Research On Realization Method Of Epoch Terrestrial Reference Frame For GNSS/VLBI/SLR/DORIS Multi-source Data Fusion

Currently,the International Terrestrial Reference Frame(ITRF)uses a set of point coordinates and linear velocities that are defined in reference epochs in accordance with the International Terrestrial Reference System(ITRS).This method of maintenance is based on the premise that the station performs linear motion.However,because of the influence of the Earth's structure and non-structural,the motion of the station is nonlinear.The linear velocity provided by ITRF cannot truly reflect the position change of the station.This article builds on the epoch reference frame to compensate for the lack of ITRF's linear speed.Its advantage is that it implicitly considers the nonlinear motion of the station and can truly reflect the position change of the station.In this paper,based on the theory and method of multi-source space geodetic technology fusion of normal equations,the epoch Terrestrial reference frame is constructed.The main research contents and results of this paper are as follows:1.The theories and algorithms of spatial geodetic data fusion based on normal equations are studied.The algorithm of epoch-based geo-reference frame is deduced;the method of datum constrained implementation in earth reference frame is studied,and the different constraint methods are experimentally analyzed.2.The program implements a combination of Single-technique technique such as GNSS,VLBI,SLR,and DORIS,and analyzes the combined results to verify the reliability of the program and the accuracy of the combined results.3.Analyze and optimize the quality of local tie data on collocated stations with different geodetic techniques by Helmert parameters.The residual RMS of the selected local tie in the N,E,and U directions was 4.4 mm,4.7 mm,and 6.4 mm,respectively.4.The program implements a combination of Inter-technique such as GNSS,VLBI,SLR,and DORIS.Combined with ITRF2014,it verifies the reliability of the program and the accuracy of the combined results,and analyzes the datum differences between the result and ITRF2014.The results show that there is no obvious systematic difference between the results and ITRF2014 scale parameters and rotation parameters,and there are millimeter-level changes in the translation parameters.5.Developed data download and epoch Terrestrial reference frame construction software to serve the establishment of the epoch earth reference frame;the position errors of the reference stations in the epoch reference frame and the long-term reference frame were analyzed;Combined with ITRF2014,the established epoch terrestrial reference frame was analyzed.The results show that the epoch terrestrial reference frame can better represent the nonlinear motion of the station and can be closer to the real motion of the station.