An ITRF combination model with preferred observation functionals and its solution using generalized condition equations

Abstract

Providing a stable and accurate reference frame is of the fundamental importance because accurate solution realization of an International Terresterial Reference Frame (ITRF) is essential to the correct interpretation of any geophysical and geologic phenomena. The existing ITRF mathematical model uses the state vectors of different stations derived from a number of terrestrial reference frames as observations. However, the station state vectors are not always directly observed but derived from different space geodetic measurements that may be lack of Earth's center of mass and orientation information, which are necessary for defining a terrestrial reference frame. This thesis aims to demonstrate an alternative approach, called Preferred Observation Functionals (POF) approach, in the solution realization of an international terrestrial reference frame from the combination of a number of auxiliary reference frames. The new formulation takes into account the inherent properties of different space geodesy measurement techniques in the solution. Three alternative formulations are demonstrated using the available TRF data. State Vector (SV) based solution is also presented for comparison with the alternative solutions. The resulting station position and velocity estimates generated from the POF approach are, in general, comparatively more precise than the SV based solution. The results also indicate the actual position difference between station position estimates obtained from the above approaches and ITRF2000 solution realization in each coordinate component are at a few centimeter levels, while the horizontal station velocity estimates generated from both approaches shows a good agreement with the ITRF2000 solution, particularly for those based on the POF approach. Those results present that the alternative combination solutions are not significantly different from the ITRF2000 official solution, but improve upon them by directly accounting for the inherent geometric and physical properties of different space geodesy measurement techniques.