A quality investigation of global vertical datum connection

Abstract

SUMMARY Vertical datum connection is investigated from the viewpoint of quality, i.e. accuracy and reliability, based on the method originally proposed by Rummel & Teunissen (1988). Three simulations are carried out. The levelling accuracy is assumed to be 1 mmkm-1 and the position accuracy of space stations 5 cm. The three error models of the geoid used are that of the Rapp-81 model, that of a tailored gravitational field and that defined by the GEM-T1 variance-covariance matrix. The results show that the quality of the vertical datum connection depends on the relative accuracy of levelling and space stations, but in particular on that of the geoid. It is also related to the number of space stations inside each datum zone and their geographical distribution. Only when an absolute determination of vertical datum is required, does the absolute accuracy of the space stations play an important role. Finally, we discuss an alternative datum connection model using terrestrial gravity anomalies and satellite derived geopotential coefficients.