A study of high frequency terrain effects in gravity field modelling

Abstract

Within the framework of the GOCE-GRAND II project and in cooperation with the Bundesamt für Kartographie und Geodasie (BKG), it is planned to validate the GOCE gravity field models by independent terrestrial data sets. Besides GPS and levelling data, gravity and terrain data shall be combined with a global spherical harmonic model to provide an independent gravimetric (quasi)geoid model, and, in addition, deflections of the vertical shall be observed with the Hannover digital zenith camera TZK2-D in a 500 km long profile to provide another completely independent data set for the GOCE validation. For this purpose, it is necessary to study the high frequency gravity field components related to the terrain, as all effects not included in the GOCE models have to be filtered out before the actual validation step. In this contribution, a digital terrain model for Germany with a grid spacing of 1" x 1" (approx. 30 m) is used to study the high frequency effects of the terrain on gravity anomalies, deflections of the vertical and geoid heights. Besides an investigation of different DTM resolutions, a covariance and spectral analysis is performed. The aim of the study is to find the optimal resolution of the terrain data for given accuracy levels.