Time Series Gravity Data (TGD)
Time-series gravity data consist of sequential gravity measurements acquired over time to monitor temporal changes in the Earth’s gravity field. They are obtained from both global satellite missions and ground-based observation networks. Satellite missions such as GRACE, GRACE Follow-On (GRACE-FO), and the planned GRACE-C and Next Generation Gravity Mission (NGGM) observe large-scale mass redistribution processes, including ice-sheet mass loss, terrestrial water storage variations, and changes in ocean mass. Time series derived from these observations are distributed as time-variable gravity field models.
Ground-based gravity networks complement satellite observations by monitoring regional and local temporal gravity variations with significantly higher temporal resolution and sensitivity. These networks provide the highest-precision time-series gravity observations currently available, measuring local gravity variations with sub-microgal precision (approximately 10⁻⁹ m/s²). They are essential for validating satellite-derived gravity models and for capturing high-frequency gravity signals that cannot be resolved from space because of orbital altitude, spatial averaging, and temporal sampling limitations.
Ground gravity networks comprise continuously operating superconducting gravimeters, which provide uninterrupted records of relative gravity changes, together with repeated observations from absolute gravimeters, which establish long-term stability and absolute reference of the measurements.
The International Geodynamics and Earth Tide Service (IGETS) of IAG’s International Gravity Field Service (IGFS) is the principal global infrastructure for monitoring temporal gravity variations. IGETS coordinates continuous, high-precision observations from approximately 68 superconducting gravimeters installed at 48 active stations worldwide. The service also contributes to the International Terrestrial Gravity Reference Frame (ITGRF), which integrates absolute gravity reference stations into a globally consistent realization of the Earth’s absolute gravity field.
The International Geodynamics and Earth Tides Service (IGETS)
IGETS collects, archives and distributes Earth tide records from long-term series from ground gravimeters, tiltmeters, strainmeters and other geodynamic sensors. IGETS has two analysis centers at the University of French Polynesia (Tahiti) and the University of Strasbourg (France). The main data center is hosted at GFZ Potsdam. The University of Strasbourg is also hosting the Central Bureau and a secondary data center. Further information is available at the IGETS overview page [link to https://geodesy.science/item/igets/] and IGETS website [link to http://igets.u-strasbg.fr/]
The main data products of IGETS are divided into raw and processed records from worldwide superconducting gravimeters. In particular, data at different processing levels provided at IGETS data base are:
- Level-1: Raw gravity and local air pressure records sampled at 1 or 2 seconds, and/or resampled to 1-minute resolution;
- Level-2: Gravity and local air pressure records corrected for instrumental perturbations, ready for tidal analysis;
- Level-3: Gravity residuals after particular geophysical corrections, including solid Earth tides, polar motion, tidal and non-tidal loading effects. Individual data DOI are issued for Level 1 datasets by the IGETS data center.
Apart from these products, IGETS is also offering:
- Superconducting gravimeter data for major earthquakes (minute and second sampling) – IGETS data;
and is supporting supplemental input data to process other main geodetic products:
- Atmospheric attraction computation service Atmacs
- Toolbox mGlobe for computing hydrological, atmospheric and non-tidal ocean loading effects
- EOST loading service (displacements, gravity, tilts)
Data Sources
