Consistent Estimate of Ultra-High Resolution Earth Surface Gravity Data (UHR-GravDat)

Ultra-high resolution Earth surface gravity data will serve important applications as, for example, high resolution gravity field modeling, unification of height systems, geophysical prospecting and hydrological water routing. The state-of-the-art global surface gravity data is, however, inhomogeneous and incomplete with inconsistencies not yet properly addressed. Marine gravity data derived by inverting satellite altimeter data provide gravity anomalies even with 1’ spacing. However, the approaches used to invert satellite altimeter data are rather sensitive to high frequency errors. Terrestrial gravity data are a very incomplete patchwork of different sources with different resolution and accuracy. The 5’ gravity anomalies, compiled for the generation of EGM2008, are non-public due to copy rights.

The general objective of the present project is to create, validate and edit a global set of consistent ultra-high resolution surface gravity data with a spatial resolution of 2.5’ (about 5 km). This shall be accomplished by (i) applying consistent standards in all processing steps required to derive marine and land based gravity data, (ii) homogeneously reprocessing the orbits of historical, actual and new altimeter missions to achieve a dense and most precise mapping for the marine gravity data, (iii) cross-calibrating sea surface heights, correcting them for the most recent estimates of the dynamic ocean topography and combining the marine geoid with satellite-only gravity fields by applying regional gravity field modeling, (iv) realizing an utmost comprehensive compilation of terrestrial and airborne gravity data, investigating and resolving inconsistencies between satellite-only gravity fields and terrestrial gravity by regional gravity field modeling, (v) synthesizing gravity by new high-resolution digital elevation models and using this in a differential form to fill gaps, in particular, in terrestrial gravity data, and (vi) validating marine gravity by ship-borne observations and terrestrial gravity by comparison with GNSS data and leveling heights.