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WHU-CASM-UGM2025 The combined global gravity field model up to degree and order 11000

WHU-CASM-UGM2025 is a combined global gravity field model up to degree and order (d/o) of 10799 in spheroidal harmonics and 11000 in spherical harmonics, developed by Wuhan University and Chinese Academy of Surveying and Mapping. It is based on XGM2019e, and augmented by ultra-high resolution topographic potentials and altmetry products.

Measurements of Gravity Differences using Scintrex CG6#362 and CG6#171 Spring Gravimeters in the Zugspitze Gravimeter Calibration System

Transportable spring gravimeters have many applications besides exploration geophysics and potential field determination, such as time-lapse measurements in hydrology and volcanology. For maximum accuracy, the time-dependent scale factor of each gravimeter must be determined before and after use. The required scale uncertainty depends on the target signals, the maximum gravity difference in the network, and the desired level of accuracy. In high alpine regions, large height differences can result in gravity differences of more than 1⋅10^6 nm/s^2. For a target uncertainty of 30 nm/s^2, the scale factor must be determined with an uncertainty below 1⋅10^(-5). The Zugspitze Calibration System, near Garmisch-Partenkirchen in the German Alps, consists of three absolute gravity (AG) stations that cover an elevation range of 2,200 m and a gravity range of 5,220 µm/s^2: W200 at Wank valley station (735 m a.s.l.) and W100 at Wank mountain station (1,738 m a.s.l.) at the cable car leading to Wank mountain, as well as the Zugspitze Geodynamic Observatory Germany (ZUGOG) at Zugspitze (2,939 m a.s.l.), where the OSG 052 superconducting gravimeter continuously measures gravity acceleration with the highest precision (1 nm/s^2) and long-term stability. Due to unmodeled temporary gravity changes, primarily caused by variations in snow water equivalent and groundwater, the system has a relative stability of approximately 5⋅10^(-5). To obtain gravimeter scale factors with an uncertainty below 1⋅10^(-5) in the Zugspitze Calibration System, we increase the precision by taking many measurements and improve the systematic uncertainty by modeling. From December 2023 to April 2026, a total of 73 difference measurements were taken between W200 and W100 using the relative gravimeters Scintrex CG6#362 from GFZ and CG6#171 from project partner LUH. Additionally, 18 difference measurements were carried out between W200 and ZUGOG. The CG6 measurements employed gravity gradients from Timmen et al. (2021) and tidal parameters from six years of SG measurements at Zugspitze. To correct for atmospheric variations, an air pressure admittance factor of -3 nm/s^2/hPa was used. The attached data have been calibrated using the initial scale factor specified by the manufacturer, and corrected for gravity gradients, tides, and atmospheric pressure variations.

C3S Globally Gridded Terrestrial Water Storage Anomalies

GRACE/GRACE-FO-derived time series of gridded terrestrial water storage anomalies with respect to the mean over the period 2003-01 - 2022-12. The product is based on monthly COST-G RL02 GRACE/GRACE-FO Level-2B Products (Meyer et al., 2025, https://doi.org/10.5880/COST-G.ICGEM_02_L2) provided at 0.5° latitude-longitude grids as defined over all continental regions. The TWS anomaly grids are provided in NetCDF format, containing three different variables: 1) 'twsa': gravity-based terrestrial water storage anomaly 2) 'std_twsa': gravity-based terrestrial water storage anomaly standard deviations 3) 'flag_filter': Flag indicating the filter strength File History: The Copernicus Climate Change Service (C3S) groups its datasets into Climate Data Records (CDRs), representing major version releases, and Intermediate Climate Data Records (ICDRs), which only extend the existing data and do not involve any processing changes. 12 September 2025: CDR: C3S_TWSA_GLOBAL_MONTHLY_200204_202503_v1.0.nc Data set covering April 2002 to March 2025 5 January 2026: ICDR: C3S_TWSA_GLOBAL_MONTHLY_200204_202509_v1.0.nc Data set covering April 2002 to September 2025

The Colombian gravimetric quasi-geoid: QgeoidCOL2023

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.

The hybrid quasi-geoid of North Macedonia: MK_HREF2022

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.

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