GRIM5‐C1: Combination solution of the global gravity field to degree and order 120

Abstract

The new satellite Earth gravity field model GRIM5‐S1 was recently prepared in a joint GFZ and GRGS effort. Based on this satellite solution and terrestrial and altimetric gravity anomalies from NIMA, a combined model GRIM5‐C1, with full variance‐covariance matrix up to degree and order 120, was computed. Surface gravity and altimetric gravity data are corrected for several systematic effects, such as ellipsoidal corrections and aliasing. A weighting scheme for gravity anomalies, according to their given standard deviations was developed. From each data set full normal equations were set up and finally combined with the GRIM5‐S1 normals. To take into account good information from the satellite‐only model a procedure was developed to identify such coefficients and appropriately weighed them in the final normal equation system. Internal error propagation and comparisons to external data sets show, that the GRIM5‐C1 model represents the best state of long wavelength gravity field models.