Global gravity field recovery by merging regional focusing patches: An integrated approach

Usually the gravity potential is modelled by a spherical harmonic expansion. Simulation tests and real-data investigations based on POD (precise orbit determination) and SST (satellite-to-satellite tracking) data demonstrated that the heterogeneity of the gravity field cannot be properly taken into account by base functions with global support. It is preferable to model the gravity field only up to a moderate safely determinable spherical harmonic degree without any regularization to cover the long and medium wavelengths characteristics; the specific detailed features tailored to the individual gravity field characteristics in areas of rough gravity field signal can be modelled additionally by space localizing base functions. In a final step, a spherical harmonic expansion up to a maximum degree, only limited by the most detailed structures of the gravity field, can be derived based on a Gauss-Legendre-Quadrature procedure. This last step can be performed without stability problems and without losing the regional details of the gravity field. The proposed integrated gravity field recovery approach integrates consistently a regional gravity field zoom-in into a global gravity field solution. The technique has been applied to the determination of gravity field models based on SST data of GRACE.