical University of Munich. The area covered by the model is located from 4.8°S to 12.8°N in latitude and from 79.3°W to 66.7°W in longitude, with a grid spacing of 5' in both latitude and longitude. The input data include terrestrial and airborne gravity data, provided by the Instituto Geográfico Agustín Codazzi (IGAC), as well as satellite altimetry data derived from the DTU21Gra model, all used at their original observation locations. A bias estimation for the airborne gravity surveys was performed using spherical radial basis functions (SRBFs), by comparing the data with the SaTop model up to degree and order 719 (Zingerle, 2022), since the surveys were conducted at different times and by different companies. The quasi-geoid computation is performed in the framework of a remove-compute-restore procedure, using the XGM2019 (Zingerle et al. 2020) as the gravity background model and the Earth2014 (Rexer et al. 2016) / ERTM2160 (Hirt et al. 2014) for the topographic gravity effects. The computation method is based on spherical radial basis functions (SRBFs), using the Shannon function and the Cubic Polynomial (CuP) function for the terrestrial and airborne data, respectively. The terrestrial, airborne, satellite altimetry and topography data observations were combined within a parameter estimation procedure, and the relative weights among them were determined by the method of variance component estimation (VCE). The comparison of the QgeoidCOL2023 quasi-geoid model against GPS/leveling shows differences with a standard deviation of about 16 cm.
The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.