Research on the Integrated Approach and its Simulation

Objectives: The Integrated Approach is a significant method that can be used to integrate multi-source spatial geodetic observations. It can achieve an overall solution for various types of observations at the observation level. This paper describes the multilevel observations combination based on the Integrated Approach. Methods: The model and technological route of the Integrated Approach are explained using ground-based GNSS (Global Navigation Satellite System) and gravity satellite observations as an example. Simulation experiments are accomplished based on self-developed software. Results: The analysis of the effects of the Integrated Approach and the step-by-step method on the parameters of the earth's gravity field, as well as the orbits of GRACE (Gravity Recovery And Climate Experiment) and GPS (Global Positioning System) satellites, is presented. The results indicate that the earth's gravity field model parameters solved by the Integrated Approach have smaller errors compared to the Simultaneous Solution, due to the additional GPS orbital observation information. The addition of GRACE satellite observations can improve the GPS satellite orbits of the Integrated Approach compared to the ground station only. On average, the 3D RMS of GPS satellite orbits is improved by about 4.7%, and the orbit 3D RMS improvement is up to 54% of short ground tracking arc. Conclusions: These results demonstrate the important role of the Integrated Approach in the recovery of the earth's gravity field and the satellite's precision orbit determination.Future research will continue to use the Integrated Approach for real observation analysis.